diff --git a/build-aux/m4/bitcoin_qt.m4 b/build-aux/m4/bitcoin_qt.m4
index c3785bdcf3b7..f9d63864eb8e 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -414,17 +414,17 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
     qt4_modules="QtCore QtGui QtNetwork"
     BITCOIN_QT_CHECK([
       if test x$bitcoin_qt_want_version = xqt5 || ( test x$bitcoin_qt_want_version = xauto && test x$auto_priority_version = xqt5 ); then
-        PKG_CHECK_MODULES([QT], [$qt5_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes],[have_qt=no])
+        PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" have_qt=yes],[have_qt=no])
       elif test x$bitcoin_qt_want_version = xqt4 || ( test x$bitcoin_qt_want_version = xauto && test x$auto_priority_version = xqt4 ); then
-        PKG_CHECK_MODULES([QT], [$qt4_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes], [have_qt=no])
+        PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes], [have_qt=no])
       fi
 
       dnl qt version is set to 'auto' and the preferred version wasn't found. Now try the other.
       if test x$have_qt = xno && test x$bitcoin_qt_want_version = xauto; then
         if test x$auto_priority_version = xqt5; then
-          PKG_CHECK_MODULES([QT], [$qt4_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes; QT_LIB_PREFIX=Qt; bitcoin_qt_got_major_vers=4], [have_qt=no])
+          PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt; bitcoin_qt_got_major_vers=4], [have_qt=no])
         else
-          PKG_CHECK_MODULES([QT], [$qt5_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes; QT_LIB_PREFIX=Qt5; bitcoin_qt_got_major_vers=5], [have_qt=no])
+          PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt5; bitcoin_qt_got_major_vers=5], [have_qt=no])
         fi
       fi
       if test x$have_qt != xyes; then
diff --git a/configure.ac b/configure.ac
index b24105efd037..2f7bcbe97734 100644
--- a/configure.ac
+++ b/configure.ac
@@ -280,6 +280,12 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
   AX_CHECK_COMPILE_FLAG([-Wunused-local-typedef],[CXXFLAGS="$CXXFLAGS -Wno-unused-local-typedef"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wdeprecated-register],[CXXFLAGS="$CXXFLAGS -Wno-deprecated-register"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough],[CXXFLAGS="$CXXFLAGS -Wno-implicit-fallthrough"],,[[$CXXFLAG_WERROR]])
+
+  # Check for optional instruction set support. Enabling these does _not_ imply that all code will
+  # be compiled with them, rather that specific objects/libs may use them after checking for runtime
+  # compatibility.
+  AX_CHECK_COMPILE_FLAG([-msse4.2],[[enable_sse42=yes; SSE42_CXXFLAGS="-msse4.2"]],,[[$CXXFLAG_WERROR]])
+
 fi
 CPPFLAGS="$CPPFLAGS -DHAVE_BUILD_INFO -D__STDC_FORMAT_MACROS"
 
@@ -1170,6 +1176,7 @@ AM_CONDITIONAL([USE_QRCODE], [test x$use_qr = xyes])
 AM_CONDITIONAL([USE_LCOV],[test x$use_lcov = xyes])
 AM_CONDITIONAL([GLIBC_BACK_COMPAT],[test x$use_glibc_compat = xyes])
 AM_CONDITIONAL([HARDEN],[test x$use_hardening = xyes])
+AM_CONDITIONAL([ENABLE_SSE42],[test x$enable_sse42 = xyes])
 
 AC_DEFINE(CLIENT_VERSION_MAJOR, _CLIENT_VERSION_MAJOR, [Major version])
 AC_DEFINE(CLIENT_VERSION_MINOR, _CLIENT_VERSION_MINOR, [Minor version])
@@ -1202,6 +1209,7 @@ AC_SUBST(HARDENED_CPPFLAGS)
 AC_SUBST(HARDENED_LDFLAGS)
 AC_SUBST(PIC_FLAGS)
 AC_SUBST(PIE_FLAGS)
+AC_SUBST(SSE42_CXXFLAGS)
 AC_SUBST(LIBTOOL_APP_LDFLAGS)
 AC_SUBST(USE_UPNP)
 AC_SUBST(USE_QRCODE)
diff --git a/contrib/devtools/commit-script-check.sh b/contrib/devtools/commit-script-check.sh
index add4bb4883d4..1c9dbc7f68ff 100755
--- a/contrib/devtools/commit-script-check.sh
+++ b/contrib/devtools/commit-script-check.sh
@@ -20,20 +20,27 @@ RET=0
 PREV_BRANCH=`git name-rev --name-only HEAD`
 PREV_HEAD=`git rev-parse HEAD`
 for i in `git rev-list --reverse $1`; do
-    git rev-list -n 1 --pretty="%s" $i | grep -q "^scripted-diff:" || continue
-    git checkout --quiet $i^ || exit
-    SCRIPT="`git rev-list --format=%b -n1 $i | sed '/^-BEGIN VERIFY SCRIPT-$/,/^-END VERIFY SCRIPT-$/{//!b};d'`"
-    if test "x$SCRIPT" = "x"; then
-        echo "Error: missing script for: $i"
-        echo "Failed"
-        RET=1
-    else
-        echo "Running script for: $i"
-        echo "$SCRIPT"
-        eval "$SCRIPT"
-        git --no-pager diff --exit-code $i && echo "OK" || (echo "Failed"; false) || RET=1
+    if git rev-list -n 1 --pretty="%s" $i | grep -q "^scripted-diff:"; then
+        git checkout --quiet $i^ || exit
+        SCRIPT="`git rev-list --format=%b -n1 $i | sed '/^-BEGIN VERIFY SCRIPT-$/,/^-END VERIFY SCRIPT-$/{//!b};d'`"
+        if test "x$SCRIPT" = "x"; then
+            echo "Error: missing script for: $i"
+            echo "Failed"
+            RET=1
+        else
+            echo "Running script for: $i"
+            echo "$SCRIPT"
+            eval "$SCRIPT"
+            git --no-pager diff --exit-code $i && echo "OK" || (echo "Failed"; false) || RET=1
+        fi
+        git reset --quiet --hard HEAD
+     else
+        if git rev-list "--format=%b" -n1 $i | grep -q '^-\(BEGIN\|END\)[ a-zA-Z]*-$'; then
+            echo "Error: script block marker but no scripted-diff in title"
+            echo "Failed"
+            RET=1
+        fi
     fi
-    git reset --quiet --hard HEAD
 done
 git checkout --quiet $PREV_BRANCH 2>/dev/null || git checkout --quiet $PREV_HEAD
 exit $RET
diff --git a/doc/developer-notes.md b/doc/developer-notes.md
index 0be01417ef3c..d0f6e2773ea0 100644
--- a/doc/developer-notes.md
+++ b/doc/developer-notes.md
@@ -404,6 +404,14 @@ Source code organization
 
   - *Rationale*: Shorter and simpler header files are easier to read, and reduce compile time
 
+- Every `.cpp` and `.h` file should `#include` every header file it directly uses classes, functions or other
+  definitions from, even if those headers are already included indirectly through other headers. One exception
+  is that a `.cpp` file does not need to re-include the includes already included in its corresponding `.h` file.
+
+  - *Rationale*: Excluding headers because they are already indirectly included results in compilation
+    failures when those indirect dependencies change. Furthermore, it obscures what the real code
+    dependencies are.
+
 - Don't import anything into the global namespace (`using namespace ...`). Use
   fully specified types such as `std::string`.
 
diff --git a/src/.clang-format b/src/.clang-format
index 1e8222754462..f1113e635362 100644
--- a/src/.clang-format
+++ b/src/.clang-format
@@ -49,6 +49,6 @@ SpacesInAngles:  false
 SpacesInContainerLiterals: true
 SpacesInCStyleCastParentheses: false
 SpacesInParentheses: false
-Standard:        Cpp03
+Standard:        Cpp11
 TabWidth:        8
 UseTab:          Never
diff --git a/src/Makefile.am b/src/Makefile.am
index 57b9ccc4a839..b28c23172e76 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -536,6 +536,7 @@ dashd_LDADD = \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBLEVELDB) \
+  $(LIBLEVELDB_SSE42) \
   $(LIBMEMENV) \
   $(LIBSECP256K1)
 
diff --git a/src/Makefile.bench.include b/src/Makefile.bench.include
index 8153e07b7788..87876c3c2dac 100644
--- a/src/Makefile.bench.include
+++ b/src/Makefile.bench.include
@@ -43,6 +43,7 @@ bench_bench_dash_LDADD = \
   $(LIBBITCOIN_CONSENSUS) \
   $(LIBBITCOIN_CRYPTO) \
   $(LIBLEVELDB) \
+  $(LIBLEVELDB_SSE42) \
   $(LIBMEMENV) \
   $(LIBSECP256K1) \
   $(LIBUNIVALUE)
diff --git a/src/Makefile.leveldb.include b/src/Makefile.leveldb.include
index 358f39cbef5d..ac38141f43d7 100644
--- a/src/Makefile.leveldb.include
+++ b/src/Makefile.leveldb.include
@@ -4,12 +4,15 @@
 
 LIBLEVELDB_INT = leveldb/libleveldb.a
 LIBMEMENV_INT  = leveldb/libmemenv.a
+LIBLEVELDB_SSE42_INT  = leveldb/libleveldb_sse42.a
 
 EXTRA_LIBRARIES += $(LIBLEVELDB_INT)
 EXTRA_LIBRARIES += $(LIBMEMENV_INT)
+EXTRA_LIBRARIES += $(LIBLEVELDB_SSE42_INT)
 
 LIBLEVELDB += $(LIBLEVELDB_INT)
 LIBMEMENV += $(LIBMEMENV_INT)
+LIBLEVELDB_SSE42 = $(LIBLEVELDB_SSE42_INT)
 
 LEVELDB_CPPFLAGS += -I$(srcdir)/leveldb/include
 LEVELDB_CPPFLAGS += -I$(srcdir)/leveldb/helpers/memenv
@@ -74,6 +77,7 @@ leveldb_libleveldb_a_SOURCES += leveldb/table/merger.h
 leveldb_libleveldb_a_SOURCES += leveldb/table/format.h
 leveldb_libleveldb_a_SOURCES += leveldb/table/iterator_wrapper.h
 leveldb_libleveldb_a_SOURCES += leveldb/util/crc32c.h
+leveldb_libleveldb_a_SOURCES += leveldb/util/env_posix_test_helper.h
 leveldb_libleveldb_a_SOURCES += leveldb/util/arena.h
 leveldb_libleveldb_a_SOURCES += leveldb/util/random.h
 leveldb_libleveldb_a_SOURCES += leveldb/util/posix_logger.h
@@ -135,3 +139,11 @@ leveldb_libmemenv_a_CPPFLAGS = $(leveldb_libleveldb_a_CPPFLAGS)
 leveldb_libmemenv_a_CXXFLAGS = $(leveldb_libleveldb_a_CXXFLAGS)
 leveldb_libmemenv_a_SOURCES =  leveldb/helpers/memenv/memenv.cc
 leveldb_libmemenv_a_SOURCES += leveldb/helpers/memenv/memenv.h
+
+leveldb_libleveldb_sse42_a_CPPFLAGS = $(leveldb_libleveldb_a_CPPFLAGS)
+leveldb_libleveldb_sse42_a_CXXFLAGS = $(leveldb_libleveldb_a_CXXFLAGS)
+if ENABLE_SSE42
+leveldb_libleveldb_sse42_a_CPPFLAGS += -DLEVELDB_PLATFORM_POSIX_SSE
+leveldb_libleveldb_sse42_a_CXXFLAGS += $(SSE42_CXXFLAGS)
+endif
+leveldb_libleveldb_sse42_a_SOURCES =  leveldb/port/port_posix_sse.cc
diff --git a/src/Makefile.qt.include b/src/Makefile.qt.include
index 9a49a45a5dfa..56a6dca1895f 100644
--- a/src/Makefile.qt.include
+++ b/src/Makefile.qt.include
@@ -645,7 +645,7 @@ endif
 if ENABLE_ZMQ
 qt_dash_qt_LDADD += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
-qt_dash_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBMEMENV) \
+qt_dash_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) \
   $(BACKTRACE_LIB) $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
   $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(BLS_LIBS)
 qt_dash_qt_LDFLAGS = $(LDFLAGS_WRAP_EXCEPTIONS) $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
diff --git a/src/Makefile.qttest.include b/src/Makefile.qttest.include
index 63324be321eb..4fee9ba7fc1f 100644
--- a/src/Makefile.qttest.include
+++ b/src/Makefile.qttest.include
@@ -63,7 +63,7 @@ if ENABLE_ZMQ
 qt_test_test_dash_qt_LDADD += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
 qt_test_test_dash_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) \
-  $(LIBMEMENV) $(BACKTRACE_LIB) $(BOOST_LIBS) $(QT_DBUS_LIBS) $(QT_TEST_LIBS) $(QT_LIBS) \
+  $(LIBLEVELDB_SSE42) $(LIBMEMENV) $(BACKTRACE_LIB) $(BOOST_LIBS) $(QT_DBUS_LIBS) $(QT_TEST_LIBS) $(QT_LIBS) \
   $(QR_LIBS) $(PROTOBUF_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
   $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(BLS_LIBS)
 qt_test_test_dash_qt_LDFLAGS = $(LDFLAGS_WRAP_EXCEPTIONS) $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index c0b422858690..0a246abdab5e 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -109,8 +109,8 @@ endif
 
 test_test_dash_SOURCES = $(BITCOIN_TESTS) $(JSON_TEST_FILES) $(RAW_TEST_FILES)
 test_test_dash_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -I$(builddir)/test/ $(TESTDEFS) $(EVENT_CFLAGS)
-test_test_dash_LDADD = $(LIBBITCOIN_SERVER) $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBMEMENV) \
-  $(BACKTRACE_LIB) $(BOOST_LIBS) $(BOOST_UNIT_TEST_FRAMEWORK_LIB) $(LIBSECP256K1) $(EVENT_LIBS) $(EVENT_PTHREADS_LIBS)
+test_test_dash_LDADD = $(LIBBITCOIN_SERVER) $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) \
+  $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) $(BACKTRACE_LIB) $(BOOST_LIBS) $(BOOST_UNIT_TEST_FRAMEWORK_LIB) $(LIBSECP256K1) $(EVENT_LIBS) $(EVENT_PTHREADS_LIBS)
 test_test_dash_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 if ENABLE_WALLET
 test_test_dash_LDADD += $(LIBBITCOIN_WALLET)
diff --git a/src/bench/coin_selection.cpp b/src/bench/coin_selection.cpp
index ec6e7a2c17b2..0e86568e5bf8 100644
--- a/src/bench/coin_selection.cpp
+++ b/src/bench/coin_selection.cpp
@@ -39,7 +39,7 @@ static void CoinSelection(benchmark::State& state)
 
     while (state.KeepRunning()) {
         // Empty wallet.
-        BOOST_FOREACH (COutput output, vCoins)
+        for (COutput output : vCoins)
             delete output.tx;
         vCoins.clear();
 
diff --git a/src/blockencodings.cpp b/src/blockencodings.cpp
index 02cac61e741d..3e2d40844ca6 100644
--- a/src/blockencodings.cpp
+++ b/src/blockencodings.cpp
@@ -172,7 +172,7 @@ ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& c
 bool PartiallyDownloadedBlock::IsTxAvailable(size_t index) const {
     assert(!header.IsNull());
     assert(index < txn_available.size());
-    return txn_available[index] ? true : false;
+    return txn_available[index] != nullptr;
 }
 
 ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) {
diff --git a/src/bloom.cpp b/src/bloom.cpp
index 3f7a49c9fe1d..1a58b8714205 100644
--- a/src/bloom.cpp
+++ b/src/bloom.cpp
@@ -272,7 +272,7 @@ bool CBloomFilter::IsRelevantAndUpdate(const CTransaction& tx)
     if (fFound)
         return true;
 
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         // Match if the filter contains an outpoint tx spends
         if (contains(txin.prevout))
diff --git a/src/checkqueue.h b/src/checkqueue.h
index 08017ff799c8..d7b7b836dcf2 100644
--- a/src/checkqueue.h
+++ b/src/checkqueue.h
@@ -120,7 +120,7 @@ class CCheckQueue
                 fOk = fAllOk;
             }
             // execute work
-            BOOST_FOREACH (T& check, vChecks)
+            for (T& check : vChecks)
                 if (fOk)
                     fOk = check();
             vChecks.clear();
@@ -150,7 +150,7 @@ class CCheckQueue
     void Add(std::vector<T>& vChecks)
     {
         boost::unique_lock<boost::mutex> lock(mutex);
-        BOOST_FOREACH (T& check, vChecks) {
+        for (T& check : vChecks) {
             queue.push_back(T());
             check.swap(queue.back());
         }
diff --git a/src/core_write.cpp b/src/core_write.cpp
index 702f9b413ae7..edb60b55db55 100644
--- a/src/core_write.cpp
+++ b/src/core_write.cpp
@@ -146,7 +146,7 @@ void ScriptPubKeyToUniv(const CScript& scriptPubKey,
     out.pushKV("type", GetTxnOutputType(type));
 
     UniValue a(UniValue::VARR);
-    BOOST_FOREACH(const CTxDestination& addr, addresses)
+    for (const CTxDestination& addr : addresses)
         a.push_back(CBitcoinAddress(addr).ToString());
     out.pushKV("addresses", a);
 }
@@ -160,7 +160,7 @@ void TxToUniv(const CTransaction& tx, const uint256& hashBlock, UniValue& entry,
     entry.pushKV("locktime", (int64_t)tx.nLockTime);
 
     UniValue vin(UniValue::VARR);
-    BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+    for (const CTxIn& txin : tx.vin) {
         UniValue in(UniValue::VOBJ);
         if (tx.IsCoinBase())
             in.pushKV("coinbase", HexStr(txin.scriptSig.begin(), txin.scriptSig.end()));
diff --git a/src/dash-tx.cpp b/src/dash-tx.cpp
index ee29754160ef..420a39a4aaef 100644
--- a/src/dash-tx.cpp
+++ b/src/dash-tx.cpp
@@ -585,7 +585,7 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
             SignSignature(keystore, prevPubKey, mergedTx, i, nHashType);
 
         // ... and merge in other signatures:
-        BOOST_FOREACH(const CTransaction& txv, txVariants) {
+        for (const CTransaction& txv : txVariants) {
             txin.scriptSig = CombineSignatures(prevPubKey, mergedTx, i, txin.scriptSig, txv.vin[i].scriptSig);
         }
         if (!VerifyScript(txin.scriptSig, prevPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, MutableTransactionSignatureChecker(&mergedTx, i)))
diff --git a/src/dbwrapper.cpp b/src/dbwrapper.cpp
index 638d669c4c0a..eb6d5ecb5fd6 100644
--- a/src/dbwrapper.cpp
+++ b/src/dbwrapper.cpp
@@ -108,7 +108,7 @@ CDBWrapper::CDBWrapper(const fs::path& path, size_t nCacheSize, bool fMemory, bo
             leveldb::Status result = leveldb::DestroyDB(path.string(), options);
             dbwrapper_private::HandleError(result);
         }
-        TryCreateDirectory(path);
+        TryCreateDirectories(path);
         LogPrintf("Opening LevelDB in %s\n", path.string());
     }
     leveldb::Status status = leveldb::DB::Open(options, path.string(), &pdb);
diff --git a/src/evo/deterministicmns.cpp b/src/evo/deterministicmns.cpp
index 921905e1aaff..393219d06484 100644
--- a/src/evo/deterministicmns.cpp
+++ b/src/evo/deterministicmns.cpp
@@ -692,10 +692,10 @@ bool CDeterministicMNManager::BuildNewListFromBlock(const CBlock& block, const C
             }
 
             if (newList.HasUniqueProperty(proTx.addr)) {
-                return _state.DoS(100, false, REJECT_CONFLICT, "bad-protx-dup-addr");
+                return _state.DoS(100, false, REJECT_DUPLICATE, "bad-protx-dup-addr");
             }
             if (newList.HasUniqueProperty(proTx.keyIDOwner) || newList.HasUniqueProperty(proTx.pubKeyOperator)) {
-                return _state.DoS(100, false, REJECT_CONFLICT, "bad-protx-dup-key");
+                return _state.DoS(100, false, REJECT_DUPLICATE, "bad-protx-dup-key");
             }
 
             dmn->nOperatorReward = proTx.nOperatorReward;
@@ -724,7 +724,7 @@ bool CDeterministicMNManager::BuildNewListFromBlock(const CBlock& block, const C
             }
 
             if (newList.HasUniqueProperty(proTx.addr) && newList.GetUniquePropertyMN(proTx.addr)->proTxHash != proTx.proTxHash) {
-                return _state.DoS(100, false, REJECT_CONFLICT, "bad-protx-dup-addr");
+                return _state.DoS(100, false, REJECT_DUPLICATE, "bad-protx-dup-addr");
             }
 
             CDeterministicMNCPtr dmn = newList.GetMN(proTx.proTxHash);
diff --git a/src/httprpc.cpp b/src/httprpc.cpp
index ce64fb444dc9..e0b943045ebb 100644
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -18,7 +18,7 @@
 #include <stdio.h>
 
 #include <boost/algorithm/string.hpp> // boost::trim
-#include <boost/foreach.hpp> //BOOST_FOREACH
+#include <boost/foreach.hpp>
 
 /** WWW-Authenticate to present with 401 Unauthorized response */
 static const char* WWW_AUTH_HEADER_DATA = "Basic realm=\"jsonrpc\"";
@@ -94,7 +94,7 @@ static bool multiUserAuthorized(std::string strUserPass)
 
     if (gArgs.IsArgSet("-rpcauth")) {
         //Search for multi-user login/pass "rpcauth" from config
-        BOOST_FOREACH(std::string strRPCAuth, gArgs.GetArgs("-rpcauth"))
+        for (std::string strRPCAuth : gArgs.GetArgs("-rpcauth"))
         {
             std::vector<std::string> vFields;
             boost::split(vFields, strRPCAuth, boost::is_any_of(":$"));
diff --git a/src/httprpc.h b/src/httprpc.h
index d35445718871..a89a8f0fbfe0 100644
--- a/src/httprpc.h
+++ b/src/httprpc.h
@@ -8,8 +8,6 @@
 #include <string>
 #include <map>
 
-class HTTPRequest;
-
 /** Start HTTP RPC subsystem.
  * Precondition; HTTP and RPC has been started.
  */
diff --git a/src/init.cpp b/src/init.cpp
index 242be406398f..dbd7bf09e275 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -746,7 +746,7 @@ void CleanupBlockRevFiles()
     // keeping a separate counter.  Once we hit a gap (or if 0 doesn't exist)
     // start removing block files.
     int nContigCounter = 0;
-    BOOST_FOREACH(const PAIRTYPE(std::string, fs::path)& item, mapBlockFiles) {
+    for (const std::pair<std::string, fs::path>& item : mapBlockFiles) {
         if (atoi(item.first) == nContigCounter) {
             nContigCounter++;
             continue;
@@ -799,7 +799,7 @@ void ThreadImport(std::vector<fs::path> vImportFiles)
     }
 
     // -loadblock=
-    BOOST_FOREACH(const fs::path& path, vImportFiles) {
+    for (const fs::path& path : vImportFiles) {
         FILE *file = fsbridge::fopen(path, "rb");
         if (file) {
             LogPrintf("Importing blocks file %s...\n", path.string());
@@ -1463,6 +1463,7 @@ bool AppInitSanityChecks()
     // ********************************************************* Step 4: sanity checks
 
     // Initialize elliptic curve code
+    RandomInit();
     ECC_Start();
     globalVerifyHandle.reset(new ECCVerifyHandle());
 
@@ -1587,7 +1588,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     }
 
     if (gArgs.IsArgSet("-uacomment")) {
-        BOOST_FOREACH(std::string cmt, gArgs.GetArgs("-uacomment"))
+        for (std::string cmt : gArgs.GetArgs("-uacomment"))
         {
             if (cmt != SanitizeString(cmt, SAFE_CHARS_UA_COMMENT))
                 return InitError(strprintf(_("User Agent comment (%s) contains unsafe characters."), cmt));
@@ -1602,7 +1603,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
 
     if (gArgs.IsArgSet("-onlynet")) {
         std::set<enum Network> nets;
-        BOOST_FOREACH(const std::string& snet, gArgs.GetArgs("-onlynet")) {
+        for (const std::string& snet : gArgs.GetArgs("-onlynet")) {
             enum Network net = ParseNetwork(snet);
             if (net == NET_UNROUTABLE)
                 return InitError(strprintf(_("Unknown network specified in -onlynet: '%s'"), snet));
@@ -1616,7 +1617,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     }
 
     if (gArgs.IsArgSet("-whitelist")) {
-        BOOST_FOREACH(const std::string& net, gArgs.GetArgs("-whitelist")) {
+        for (const std::string& net : gArgs.GetArgs("-whitelist")) {
             CSubNet subnet;
             LookupSubNet(net.c_str(), subnet);
             if (!subnet.IsValid())
@@ -1678,7 +1679,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (fListen) {
         bool fBound = false;
         if (gArgs.IsArgSet("-bind")) {
-            BOOST_FOREACH(const std::string& strBind, gArgs.GetArgs("-bind")) {
+            for (const std::string& strBind : gArgs.GetArgs("-bind")) {
                 CService addrBind;
                 if (!Lookup(strBind.c_str(), addrBind, GetListenPort(), false))
                     return InitError(ResolveErrMsg("bind", strBind));
@@ -1686,7 +1687,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
             }
         }
         if (gArgs.IsArgSet("-whitebind")) {
-            BOOST_FOREACH(const std::string& strBind, gArgs.GetArgs("-whitebind")) {
+            for (const std::string& strBind : gArgs.GetArgs("-whitebind")) {
                 CService addrBind;
                 if (!Lookup(strBind.c_str(), addrBind, 0, false))
                     return InitError(ResolveErrMsg("whitebind", strBind));
@@ -1706,7 +1707,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     }
 
     if (gArgs.IsArgSet("-externalip")) {
-        BOOST_FOREACH(const std::string& strAddr, gArgs.GetArgs("-externalip")) {
+        for (const std::string& strAddr : gArgs.GetArgs("-externalip")) {
             CService addrLocal;
             if (Lookup(strAddr.c_str(), addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
                 AddLocal(addrLocal, LOCAL_MANUAL);
@@ -1761,8 +1762,6 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     fReindex = gArgs.GetBoolArg("-reindex", false);
     bool fReindexChainState = gArgs.GetBoolArg("-reindex-chainstate", false);
 
-    fs::create_directories(GetDataDir() / "blocks");
-
     // cache size calculations
     int64_t nTotalCache = (gArgs.GetArg("-dbcache", nDefaultDbCache) << 20);
     nTotalCache = std::max(nTotalCache, nMinDbCache << 20); // total cache cannot be less than nMinDbCache
@@ -2094,7 +2093,7 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     std::vector<fs::path> vImportFiles;
     if (gArgs.IsArgSet("-loadblock"))
     {
-        BOOST_FOREACH(const std::string& strFile, gArgs.GetArgs("-loadblock"))
+        for (const std::string& strFile : gArgs.GetArgs("-loadblock"))
             vImportFiles.push_back(strFile);
     }
 
diff --git a/src/leveldb/Makefile b/src/leveldb/Makefile
index 07a5a1ead6fd..f7cc7d736c4f 100644
--- a/src/leveldb/Makefile
+++ b/src/leveldb/Makefile
@@ -44,6 +44,7 @@ TESTS = \
 	util/cache_test \
 	util/coding_test \
 	util/crc32c_test \
+	util/env_posix_test \
 	util/env_test \
 	util/hash_test
 
@@ -121,7 +122,7 @@ SHARED_MEMENVLIB = $(SHARED_OUTDIR)/libmemenv.a
 else
 # Update db.h if you change these.
 SHARED_VERSION_MAJOR = 1
-SHARED_VERSION_MINOR = 19
+SHARED_VERSION_MINOR = 20
 SHARED_LIB1 = libleveldb.$(PLATFORM_SHARED_EXT)
 SHARED_LIB2 = $(SHARED_LIB1).$(SHARED_VERSION_MAJOR)
 SHARED_LIB3 = $(SHARED_LIB1).$(SHARED_VERSION_MAJOR).$(SHARED_VERSION_MINOR)
@@ -337,6 +338,9 @@ $(STATIC_OUTDIR)/db_test:db/db_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS)
 $(STATIC_OUTDIR)/dbformat_test:db/dbformat_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS)
 	$(CXX) $(LDFLAGS) $(CXXFLAGS) db/dbformat_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS) -o $@ $(LIBS)
 
+$(STATIC_OUTDIR)/env_posix_test:util/env_posix_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) $(LDFLAGS) $(CXXFLAGS) util/env_posix_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS) -o $@ $(LIBS)
+
 $(STATIC_OUTDIR)/env_test:util/env_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS)
 	$(CXX) $(LDFLAGS) $(CXXFLAGS) util/env_test.cc $(STATIC_LIBOBJECTS) $(TESTHARNESS) -o $@ $(LIBS)
 
@@ -412,3 +416,9 @@ $(SHARED_OUTDIR)/%.o: %.cc
 
 $(SHARED_OUTDIR)/%.o: %.c
 	$(CC) $(CFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
+
+$(STATIC_OUTDIR)/port/port_posix_sse.o: port/port_posix_sse.cc
+	$(CXX) $(CXXFLAGS) $(PLATFORM_SSEFLAGS) -c $< -o $@
+
+$(SHARED_OUTDIR)/port/port_posix_sse.o: port/port_posix_sse.cc
+	$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) $(PLATFORM_SSEFLAGS) -c $< -o $@
diff --git a/src/leveldb/README.md b/src/leveldb/README.md
index c75b185e0e74..a010c508585e 100644
--- a/src/leveldb/README.md
+++ b/src/leveldb/README.md
@@ -16,7 +16,7 @@ Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
   * External activity (file system operations etc.) is relayed through a virtual interface so users can customize the operating system interactions.
 
 # Documentation
-  [LevelDB library documentation](https://rawgit.com/google/leveldb/master/doc/index.html) is online and bundled with the source code.
+  [LevelDB library documentation](https://github.com/google/leveldb/blob/master/doc/index.md) is online and bundled with the source code.
 
 
 # Limitations
@@ -113,29 +113,30 @@ by the one or two disk seeks needed to fetch the data from disk.
 Write performance will be mostly unaffected by whether or not the
 working set fits in memory.
 
-    readrandom   :      16.677 micros/op;  (approximately 60,000 reads per second)
-    readseq      :       0.476 micros/op;  232.3 MB/s
-    readreverse  :       0.724 micros/op;  152.9 MB/s
+    readrandom  : 16.677 micros/op;  (approximately 60,000 reads per second)
+    readseq     :  0.476 micros/op;  232.3 MB/s
+    readreverse :  0.724 micros/op;  152.9 MB/s
 
 LevelDB compacts its underlying storage data in the background to
 improve read performance.  The results listed above were done
 immediately after a lot of random writes.  The results after
 compactions (which are usually triggered automatically) are better.
 
-    readrandom   :      11.602 micros/op;  (approximately 85,000 reads per second)
-    readseq      :       0.423 micros/op;  261.8 MB/s
-    readreverse  :       0.663 micros/op;  166.9 MB/s
+    readrandom  : 11.602 micros/op;  (approximately 85,000 reads per second)
+    readseq     :  0.423 micros/op;  261.8 MB/s
+    readreverse :  0.663 micros/op;  166.9 MB/s
 
 Some of the high cost of reads comes from repeated decompression of blocks
 read from disk.  If we supply enough cache to the leveldb so it can hold the
 uncompressed blocks in memory, the read performance improves again:
 
-    readrandom   :       9.775 micros/op;  (approximately 100,000 reads per second before compaction)
-    readrandom   :       5.215 micros/op;  (approximately 190,000 reads per second after compaction)
+    readrandom  : 9.775 micros/op;  (approximately 100,000 reads per second before compaction)
+    readrandom  : 5.215 micros/op;  (approximately 190,000 reads per second after compaction)
 
 ## Repository contents
 
-See doc/index.html for more explanation. See doc/impl.html for a brief overview of the implementation.
+See [doc/index.md](doc/index.md) for more explanation. See
+[doc/impl.md](doc/impl.md) for a brief overview of the implementation.
 
 The public interface is in include/*.h.  Callers should not include or
 rely on the details of any other header files in this package.  Those
@@ -148,7 +149,7 @@ Guide to header files:
 * **include/options.h**: Control over the behavior of an entire database,
 and also control over the behavior of individual reads and writes.
 
-* **include/comparator.h**: Abstraction for user-specified comparison function. 
+* **include/comparator.h**: Abstraction for user-specified comparison function.
 If you want just bytewise comparison of keys, you can use the default
 comparator, but clients can write their own comparator implementations if they
 want custom ordering (e.g. to handle different character encodings, etc.)
@@ -165,7 +166,7 @@ length into some other byte array.
 * **include/status.h**: Status is returned from many of the public interfaces
 and is used to report success and various kinds of errors.
 
-* **include/env.h**: 
+* **include/env.h**:
 Abstraction of the OS environment.  A posix implementation of this interface is
 in util/env_posix.cc
 
diff --git a/src/leveldb/build_detect_platform b/src/leveldb/build_detect_platform
index d7edab1d87bb..4a9471590096 100755
--- a/src/leveldb/build_detect_platform
+++ b/src/leveldb/build_detect_platform
@@ -63,6 +63,7 @@ PLATFORM_SHARED_EXT="so"
 PLATFORM_SHARED_LDFLAGS="-shared -Wl,-soname -Wl,"
 PLATFORM_SHARED_CFLAGS="-fPIC"
 PLATFORM_SHARED_VERSIONED=true
+PLATFORM_SSEFLAGS=
 
 MEMCMP_FLAG=
 if [ "$CXX" = "g++" ]; then
@@ -77,6 +78,7 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -lpthread -DOS_LINUX -DCYGWIN"
         PLATFORM_LDFLAGS="-lpthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     Darwin)
         PLATFORM=OS_MACOSX
@@ -85,24 +87,28 @@ case "$TARGET_OS" in
         [ -z "$INSTALL_PATH" ] && INSTALL_PATH=`pwd`
         PLATFORM_SHARED_LDFLAGS="-dynamiclib -install_name $INSTALL_PATH/"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     Linux)
         PLATFORM=OS_LINUX
         COMMON_FLAGS="$MEMCMP_FLAG -pthread -DOS_LINUX"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     SunOS)
         PLATFORM=OS_SOLARIS
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_SOLARIS"
         PLATFORM_LIBS="-lpthread -lrt"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     FreeBSD)
         PLATFORM=OS_FREEBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_FREEBSD"
         PLATFORM_LIBS="-lpthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     GNU/kFreeBSD)
         PLATFORM=OS_KFREEBSD
@@ -115,24 +121,28 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_NETBSD"
         PLATFORM_LIBS="-lpthread -lgcc_s"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     OpenBSD)
         PLATFORM=OS_OPENBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_OPENBSD"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     DragonFly)
         PLATFORM=OS_DRAGONFLYBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_DRAGONFLYBSD"
         PLATFORM_LIBS="-lpthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     OS_ANDROID_CROSSCOMPILE)
         PLATFORM=OS_ANDROID
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_ANDROID -DLEVELDB_PLATFORM_POSIX"
         PLATFORM_LDFLAGS=""  # All pthread features are in the Android C library
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         CROSS_COMPILE=true
         ;;
     HP-UX)
@@ -140,6 +150,7 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_HPUX"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         # man ld: +h internal_name
         PLATFORM_SHARED_LDFLAGS="-shared -Wl,+h -Wl,"
         ;;
@@ -148,6 +159,7 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -DOS_MACOSX"
         [ -z "$INSTALL_PATH" ] && INSTALL_PATH=`pwd`
         PORT_FILE=port/port_posix.cc
+        PORT_SSE_FILE=port/port_posix_sse.cc
         PLATFORM_SHARED_EXT=
         PLATFORM_SHARED_LDFLAGS=
         PLATFORM_SHARED_CFLAGS=
@@ -182,7 +194,7 @@ set +f # re-enable globbing
 
 # The sources consist of the portable files, plus the platform-specific port
 # file.
-echo "SOURCES=$PORTABLE_FILES $PORT_FILE" >> $OUTPUT
+echo "SOURCES=$PORTABLE_FILES $PORT_FILE $PORT_SSE_FILE" >> $OUTPUT
 echo "MEMENV_SOURCES=helpers/memenv/memenv.cc" >> $OUTPUT
 
 if [ "$CROSS_COMPILE" = "true" ]; then
@@ -213,6 +225,21 @@ EOF
     fi
 
     rm -f $CXXOUTPUT 2>/dev/null
+
+    # Test if gcc SSE 4.2 is supported
+    $CXX $CXXFLAGS -x c++ - -o $CXXOUTPUT -msse4.2 2>/dev/null  <<EOF
+      int main() {}
+EOF
+    if [ "$?" = 0 ]; then
+        PLATFORM_SSEFLAGS="-msse4.2"
+    fi
+
+    rm -f $CXXOUTPUT 2>/dev/null
+fi
+
+# Use the SSE 4.2 CRC32C intrinsics iff runtime checks indicate compiler supports them.
+if [ -n "$PLATFORM_SSEFLAGS" ]; then
+    PLATFORM_SSEFLAGS="$PLATFORM_SSEFLAGS -DLEVELDB_PLATFORM_POSIX_SSE"
 fi
 
 PLATFORM_CCFLAGS="$PLATFORM_CCFLAGS $COMMON_FLAGS"
@@ -225,6 +252,7 @@ echo "PLATFORM_LDFLAGS=$PLATFORM_LDFLAGS" >> $OUTPUT
 echo "PLATFORM_LIBS=$PLATFORM_LIBS" >> $OUTPUT
 echo "PLATFORM_CCFLAGS=$PLATFORM_CCFLAGS" >> $OUTPUT
 echo "PLATFORM_CXXFLAGS=$PLATFORM_CXXFLAGS" >> $OUTPUT
+echo "PLATFORM_SSEFLAGS=$PLATFORM_SSEFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_CFLAGS=$PLATFORM_SHARED_CFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_EXT=$PLATFORM_SHARED_EXT" >> $OUTPUT
 echo "PLATFORM_SHARED_LDFLAGS=$PLATFORM_SHARED_LDFLAGS" >> $OUTPUT
diff --git a/src/leveldb/db/db_bench.cc b/src/leveldb/db/db_bench.cc
index 7a0f5e08cdd5..3ad19a512b56 100644
--- a/src/leveldb/db/db_bench.cc
+++ b/src/leveldb/db/db_bench.cc
@@ -84,6 +84,14 @@ static bool FLAGS_histogram = false;
 // (initialized to default value by "main")
 static int FLAGS_write_buffer_size = 0;
 
+// Number of bytes written to each file.
+// (initialized to default value by "main")
+static int FLAGS_max_file_size = 0;
+
+// Approximate size of user data packed per block (before compression.
+// (initialized to default value by "main")
+static int FLAGS_block_size = 0;
+
 // Number of bytes to use as a cache of uncompressed data.
 // Negative means use default settings.
 static int FLAGS_cache_size = -1;
@@ -109,6 +117,7 @@ static const char* FLAGS_db = NULL;
 namespace leveldb {
 
 namespace {
+leveldb::Env* g_env = NULL;
 
 // Helper for quickly generating random data.
 class RandomGenerator {
@@ -186,7 +195,7 @@ class Stats {
     done_ = 0;
     bytes_ = 0;
     seconds_ = 0;
-    start_ = Env::Default()->NowMicros();
+    start_ = g_env->NowMicros();
     finish_ = start_;
     message_.clear();
   }
@@ -204,7 +213,7 @@ class Stats {
   }
 
   void Stop() {
-    finish_ = Env::Default()->NowMicros();
+    finish_ = g_env->NowMicros();
     seconds_ = (finish_ - start_) * 1e-6;
   }
 
@@ -214,7 +223,7 @@ class Stats {
 
   void FinishedSingleOp() {
     if (FLAGS_histogram) {
-      double now = Env::Default()->NowMicros();
+      double now = g_env->NowMicros();
       double micros = now - last_op_finish_;
       hist_.Add(micros);
       if (micros > 20000) {
@@ -404,10 +413,10 @@ class Benchmark {
     reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
     heap_counter_(0) {
     std::vector<std::string> files;
-    Env::Default()->GetChildren(FLAGS_db, &files);
+    g_env->GetChildren(FLAGS_db, &files);
     for (size_t i = 0; i < files.size(); i++) {
       if (Slice(files[i]).starts_with("heap-")) {
-        Env::Default()->DeleteFile(std::string(FLAGS_db) + "/" + files[i]);
+        g_env->DeleteFile(std::string(FLAGS_db) + "/" + files[i]);
       }
     }
     if (!FLAGS_use_existing_db) {
@@ -589,7 +598,7 @@ class Benchmark {
       arg[i].shared = &shared;
       arg[i].thread = new ThreadState(i);
       arg[i].thread->shared = &shared;
-      Env::Default()->StartThread(ThreadBody, &arg[i]);
+      g_env->StartThread(ThreadBody, &arg[i]);
     }
 
     shared.mu.Lock();
@@ -700,9 +709,12 @@ class Benchmark {
   void Open() {
     assert(db_ == NULL);
     Options options;
+    options.env = g_env;
     options.create_if_missing = !FLAGS_use_existing_db;
     options.block_cache = cache_;
     options.write_buffer_size = FLAGS_write_buffer_size;
+    options.max_file_size = FLAGS_max_file_size;
+    options.block_size = FLAGS_block_size;
     options.max_open_files = FLAGS_open_files;
     options.filter_policy = filter_policy_;
     options.reuse_logs = FLAGS_reuse_logs;
@@ -925,7 +937,7 @@ class Benchmark {
     char fname[100];
     snprintf(fname, sizeof(fname), "%s/heap-%04d", FLAGS_db, ++heap_counter_);
     WritableFile* file;
-    Status s = Env::Default()->NewWritableFile(fname, &file);
+    Status s = g_env->NewWritableFile(fname, &file);
     if (!s.ok()) {
       fprintf(stderr, "%s\n", s.ToString().c_str());
       return;
@@ -934,7 +946,7 @@ class Benchmark {
     delete file;
     if (!ok) {
       fprintf(stderr, "heap profiling not supported\n");
-      Env::Default()->DeleteFile(fname);
+      g_env->DeleteFile(fname);
     }
   }
 };
@@ -943,6 +955,8 @@ class Benchmark {
 
 int main(int argc, char** argv) {
   FLAGS_write_buffer_size = leveldb::Options().write_buffer_size;
+  FLAGS_max_file_size = leveldb::Options().max_file_size;
+  FLAGS_block_size = leveldb::Options().block_size;
   FLAGS_open_files = leveldb::Options().max_open_files;
   std::string default_db_path;
 
@@ -973,6 +987,10 @@ int main(int argc, char** argv) {
       FLAGS_value_size = n;
     } else if (sscanf(argv[i], "--write_buffer_size=%d%c", &n, &junk) == 1) {
       FLAGS_write_buffer_size = n;
+    } else if (sscanf(argv[i], "--max_file_size=%d%c", &n, &junk) == 1) {
+      FLAGS_max_file_size = n;
+    } else if (sscanf(argv[i], "--block_size=%d%c", &n, &junk) == 1) {
+      FLAGS_block_size = n;
     } else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
       FLAGS_cache_size = n;
     } else if (sscanf(argv[i], "--bloom_bits=%d%c", &n, &junk) == 1) {
@@ -987,9 +1005,11 @@ int main(int argc, char** argv) {
     }
   }
 
+  leveldb::g_env = leveldb::Env::Default();
+
   // Choose a location for the test database if none given with --db=<path>
   if (FLAGS_db == NULL) {
-      leveldb::Env::Default()->GetTestDirectory(&default_db_path);
+      leveldb::g_env->GetTestDirectory(&default_db_path);
       default_db_path += "/dbbench";
       FLAGS_db = default_db_path.c_str();
   }
diff --git a/src/leveldb/db/db_impl.cc b/src/leveldb/db/db_impl.cc
index 60f4e66e5579..f43ad7679436 100644
--- a/src/leveldb/db/db_impl.cc
+++ b/src/leveldb/db/db_impl.cc
@@ -96,6 +96,7 @@ Options SanitizeOptions(const std::string& dbname,
   result.filter_policy = (src.filter_policy != NULL) ? ipolicy : NULL;
   ClipToRange(&result.max_open_files,    64 + kNumNonTableCacheFiles, 50000);
   ClipToRange(&result.write_buffer_size, 64<<10,                      1<<30);
+  ClipToRange(&result.max_file_size,     1<<20,                       1<<30);
   ClipToRange(&result.block_size,        1<<10,                       4<<20);
   if (result.info_log == NULL) {
     // Open a log file in the same directory as the db
diff --git a/src/leveldb/db/log_format.h b/src/leveldb/db/log_format.h
index a8c06efe185a..356e69fca231 100644
--- a/src/leveldb/db/log_format.h
+++ b/src/leveldb/db/log_format.h
@@ -3,7 +3,7 @@
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 //
 // Log format information shared by reader and writer.
-// See ../doc/log_format.txt for more detail.
+// See ../doc/log_format.md for more detail.
 
 #ifndef STORAGE_LEVELDB_DB_LOG_FORMAT_H_
 #define STORAGE_LEVELDB_DB_LOG_FORMAT_H_
diff --git a/src/leveldb/db/version_set.cc b/src/leveldb/db/version_set.cc
index a5e0f77a6a91..b1256f90e1c2 100644
--- a/src/leveldb/db/version_set.cc
+++ b/src/leveldb/db/version_set.cc
@@ -20,21 +20,29 @@
 
 namespace leveldb {
 
-static const int kTargetFileSize = 2 * 1048576;
+static int TargetFileSize(const Options* options) {
+  return options->max_file_size;
+}
 
 // Maximum bytes of overlaps in grandparent (i.e., level+2) before we
 // stop building a single file in a level->level+1 compaction.
-static const int64_t kMaxGrandParentOverlapBytes = 10 * kTargetFileSize;
+static int64_t MaxGrandParentOverlapBytes(const Options* options) {
+  return 10 * TargetFileSize(options);
+}
 
 // Maximum number of bytes in all compacted files.  We avoid expanding
 // the lower level file set of a compaction if it would make the
 // total compaction cover more than this many bytes.
-static const int64_t kExpandedCompactionByteSizeLimit = 25 * kTargetFileSize;
+static int64_t ExpandedCompactionByteSizeLimit(const Options* options) {
+  return 25 * TargetFileSize(options);
+}
 
-static double MaxBytesForLevel(int level) {
+static double MaxBytesForLevel(const Options* options, int level) {
   // Note: the result for level zero is not really used since we set
   // the level-0 compaction threshold based on number of files.
-  double result = 10 * 1048576.0;  // Result for both level-0 and level-1
+
+  // Result for both level-0 and level-1
+  double result = 10. * 1048576.0;
   while (level > 1) {
     result *= 10;
     level--;
@@ -42,8 +50,9 @@ static double MaxBytesForLevel(int level) {
   return result;
 }
 
-static uint64_t MaxFileSizeForLevel(int level) {
-  return kTargetFileSize;  // We could vary per level to reduce number of files?
+static uint64_t MaxFileSizeForLevel(const Options* options, int level) {
+  // We could vary per level to reduce number of files?
+  return TargetFileSize(options);
 }
 
 static int64_t TotalFileSize(const std::vector<FileMetaData*>& files) {
@@ -508,7 +517,7 @@ int Version::PickLevelForMemTableOutput(
         // Check that file does not overlap too many grandparent bytes.
         GetOverlappingInputs(level + 2, &start, &limit, &overlaps);
         const int64_t sum = TotalFileSize(overlaps);
-        if (sum > kMaxGrandParentOverlapBytes) {
+        if (sum > MaxGrandParentOverlapBytes(vset_->options_)) {
           break;
         }
       }
@@ -1027,7 +1036,7 @@ bool VersionSet::ReuseManifest(const std::string& dscname,
       manifest_type != kDescriptorFile ||
       !env_->GetFileSize(dscname, &manifest_size).ok() ||
       // Make new compacted MANIFEST if old one is too big
-      manifest_size >= kTargetFileSize) {
+      manifest_size >= TargetFileSize(options_)) {
     return false;
   }
 
@@ -1076,7 +1085,8 @@ void VersionSet::Finalize(Version* v) {
     } else {
       // Compute the ratio of current size to size limit.
       const uint64_t level_bytes = TotalFileSize(v->files_[level]);
-      score = static_cast<double>(level_bytes) / MaxBytesForLevel(level);
+      score =
+          static_cast<double>(level_bytes) / MaxBytesForLevel(options_, level);
     }
 
     if (score > best_score) {
@@ -1290,7 +1300,7 @@ Compaction* VersionSet::PickCompaction() {
     level = current_->compaction_level_;
     assert(level >= 0);
     assert(level+1 < config::kNumLevels);
-    c = new Compaction(level);
+    c = new Compaction(options_, level);
 
     // Pick the first file that comes after compact_pointer_[level]
     for (size_t i = 0; i < current_->files_[level].size(); i++) {
@@ -1307,7 +1317,7 @@ Compaction* VersionSet::PickCompaction() {
     }
   } else if (seek_compaction) {
     level = current_->file_to_compact_level_;
-    c = new Compaction(level);
+    c = new Compaction(options_, level);
     c->inputs_[0].push_back(current_->file_to_compact_);
   } else {
     return NULL;
@@ -1352,7 +1362,8 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
     const int64_t inputs1_size = TotalFileSize(c->inputs_[1]);
     const int64_t expanded0_size = TotalFileSize(expanded0);
     if (expanded0.size() > c->inputs_[0].size() &&
-        inputs1_size + expanded0_size < kExpandedCompactionByteSizeLimit) {
+        inputs1_size + expanded0_size <
+            ExpandedCompactionByteSizeLimit(options_)) {
       InternalKey new_start, new_limit;
       GetRange(expanded0, &new_start, &new_limit);
       std::vector<FileMetaData*> expanded1;
@@ -1414,7 +1425,7 @@ Compaction* VersionSet::CompactRange(
   // and we must not pick one file and drop another older file if the
   // two files overlap.
   if (level > 0) {
-    const uint64_t limit = MaxFileSizeForLevel(level);
+    const uint64_t limit = MaxFileSizeForLevel(options_, level);
     uint64_t total = 0;
     for (size_t i = 0; i < inputs.size(); i++) {
       uint64_t s = inputs[i]->file_size;
@@ -1426,7 +1437,7 @@ Compaction* VersionSet::CompactRange(
     }
   }
 
-  Compaction* c = new Compaction(level);
+  Compaction* c = new Compaction(options_, level);
   c->input_version_ = current_;
   c->input_version_->Ref();
   c->inputs_[0] = inputs;
@@ -1434,9 +1445,9 @@ Compaction* VersionSet::CompactRange(
   return c;
 }
 
-Compaction::Compaction(int level)
+Compaction::Compaction(const Options* options, int level)
     : level_(level),
-      max_output_file_size_(MaxFileSizeForLevel(level)),
+      max_output_file_size_(MaxFileSizeForLevel(options, level)),
       input_version_(NULL),
       grandparent_index_(0),
       seen_key_(false),
@@ -1453,12 +1464,13 @@ Compaction::~Compaction() {
 }
 
 bool Compaction::IsTrivialMove() const {
+  const VersionSet* vset = input_version_->vset_;
   // Avoid a move if there is lots of overlapping grandparent data.
   // Otherwise, the move could create a parent file that will require
   // a very expensive merge later on.
-  return (num_input_files(0) == 1 &&
-          num_input_files(1) == 0 &&
-          TotalFileSize(grandparents_) <= kMaxGrandParentOverlapBytes);
+  return (num_input_files(0) == 1 && num_input_files(1) == 0 &&
+          TotalFileSize(grandparents_) <=
+              MaxGrandParentOverlapBytes(vset->options_));
 }
 
 void Compaction::AddInputDeletions(VersionEdit* edit) {
@@ -1491,8 +1503,9 @@ bool Compaction::IsBaseLevelForKey(const Slice& user_key) {
 }
 
 bool Compaction::ShouldStopBefore(const Slice& internal_key) {
+  const VersionSet* vset = input_version_->vset_;
   // Scan to find earliest grandparent file that contains key.
-  const InternalKeyComparator* icmp = &input_version_->vset_->icmp_;
+  const InternalKeyComparator* icmp = &vset->icmp_;
   while (grandparent_index_ < grandparents_.size() &&
       icmp->Compare(internal_key,
                     grandparents_[grandparent_index_]->largest.Encode()) > 0) {
@@ -1503,7 +1516,7 @@ bool Compaction::ShouldStopBefore(const Slice& internal_key) {
   }
   seen_key_ = true;
 
-  if (overlapped_bytes_ > kMaxGrandParentOverlapBytes) {
+  if (overlapped_bytes_ > MaxGrandParentOverlapBytes(vset->options_)) {
     // Too much overlap for current output; start new output
     overlapped_bytes_ = 0;
     return true;
diff --git a/src/leveldb/db/version_set.h b/src/leveldb/db/version_set.h
index 1dec74567380..c4e7ac360b87 100644
--- a/src/leveldb/db/version_set.h
+++ b/src/leveldb/db/version_set.h
@@ -366,7 +366,7 @@ class Compaction {
   friend class Version;
   friend class VersionSet;
 
-  explicit Compaction(int level);
+  Compaction(const Options* options, int level);
 
   int level_;
   uint64_t max_output_file_size_;
diff --git a/src/leveldb/doc/doc.css b/src/leveldb/doc/doc.css
deleted file mode 100644
index 700c564e4338..000000000000
--- a/src/leveldb/doc/doc.css
+++ /dev/null
@@ -1,89 +0,0 @@
-body {
-  margin-left: 0.5in;
-  margin-right: 0.5in;
-  background: white;
-  color: black;
-}
-
-h1 {
-  margin-left: -0.2in;
-  font-size: 14pt;
-}
-h2 {
-  margin-left: -0in;
-  font-size: 12pt;
-}
-h3 {
-  margin-left: -0in;
-}
-h4 {
-  margin-left: -0in;
-}
-hr {
-  margin-left: -0in;
-}
-
-/* Definition lists: definition term bold */
-dt {
-  font-weight: bold;
-}
-
-address {
-  text-align: center;
-}
-code,samp,var {
-  color: blue;
-}
-kbd {
-  color: #600000;
-}
-div.note p {
-  float: right;
-  width: 3in;
-  margin-right: 0%;
-  padding: 1px;
-  border: 2px solid #6060a0;
-  background-color: #fffff0;
-}
-
-ul {
-  margin-top: -0em;
-  margin-bottom: -0em;
-}
-
-ol {
-  margin-top: -0em;
-  margin-bottom: -0em;
-}
-
-UL.nobullets {
-  list-style-type: none;
-  list-style-image: none;
-  margin-left: -1em;
-}
-
-p {
-  margin: 1em 0 1em 0;
-  padding: 0 0 0 0;
-}
-
-pre {
-  line-height: 1.3em;
-  padding: 0.4em 0 0.8em 0;
-  margin:  0 0 0 0;
-  border:  0 0 0 0;
-  color: blue;
-}
-
-.datatable {
-  margin-left: auto;
-  margin-right: auto;
-  margin-top: 2em;
-  margin-bottom: 2em;
-  border: 1px solid;
-}
-
-.datatable td,th {
-  padding: 0 0.5em 0 0.5em;
-  text-align: right;
-}
diff --git a/src/leveldb/doc/impl.html b/src/leveldb/doc/impl.html
deleted file mode 100644
index 6a468be0955d..000000000000
--- a/src/leveldb/doc/impl.html
+++ /dev/null
@@ -1,213 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-<link rel="stylesheet" type="text/css" href="doc.css" />
-<title>Leveldb file layout and compactions</title>
-</head>
-
-<body>
-
-<h1>Files</h1>
-
-The implementation of leveldb is similar in spirit to the
-representation of a single
-<a href="http://research.google.com/archive/bigtable.html">
-Bigtable tablet (section 5.3)</a>.
-However the organization of the files that make up the representation
-is somewhat different and is explained below.
-
-<p>
-Each database is represented by a set of files stored in a directory.
-There are several different types of files as documented below:
-<p>
-<h2>Log files</h2>
-<p>
-A log file (*.log) stores a sequence of recent updates.  Each update
-is appended to the current log file.  When the log file reaches a
-pre-determined size (approximately 4MB by default), it is converted
-to a sorted table (see below) and a new log file is created for future
-updates.
-<p>
-A copy of the current log file is kept in an in-memory structure (the
-<code>memtable</code>).  This copy is consulted on every read so that read
-operations reflect all logged updates.
-<p>
-<h2>Sorted tables</h2>
-<p>
-A sorted table (*.sst) stores a sequence of entries sorted by key.
-Each entry is either a value for the key, or a deletion marker for the
-key.  (Deletion markers are kept around to hide obsolete values
-present in older sorted tables).
-<p>
-The set of sorted tables are organized into a sequence of levels.  The
-sorted table generated from a log file is placed in a special <code>young</code>
-level (also called level-0).  When the number of young files exceeds a
-certain threshold (currently four), all of the young files are merged
-together with all of the overlapping level-1 files to produce a
-sequence of new level-1 files (we create a new level-1 file for every
-2MB of data.)
-<p>
-Files in the young level may contain overlapping keys.  However files
-in other levels have distinct non-overlapping key ranges.  Consider
-level number L where L >= 1.  When the combined size of files in
-level-L exceeds (10^L) MB (i.e., 10MB for level-1, 100MB for level-2,
-...), one file in level-L, and all of the overlapping files in
-level-(L+1) are merged to form a set of new files for level-(L+1).
-These merges have the effect of gradually migrating new updates from
-the young level to the largest level using only bulk reads and writes
-(i.e., minimizing expensive seeks).
-
-<h2>Manifest</h2>
-<p>
-A MANIFEST file lists the set of sorted tables that make up each
-level, the corresponding key ranges, and other important metadata.
-A new MANIFEST file (with a new number embedded in the file name)
-is created whenever the database is reopened.  The MANIFEST file is
-formatted as a log, and changes made to the serving state (as files
-are added or removed) are appended to this log.
-<p>
-<h2>Current</h2>
-<p>
-CURRENT is a simple text file that contains the name of the latest
-MANIFEST file.
-<p>
-<h2>Info logs</h2>
-<p>
-Informational messages are printed to files named LOG and LOG.old.
-<p>
-<h2>Others</h2>
-<p>
-Other files used for miscellaneous purposes may also be present
-(LOCK, *.dbtmp).
-
-<h1>Level 0</h1>
-When the log file grows above a certain size (1MB by default):
-<ul>
-<li>Create a brand new memtable and log file and direct future updates here
-<li>In the background:
-<ul>
-<li>Write the contents of the previous memtable to an sstable
-<li>Discard the memtable
-<li>Delete the old log file and the old memtable
-<li>Add the new sstable to the young (level-0) level.
-</ul>
-</ul>
-
-<h1>Compactions</h1>
-
-<p>
-When the size of level L exceeds its limit, we compact it in a
-background thread.  The compaction picks a file from level L and all
-overlapping files from the next level L+1.  Note that if a level-L
-file overlaps only part of a level-(L+1) file, the entire file at
-level-(L+1) is used as an input to the compaction and will be
-discarded after the compaction.  Aside: because level-0 is special
-(files in it may overlap each other), we treat compactions from
-level-0 to level-1 specially: a level-0 compaction may pick more than
-one level-0 file in case some of these files overlap each other.
-
-<p>
-A compaction merges the contents of the picked files to produce a
-sequence of level-(L+1) files.  We switch to producing a new
-level-(L+1) file after the current output file has reached the target
-file size (2MB).  We also switch to a new output file when the key
-range of the current output file has grown enough to overlap more than
-ten level-(L+2) files.  This last rule ensures that a later compaction
-of a level-(L+1) file will not pick up too much data from level-(L+2).
-
-<p>
-The old files are discarded and the new files are added to the serving
-state.
-
-<p>
-Compactions for a particular level rotate through the key space.  In
-more detail, for each level L, we remember the ending key of the last
-compaction at level L.  The next compaction for level L will pick the
-first file that starts after this key (wrapping around to the
-beginning of the key space if there is no such file).
-
-<p>
-Compactions drop overwritten values.  They also drop deletion markers
-if there are no higher numbered levels that contain a file whose range
-overlaps the current key.
-
-<h2>Timing</h2>
-
-Level-0 compactions will read up to four 1MB files from level-0, and
-at worst all the level-1 files (10MB).  I.e., we will read 14MB and
-write 14MB.
-
-<p>
-Other than the special level-0 compactions, we will pick one 2MB file
-from level L.  In the worst case, this will overlap ~ 12 files from
-level L+1 (10 because level-(L+1) is ten times the size of level-L,
-and another two at the boundaries since the file ranges at level-L
-will usually not be aligned with the file ranges at level-L+1).  The
-compaction will therefore read 26MB and write 26MB.  Assuming a disk
-IO rate of 100MB/s (ballpark range for modern drives), the worst
-compaction cost will be approximately 0.5 second.
-
-<p>
-If we throttle the background writing to something small, say 10% of
-the full 100MB/s speed, a compaction may take up to 5 seconds.  If the
-user is writing at 10MB/s, we might build up lots of level-0 files
-(~50 to hold the 5*10MB).  This may significantly increase the cost of
-reads due to the overhead of merging more files together on every
-read.
-
-<p>
-Solution 1: To reduce this problem, we might want to increase the log
-switching threshold when the number of level-0 files is large.  Though
-the downside is that the larger this threshold, the more memory we will
-need to hold the corresponding memtable.
-
-<p>
-Solution 2: We might want to decrease write rate artificially when the
-number of level-0 files goes up.
-
-<p>
-Solution 3: We work on reducing the cost of very wide merges.
-Perhaps most of the level-0 files will have their blocks sitting
-uncompressed in the cache and we will only need to worry about the
-O(N) complexity in the merging iterator.
-
-<h2>Number of files</h2>
-
-Instead of always making 2MB files, we could make larger files for
-larger levels to reduce the total file count, though at the expense of
-more bursty compactions.  Alternatively, we could shard the set of
-files into multiple directories.
-
-<p>
-An experiment on an <code>ext3</code> filesystem on Feb 04, 2011 shows
-the following timings to do 100K file opens in directories with
-varying number of files:
-<table class="datatable">
-<tr><th>Files in directory</th><th>Microseconds to open a file</th></tr>
-<tr><td>1000</td><td>9</td>
-<tr><td>10000</td><td>10</td>
-<tr><td>100000</td><td>16</td>
-</table>
-So maybe even the sharding is not necessary on modern filesystems?
-
-<h1>Recovery</h1>
-
-<ul>
-<li> Read CURRENT to find name of the latest committed MANIFEST
-<li> Read the named MANIFEST file
-<li> Clean up stale files
-<li> We could open all sstables here, but it is probably better to be lazy...
-<li> Convert log chunk to a new level-0 sstable
-<li> Start directing new writes to a new log file with recovered sequence#
-</ul>
-
-<h1>Garbage collection of files</h1>
-
-<code>DeleteObsoleteFiles()</code> is called at the end of every
-compaction and at the end of recovery.  It finds the names of all
-files in the database.  It deletes all log files that are not the
-current log file.  It deletes all table files that are not referenced
-from some level and are not the output of an active compaction.
-
-</body>
-</html>
diff --git a/src/leveldb/doc/impl.md b/src/leveldb/doc/impl.md
new file mode 100644
index 000000000000..4b13f2a6ba73
--- /dev/null
+++ b/src/leveldb/doc/impl.md
@@ -0,0 +1,170 @@
+## Files
+
+The implementation of leveldb is similar in spirit to the representation of a
+single [Bigtable tablet (section 5.3)](http://research.google.com/archive/bigtable.html).
+However the organization of the files that make up the representation is
+somewhat different and is explained below.
+
+Each database is represented by a set of files stored in a directory. There are
+several different types of files as documented below:
+
+### Log files
+
+A log file (*.log) stores a sequence of recent updates. Each update is appended
+to the current log file. When the log file reaches a pre-determined size
+(approximately 4MB by default), it is converted to a sorted table (see below)
+and a new log file is created for future updates.
+
+A copy of the current log file is kept in an in-memory structure (the
+`memtable`). This copy is consulted on every read so that read operations
+reflect all logged updates.
+
+## Sorted tables
+
+A sorted table (*.ldb) stores a sequence of entries sorted by key. Each entry is
+either a value for the key, or a deletion marker for the key. (Deletion markers
+are kept around to hide obsolete values present in older sorted tables).
+
+The set of sorted tables are organized into a sequence of levels. The sorted
+table generated from a log file is placed in a special **young** level (also
+called level-0). When the number of young files exceeds a certain threshold
+(currently four), all of the young files are merged together with all of the
+overlapping level-1 files to produce a sequence of new level-1 files (we create
+a new level-1 file for every 2MB of data.)
+
+Files in the young level may contain overlapping keys. However files in other
+levels have distinct non-overlapping key ranges. Consider level number L where
+L >= 1. When the combined size of files in level-L exceeds (10^L) MB (i.e., 10MB
+for level-1, 100MB for level-2, ...), one file in level-L, and all of the
+overlapping files in level-(L+1) are merged to form a set of new files for
+level-(L+1). These merges have the effect of gradually migrating new updates
+from the young level to the largest level using only bulk reads and writes
+(i.e., minimizing expensive seeks).
+
+### Manifest
+
+A MANIFEST file lists the set of sorted tables that make up each level, the
+corresponding key ranges, and other important metadata. A new MANIFEST file
+(with a new number embedded in the file name) is created whenever the database
+is reopened. The MANIFEST file is formatted as a log, and changes made to the
+serving state (as files are added or removed) are appended to this log.
+
+### Current
+
+CURRENT is a simple text file that contains the name of the latest MANIFEST
+file.
+
+### Info logs
+
+Informational messages are printed to files named LOG and LOG.old.
+
+### Others
+
+Other files used for miscellaneous purposes may also be present (LOCK, *.dbtmp).
+
+## Level 0
+
+When the log file grows above a certain size (1MB by default):
+Create a brand new memtable and log file and direct future updates here
+In the background:
+Write the contents of the previous memtable to an sstable
+Discard the memtable
+Delete the old log file and the old memtable
+Add the new sstable to the young (level-0) level.
+
+## Compactions
+
+When the size of level L exceeds its limit, we compact it in a background
+thread. The compaction picks a file from level L and all overlapping files from
+the next level L+1. Note that if a level-L file overlaps only part of a
+level-(L+1) file, the entire file at level-(L+1) is used as an input to the
+compaction and will be discarded after the compaction.  Aside: because level-0
+is special (files in it may overlap each other), we treat compactions from
+level-0 to level-1 specially: a level-0 compaction may pick more than one
+level-0 file in case some of these files overlap each other.
+
+A compaction merges the contents of the picked files to produce a sequence of
+level-(L+1) files. We switch to producing a new level-(L+1) file after the
+current output file has reached the target file size (2MB). We also switch to a
+new output file when the key range of the current output file has grown enough
+to overlap more than ten level-(L+2) files.  This last rule ensures that a later
+compaction of a level-(L+1) file will not pick up too much data from
+level-(L+2).
+
+The old files are discarded and the new files are added to the serving state.
+
+Compactions for a particular level rotate through the key space. In more detail,
+for each level L, we remember the ending key of the last compaction at level L.
+The next compaction for level L will pick the first file that starts after this
+key (wrapping around to the beginning of the key space if there is no such
+file).
+
+Compactions drop overwritten values. They also drop deletion markers if there
+are no higher numbered levels that contain a file whose range overlaps the
+current key.
+
+### Timing
+
+Level-0 compactions will read up to four 1MB files from level-0, and at worst
+all the level-1 files (10MB). I.e., we will read 14MB and write 14MB.
+
+Other than the special level-0 compactions, we will pick one 2MB file from level
+L. In the worst case, this will overlap ~ 12 files from level L+1 (10 because
+level-(L+1) is ten times the size of level-L, and another two at the boundaries
+since the file ranges at level-L will usually not be aligned with the file
+ranges at level-L+1). The compaction will therefore read 26MB and write 26MB.
+Assuming a disk IO rate of 100MB/s (ballpark range for modern drives), the worst
+compaction cost will be approximately 0.5 second.
+
+If we throttle the background writing to something small, say 10% of the full
+100MB/s speed, a compaction may take up to 5 seconds. If the user is writing at
+10MB/s, we might build up lots of level-0 files (~50 to hold the 5*10MB). This
+may significantly increase the cost of reads due to the overhead of merging more
+files together on every read.
+
+Solution 1: To reduce this problem, we might want to increase the log switching
+threshold when the number of level-0 files is large. Though the downside is that
+the larger this threshold, the more memory we will need to hold the
+corresponding memtable.
+
+Solution 2: We might want to decrease write rate artificially when the number of
+level-0 files goes up.
+
+Solution 3: We work on reducing the cost of very wide merges. Perhaps most of
+the level-0 files will have their blocks sitting uncompressed in the cache and
+we will only need to worry about the O(N) complexity in the merging iterator.
+
+### Number of files
+
+Instead of always making 2MB files, we could make larger files for larger levels
+to reduce the total file count, though at the expense of more bursty
+compactions.  Alternatively, we could shard the set of files into multiple
+directories.
+
+An experiment on an ext3 filesystem on Feb 04, 2011 shows the following timings
+to do 100K file opens in directories with varying number of files:
+
+
+| Files in directory | Microseconds to open a file |
+|-------------------:|----------------------------:|
+|               1000 |                           9 |
+|              10000 |                          10 |
+|             100000 |                          16 |
+
+So maybe even the sharding is not necessary on modern filesystems?
+
+## Recovery
+
+* Read CURRENT to find name of the latest committed MANIFEST
+* Read the named MANIFEST file
+* Clean up stale files
+* We could open all sstables here, but it is probably better to be lazy...
+* Convert log chunk to a new level-0 sstable
+* Start directing new writes to a new log file with recovered sequence#
+
+## Garbage collection of files
+
+`DeleteObsoleteFiles()` is called at the end of every compaction and at the end
+of recovery. It finds the names of all files in the database. It deletes all log
+files that are not the current log file. It deletes all table files that are not
+referenced from some level and are not the output of an active compaction.
diff --git a/src/leveldb/doc/index.html b/src/leveldb/doc/index.html
deleted file mode 100644
index 2155192581e7..000000000000
--- a/src/leveldb/doc/index.html
+++ /dev/null
@@ -1,549 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-<link rel="stylesheet" type="text/css" href="doc.css" />
-<title>Leveldb</title>
-</head>
-
-<body>
-<h1>Leveldb</h1>
-<address>Jeff Dean, Sanjay Ghemawat</address>
-<p>
-The <code>leveldb</code> library provides a persistent key value store.  Keys and
-values are arbitrary byte arrays.  The keys are ordered within the key
-value store according to a user-specified comparator function.
-
-<p>
-<h1>Opening A Database</h1>
-<p>
-A <code>leveldb</code> database has a name which corresponds to a file system
-directory.  All of the contents of database are stored in this
-directory.  The following example shows how to open a database,
-creating it if necessary:
-<p>
-<pre>
-  #include &lt;cassert&gt;
-  #include "leveldb/db.h"
-
-  leveldb::DB* db;
-  leveldb::Options options;
-  options.create_if_missing = true;
-  leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &amp;db);
-  assert(status.ok());
-  ...
-</pre>
-If you want to raise an error if the database already exists, add
-the following line before the <code>leveldb::DB::Open</code> call:
-<pre>
-  options.error_if_exists = true;
-</pre>
-<h1>Status</h1>
-<p>
-You may have noticed the <code>leveldb::Status</code> type above.  Values of this
-type are returned by most functions in <code>leveldb</code> that may encounter an
-error.  You can check if such a result is ok, and also print an
-associated error message:
-<p>
-<pre>
-   leveldb::Status s = ...;
-   if (!s.ok()) cerr &lt;&lt; s.ToString() &lt;&lt; endl;
-</pre>
-<h1>Closing A Database</h1>
-<p>
-When you are done with a database, just delete the database object.
-Example:
-<p>
-<pre>
-  ... open the db as described above ...
-  ... do something with db ...
-  delete db;
-</pre>
-<h1>Reads And Writes</h1>
-<p>
-The database provides <code>Put</code>, <code>Delete</code>, and <code>Get</code> methods to
-modify/query the database.  For example, the following code
-moves the value stored under key1 to key2.
-<pre>
-  std::string value;
-  leveldb::Status s = db-&gt;Get(leveldb::ReadOptions(), key1, &amp;value);
-  if (s.ok()) s = db-&gt;Put(leveldb::WriteOptions(), key2, value);
-  if (s.ok()) s = db-&gt;Delete(leveldb::WriteOptions(), key1);
-</pre>
-
-<h1>Atomic Updates</h1>
-<p>
-Note that if the process dies after the Put of key2 but before the
-delete of key1, the same value may be left stored under multiple keys.
-Such problems can be avoided by using the <code>WriteBatch</code> class to
-atomically apply a set of updates:
-<p>
-<pre>
-  #include "leveldb/write_batch.h"
-  ...
-  std::string value;
-  leveldb::Status s = db-&gt;Get(leveldb::ReadOptions(), key1, &amp;value);
-  if (s.ok()) {
-    leveldb::WriteBatch batch;
-    batch.Delete(key1);
-    batch.Put(key2, value);
-    s = db-&gt;Write(leveldb::WriteOptions(), &amp;batch);
-  }
-</pre>
-The <code>WriteBatch</code> holds a sequence of edits to be made to the database,
-and these edits within the batch are applied in order.  Note that we
-called <code>Delete</code> before <code>Put</code> so that if <code>key1</code> is identical to <code>key2</code>,
-we do not end up erroneously dropping the value entirely.
-<p>
-Apart from its atomicity benefits, <code>WriteBatch</code> may also be used to
-speed up bulk updates by placing lots of individual mutations into the
-same batch.
-
-<h1>Synchronous Writes</h1>
-By default, each write to <code>leveldb</code> is asynchronous: it
-returns after pushing the write from the process into the operating
-system.  The transfer from operating system memory to the underlying
-persistent storage happens asynchronously.  The <code>sync</code> flag
-can be turned on for a particular write to make the write operation
-not return until the data being written has been pushed all the way to
-persistent storage.  (On Posix systems, this is implemented by calling
-either <code>fsync(...)</code> or <code>fdatasync(...)</code> or
-<code>msync(..., MS_SYNC)</code> before the write operation returns.)
-<pre>
-  leveldb::WriteOptions write_options;
-  write_options.sync = true;
-  db-&gt;Put(write_options, ...);
-</pre>
-Asynchronous writes are often more than a thousand times as fast as
-synchronous writes.  The downside of asynchronous writes is that a
-crash of the machine may cause the last few updates to be lost.  Note
-that a crash of just the writing process (i.e., not a reboot) will not
-cause any loss since even when <code>sync</code> is false, an update
-is pushed from the process memory into the operating system before it
-is considered done.
-
-<p>
-Asynchronous writes can often be used safely.  For example, when
-loading a large amount of data into the database you can handle lost
-updates by restarting the bulk load after a crash.  A hybrid scheme is
-also possible where every Nth write is synchronous, and in the event
-of a crash, the bulk load is restarted just after the last synchronous
-write finished by the previous run.  (The synchronous write can update
-a marker that describes where to restart on a crash.)
-
-<p>
-<code>WriteBatch</code> provides an alternative to asynchronous writes.
-Multiple updates may be placed in the same <code>WriteBatch</code> and
-applied together using a synchronous write (i.e.,
-<code>write_options.sync</code> is set to true).  The extra cost of
-the synchronous write will be amortized across all of the writes in
-the batch.
-
-<p>
-<h1>Concurrency</h1>
-<p>
-A database may only be opened by one process at a time.
-The <code>leveldb</code> implementation acquires a lock from the
-operating system to prevent misuse.  Within a single process, the
-same <code>leveldb::DB</code> object may be safely shared by multiple
-concurrent threads.  I.e., different threads may write into or fetch
-iterators or call <code>Get</code> on the same database without any
-external synchronization (the leveldb implementation will
-automatically do the required synchronization).  However other objects
-(like Iterator and WriteBatch) may require external synchronization.
-If two threads share such an object, they must protect access to it
-using their own locking protocol.  More details are available in
-the public header files.
-<p>
-<h1>Iteration</h1>
-<p>
-The following example demonstrates how to print all key,value pairs
-in a database.
-<p>
-<pre>
-  leveldb::Iterator* it = db-&gt;NewIterator(leveldb::ReadOptions());
-  for (it-&gt;SeekToFirst(); it-&gt;Valid(); it-&gt;Next()) {
-    cout &lt;&lt; it-&gt;key().ToString() &lt;&lt; ": "  &lt;&lt; it-&gt;value().ToString() &lt;&lt; endl;
-  }
-  assert(it-&gt;status().ok());  // Check for any errors found during the scan
-  delete it;
-</pre>
-The following variation shows how to process just the keys in the
-range <code>[start,limit)</code>:
-<p>
-<pre>
-  for (it-&gt;Seek(start);
-       it-&gt;Valid() &amp;&amp; it-&gt;key().ToString() &lt; limit;
-       it-&gt;Next()) {
-    ...
-  }
-</pre>
-You can also process entries in reverse order.  (Caveat: reverse
-iteration may be somewhat slower than forward iteration.)
-<p>
-<pre>
-  for (it-&gt;SeekToLast(); it-&gt;Valid(); it-&gt;Prev()) {
-    ...
-  }
-</pre>
-<h1>Snapshots</h1>
-<p>
-Snapshots provide consistent read-only views over the entire state of
-the key-value store.  <code>ReadOptions::snapshot</code> may be non-NULL to indicate
-that a read should operate on a particular version of the DB state.
-If <code>ReadOptions::snapshot</code> is NULL, the read will operate on an
-implicit snapshot of the current state.
-<p>
-Snapshots are created by the DB::GetSnapshot() method:
-<p>
-<pre>
-  leveldb::ReadOptions options;
-  options.snapshot = db-&gt;GetSnapshot();
-  ... apply some updates to db ...
-  leveldb::Iterator* iter = db-&gt;NewIterator(options);
-  ... read using iter to view the state when the snapshot was created ...
-  delete iter;
-  db-&gt;ReleaseSnapshot(options.snapshot);
-</pre>
-Note that when a snapshot is no longer needed, it should be released
-using the DB::ReleaseSnapshot interface.  This allows the
-implementation to get rid of state that was being maintained just to
-support reading as of that snapshot.
-<h1>Slice</h1>
-<p>
-The return value of the <code>it->key()</code> and <code>it->value()</code> calls above
-are instances of the <code>leveldb::Slice</code> type.  <code>Slice</code> is a simple
-structure that contains a length and a pointer to an external byte
-array.  Returning a <code>Slice</code> is a cheaper alternative to returning a
-<code>std::string</code> since we do not need to copy potentially large keys and
-values.  In addition, <code>leveldb</code> methods do not return null-terminated
-C-style strings since <code>leveldb</code> keys and values are allowed to
-contain '\0' bytes.
-<p>
-C++ strings and null-terminated C-style strings can be easily converted
-to a Slice:
-<p>
-<pre>
-   leveldb::Slice s1 = "hello";
-
-   std::string str("world");
-   leveldb::Slice s2 = str;
-</pre>
-A Slice can be easily converted back to a C++ string:
-<pre>
-   std::string str = s1.ToString();
-   assert(str == std::string("hello"));
-</pre>
-Be careful when using Slices since it is up to the caller to ensure that
-the external byte array into which the Slice points remains live while
-the Slice is in use.  For example, the following is buggy:
-<p>
-<pre>
-   leveldb::Slice slice;
-   if (...) {
-     std::string str = ...;
-     slice = str;
-   }
-   Use(slice);
-</pre>
-When the <code>if</code> statement goes out of scope, <code>str</code> will be destroyed and the
-backing storage for <code>slice</code> will disappear.
-<p>
-<h1>Comparators</h1>
-<p>
-The preceding examples used the default ordering function for key,
-which orders bytes lexicographically.  You can however supply a custom
-comparator when opening a database.  For example, suppose each
-database key consists of two numbers and we should sort by the first
-number, breaking ties by the second number.  First, define a proper
-subclass of <code>leveldb::Comparator</code> that expresses these rules:
-<p>
-<pre>
-  class TwoPartComparator : public leveldb::Comparator {
-   public:
-    // Three-way comparison function:
-    //   if a &lt; b: negative result
-    //   if a &gt; b: positive result
-    //   else: zero result
-    int Compare(const leveldb::Slice&amp; a, const leveldb::Slice&amp; b) const {
-      int a1, a2, b1, b2;
-      ParseKey(a, &amp;a1, &amp;a2);
-      ParseKey(b, &amp;b1, &amp;b2);
-      if (a1 &lt; b1) return -1;
-      if (a1 &gt; b1) return +1;
-      if (a2 &lt; b2) return -1;
-      if (a2 &gt; b2) return +1;
-      return 0;
-    }
-
-    // Ignore the following methods for now:
-    const char* Name() const { return "TwoPartComparator"; }
-    void FindShortestSeparator(std::string*, const leveldb::Slice&amp;) const { }
-    void FindShortSuccessor(std::string*) const { }
-  };
-</pre>
-Now create a database using this custom comparator:
-<p>
-<pre>
-  TwoPartComparator cmp;
-  leveldb::DB* db;
-  leveldb::Options options;
-  options.create_if_missing = true;
-  options.comparator = &amp;cmp;
-  leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &amp;db);
-  ...
-</pre>
-<h2>Backwards compatibility</h2>
-<p>
-The result of the comparator's <code>Name</code> method is attached to the
-database when it is created, and is checked on every subsequent
-database open.  If the name changes, the <code>leveldb::DB::Open</code> call will
-fail.  Therefore, change the name if and only if the new key format
-and comparison function are incompatible with existing databases, and
-it is ok to discard the contents of all existing databases.
-<p>
-You can however still gradually evolve your key format over time with
-a little bit of pre-planning.  For example, you could store a version
-number at the end of each key (one byte should suffice for most uses).
-When you wish to switch to a new key format (e.g., adding an optional
-third part to the keys processed by <code>TwoPartComparator</code>),
-(a) keep the same comparator name (b) increment the version number
-for new keys (c) change the comparator function so it uses the
-version numbers found in the keys to decide how to interpret them.
-<p>
-<h1>Performance</h1>
-<p>
-Performance can be tuned by changing the default values of the
-types defined in <code>include/leveldb/options.h</code>.
-
-<p>
-<h2>Block size</h2>
-<p>
-<code>leveldb</code> groups adjacent keys together into the same block and such a
-block is the unit of transfer to and from persistent storage.  The
-default block size is approximately 4096 uncompressed bytes.
-Applications that mostly do bulk scans over the contents of the
-database may wish to increase this size.  Applications that do a lot
-of point reads of small values may wish to switch to a smaller block
-size if performance measurements indicate an improvement.  There isn't
-much benefit in using blocks smaller than one kilobyte, or larger than
-a few megabytes.  Also note that compression will be more effective
-with larger block sizes.
-<p>
-<h2>Compression</h2>
-<p>
-Each block is individually compressed before being written to
-persistent storage.  Compression is on by default since the default
-compression method is very fast, and is automatically disabled for
-uncompressible data.  In rare cases, applications may want to disable
-compression entirely, but should only do so if benchmarks show a
-performance improvement:
-<p>
-<pre>
-  leveldb::Options options;
-  options.compression = leveldb::kNoCompression;
-  ... leveldb::DB::Open(options, name, ...) ....
-</pre>
-<h2>Cache</h2>
-<p>
-The contents of the database are stored in a set of files in the
-filesystem and each file stores a sequence of compressed blocks.  If
-<code>options.cache</code> is non-NULL, it is used to cache frequently used
-uncompressed block contents.
-<p>
-<pre>
-  #include "leveldb/cache.h"
-
-  leveldb::Options options;
-  options.cache = leveldb::NewLRUCache(100 * 1048576);  // 100MB cache
-  leveldb::DB* db;
-  leveldb::DB::Open(options, name, &db);
-  ... use the db ...
-  delete db
-  delete options.cache;
-</pre>
-Note that the cache holds uncompressed data, and therefore it should
-be sized according to application level data sizes, without any
-reduction from compression.  (Caching of compressed blocks is left to
-the operating system buffer cache, or any custom <code>Env</code>
-implementation provided by the client.)
-<p>
-When performing a bulk read, the application may wish to disable
-caching so that the data processed by the bulk read does not end up
-displacing most of the cached contents.  A per-iterator option can be
-used to achieve this:
-<p>
-<pre>
-  leveldb::ReadOptions options;
-  options.fill_cache = false;
-  leveldb::Iterator* it = db-&gt;NewIterator(options);
-  for (it-&gt;SeekToFirst(); it-&gt;Valid(); it-&gt;Next()) {
-    ...
-  }
-</pre>
-<h2>Key Layout</h2>
-<p>
-Note that the unit of disk transfer and caching is a block.  Adjacent
-keys (according to the database sort order) will usually be placed in
-the same block.  Therefore the application can improve its performance
-by placing keys that are accessed together near each other and placing
-infrequently used keys in a separate region of the key space.
-<p>
-For example, suppose we are implementing a simple file system on top
-of <code>leveldb</code>.  The types of entries we might wish to store are:
-<p>
-<pre>
-   filename -&gt; permission-bits, length, list of file_block_ids
-   file_block_id -&gt; data
-</pre>
-We might want to prefix <code>filename</code> keys with one letter (say '/') and the
-<code>file_block_id</code> keys with a different letter (say '0') so that scans
-over just the metadata do not force us to fetch and cache bulky file
-contents.
-<p>
-<h2>Filters</h2>
-<p>
-Because of the way <code>leveldb</code> data is organized on disk,
-a single <code>Get()</code> call may involve multiple reads from disk.
-The optional <code>FilterPolicy</code> mechanism can be used to reduce
-the number of disk reads substantially.
-<pre>
-   leveldb::Options options;
-   options.filter_policy = NewBloomFilterPolicy(10);
-   leveldb::DB* db;
-   leveldb::DB::Open(options, "/tmp/testdb", &amp;db);
-   ... use the database ...
-   delete db;
-   delete options.filter_policy;
-</pre>
-The preceding code associates a
-<a href="http://en.wikipedia.org/wiki/Bloom_filter">Bloom filter</a>
-based filtering policy with the database.  Bloom filter based
-filtering relies on keeping some number of bits of data in memory per
-key (in this case 10 bits per key since that is the argument we passed
-to NewBloomFilterPolicy).  This filter will reduce the number of unnecessary
-disk reads needed for <code>Get()</code> calls by a factor of
-approximately a 100.  Increasing the bits per key will lead to a
-larger reduction at the cost of more memory usage.  We recommend that
-applications whose working set does not fit in memory and that do a
-lot of random reads set a filter policy.
-<p>
-If you are using a custom comparator, you should ensure that the filter
-policy you are using is compatible with your comparator.  For example,
-consider a comparator that ignores trailing spaces when comparing keys.
-<code>NewBloomFilterPolicy</code> must not be used with such a comparator.
-Instead, the application should provide a custom filter policy that
-also ignores trailing spaces.  For example:
-<pre>
-  class CustomFilterPolicy : public leveldb::FilterPolicy {
-   private:
-    FilterPolicy* builtin_policy_;
-   public:
-    CustomFilterPolicy() : builtin_policy_(NewBloomFilterPolicy(10)) { }
-    ~CustomFilterPolicy() { delete builtin_policy_; }
-
-    const char* Name() const { return "IgnoreTrailingSpacesFilter"; }
-
-    void CreateFilter(const Slice* keys, int n, std::string* dst) const {
-      // Use builtin bloom filter code after removing trailing spaces
-      std::vector&lt;Slice&gt; trimmed(n);
-      for (int i = 0; i &lt; n; i++) {
-        trimmed[i] = RemoveTrailingSpaces(keys[i]);
-      }
-      return builtin_policy_-&gt;CreateFilter(&amp;trimmed[i], n, dst);
-    }
-
-    bool KeyMayMatch(const Slice& key, const Slice& filter) const {
-      // Use builtin bloom filter code after removing trailing spaces
-      return builtin_policy_-&gt;KeyMayMatch(RemoveTrailingSpaces(key), filter);
-    }
-  };
-</pre>
-<p>
-Advanced applications may provide a filter policy that does not use
-a bloom filter but uses some other mechanism for summarizing a set
-of keys.  See <code>leveldb/filter_policy.h</code> for detail.
-<p>
-<h1>Checksums</h1>
-<p>
-<code>leveldb</code> associates checksums with all data it stores in the file system.
-There are two separate controls provided over how aggressively these
-checksums are verified:
-<p>
-<ul>
-<li> <code>ReadOptions::verify_checksums</code> may be set to true to force
-  checksum verification of all data that is read from the file system on
-  behalf of a particular read.  By default, no such verification is
-  done.
-<p>
-<li> <code>Options::paranoid_checks</code> may be set to true before opening a
-  database to make the database implementation raise an error as soon as
-  it detects an internal corruption.  Depending on which portion of the
-  database has been corrupted, the error may be raised when the database
-  is opened, or later by another database operation.  By default,
-  paranoid checking is off so that the database can be used even if
-  parts of its persistent storage have been corrupted.
-<p>
-  If a database is corrupted (perhaps it cannot be opened when
-  paranoid checking is turned on), the <code>leveldb::RepairDB</code> function
-  may be used to recover as much of the data as possible
-<p>
-</ul>
-<h1>Approximate Sizes</h1>
-<p>
-The <code>GetApproximateSizes</code> method can used to get the approximate
-number of bytes of file system space used by one or more key ranges.
-<p>
-<pre>
-   leveldb::Range ranges[2];
-   ranges[0] = leveldb::Range("a", "c");
-   ranges[1] = leveldb::Range("x", "z");
-   uint64_t sizes[2];
-   leveldb::Status s = db-&gt;GetApproximateSizes(ranges, 2, sizes);
-</pre>
-The preceding call will set <code>sizes[0]</code> to the approximate number of
-bytes of file system space used by the key range <code>[a..c)</code> and
-<code>sizes[1]</code> to the approximate number of bytes used by the key range
-<code>[x..z)</code>.
-<p>
-<h1>Environment</h1>
-<p>
-All file operations (and other operating system calls) issued by the
-<code>leveldb</code> implementation are routed through a <code>leveldb::Env</code> object.
-Sophisticated clients may wish to provide their own <code>Env</code>
-implementation to get better control.  For example, an application may
-introduce artificial delays in the file IO paths to limit the impact
-of <code>leveldb</code> on other activities in the system.
-<p>
-<pre>
-  class SlowEnv : public leveldb::Env {
-    .. implementation of the Env interface ...
-  };
-
-  SlowEnv env;
-  leveldb::Options options;
-  options.env = &amp;env;
-  Status s = leveldb::DB::Open(options, ...);
-</pre>
-<h1>Porting</h1>
-<p>
-<code>leveldb</code> may be ported to a new platform by providing platform
-specific implementations of the types/methods/functions exported by
-<code>leveldb/port/port.h</code>.  See <code>leveldb/port/port_example.h</code> for more
-details.
-<p>
-In addition, the new platform may need a new default <code>leveldb::Env</code>
-implementation.  See <code>leveldb/util/env_posix.h</code> for an example.
-
-<h1>Other Information</h1>
-
-<p>
-Details about the <code>leveldb</code> implementation may be found in
-the following documents:
-<ul>
-<li> <a href="impl.html">Implementation notes</a>
-<li> <a href="table_format.txt">Format of an immutable Table file</a>
-<li> <a href="log_format.txt">Format of a log file</a>
-</ul>
-
-</body>
-</html>
diff --git a/src/leveldb/doc/index.md b/src/leveldb/doc/index.md
new file mode 100644
index 000000000000..be8569692bb0
--- /dev/null
+++ b/src/leveldb/doc/index.md
@@ -0,0 +1,523 @@
+leveldb
+=======
+
+_Jeff Dean, Sanjay Ghemawat_
+
+The leveldb library provides a persistent key value store. Keys and values are
+arbitrary byte arrays.  The keys are ordered within the key value store
+according to a user-specified comparator function.
+
+## Opening A Database
+
+A leveldb database has a name which corresponds to a file system directory. All
+of the contents of database are stored in this directory. The following example
+shows how to open a database, creating it if necessary:
+
+```c++
+#include <cassert>
+#include "leveldb/db.h"
+
+leveldb::DB* db;
+leveldb::Options options;
+options.create_if_missing = true;
+leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &db);
+assert(status.ok());
+...
+```
+
+If you want to raise an error if the database already exists, add the following
+line before the `leveldb::DB::Open` call:
+
+```c++
+options.error_if_exists = true;
+```
+
+## Status
+
+You may have noticed the `leveldb::Status` type above. Values of this type are
+returned by most functions in leveldb that may encounter an error. You can check
+if such a result is ok, and also print an associated error message:
+
+```c++
+leveldb::Status s = ...;
+if (!s.ok()) cerr << s.ToString() << endl;
+```
+
+## Closing A Database
+
+When you are done with a database, just delete the database object. Example:
+
+```c++
+... open the db as described above ...
+... do something with db ...
+delete db;
+```
+
+## Reads And Writes
+
+The database provides Put, Delete, and Get methods to modify/query the database.
+For example, the following code moves the value stored under key1 to key2.
+
+```c++
+std::string value;
+leveldb::Status s = db->Get(leveldb::ReadOptions(), key1, &value);
+if (s.ok()) s = db->Put(leveldb::WriteOptions(), key2, value);
+if (s.ok()) s = db->Delete(leveldb::WriteOptions(), key1);
+```
+
+## Atomic Updates
+
+Note that if the process dies after the Put of key2 but before the delete of
+key1, the same value may be left stored under multiple keys. Such problems can
+be avoided by using the `WriteBatch` class to atomically apply a set of updates:
+
+```c++
+#include "leveldb/write_batch.h"
+...
+std::string value;
+leveldb::Status s = db->Get(leveldb::ReadOptions(), key1, &value);
+if (s.ok()) {
+  leveldb::WriteBatch batch;
+  batch.Delete(key1);
+  batch.Put(key2, value);
+  s = db->Write(leveldb::WriteOptions(), &batch);
+}
+```
+
+The `WriteBatch` holds a sequence of edits to be made to the database, and these
+edits within the batch are applied in order. Note that we called Delete before
+Put so that if key1 is identical to key2, we do not end up erroneously dropping
+the value entirely.
+
+Apart from its atomicity benefits, `WriteBatch` may also be used to speed up
+bulk updates by placing lots of individual mutations into the same batch.
+
+## Synchronous Writes
+
+By default, each write to leveldb is asynchronous: it returns after pushing the
+write from the process into the operating system. The transfer from operating
+system memory to the underlying persistent storage happens asynchronously. The
+sync flag can be turned on for a particular write to make the write operation
+not return until the data being written has been pushed all the way to
+persistent storage. (On Posix systems, this is implemented by calling either
+`fsync(...)` or `fdatasync(...)` or `msync(..., MS_SYNC)` before the write
+operation returns.)
+
+```c++
+leveldb::WriteOptions write_options;
+write_options.sync = true;
+db->Put(write_options, ...);
+```
+
+Asynchronous writes are often more than a thousand times as fast as synchronous
+writes. The downside of asynchronous writes is that a crash of the machine may
+cause the last few updates to be lost. Note that a crash of just the writing
+process (i.e., not a reboot) will not cause any loss since even when sync is
+false, an update is pushed from the process memory into the operating system
+before it is considered done.
+
+Asynchronous writes can often be used safely. For example, when loading a large
+amount of data into the database you can handle lost updates by restarting the
+bulk load after a crash. A hybrid scheme is also possible where every Nth write
+is synchronous, and in the event of a crash, the bulk load is restarted just
+after the last synchronous write finished by the previous run. (The synchronous
+write can update a marker that describes where to restart on a crash.)
+
+`WriteBatch` provides an alternative to asynchronous writes. Multiple updates
+may be placed in the same WriteBatch and applied together using a synchronous
+write (i.e., `write_options.sync` is set to true). The extra cost of the
+synchronous write will be amortized across all of the writes in the batch.
+
+## Concurrency
+
+A database may only be opened by one process at a time. The leveldb
+implementation acquires a lock from the operating system to prevent misuse.
+Within a single process, the same `leveldb::DB` object may be safely shared by
+multiple concurrent threads. I.e., different threads may write into or fetch
+iterators or call Get on the same database without any external synchronization
+(the leveldb implementation will automatically do the required synchronization).
+However other objects (like Iterator and `WriteBatch`) may require external
+synchronization. If two threads share such an object, they must protect access
+to it using their own locking protocol. More details are available in the public
+header files.
+
+## Iteration
+
+The following example demonstrates how to print all key,value pairs in a
+database.
+
+```c++
+leveldb::Iterator* it = db->NewIterator(leveldb::ReadOptions());
+for (it->SeekToFirst(); it->Valid(); it->Next()) {
+  cout << it->key().ToString() << ": "  << it->value().ToString() << endl;
+}
+assert(it->status().ok());  // Check for any errors found during the scan
+delete it;
+```
+
+The following variation shows how to process just the keys in the range
+[start,limit):
+
+```c++
+for (it->Seek(start);
+   it->Valid() && it->key().ToString() < limit;
+   it->Next()) {
+  ...
+}
+```
+
+You can also process entries in reverse order. (Caveat: reverse iteration may be
+somewhat slower than forward iteration.)
+
+```c++
+for (it->SeekToLast(); it->Valid(); it->Prev()) {
+  ...
+}
+```
+
+## Snapshots
+
+Snapshots provide consistent read-only views over the entire state of the
+key-value store.  `ReadOptions::snapshot` may be non-NULL to indicate that a
+read should operate on a particular version of the DB state. If
+`ReadOptions::snapshot` is NULL, the read will operate on an implicit snapshot
+of the current state.
+
+Snapshots are created by the `DB::GetSnapshot()` method:
+
+```c++
+leveldb::ReadOptions options;
+options.snapshot = db->GetSnapshot();
+... apply some updates to db ...
+leveldb::Iterator* iter = db->NewIterator(options);
+... read using iter to view the state when the snapshot was created ...
+delete iter;
+db->ReleaseSnapshot(options.snapshot);
+```
+
+Note that when a snapshot is no longer needed, it should be released using the
+`DB::ReleaseSnapshot` interface. This allows the implementation to get rid of
+state that was being maintained just to support reading as of that snapshot.
+
+## Slice
+
+The return value of the `it->key()` and `it->value()` calls above are instances
+of the `leveldb::Slice` type. Slice is a simple structure that contains a length
+and a pointer to an external byte array. Returning a Slice is a cheaper
+alternative to returning a `std::string` since we do not need to copy
+potentially large keys and values. In addition, leveldb methods do not return
+null-terminated C-style strings since leveldb keys and values are allowed to
+contain `'\0'` bytes.
+
+C++ strings and null-terminated C-style strings can be easily converted to a
+Slice:
+
+```c++
+leveldb::Slice s1 = "hello";
+
+std::string str("world");
+leveldb::Slice s2 = str;
+```
+
+A Slice can be easily converted back to a C++ string:
+
+```c++
+std::string str = s1.ToString();
+assert(str == std::string("hello"));
+```
+
+Be careful when using Slices since it is up to the caller to ensure that the
+external byte array into which the Slice points remains live while the Slice is
+in use. For example, the following is buggy:
+
+```c++
+leveldb::Slice slice;
+if (...) {
+  std::string str = ...;
+  slice = str;
+}
+Use(slice);
+```
+
+When the if statement goes out of scope, str will be destroyed and the backing
+storage for slice will disappear.
+
+## Comparators
+
+The preceding examples used the default ordering function for key, which orders
+bytes lexicographically. You can however supply a custom comparator when opening
+a database.  For example, suppose each database key consists of two numbers and
+we should sort by the first number, breaking ties by the second number. First,
+define a proper subclass of `leveldb::Comparator` that expresses these rules:
+
+```c++
+class TwoPartComparator : public leveldb::Comparator {
+ public:
+  // Three-way comparison function:
+  //   if a < b: negative result
+  //   if a > b: positive result
+  //   else: zero result
+  int Compare(const leveldb::Slice& a, const leveldb::Slice& b) const {
+    int a1, a2, b1, b2;
+    ParseKey(a, &a1, &a2);
+    ParseKey(b, &b1, &b2);
+    if (a1 < b1) return -1;
+    if (a1 > b1) return +1;
+    if (a2 < b2) return -1;
+    if (a2 > b2) return +1;
+    return 0;
+  }
+
+  // Ignore the following methods for now:
+  const char* Name() const { return "TwoPartComparator"; }
+  void FindShortestSeparator(std::string*, const leveldb::Slice&) const {}
+  void FindShortSuccessor(std::string*) const {}
+};
+```
+
+Now create a database using this custom comparator:
+
+```c++
+TwoPartComparator cmp;
+leveldb::DB* db;
+leveldb::Options options;
+options.create_if_missing = true;
+options.comparator = &cmp;
+leveldb::Status status = leveldb::DB::Open(options, "/tmp/testdb", &db);
+...
+```
+
+### Backwards compatibility
+
+The result of the comparator's Name method is attached to the database when it
+is created, and is checked on every subsequent database open. If the name
+changes, the `leveldb::DB::Open` call will fail. Therefore, change the name if
+and only if the new key format and comparison function are incompatible with
+existing databases, and it is ok to discard the contents of all existing
+databases.
+
+You can however still gradually evolve your key format over time with a little
+bit of pre-planning. For example, you could store a version number at the end of
+each key (one byte should suffice for most uses). When you wish to switch to a
+new key format (e.g., adding an optional third part to the keys processed by
+`TwoPartComparator`), (a) keep the same comparator name (b) increment the
+version number for new keys (c) change the comparator function so it uses the
+version numbers found in the keys to decide how to interpret them.
+
+## Performance
+
+Performance can be tuned by changing the default values of the types defined in
+`include/leveldb/options.h`.
+
+### Block size
+
+leveldb groups adjacent keys together into the same block and such a block is
+the unit of transfer to and from persistent storage. The default block size is
+approximately 4096 uncompressed bytes.  Applications that mostly do bulk scans
+over the contents of the database may wish to increase this size. Applications
+that do a lot of point reads of small values may wish to switch to a smaller
+block size if performance measurements indicate an improvement. There isn't much
+benefit in using blocks smaller than one kilobyte, or larger than a few
+megabytes. Also note that compression will be more effective with larger block
+sizes.
+
+### Compression
+
+Each block is individually compressed before being written to persistent
+storage. Compression is on by default since the default compression method is
+very fast, and is automatically disabled for uncompressible data. In rare cases,
+applications may want to disable compression entirely, but should only do so if
+benchmarks show a performance improvement:
+
+```c++
+leveldb::Options options;
+options.compression = leveldb::kNoCompression;
+... leveldb::DB::Open(options, name, ...) ....
+```
+
+### Cache
+
+The contents of the database are stored in a set of files in the filesystem and
+each file stores a sequence of compressed blocks. If options.cache is non-NULL,
+it is used to cache frequently used uncompressed block contents.
+
+```c++
+#include "leveldb/cache.h"
+
+leveldb::Options options;
+options.cache = leveldb::NewLRUCache(100 * 1048576);  // 100MB cache
+leveldb::DB* db;
+leveldb::DB::Open(options, name, &db);
+... use the db ...
+delete db
+delete options.cache;
+```
+
+Note that the cache holds uncompressed data, and therefore it should be sized
+according to application level data sizes, without any reduction from
+compression. (Caching of compressed blocks is left to the operating system
+buffer cache, or any custom Env implementation provided by the client.)
+
+When performing a bulk read, the application may wish to disable caching so that
+the data processed by the bulk read does not end up displacing most of the
+cached contents. A per-iterator option can be used to achieve this:
+
+```c++
+leveldb::ReadOptions options;
+options.fill_cache = false;
+leveldb::Iterator* it = db->NewIterator(options);
+for (it->SeekToFirst(); it->Valid(); it->Next()) {
+  ...
+}
+```
+
+### Key Layout
+
+Note that the unit of disk transfer and caching is a block. Adjacent keys
+(according to the database sort order) will usually be placed in the same block.
+Therefore the application can improve its performance by placing keys that are
+accessed together near each other and placing infrequently used keys in a
+separate region of the key space.
+
+For example, suppose we are implementing a simple file system on top of leveldb.
+The types of entries we might wish to store are:
+
+    filename -> permission-bits, length, list of file_block_ids
+    file_block_id -> data
+
+We might want to prefix filename keys with one letter (say '/') and the
+`file_block_id` keys with a different letter (say '0') so that scans over just
+the metadata do not force us to fetch and cache bulky file contents.
+
+### Filters
+
+Because of the way leveldb data is organized on disk, a single `Get()` call may
+involve multiple reads from disk. The optional FilterPolicy mechanism can be
+used to reduce the number of disk reads substantially.
+
+```c++
+leveldb::Options options;
+options.filter_policy = NewBloomFilterPolicy(10);
+leveldb::DB* db;
+leveldb::DB::Open(options, "/tmp/testdb", &db);
+... use the database ...
+delete db;
+delete options.filter_policy;
+```
+
+The preceding code associates a Bloom filter based filtering policy with the
+database.  Bloom filter based filtering relies on keeping some number of bits of
+data in memory per key (in this case 10 bits per key since that is the argument
+we passed to `NewBloomFilterPolicy`). This filter will reduce the number of
+unnecessary disk reads needed for Get() calls by a factor of approximately
+a 100. Increasing the bits per key will lead to a larger reduction at the cost
+of more memory usage. We recommend that applications whose working set does not
+fit in memory and that do a lot of random reads set a filter policy.
+
+If you are using a custom comparator, you should ensure that the filter policy
+you are using is compatible with your comparator. For example, consider a
+comparator that ignores trailing spaces when comparing keys.
+`NewBloomFilterPolicy` must not be used with such a comparator. Instead, the
+application should provide a custom filter policy that also ignores trailing
+spaces. For example:
+
+```c++
+class CustomFilterPolicy : public leveldb::FilterPolicy {
+ private:
+  FilterPolicy* builtin_policy_;
+
+ public:
+  CustomFilterPolicy() : builtin_policy_(NewBloomFilterPolicy(10)) {}
+  ~CustomFilterPolicy() { delete builtin_policy_; }
+
+  const char* Name() const { return "IgnoreTrailingSpacesFilter"; }
+
+  void CreateFilter(const Slice* keys, int n, std::string* dst) const {
+    // Use builtin bloom filter code after removing trailing spaces
+    std::vector<Slice> trimmed(n);
+    for (int i = 0; i < n; i++) {
+      trimmed[i] = RemoveTrailingSpaces(keys[i]);
+    }
+    return builtin_policy_->CreateFilter(&trimmed[i], n, dst);
+  }
+};
+```
+
+Advanced applications may provide a filter policy that does not use a bloom
+filter but uses some other mechanism for summarizing a set of keys. See
+`leveldb/filter_policy.h` for detail.
+
+## Checksums
+
+leveldb associates checksums with all data it stores in the file system. There
+are two separate controls provided over how aggressively these checksums are
+verified:
+
+`ReadOptions::verify_checksums` may be set to true to force checksum
+verification of all data that is read from the file system on behalf of a
+particular read.  By default, no such verification is done.
+
+`Options::paranoid_checks` may be set to true before opening a database to make
+the database implementation raise an error as soon as it detects an internal
+corruption. Depending on which portion of the database has been corrupted, the
+error may be raised when the database is opened, or later by another database
+operation. By default, paranoid checking is off so that the database can be used
+even if parts of its persistent storage have been corrupted.
+
+If a database is corrupted (perhaps it cannot be opened when paranoid checking
+is turned on), the `leveldb::RepairDB` function may be used to recover as much
+of the data as possible
+
+## Approximate Sizes
+
+The `GetApproximateSizes` method can used to get the approximate number of bytes
+of file system space used by one or more key ranges.
+
+```c++
+leveldb::Range ranges[2];
+ranges[0] = leveldb::Range("a", "c");
+ranges[1] = leveldb::Range("x", "z");
+uint64_t sizes[2];
+leveldb::Status s = db->GetApproximateSizes(ranges, 2, sizes);
+```
+
+The preceding call will set `sizes[0]` to the approximate number of bytes of
+file system space used by the key range `[a..c)` and `sizes[1]` to the
+approximate number of bytes used by the key range `[x..z)`.
+
+## Environment
+
+All file operations (and other operating system calls) issued by the leveldb
+implementation are routed through a `leveldb::Env` object. Sophisticated clients
+may wish to provide their own Env implementation to get better control.
+For example, an application may introduce artificial delays in the file IO
+paths to limit the impact of leveldb on other activities in the system.
+
+```c++
+class SlowEnv : public leveldb::Env {
+  ... implementation of the Env interface ...
+};
+
+SlowEnv env;
+leveldb::Options options;
+options.env = &env;
+Status s = leveldb::DB::Open(options, ...);
+```
+
+## Porting
+
+leveldb may be ported to a new platform by providing platform specific
+implementations of the types/methods/functions exported by
+`leveldb/port/port.h`.  See `leveldb/port/port_example.h` for more details.
+
+In addition, the new platform may need a new default `leveldb::Env`
+implementation.  See `leveldb/util/env_posix.h` for an example.
+
+## Other Information
+
+Details about the leveldb implementation may be found in the following
+documents:
+
+1. [Implementation notes](impl.md)
+2. [Format of an immutable Table file](table_format.md)
+3. [Format of a log file](log_format.md)
diff --git a/src/leveldb/doc/log_format.md b/src/leveldb/doc/log_format.md
new file mode 100644
index 000000000000..f32cb5d7dac4
--- /dev/null
+++ b/src/leveldb/doc/log_format.md
@@ -0,0 +1,75 @@
+leveldb Log format
+==================
+The log file contents are a sequence of 32KB blocks.  The only exception is that
+the tail of the file may contain a partial block.
+
+Each block consists of a sequence of records:
+
+    block := record* trailer?
+    record :=
+      checksum: uint32     // crc32c of type and data[] ; little-endian
+      length: uint16       // little-endian
+      type: uint8          // One of FULL, FIRST, MIDDLE, LAST
+      data: uint8[length]
+
+A record never starts within the last six bytes of a block (since it won't fit).
+Any leftover bytes here form the trailer, which must consist entirely of zero
+bytes and must be skipped by readers.
+
+Aside: if exactly seven bytes are left in the current block, and a new non-zero
+length record is added, the writer must emit a FIRST record (which contains zero
+bytes of user data) to fill up the trailing seven bytes of the block and then
+emit all of the user data in subsequent blocks.
+
+More types may be added in the future.  Some Readers may skip record types they
+do not understand, others may report that some data was skipped.
+
+    FULL == 1
+    FIRST == 2
+    MIDDLE == 3
+    LAST == 4
+
+The FULL record contains the contents of an entire user record.
+
+FIRST, MIDDLE, LAST are types used for user records that have been split into
+multiple fragments (typically because of block boundaries).  FIRST is the type
+of the first fragment of a user record, LAST is the type of the last fragment of
+a user record, and MIDDLE is the type of all interior fragments of a user
+record.
+
+Example: consider a sequence of user records:
+
+    A: length 1000
+    B: length 97270
+    C: length 8000
+
+**A** will be stored as a FULL record in the first block.
+
+**B** will be split into three fragments: first fragment occupies the rest of
+the first block, second fragment occupies the entirety of the second block, and
+the third fragment occupies a prefix of the third block.  This will leave six
+bytes free in the third block, which will be left empty as the trailer.
+
+**C** will be stored as a FULL record in the fourth block.
+
+----
+
+## Some benefits over the recordio format:
+
+1. We do not need any heuristics for resyncing - just go to next block boundary
+   and scan.  If there is a corruption, skip to the next block.  As a
+   side-benefit, we do not get confused when part of the contents of one log
+   file are embedded as a record inside another log file.
+
+2. Splitting at approximate boundaries (e.g., for mapreduce) is simple: find the
+   next block boundary and skip records until we hit a FULL or FIRST record.
+
+3. We do not need extra buffering for large records.
+
+## Some downsides compared to recordio format:
+
+1. No packing of tiny records.  This could be fixed by adding a new record type,
+   so it is a shortcoming of the current implementation, not necessarily the
+   format.
+
+2. No compression.  Again, this could be fixed by adding new record types.
diff --git a/src/leveldb/doc/log_format.txt b/src/leveldb/doc/log_format.txt
deleted file mode 100644
index 4cca5ef6ead3..000000000000
--- a/src/leveldb/doc/log_format.txt
+++ /dev/null
@@ -1,75 +0,0 @@
-The log file contents are a sequence of 32KB blocks.  The only
-exception is that the tail of the file may contain a partial block.
-
-Each block consists of a sequence of records:
-   block := record* trailer?
-   record :=
-	checksum: uint32	// crc32c of type and data[] ; little-endian
-	length: uint16		// little-endian
-	type: uint8		// One of FULL, FIRST, MIDDLE, LAST
-	data: uint8[length]
-
-A record never starts within the last six bytes of a block (since it
-won't fit).  Any leftover bytes here form the trailer, which must
-consist entirely of zero bytes and must be skipped by readers.
-
-Aside: if exactly seven bytes are left in the current block, and a new
-non-zero length record is added, the writer must emit a FIRST record
-(which contains zero bytes of user data) to fill up the trailing seven
-bytes of the block and then emit all of the user data in subsequent
-blocks.
-
-More types may be added in the future.  Some Readers may skip record
-types they do not understand, others may report that some data was
-skipped.
-
-FULL == 1
-FIRST == 2
-MIDDLE == 3
-LAST == 4
-
-The FULL record contains the contents of an entire user record.
-
-FIRST, MIDDLE, LAST are types used for user records that have been
-split into multiple fragments (typically because of block boundaries).
-FIRST is the type of the first fragment of a user record, LAST is the
-type of the last fragment of a user record, and MIDDLE is the type of
-all interior fragments of a user record.
-
-Example: consider a sequence of user records:
-   A: length 1000
-   B: length 97270
-   C: length 8000
-A will be stored as a FULL record in the first block.
-
-B will be split into three fragments: first fragment occupies the rest
-of the first block, second fragment occupies the entirety of the
-second block, and the third fragment occupies a prefix of the third
-block.  This will leave six bytes free in the third block, which will
-be left empty as the trailer.
-
-C will be stored as a FULL record in the fourth block.
-
-===================
-
-Some benefits over the recordio format:
-
-(1) We do not need any heuristics for resyncing - just go to next
-block boundary and scan.  If there is a corruption, skip to the next
-block.  As a side-benefit, we do not get confused when part of the
-contents of one log file are embedded as a record inside another log
-file.
-
-(2) Splitting at approximate boundaries (e.g., for mapreduce) is
-simple: find the next block boundary and skip records until we
-hit a FULL or FIRST record.
-
-(3) We do not need extra buffering for large records.
-
-Some downsides compared to recordio format:
-
-(1) No packing of tiny records.  This could be fixed by adding a new
-record type, so it is a shortcoming of the current implementation,
-not necessarily the format.
-
-(2) No compression.  Again, this could be fixed by adding new record types.
diff --git a/src/leveldb/doc/table_format.md b/src/leveldb/doc/table_format.md
new file mode 100644
index 000000000000..5fe7e72411b8
--- /dev/null
+++ b/src/leveldb/doc/table_format.md
@@ -0,0 +1,107 @@
+leveldb File format
+===================
+
+    <beginning_of_file>
+    [data block 1]
+    [data block 2]
+    ...
+    [data block N]
+    [meta block 1]
+    ...
+    [meta block K]
+    [metaindex block]
+    [index block]
+    [Footer]        (fixed size; starts at file_size - sizeof(Footer))
+    <end_of_file>
+
+The file contains internal pointers.  Each such pointer is called
+a BlockHandle and contains the following information:
+
+    offset:   varint64
+    size:     varint64
+
+See [varints](https://developers.google.com/protocol-buffers/docs/encoding#varints)
+for an explanation of varint64 format.
+
+1.  The sequence of key/value pairs in the file are stored in sorted
+order and partitioned into a sequence of data blocks.  These blocks
+come one after another at the beginning of the file.  Each data block
+is formatted according to the code in `block_builder.cc`, and then
+optionally compressed.
+
+2. After the data blocks we store a bunch of meta blocks.  The
+supported meta block types are described below.  More meta block types
+may be added in the future.  Each meta block is again formatted using
+`block_builder.cc` and then optionally compressed.
+
+3. A "metaindex" block.  It contains one entry for every other meta
+block where the key is the name of the meta block and the value is a
+BlockHandle pointing to that meta block.
+
+4. An "index" block.  This block contains one entry per data block,
+where the key is a string >= last key in that data block and before
+the first key in the successive data block.  The value is the
+BlockHandle for the data block.
+
+5. At the very end of the file is a fixed length footer that contains
+the BlockHandle of the metaindex and index blocks as well as a magic number.
+
+        metaindex_handle: char[p];     // Block handle for metaindex
+        index_handle:     char[q];     // Block handle for index
+        padding:          char[40-p-q];// zeroed bytes to make fixed length
+                                       // (40==2*BlockHandle::kMaxEncodedLength)
+        magic:            fixed64;     // == 0xdb4775248b80fb57 (little-endian)
+
+## "filter" Meta Block
+
+If a `FilterPolicy` was specified when the database was opened, a
+filter block is stored in each table.  The "metaindex" block contains
+an entry that maps from `filter.<N>` to the BlockHandle for the filter
+block where `<N>` is the string returned by the filter policy's
+`Name()` method.
+
+The filter block stores a sequence of filters, where filter i contains
+the output of `FilterPolicy::CreateFilter()` on all keys that are stored
+in a block whose file offset falls within the range
+
+    [ i*base ... (i+1)*base-1 ]
+
+Currently, "base" is 2KB.  So for example, if blocks X and Y start in
+the range `[ 0KB .. 2KB-1 ]`, all of the keys in X and Y will be
+converted to a filter by calling `FilterPolicy::CreateFilter()`, and the
+resulting filter will be stored as the first filter in the filter
+block.
+
+The filter block is formatted as follows:
+
+    [filter 0]
+    [filter 1]
+    [filter 2]
+    ...
+    [filter N-1]
+
+    [offset of filter 0]                  : 4 bytes
+    [offset of filter 1]                  : 4 bytes
+    [offset of filter 2]                  : 4 bytes
+    ...
+    [offset of filter N-1]                : 4 bytes
+
+    [offset of beginning of offset array] : 4 bytes
+    lg(base)                              : 1 byte
+
+The offset array at the end of the filter block allows efficient
+mapping from a data block offset to the corresponding filter.
+
+## "stats" Meta Block
+
+This meta block contains a bunch of stats.  The key is the name
+of the statistic.  The value contains the statistic.
+
+TODO(postrelease): record following stats.
+
+    data size
+    index size
+    key size (uncompressed)
+    value size (uncompressed)
+    number of entries
+    number of data blocks
diff --git a/src/leveldb/doc/table_format.txt b/src/leveldb/doc/table_format.txt
deleted file mode 100644
index ca8f9b4460ad..000000000000
--- a/src/leveldb/doc/table_format.txt
+++ /dev/null
@@ -1,104 +0,0 @@
-File format
-===========
-
-  <beginning_of_file>
-  [data block 1]
-  [data block 2]
-  ...
-  [data block N]
-  [meta block 1]
-  ...
-  [meta block K]
-  [metaindex block]
-  [index block]
-  [Footer]        (fixed size; starts at file_size - sizeof(Footer))
-  <end_of_file>
-
-The file contains internal pointers.  Each such pointer is called
-a BlockHandle and contains the following information:
-  offset:	    varint64
-  size:		    varint64
-See https://developers.google.com/protocol-buffers/docs/encoding#varints
-for an explanation of varint64 format.
-
-(1) The sequence of key/value pairs in the file are stored in sorted
-order and partitioned into a sequence of data blocks.  These blocks
-come one after another at the beginning of the file.  Each data block
-is formatted according to the code in block_builder.cc, and then
-optionally compressed.
-
-(2) After the data blocks we store a bunch of meta blocks.  The
-supported meta block types are described below.  More meta block types
-may be added in the future.  Each meta block is again formatted using
-block_builder.cc and then optionally compressed.
-
-(3) A "metaindex" block.  It contains one entry for every other meta
-block where the key is the name of the meta block and the value is a
-BlockHandle pointing to that meta block.
-
-(4) An "index" block.  This block contains one entry per data block,
-where the key is a string >= last key in that data block and before
-the first key in the successive data block.  The value is the
-BlockHandle for the data block.
-
-(6) At the very end of the file is a fixed length footer that contains
-the BlockHandle of the metaindex and index blocks as well as a magic number.
-       metaindex_handle: char[p];    // Block handle for metaindex
-       index_handle:     char[q];    // Block handle for index
-       padding:          char[40-p-q]; // zeroed bytes to make fixed length
-                                       // (40==2*BlockHandle::kMaxEncodedLength)
-       magic:            fixed64;    // == 0xdb4775248b80fb57 (little-endian)
-
-"filter" Meta Block
--------------------
-
-If a "FilterPolicy" was specified when the database was opened, a
-filter block is stored in each table.  The "metaindex" block contains
-an entry that maps from "filter.<N>" to the BlockHandle for the filter
-block where "<N>" is the string returned by the filter policy's
-"Name()" method.
-
-The filter block stores a sequence of filters, where filter i contains
-the output of FilterPolicy::CreateFilter() on all keys that are stored
-in a block whose file offset falls within the range
-
-    [ i*base ... (i+1)*base-1 ]
-
-Currently, "base" is 2KB.  So for example, if blocks X and Y start in
-the range [ 0KB .. 2KB-1 ], all of the keys in X and Y will be
-converted to a filter by calling FilterPolicy::CreateFilter(), and the
-resulting filter will be stored as the first filter in the filter
-block.
-
-The filter block is formatted as follows:
-
-     [filter 0]
-     [filter 1]
-     [filter 2]
-     ...
-     [filter N-1]
-
-     [offset of filter 0]                  : 4 bytes
-     [offset of filter 1]                  : 4 bytes
-     [offset of filter 2]                  : 4 bytes
-     ...
-     [offset of filter N-1]                : 4 bytes
-
-     [offset of beginning of offset array] : 4 bytes
-     lg(base)                              : 1 byte
-
-The offset array at the end of the filter block allows efficient
-mapping from a data block offset to the corresponding filter.
-
-"stats" Meta Block
-------------------
-
-This meta block contains a bunch of stats.  The key is the name
-of the statistic.  The value contains the statistic.
-TODO(postrelease): record following stats.
-  data size
-  index size
-  key size (uncompressed)
-  value size (uncompressed)
-  number of entries
-  number of data blocks
diff --git a/src/leveldb/include/leveldb/db.h b/src/leveldb/include/leveldb/db.h
index 9752cbad512d..bfab10a0b725 100644
--- a/src/leveldb/include/leveldb/db.h
+++ b/src/leveldb/include/leveldb/db.h
@@ -14,7 +14,7 @@ namespace leveldb {
 
 // Update Makefile if you change these
 static const int kMajorVersion = 1;
-static const int kMinorVersion = 19;
+static const int kMinorVersion = 20;
 
 struct Options;
 struct ReadOptions;
diff --git a/src/leveldb/include/leveldb/options.h b/src/leveldb/include/leveldb/options.h
index 83a1ef39a481..976e38122aaf 100644
--- a/src/leveldb/include/leveldb/options.h
+++ b/src/leveldb/include/leveldb/options.h
@@ -112,6 +112,18 @@ struct Options {
   // Default: 16
   int block_restart_interval;
 
+  // Leveldb will write up to this amount of bytes to a file before
+  // switching to a new one.
+  // Most clients should leave this parameter alone.  However if your
+  // filesystem is more efficient with larger files, you could
+  // consider increasing the value.  The downside will be longer
+  // compactions and hence longer latency/performance hiccups.
+  // Another reason to increase this parameter might be when you are
+  // initially populating a large database.
+  //
+  // Default: 2MB
+  size_t max_file_size;
+
   // Compress blocks using the specified compression algorithm.  This
   // parameter can be changed dynamically.
   //
diff --git a/src/leveldb/port/port_example.h b/src/leveldb/port/port_example.h
index ab9e489b32d8..97bd669a5ed6 100644
--- a/src/leveldb/port/port_example.h
+++ b/src/leveldb/port/port_example.h
@@ -129,6 +129,12 @@ extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
 // The concatenation of all "data[0,n-1]" fragments is the heap profile.
 extern bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg);
 
+// Extend the CRC to include the first n bytes of buf.
+//
+// Returns zero if the CRC cannot be extended using acceleration, else returns
+// the newly extended CRC value (which may also be zero).
+uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
+
 }  // namespace port
 }  // namespace leveldb
 
diff --git a/src/leveldb/port/port_posix.h b/src/leveldb/port/port_posix.h
index ccca9939d3dc..7e8213b22eca 100644
--- a/src/leveldb/port/port_posix.h
+++ b/src/leveldb/port/port_posix.h
@@ -152,6 +152,8 @@ inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
   return false;
 }
 
+uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
+
 } // namespace port
 } // namespace leveldb
 
diff --git a/src/leveldb/port/port_posix_sse.cc b/src/leveldb/port/port_posix_sse.cc
new file mode 100644
index 000000000000..1e519ba0b64b
--- /dev/null
+++ b/src/leveldb/port/port_posix_sse.cc
@@ -0,0 +1,129 @@
+// Copyright 2016 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// A portable implementation of crc32c, optimized to handle
+// four bytes at a time.
+//
+// In a separate source file to allow this accelerated CRC32C function to be
+// compiled with the appropriate compiler flags to enable x86 SSE 4.2
+// instructions.
+
+#include <stdint.h>
+#include <string.h>
+#include "port/port.h"
+
+#if defined(LEVELDB_PLATFORM_POSIX_SSE)
+
+#if defined(_MSC_VER)
+#include <intrin.h>
+#elif defined(__GNUC__) && defined(__SSE4_2__)
+#include <nmmintrin.h>
+#include <cpuid.h>
+#endif
+
+#endif  // defined(LEVELDB_PLATFORM_POSIX_SSE)
+
+namespace leveldb {
+namespace port {
+
+#if defined(LEVELDB_PLATFORM_POSIX_SSE)
+
+// Used to fetch a naturally-aligned 32-bit word in little endian byte-order
+static inline uint32_t LE_LOAD32(const uint8_t *p) {
+  // SSE is x86 only, so ensured that |p| is always little-endian.
+  uint32_t word;
+  memcpy(&word, p, sizeof(word));
+  return word;
+}
+
+#if defined(_M_X64) || defined(__x86_64__)  // LE_LOAD64 is only used on x64.
+
+// Used to fetch a naturally-aligned 64-bit word in little endian byte-order
+static inline uint64_t LE_LOAD64(const uint8_t *p) {
+  uint64_t dword;
+  memcpy(&dword, p, sizeof(dword));
+  return dword;
+}
+
+#endif  // defined(_M_X64) || defined(__x86_64__)
+
+static inline bool HaveSSE42() {
+#if defined(_MSC_VER)
+  int cpu_info[4];
+  __cpuid(cpu_info, 1);
+  return (cpu_info[2] & (1 << 20)) != 0;
+#elif defined(__GNUC__)
+  unsigned int eax, ebx, ecx, edx;
+  __get_cpuid(1, &eax, &ebx, &ecx, &edx);
+  return (ecx & (1 << 20)) != 0;
+#else
+  return false;
+#endif
+}
+
+#endif  // defined(LEVELDB_PLATFORM_POSIX_SSE)
+
+// For further improvements see Intel publication at:
+// http://download.intel.com/design/intarch/papers/323405.pdf
+uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size) {
+#if !defined(LEVELDB_PLATFORM_POSIX_SSE)
+  return 0;
+#else
+  static bool have = HaveSSE42();
+  if (!have) {
+    return 0;
+  }
+
+  const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
+  const uint8_t *e = p + size;
+  uint32_t l = crc ^ 0xffffffffu;
+
+#define STEP1 do {                              \
+    l = _mm_crc32_u8(l, *p++);                  \
+} while (0)
+#define STEP4 do {                              \
+    l = _mm_crc32_u32(l, LE_LOAD32(p));         \
+    p += 4;                                     \
+} while (0)
+#define STEP8 do {                              \
+    l = _mm_crc32_u64(l, LE_LOAD64(p));         \
+    p += 8;                                     \
+} while (0)
+
+  if (size > 16) {
+    // Process unaligned bytes
+    for (unsigned int i = reinterpret_cast<uintptr_t>(p) % 8; i; --i) {
+      STEP1;
+    }
+
+    // _mm_crc32_u64 is only available on x64.
+#if defined(_M_X64) || defined(__x86_64__)
+    // Process 8 bytes at a time
+    while ((e-p) >= 8) {
+      STEP8;
+    }
+    // Process 4 bytes at a time
+    if ((e-p) >= 4) {
+      STEP4;
+    }
+#else  // !(defined(_M_X64) || defined(__x86_64__))
+    // Process 4 bytes at a time
+    while ((e-p) >= 4) {
+      STEP4;
+    }
+#endif  // defined(_M_X64) || defined(__x86_64__)
+  }
+  // Process the last few bytes
+  while (p != e) {
+    STEP1;
+  }
+#undef STEP8
+#undef STEP4
+#undef STEP1
+  return l ^ 0xffffffffu;
+#endif  // defined(LEVELDB_PLATFORM_POSIX_SSE)
+}
+
+}  // namespace port
+}  // namespace leveldb
diff --git a/src/leveldb/port/port_win.h b/src/leveldb/port/port_win.h
index 45bf2f0ea749..500900482283 100644
--- a/src/leveldb/port/port_win.h
+++ b/src/leveldb/port/port_win.h
@@ -168,6 +168,8 @@ inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
   return false;
 }
 
+uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
+
 }
 }
 
diff --git a/src/leveldb/table/filter_block.cc b/src/leveldb/table/filter_block.cc
index 4e78b954f8d9..1ed5134170e5 100644
--- a/src/leveldb/table/filter_block.cc
+++ b/src/leveldb/table/filter_block.cc
@@ -9,7 +9,7 @@
 
 namespace leveldb {
 
-// See doc/table_format.txt for an explanation of the filter block format.
+// See doc/table_format.md for an explanation of the filter block format.
 
 // Generate new filter every 2KB of data
 static const size_t kFilterBaseLg = 11;
diff --git a/src/leveldb/util/crc32c.cc b/src/leveldb/util/crc32c.cc
index 6db9e770774d..edd61cfd6fca 100644
--- a/src/leveldb/util/crc32c.cc
+++ b/src/leveldb/util/crc32c.cc
@@ -8,6 +8,8 @@
 #include "util/crc32c.h"
 
 #include <stdint.h>
+
+#include "port/port.h"
 #include "util/coding.h"
 
 namespace leveldb {
@@ -283,7 +285,23 @@ static inline uint32_t LE_LOAD32(const uint8_t *p) {
   return DecodeFixed32(reinterpret_cast<const char*>(p));
 }
 
+// Determine if the CPU running this program can accelerate the CRC32C
+// calculation.
+static bool CanAccelerateCRC32C() {
+  // port::AcceleretedCRC32C returns zero when unable to accelerate.
+  static const char kTestCRCBuffer[] = "TestCRCBuffer";
+  static const char kBufSize = sizeof(kTestCRCBuffer) - 1;
+  static const uint32_t kTestCRCValue = 0xdcbc59fa;
+
+  return port::AcceleratedCRC32C(0, kTestCRCBuffer, kBufSize) == kTestCRCValue;
+}
+
 uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
+  static bool accelerate = CanAccelerateCRC32C();
+  if (accelerate) {
+    return port::AcceleratedCRC32C(crc, buf, size);
+  }
+
   const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
   const uint8_t *e = p + size;
   uint32_t l = crc ^ 0xffffffffu;
diff --git a/src/leveldb/util/env_posix.cc b/src/leveldb/util/env_posix.cc
index e0fca52f4632..dd852af354c8 100644
--- a/src/leveldb/util/env_posix.cc
+++ b/src/leveldb/util/env_posix.cc
@@ -11,12 +11,14 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
 #include <deque>
+#include <limits>
 #include <set>
 #include "leveldb/env.h"
 #include "leveldb/slice.h"
@@ -24,15 +26,70 @@
 #include "util/logging.h"
 #include "util/mutexlock.h"
 #include "util/posix_logger.h"
+#include "util/env_posix_test_helper.h"
 
 namespace leveldb {
 
 namespace {
 
+static int open_read_only_file_limit = -1;
+static int mmap_limit = -1;
+
 static Status IOError(const std::string& context, int err_number) {
   return Status::IOError(context, strerror(err_number));
 }
 
+// Helper class to limit resource usage to avoid exhaustion.
+// Currently used to limit read-only file descriptors and mmap file usage
+// so that we do not end up running out of file descriptors, virtual memory,
+// or running into kernel performance problems for very large databases.
+class Limiter {
+ public:
+  // Limit maximum number of resources to |n|.
+  Limiter(intptr_t n) {
+    SetAllowed(n);
+  }
+
+  // If another resource is available, acquire it and return true.
+  // Else return false.
+  bool Acquire() {
+    if (GetAllowed() <= 0) {
+      return false;
+    }
+    MutexLock l(&mu_);
+    intptr_t x = GetAllowed();
+    if (x <= 0) {
+      return false;
+    } else {
+      SetAllowed(x - 1);
+      return true;
+    }
+  }
+
+  // Release a resource acquired by a previous call to Acquire() that returned
+  // true.
+  void Release() {
+    MutexLock l(&mu_);
+    SetAllowed(GetAllowed() + 1);
+  }
+
+ private:
+  port::Mutex mu_;
+  port::AtomicPointer allowed_;
+
+  intptr_t GetAllowed() const {
+    return reinterpret_cast<intptr_t>(allowed_.Acquire_Load());
+  }
+
+  // REQUIRES: mu_ must be held
+  void SetAllowed(intptr_t v) {
+    allowed_.Release_Store(reinterpret_cast<void*>(v));
+  }
+
+  Limiter(const Limiter&);
+  void operator=(const Limiter&);
+};
+
 class PosixSequentialFile: public SequentialFile {
  private:
   std::string filename_;
@@ -70,73 +127,51 @@ class PosixSequentialFile: public SequentialFile {
 class PosixRandomAccessFile: public RandomAccessFile {
  private:
   std::string filename_;
+  bool temporary_fd_;  // If true, fd_ is -1 and we open on every read.
   int fd_;
+  Limiter* limiter_;
 
  public:
-  PosixRandomAccessFile(const std::string& fname, int fd)
-      : filename_(fname), fd_(fd) { }
-  virtual ~PosixRandomAccessFile() { close(fd_); }
+  PosixRandomAccessFile(const std::string& fname, int fd, Limiter* limiter)
+      : filename_(fname), fd_(fd), limiter_(limiter) {
+    temporary_fd_ = !limiter->Acquire();
+    if (temporary_fd_) {
+      // Open file on every access.
+      close(fd_);
+      fd_ = -1;
+    }
+  }
+
+  virtual ~PosixRandomAccessFile() {
+    if (!temporary_fd_) {
+      close(fd_);
+      limiter_->Release();
+    }
+  }
 
   virtual Status Read(uint64_t offset, size_t n, Slice* result,
                       char* scratch) const {
+    int fd = fd_;
+    if (temporary_fd_) {
+      fd = open(filename_.c_str(), O_RDONLY);
+      if (fd < 0) {
+        return IOError(filename_, errno);
+      }
+    }
+
     Status s;
-    ssize_t r = pread(fd_, scratch, n, static_cast<off_t>(offset));
+    ssize_t r = pread(fd, scratch, n, static_cast<off_t>(offset));
     *result = Slice(scratch, (r < 0) ? 0 : r);
     if (r < 0) {
       // An error: return a non-ok status
       s = IOError(filename_, errno);
     }
-    return s;
-  }
-};
-
-// Helper class to limit mmap file usage so that we do not end up
-// running out virtual memory or running into kernel performance
-// problems for very large databases.
-class MmapLimiter {
- public:
-  // Up to 1000 mmaps for 64-bit binaries; none for smaller pointer sizes.
-  MmapLimiter() {
-    SetAllowed(sizeof(void*) >= 8 ? 1000 : 0);
-  }
-
-  // If another mmap slot is available, acquire it and return true.
-  // Else return false.
-  bool Acquire() {
-    if (GetAllowed() <= 0) {
-      return false;
-    }
-    MutexLock l(&mu_);
-    intptr_t x = GetAllowed();
-    if (x <= 0) {
-      return false;
-    } else {
-      SetAllowed(x - 1);
-      return true;
+    if (temporary_fd_) {
+      // Close the temporary file descriptor opened earlier.
+      close(fd);
     }
+    return s;
   }
-
-  // Release a slot acquired by a previous call to Acquire() that returned true.
-  void Release() {
-    MutexLock l(&mu_);
-    SetAllowed(GetAllowed() + 1);
-  }
-
- private:
-  port::Mutex mu_;
-  port::AtomicPointer allowed_;
-
-  intptr_t GetAllowed() const {
-    return reinterpret_cast<intptr_t>(allowed_.Acquire_Load());
-  }
-
-  // REQUIRES: mu_ must be held
-  void SetAllowed(intptr_t v) {
-    allowed_.Release_Store(reinterpret_cast<void*>(v));
-  }
-
-  MmapLimiter(const MmapLimiter&);
-  void operator=(const MmapLimiter&);
 };
 
 // mmap() based random-access
@@ -145,12 +180,12 @@ class PosixMmapReadableFile: public RandomAccessFile {
   std::string filename_;
   void* mmapped_region_;
   size_t length_;
-  MmapLimiter* limiter_;
+  Limiter* limiter_;
 
  public:
   // base[0,length-1] contains the mmapped contents of the file.
   PosixMmapReadableFile(const std::string& fname, void* base, size_t length,
-                        MmapLimiter* limiter)
+                        Limiter* limiter)
       : filename_(fname), mmapped_region_(base), length_(length),
         limiter_(limiter) {
   }
@@ -231,7 +266,7 @@ class PosixWritableFile : public WritableFile {
       if (fd < 0) {
         s = IOError(dir, errno);
       } else {
-        if (fsync(fd) < 0) {
+        if (fsync(fd) < 0 && errno != EINVAL) {
           s = IOError(dir, errno);
         }
         close(fd);
@@ -333,7 +368,7 @@ class PosixEnv : public Env {
         mmap_limit_.Release();
       }
     } else {
-      *result = new PosixRandomAccessFile(fname, fd);
+      *result = new PosixRandomAccessFile(fname, fd, &fd_limit_);
     }
     return s;
   }
@@ -533,10 +568,42 @@ class PosixEnv : public Env {
   BGQueue queue_;
 
   PosixLockTable locks_;
-  MmapLimiter mmap_limit_;
+  Limiter mmap_limit_;
+  Limiter fd_limit_;
 };
 
-PosixEnv::PosixEnv() : started_bgthread_(false) {
+// Return the maximum number of concurrent mmaps.
+static int MaxMmaps() {
+  if (mmap_limit >= 0) {
+    return mmap_limit;
+  }
+  // Up to 1000 mmaps for 64-bit binaries; none for smaller pointer sizes.
+  mmap_limit = sizeof(void*) >= 8 ? 1000 : 0;
+  return mmap_limit;
+}
+
+// Return the maximum number of read-only files to keep open.
+static intptr_t MaxOpenFiles() {
+  if (open_read_only_file_limit >= 0) {
+    return open_read_only_file_limit;
+  }
+  struct rlimit rlim;
+  if (getrlimit(RLIMIT_NOFILE, &rlim)) {
+    // getrlimit failed, fallback to hard-coded default.
+    open_read_only_file_limit = 50;
+  } else if (rlim.rlim_cur == RLIM_INFINITY) {
+    open_read_only_file_limit = std::numeric_limits<int>::max();
+  } else {
+    // Allow use of 20% of available file descriptors for read-only files.
+    open_read_only_file_limit = rlim.rlim_cur / 5;
+  }
+  return open_read_only_file_limit;
+}
+
+PosixEnv::PosixEnv()
+    : started_bgthread_(false),
+      mmap_limit_(MaxMmaps()),
+      fd_limit_(MaxOpenFiles()) {
   PthreadCall("mutex_init", pthread_mutex_init(&mu_, NULL));
   PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, NULL));
 }
@@ -611,6 +678,16 @@ static pthread_once_t once = PTHREAD_ONCE_INIT;
 static Env* default_env;
 static void InitDefaultEnv() { default_env = new PosixEnv; }
 
+void EnvPosixTestHelper::SetReadOnlyFDLimit(int limit) {
+  assert(default_env == NULL);
+  open_read_only_file_limit = limit;
+}
+
+void EnvPosixTestHelper::SetReadOnlyMMapLimit(int limit) {
+  assert(default_env == NULL);
+  mmap_limit = limit;
+}
+
 Env* Env::Default() {
   pthread_once(&once, InitDefaultEnv);
   return default_env;
diff --git a/src/leveldb/util/env_posix_test.cc b/src/leveldb/util/env_posix_test.cc
new file mode 100644
index 000000000000..295f8ae4409f
--- /dev/null
+++ b/src/leveldb/util/env_posix_test.cc
@@ -0,0 +1,66 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include "leveldb/env.h"
+
+#include "port/port.h"
+#include "util/testharness.h"
+#include "util/env_posix_test_helper.h"
+
+namespace leveldb {
+
+static const int kDelayMicros = 100000;
+static const int kReadOnlyFileLimit = 4;
+static const int kMMapLimit = 4;
+
+class EnvPosixTest {
+ public:
+  Env* env_;
+  EnvPosixTest() : env_(Env::Default()) { }
+
+  static void SetFileLimits(int read_only_file_limit, int mmap_limit) {
+    EnvPosixTestHelper::SetReadOnlyFDLimit(read_only_file_limit);
+    EnvPosixTestHelper::SetReadOnlyMMapLimit(mmap_limit);
+  }
+};
+
+TEST(EnvPosixTest, TestOpenOnRead) {
+  // Write some test data to a single file that will be opened |n| times.
+  std::string test_dir;
+  ASSERT_OK(env_->GetTestDirectory(&test_dir));
+  std::string test_file = test_dir + "/open_on_read.txt";
+
+  FILE* f = fopen(test_file.c_str(), "w");
+  ASSERT_TRUE(f != NULL);
+  const char kFileData[] = "abcdefghijklmnopqrstuvwxyz";
+  fputs(kFileData, f);
+  fclose(f);
+
+  // Open test file some number above the sum of the two limits to force
+  // open-on-read behavior of POSIX Env leveldb::RandomAccessFile.
+  const int kNumFiles = kReadOnlyFileLimit + kMMapLimit + 5;
+  leveldb::RandomAccessFile* files[kNumFiles] = {0};
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_OK(env_->NewRandomAccessFile(test_file, &files[i]));
+  }
+  char scratch;
+  Slice read_result;
+  for (int i = 0; i < kNumFiles; i++) {
+    ASSERT_OK(files[i]->Read(i, 1, &read_result, &scratch));
+    ASSERT_EQ(kFileData[i], read_result[0]);
+  }
+  for (int i = 0; i < kNumFiles; i++) {
+    delete files[i];
+  }
+  ASSERT_OK(env_->DeleteFile(test_file));
+}
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  // All tests currently run with the same read-only file limits.
+  leveldb::EnvPosixTest::SetFileLimits(leveldb::kReadOnlyFileLimit,
+                                       leveldb::kMMapLimit);
+  return leveldb::test::RunAllTests();
+}
diff --git a/src/leveldb/util/env_posix_test_helper.h b/src/leveldb/util/env_posix_test_helper.h
new file mode 100644
index 000000000000..038696059826
--- /dev/null
+++ b/src/leveldb/util/env_posix_test_helper.h
@@ -0,0 +1,28 @@
+// Copyright 2017 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
+#define STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
+
+namespace leveldb {
+
+class EnvPosixTest;
+
+// A helper for the POSIX Env to facilitate testing.
+class EnvPosixTestHelper {
+ private:
+  friend class EnvPosixTest;
+
+  // Set the maximum number of read-only files that will be opened.
+  // Must be called before creating an Env.
+  static void SetReadOnlyFDLimit(int limit);
+
+  // Set the maximum number of read-only files that will be mapped via mmap.
+  // Must be called before creating an Env.
+  static void SetReadOnlyMMapLimit(int limit);
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_UTIL_ENV_POSIX_TEST_HELPER_H_
diff --git a/src/leveldb/util/env_test.cc b/src/leveldb/util/env_test.cc
index b72cb4438425..839ae56a1a49 100644
--- a/src/leveldb/util/env_test.cc
+++ b/src/leveldb/util/env_test.cc
@@ -10,29 +10,31 @@
 namespace leveldb {
 
 static const int kDelayMicros = 100000;
+static const int kReadOnlyFileLimit = 4;
+static const int kMMapLimit = 4;
 
-class EnvPosixTest {
+class EnvTest {
  private:
   port::Mutex mu_;
   std::string events_;
 
  public:
   Env* env_;
-  EnvPosixTest() : env_(Env::Default()) { }
+  EnvTest() : env_(Env::Default()) { }
 };
 
 static void SetBool(void* ptr) {
   reinterpret_cast<port::AtomicPointer*>(ptr)->NoBarrier_Store(ptr);
 }
 
-TEST(EnvPosixTest, RunImmediately) {
+TEST(EnvTest, RunImmediately) {
   port::AtomicPointer called (NULL);
   env_->Schedule(&SetBool, &called);
-  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  env_->SleepForMicroseconds(kDelayMicros);
   ASSERT_TRUE(called.NoBarrier_Load() != NULL);
 }
 
-TEST(EnvPosixTest, RunMany) {
+TEST(EnvTest, RunMany) {
   port::AtomicPointer last_id (NULL);
 
   struct CB {
@@ -59,7 +61,7 @@ TEST(EnvPosixTest, RunMany) {
   env_->Schedule(&CB::Run, &cb3);
   env_->Schedule(&CB::Run, &cb4);
 
-  Env::Default()->SleepForMicroseconds(kDelayMicros);
+  env_->SleepForMicroseconds(kDelayMicros);
   void* cur = last_id.Acquire_Load();
   ASSERT_EQ(4, reinterpret_cast<uintptr_t>(cur));
 }
@@ -78,7 +80,7 @@ static void ThreadBody(void* arg) {
   s->mu.Unlock();
 }
 
-TEST(EnvPosixTest, StartThread) {
+TEST(EnvTest, StartThread) {
   State state;
   state.val = 0;
   state.num_running = 3;
@@ -92,7 +94,7 @@ TEST(EnvPosixTest, StartThread) {
     if (num == 0) {
       break;
     }
-    Env::Default()->SleepForMicroseconds(kDelayMicros);
+    env_->SleepForMicroseconds(kDelayMicros);
   }
   ASSERT_EQ(state.val, 3);
 }
diff --git a/src/leveldb/util/env_win.cc b/src/leveldb/util/env_win.cc
index b074b7579ec2..d32c4e676c3f 100644
--- a/src/leveldb/util/env_win.cc
+++ b/src/leveldb/util/env_win.cc
@@ -1,7 +1,7 @@
 // This file contains source that originates from:
 // http://code.google.com/p/leveldbwin/source/browse/trunk/win32_impl_src/env_win32.h
 // http://code.google.com/p/leveldbwin/source/browse/trunk/win32_impl_src/port_win32.cc
-// Those files dont' have any explict license headers but the 
+// Those files don't have any explicit license headers but the 
 // project (http://code.google.com/p/leveldbwin/) lists the 'New BSD License'
 // as the license.
 #if defined(LEVELDB_PLATFORM_WINDOWS)
@@ -355,11 +355,13 @@ BOOL Win32SequentialFile::_Init()
 	ToWidePath(_filename, path);
 	_hFile = CreateFileW(path.c_str(),
                          GENERIC_READ,
-                         FILE_SHARE_READ,
+                         FILE_SHARE_READ | FILE_SHARE_WRITE,
                          NULL,
                          OPEN_EXISTING,
-                         FILE_ATTRIBUTE_NORMAL,
+                         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
                          NULL);
+    if (_hFile == INVALID_HANDLE_VALUE)
+        _hFile = NULL;
     return _hFile ? TRUE : FALSE;
 }
 
@@ -403,7 +405,7 @@ BOOL Win32RandomAccessFile::_Init( LPCWSTR path )
 {
     BOOL bRet = FALSE;
     if(!_hFile)
-        _hFile = ::CreateFileW(path,GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EXISTING,
+        _hFile = ::CreateFileW(path,GENERIC_READ,FILE_SHARE_READ|FILE_SHARE_WRITE,NULL,OPEN_EXISTING,
         FILE_ATTRIBUTE_NORMAL | FILE_FLAG_RANDOM_ACCESS,NULL);
     if(!_hFile || _hFile == INVALID_HANDLE_VALUE )
         _hFile = NULL;
@@ -669,7 +671,7 @@ Status Win32Env::GetFileSize( const std::string& fname, uint64_t* file_size )
 	ToWidePath(ModifyPath(path), wpath);
 
     HANDLE file = ::CreateFileW(wpath.c_str(),
-        GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
+        GENERIC_READ,FILE_SHARE_READ|FILE_SHARE_WRITE,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
     LARGE_INTEGER li;
     if(::GetFileSizeEx(file,&li)){
         *file_size = (uint64_t)li.QuadPart;
diff --git a/src/leveldb/util/options.cc b/src/leveldb/util/options.cc
index 8b618fb1ae85..b5e622761357 100644
--- a/src/leveldb/util/options.cc
+++ b/src/leveldb/util/options.cc
@@ -21,6 +21,7 @@ Options::Options()
       block_cache(NULL),
       block_size(4096),
       block_restart_interval(16),
+      max_file_size(2<<20),
       compression(kSnappyCompression),
       reuse_logs(false),
       filter_policy(NULL) {
diff --git a/src/miner.cpp b/src/miner.cpp
index 79218bc6221f..261052d77c44 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -275,7 +275,7 @@ bool BlockAssembler::TestPackage(uint64_t packageSize, unsigned int packageSigOp
 // - safe TXs in regard to ChainLocks
 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 {
-    BOOST_FOREACH (const CTxMemPool::txiter it, package) {
+    for (const CTxMemPool::txiter it : package) {
         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
             return false;
         if (!llmq::chainLocksHandler->IsTxSafeForMining(it->GetTx().GetHash())) {
@@ -308,11 +308,11 @@ int BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& already
         indexed_modified_transaction_set &mapModifiedTx)
 {
     int nDescendantsUpdated = 0;
-    BOOST_FOREACH(const CTxMemPool::txiter it, alreadyAdded) {
+    for (const CTxMemPool::txiter it : alreadyAdded) {
         CTxMemPool::setEntries descendants;
         mempool.CalculateDescendants(it, descendants);
         // Insert all descendants (not yet in block) into the modified set
-        BOOST_FOREACH(CTxMemPool::txiter desc, descendants) {
+        for (CTxMemPool::txiter desc : descendants) {
             if (alreadyAdded.count(desc))
                 continue;
             ++nDescendantsUpdated;
diff --git a/src/miner.h b/src/miner.h
index 995cce10c747..0fd97c20e1b5 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -17,9 +17,7 @@
 class CBlockIndex;
 class CChainParams;
 class CConnman;
-class CReserveKey;
 class CScript;
-class CWallet;
 
 namespace Consensus { struct Params; };
 
diff --git a/src/net.cpp b/src/net.cpp
index 8a8e94a17f99..ee12a26863d8 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -305,7 +305,7 @@ bool IsReachable(const CNetAddr& addr)
 CNode* CConnman::FindNode(const CNetAddr& ip)
 {
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes)
+    for (CNode* pnode : vNodes)
         if ((CNetAddr)pnode->addr == ip)
             return (pnode);
     return NULL;
@@ -314,7 +314,7 @@ CNode* CConnman::FindNode(const CNetAddr& ip)
 CNode* CConnman::FindNode(const CSubNet& subNet)
 {
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes)
+    for (CNode* pnode : vNodes)
     if (subNet.Match((CNetAddr)pnode->addr))
         return (pnode);
     return NULL;
@@ -323,7 +323,7 @@ CNode* CConnman::FindNode(const CSubNet& subNet)
 CNode* CConnman::FindNode(const std::string& addrName)
 {
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes) {
+    for (CNode* pnode : vNodes) {
         if (pnode->GetAddrName() == addrName) {
             return (pnode);
         }
@@ -334,7 +334,7 @@ CNode* CConnman::FindNode(const std::string& addrName)
 CNode* CConnman::FindNode(const CService& addr)
 {
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes)
+    for (CNode* pnode : vNodes)
         if((CService)pnode->addr == addr)
             return (pnode);
     return NULL;
@@ -343,7 +343,7 @@ CNode* CConnman::FindNode(const CService& addr)
 bool CConnman::CheckIncomingNonce(uint64_t nonce)
 {
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes) {
+    for (CNode* pnode : vNodes) {
         if (!pnode->fSuccessfullyConnected && !pnode->fInbound && pnode->GetLocalNonce() == nonce)
             return false;
     }
@@ -537,7 +537,7 @@ void CConnman::Ban(const CSubNet& subNet, const BanReason &banReason, int64_t ba
         clientInterface->BannedListChanged();
     {
         LOCK(cs_vNodes);
-        BOOST_FOREACH(CNode* pnode, vNodes) {
+        for (CNode* pnode : vNodes) {
             if (subNet.Match((CNetAddr)pnode->addr))
                 pnode->fDisconnect = true;
         }
@@ -615,7 +615,7 @@ void CConnman::SetBannedSetDirty(bool dirty)
 
 bool CConnman::IsWhitelistedRange(const CNetAddr &addr) {
     LOCK(cs_vWhitelistedRange);
-    BOOST_FOREACH(const CSubNet& subnet, vWhitelistedRange) {
+    for (const CSubNet& subnet : vWhitelistedRange) {
         if (subnet.Match(addr))
             return true;
     }
@@ -986,7 +986,7 @@ bool CConnman::AttemptToEvictConnection()
     {
         LOCK(cs_vNodes);
 
-        BOOST_FOREACH(CNode *node, vNodes) {
+        for (CNode *node : vNodes) {
             if (node->fWhitelisted)
                 continue;
             if (!node->fInbound)
@@ -1066,7 +1066,7 @@ bool CConnman::AttemptToEvictConnection()
     unsigned int nMostConnections = 0;
     int64_t nMostConnectionsTime = 0;
     std::map<uint64_t, std::vector<NodeEvictionCandidate> > mapNetGroupNodes;
-    BOOST_FOREACH(const NodeEvictionCandidate &node, vEvictionCandidates) {
+    for (const NodeEvictionCandidate &node : vEvictionCandidates) {
         mapNetGroupNodes[node.nKeyedNetGroup].push_back(node);
         int64_t grouptime = mapNetGroupNodes[node.nKeyedNetGroup][0].nTimeConnected;
         size_t groupsize = mapNetGroupNodes[node.nKeyedNetGroup].size();
@@ -1111,7 +1111,7 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
     bool whitelisted = hListenSocket.whitelisted || IsWhitelistedRange(addr);
     {
         LOCK(cs_vNodes);
-        BOOST_FOREACH(CNode* pnode, vNodes) {
+        for (CNode* pnode : vNodes) {
             if (pnode->fInbound) {
                 nInbound++;
                 if (!pnode->verifiedProRegTxHash.IsNull()) {
@@ -1206,7 +1206,7 @@ void CConnman::ThreadSocketHandler()
             LOCK(cs_vNodes);
             // Disconnect unused nodes
             std::vector<CNode*> vNodesCopy = vNodes;
-            BOOST_FOREACH(CNode* pnode, vNodesCopy)
+            for (CNode* pnode : vNodesCopy)
             {
                 if (pnode->fDisconnect)
                 {
@@ -1232,7 +1232,7 @@ void CConnman::ThreadSocketHandler()
         {
             // Delete disconnected nodes
             std::list<CNode*> vNodesDisconnectedCopy = vNodesDisconnected;
-            BOOST_FOREACH(CNode* pnode, vNodesDisconnectedCopy)
+            for (CNode* pnode : vNodesDisconnectedCopy)
             {
                 // wait until threads are done using it
                 if (pnode->GetRefCount() <= 0) {
@@ -1292,7 +1292,7 @@ void CConnman::ThreadSocketHandler()
         have_fds = true;
 #endif
 
-        BOOST_FOREACH(const ListenSocket& hListenSocket, vhListenSocket) {
+        for (const ListenSocket& hListenSocket : vhListenSocket) {
             FD_SET(hListenSocket.socket, &fdsetRecv);
             hSocketMax = std::max(hSocketMax, hListenSocket.socket);
             have_fds = true;
@@ -1300,7 +1300,7 @@ void CConnman::ThreadSocketHandler()
 
         {
             LOCK(cs_vNodes);
-            BOOST_FOREACH(CNode* pnode, vNodes)
+            for (CNode* pnode : vNodes)
             {
                 // Implement the following logic:
                 // * If there is data to send, select() for sending data. As this only
@@ -1377,7 +1377,7 @@ void CConnman::ThreadSocketHandler()
         //
         // Accept new connections
         //
-        BOOST_FOREACH(const ListenSocket& hListenSocket, vhListenSocket)
+        for (const ListenSocket& hListenSocket : vhListenSocket)
         {
             if (hListenSocket.socket != INVALID_SOCKET && FD_ISSET(hListenSocket.socket, &fdsetRecv))
             {
@@ -1389,7 +1389,7 @@ void CConnman::ThreadSocketHandler()
         // Service each socket
         //
         std::vector<CNode*> vNodesCopy = CopyNodeVector();
-        BOOST_FOREACH(CNode* pnode, vNodesCopy)
+        for (CNode* pnode : vNodesCopy)
         {
             if (interruptNet)
                 return;
@@ -1703,7 +1703,7 @@ void CConnman::ThreadDNSAddressSeed()
 
     LogPrintf("Loading addresses from DNS seeds (could take a while)\n");
 
-    BOOST_FOREACH(const CDNSSeedData &seed, vSeeds) {
+    for (const CDNSSeedData &seed : vSeeds) {
         if (interruptNet) {
             return;
         }
@@ -1715,7 +1715,7 @@ void CConnman::ThreadDNSAddressSeed()
             ServiceFlags requiredServiceBits = nRelevantServices;
             if (LookupHost(GetDNSHost(seed, &requiredServiceBits).c_str(), vIPs, 0, true))
             {
-                BOOST_FOREACH(const CNetAddr& ip, vIPs)
+                for (const CNetAddr& ip : vIPs)
                 {
                     int nOneDay = 24*3600;
                     CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
@@ -1796,7 +1796,7 @@ void CConnman::ThreadOpenConnections()
         for (int64_t nLoop = 0;; nLoop++)
         {
             ProcessOneShot();
-            BOOST_FOREACH(const std::string& strAddr, gArgs.GetArgs("-connect"))
+            for (const std::string& strAddr : gArgs.GetArgs("-connect"))
             {
                 CAddress addr(CService(), NODE_NONE);
                 OpenNetworkConnection(addr, false, NULL, strAddr.c_str());
@@ -1852,7 +1852,7 @@ void CConnman::ThreadOpenConnections()
         std::set<std::vector<unsigned char> > setConnected;
         if (!Params().AllowMultipleAddressesFromGroup()) {
             LOCK(cs_vNodes);
-            BOOST_FOREACH(CNode* pnode, vNodes) {
+            for (CNode* pnode : vNodes) {
                 if (!pnode->fInbound && !pnode->fAddnode && !pnode->fMasternode) {
 
                     // Count the peers that have all relevant services
@@ -1978,7 +1978,7 @@ std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo()
     {
         LOCK(cs_vAddedNodes);
         ret.reserve(vAddedNodes.size());
-        BOOST_FOREACH(const std::string& strAddNode, vAddedNodes)
+        for (const std::string& strAddNode : vAddedNodes)
             lAddresses.push_back(strAddNode);
     }
 
@@ -1999,7 +1999,7 @@ std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo()
         }
     }
 
-    BOOST_FOREACH(const std::string& strAddNode, lAddresses) {
+    for (const std::string& strAddNode : lAddresses) {
         CService service(LookupNumeric(strAddNode.c_str(), Params().GetDefaultPort()));
         if (service.IsValid()) {
             // strAddNode is an IP:port
@@ -2203,7 +2203,7 @@ void CConnman::ThreadMessageHandler()
 
         bool fMoreWork = false;
 
-        BOOST_FOREACH(CNode* pnode, vNodesCopy)
+        for (CNode* pnode : vNodesCopy)
         {
             if (pnode->fDisconnect)
                 continue;
@@ -2349,7 +2349,7 @@ void Discover(boost::thread_group& threadGroup)
         std::vector<CNetAddr> vaddr;
         if (LookupHost(pszHostName, vaddr, 0, true))
         {
-            BOOST_FOREACH (const CNetAddr &addr, vaddr)
+            for (const CNetAddr &addr : vaddr)
             {
                 if (AddLocal(addr, LOCAL_IF))
                     LogPrintf("%s: %s - %s\n", __func__, pszHostName, addr.ToString());
@@ -2396,7 +2396,7 @@ void CConnman::SetNetworkActive(bool active)
 
         LOCK(cs_vNodes);
         // Close sockets to all nodes
-        BOOST_FOREACH(CNode* pnode, vNodes) {
+        for (CNode* pnode : vNodes) {
             pnode->CloseSocketDisconnect();
         }
     } else {
@@ -2642,18 +2642,18 @@ void CConnman::Stop()
     }
 
     // Close sockets
-    BOOST_FOREACH(CNode* pnode, vNodes)
+    for (CNode* pnode : vNodes)
         pnode->CloseSocketDisconnect();
-    BOOST_FOREACH(ListenSocket& hListenSocket, vhListenSocket)
+    for (ListenSocket& hListenSocket : vhListenSocket)
         if (hListenSocket.socket != INVALID_SOCKET)
             if (!CloseSocket(hListenSocket.socket))
                 LogPrintf("CloseSocket(hListenSocket) failed with error %s\n", NetworkErrorString(WSAGetLastError()));
 
     // clean up some globals (to help leak detection)
-    BOOST_FOREACH(CNode *pnode, vNodes) {
+    for (CNode *pnode : vNodes) {
         DeleteNode(pnode);
     }
-    BOOST_FOREACH(CNode *pnode, vNodesDisconnected) {
+    for (CNode *pnode : vNodesDisconnected) {
         DeleteNode(pnode);
     }
     vNodes.clear();
@@ -2894,7 +2894,7 @@ void CConnman::RelayTransaction(const CTransaction& tx)
     }
     CInv inv(nInv, hash);
     LOCK(cs_vNodes);
-    BOOST_FOREACH(CNode* pnode, vNodes)
+    for (CNode* pnode : vNodes)
     {
         pnode->PushInventory(inv);
     }
@@ -3135,7 +3135,7 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
     fPauseSend = false;
     nProcessQueueSize = 0;
 
-    BOOST_FOREACH(const std::string &msg, getAllNetMessageTypes())
+    for (const std::string &msg : getAllNetMessageTypes())
         mapRecvBytesPerMsgCmd[msg] = 0;
     mapRecvBytesPerMsgCmd[NET_MESSAGE_COMMAND_OTHER] = 0;
 
diff --git a/src/net.h b/src/net.h
index 6d648d5bd8b1..8d22b6c4a729 100644
--- a/src/net.h
+++ b/src/net.h
@@ -125,7 +125,6 @@ struct AddedNodeInfo
     bool fInbound;
 };
 
-class CTransaction;
 class CNodeStats;
 class CClientUIInterface;
 
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index da1c2232c709..24c0cd7d4f9d 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -323,7 +323,7 @@ void FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
         fUpdateConnectionTime = true;
     }
 
-    BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight) {
+    for (const QueuedBlock& entry : state->vBlocksInFlight) {
         mapBlocksInFlight.erase(entry.hash);
     }
     EraseOrphansFor(nodeid);
@@ -377,7 +377,9 @@ bool MarkBlockAsInFlight(NodeId nodeid, const uint256& hash, const CBlockIndex *
     // Short-circuit most stuff in case its from the same node
     std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
     if (itInFlight != mapBlocksInFlight.end() && itInFlight->second.first == nodeid) {
-        *pit = &itInFlight->second.second;
+        if (pit) {
+            *pit = &itInFlight->second.second;
+        }
         return false;
     }
 
@@ -558,7 +560,7 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con
         // are not yet downloaded and not in flight to vBlocks. In the mean time, update
         // pindexLastCommonBlock as long as all ancestors are already downloaded, or if it's
         // already part of our chain (and therefore don't need it even if pruned).
-        BOOST_FOREACH(const CBlockIndex* pindex, vToFetch) {
+        for (const CBlockIndex* pindex : vToFetch) {
             if (!pindex->IsValid(BLOCK_VALID_TREE)) {
                 // We consider the chain that this peer is on invalid.
                 return;
@@ -598,7 +600,7 @@ bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
     stats.nMisbehavior = state->nMisbehavior;
     stats.nSyncHeight = state->pindexBestKnownBlock ? state->pindexBestKnownBlock->nHeight : -1;
     stats.nCommonHeight = state->pindexLastCommonBlock ? state->pindexLastCommonBlock->nHeight : -1;
-    BOOST_FOREACH(const QueuedBlock& queue, state->vBlocksInFlight) {
+    for (const QueuedBlock& queue : state->vBlocksInFlight) {
         if (queue.pindex)
             stats.vHeightInFlight.push_back(queue.pindex->nHeight);
     }
@@ -659,7 +661,7 @@ bool AddOrphanTx(const CTransactionRef& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRE
 
     auto ret = mapOrphanTransactions.emplace(hash, COrphanTx{tx, peer, GetTime() + ORPHAN_TX_EXPIRE_TIME});
     assert(ret.second);
-    BOOST_FOREACH(const CTxIn& txin, tx->vin) {
+    for (const CTxIn& txin : tx->vin) {
         mapOrphanTransactionsByPrev[txin.prevout].insert(ret.first);
     }
 
@@ -675,7 +677,7 @@ int static EraseOrphanTx(uint256 hash) EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
     std::map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
     if (it == mapOrphanTransactions.end())
         return 0;
-    BOOST_FOREACH(const CTxIn& txin, it->second.tx->vin)
+    for (const CTxIn& txin : it->second.tx->vin)
     {
         auto itPrev = mapOrphanTransactionsByPrev.find(txin.prevout);
         if (itPrev == mapOrphanTransactionsByPrev.end())
@@ -826,7 +828,7 @@ void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pb
     // Erase orphan transactions include or precluded by this block
     if (vOrphanErase.size()) {
         int nErased = 0;
-        BOOST_FOREACH(uint256 &orphanHash, vOrphanErase) {
+        for (uint256 &orphanHash : vOrphanErase) {
             nErased += EraseOrphanTx(orphanHash);
         }
         LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx included or conflicted by block\n", nErased);
@@ -1147,7 +1149,7 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
                 // Thus, the protocol spec specified allows for us to provide duplicate txn here,
                 // however we MUST always provide at least what the remote peer needs
                 typedef std::pair<unsigned int, uint256> PairType;
-                BOOST_FOREACH(PairType& pair, merkleBlock.vMatchedTxn)
+                for (PairType& pair : merkleBlock.vMatchedTxn)
                     connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::TX, *pblock->vtx[pair.first]));
             }
             // else
@@ -1708,7 +1710,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         std::vector<CAddress> vAddrOk;
         int64_t nNow = GetAdjustedTime();
         int64_t nSince = nNow - 10 * 60;
-        BOOST_FOREACH(CAddress& addr, vAddr)
+        for (CAddress& addr : vAddr)
         {
             if (interruptMsgProc)
                 return true;
@@ -2216,20 +2218,20 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 }
             }
 
-            BOOST_FOREACH(uint256 hash, vEraseQueue)
+            for (uint256 hash : vEraseQueue)
                 EraseOrphanTx(hash);
         }
         else if (fMissingInputs)
         {
             bool fRejectedParents = false; // It may be the case that the orphans parents have all been rejected
-            BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+            for (const CTxIn& txin : tx.vin) {
                 if (recentRejects->contains(txin.prevout.hash)) {
                     fRejectedParents = true;
                     break;
                 }
             }
             if (!fRejectedParents) {
-                BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+                for (const CTxIn& txin : tx.vin) {
                     CInv _inv(MSG_TX, txin.prevout.hash);
                     pfrom->AddInventoryKnown(_inv);
                     if (!AlreadyHave(_inv)) pfrom->AskFor(_inv);
@@ -2748,7 +2750,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         pfrom->vAddrToSend.clear();
         std::vector<CAddress> vAddr = connman.GetAddresses();
         FastRandomContext insecure_rand;
-        BOOST_FOREACH(const CAddress &addr, vAddr)
+        for (const CAddress &addr : vAddr)
             pfrom->PushAddress(addr, insecure_rand);
     }
 
@@ -2944,7 +2946,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
     else {
         bool found = false;
         const std::vector<std::string> &allMessages = getAllNetMessageTypes();
-        BOOST_FOREACH(const std::string msg, allMessages) {
+        for (const std::string msg : allMessages) {
             if(msg == strCommand) {
                 found = true;
                 break;
@@ -2984,7 +2986,7 @@ static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman& connman)
     AssertLockHeld(cs_main);
     CNodeState &state = *State(pnode->GetId());
 
-    BOOST_FOREACH(const CBlockReject& reject, state.rejects) {
+    for (const CBlockReject& reject : state.rejects) {
         connman.PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, (std::string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock));
     }
     state.rejects.clear();
@@ -3205,7 +3207,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             pto->nNextAddrSend = PoissonNextSend(nNow, AVG_ADDRESS_BROADCAST_INTERVAL);
             std::vector<CAddress> vAddr;
             vAddr.reserve(pto->vAddrToSend.size());
-            BOOST_FOREACH(const CAddress& addr, pto->vAddrToSend)
+            for (const CAddress& addr : pto->vAddrToSend)
             {
                 if (!pto->addrKnown.contains(addr.GetKey()))
                 {
@@ -3284,7 +3286,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 // Try to find first header that our peer doesn't have, and
                 // then send all headers past that one.  If we come across any
                 // headers that aren't on chainActive, give up.
-                BOOST_FOREACH(const uint256 &hash, pto->vBlockHashesToAnnounce) {
+                for (const uint256 &hash : pto->vBlockHashesToAnnounce) {
                     BlockMap::iterator mi = mapBlockIndex.find(hash);
                     assert(mi != mapBlockIndex.end());
                     const CBlockIndex *pindex = mi->second;
@@ -3412,7 +3414,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             vInv.reserve(std::max<size_t>(pto->vInventoryBlockToSend.size(), INVENTORY_BROADCAST_MAX_PER_1MB_BLOCK * MaxBlockSize(true) / 1000000));
 
             // Add blocks
-            BOOST_FOREACH(const uint256& hash, pto->vInventoryBlockToSend) {
+            for (const uint256& hash : pto->vInventoryBlockToSend) {
                 vInv.push_back(CInv(MSG_BLOCK, hash));
                 if (vInv.size() == MAX_INV_SZ) {
                     connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
@@ -3606,7 +3608,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             std::vector<const CBlockIndex*> vToDownload;
             NodeId staller = -1;
             FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - state.nBlocksInFlight, vToDownload, staller, consensusParams);
-            BOOST_FOREACH(const CBlockIndex *pindex, vToDownload) {
+            for (const CBlockIndex *pindex : vToDownload) {
                 vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                 MarkBlockAsInFlight(pto->GetId(), pindex->GetBlockHash(), pindex);
                 LogPrint(BCLog::NET, "Requesting block %s (%d) peer=%d\n", pindex->GetBlockHash().ToString(),
diff --git a/src/policy/policy.cpp b/src/policy/policy.cpp
index 1b1b30017f97..cf07968e15df 100644
--- a/src/policy/policy.cpp
+++ b/src/policy/policy.cpp
@@ -92,7 +92,7 @@ bool IsStandardTx(const CTransaction& tx, std::string& reason)
         return false;
     }
 
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
         // keys (remember the 520 byte limit on redeemScript size). That works
@@ -113,7 +113,7 @@ bool IsStandardTx(const CTransaction& tx, std::string& reason)
 
     unsigned int nDataOut = 0;
     txnouttype whichType;
-    BOOST_FOREACH(const CTxOut& txout, tx.vout) {
+    for (const CTxOut& txout : tx.vout) {
         if (!::IsStandard(txout.scriptPubKey, whichType)) {
             reason = "scriptpubkey";
             return false;
diff --git a/src/prevector.h b/src/prevector.h
index 717d42f92b68..597838a175c1 100644
--- a/src/prevector.h
+++ b/src/prevector.h
@@ -387,6 +387,12 @@ class prevector {
     }
 
     iterator erase(iterator first, iterator last) {
+        // Erase is not allowed to the change the object's capacity. That means
+        // that when starting with an indirectly allocated prevector with
+        // size and capacity > N, the result may be a still indirectly allocated
+        // prevector with size <= N and capacity > N. A shrink_to_fit() call is
+        // necessary to switch to the (more efficient) directly allocated
+        // representation (with capacity N and size <= N).
         iterator p = first;
         char* endp = (char*)&(*end());
         if (!std::is_trivially_destructible<T>::value) {
diff --git a/src/qt/addressbookpage.cpp b/src/qt/addressbookpage.cpp
index a30c06ecae0e..4adceae6246e 100644
--- a/src/qt/addressbookpage.cpp
+++ b/src/qt/addressbookpage.cpp
@@ -280,7 +280,7 @@ void AddressBookPage::done(int retval)
     // Figure out which address was selected, and return it
     QModelIndexList indexes = table->selectionModel()->selectedRows(AddressTableModel::Address);
 
-    Q_FOREACH (const QModelIndex& index, indexes) {
+    for (const QModelIndex& index : indexes) {
         QVariant address = table->model()->data(index);
         returnValue = address.toString();
     }
diff --git a/src/qt/addressbookpage.h b/src/qt/addressbookpage.h
index 55e8101a412c..93911a1ff8dd 100644
--- a/src/qt/addressbookpage.h
+++ b/src/qt/addressbookpage.h
@@ -8,7 +8,6 @@
 #include <QDialog>
 
 class AddressTableModel;
-class OptionsModel;
 class PlatformStyle;
 
 namespace Ui {
@@ -20,7 +19,6 @@ class QItemSelection;
 class QMenu;
 class QModelIndex;
 class QSortFilterProxyModel;
-class QTableView;
 QT_END_NAMESPACE
 
 /** Widget that shows a list of sending or receiving addresses.
diff --git a/src/qt/addresstablemodel.cpp b/src/qt/addresstablemodel.cpp
index 61a024ded318..9c8b03992a4c 100644
--- a/src/qt/addresstablemodel.cpp
+++ b/src/qt/addresstablemodel.cpp
@@ -82,7 +82,7 @@ class AddressTablePriv
         cachedAddressTable.clear();
         {
             LOCK(wallet->cs_wallet);
-            BOOST_FOREACH(const PAIRTYPE(CTxDestination, CAddressBookData)& item, wallet->mapAddressBook)
+            for (const std::pair<CTxDestination, CAddressBookData>& item : wallet->mapAddressBook)
             {
                 const CBitcoinAddress& address = item.first;
                 bool fMine = IsMine(*wallet, address.Get());
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 2c0ab0e950a6..cc90e89d6415 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -1254,7 +1254,7 @@ void BitcoinGUI::dropEvent(QDropEvent *event)
 {
     if(event->mimeData()->hasUrls())
     {
-        Q_FOREACH(const QUrl &uri, event->mimeData()->urls())
+        for (const QUrl &uri : event->mimeData()->urls())
         {
             Q_EMIT receivedURI(uri.toString());
         }
@@ -1476,7 +1476,7 @@ UnitDisplayStatusBarControl::UnitDisplayStatusBarControl(const PlatformStyle *pl
     QList<BitcoinUnits::Unit> units = BitcoinUnits::availableUnits();
     int max_width = 0;
     const QFontMetrics fm(font());
-    Q_FOREACH (const BitcoinUnits::Unit unit, units)
+    for (const BitcoinUnits::Unit unit : units)
     {
         max_width = qMax(max_width, fm.width(BitcoinUnits::name(unit)));
     }
@@ -1495,7 +1495,7 @@ void UnitDisplayStatusBarControl::mousePressEvent(QMouseEvent *event)
 void UnitDisplayStatusBarControl::createContextMenu()
 {
     menu = new QMenu(this);
-    Q_FOREACH(BitcoinUnits::Unit u, BitcoinUnits::availableUnits())
+    for (BitcoinUnits::Unit u : BitcoinUnits::availableUnits())
     {
         QAction *menuAction = new QAction(QString(BitcoinUnits::name(u)), this);
         menuAction->setData(QVariant(u));
diff --git a/src/qt/bitcoingui.h b/src/qt/bitcoingui.h
index e01da23c4e83..df1fd19933ea 100644
--- a/src/qt/bitcoingui.h
+++ b/src/qt/bitcoingui.h
@@ -32,8 +32,6 @@ class WalletModel;
 class HelpMessageDialog;
 class ModalOverlay;
 
-class CWallet;
-
 QT_BEGIN_NAMESPACE
 class QAction;
 class QProgressBar;
diff --git a/src/qt/clientmodel.h b/src/qt/clientmodel.h
index 9c86be225683..5fb12ec21d57 100644
--- a/src/qt/clientmodel.h
+++ b/src/qt/clientmodel.h
@@ -14,13 +14,10 @@
 
 #include <atomic>
 
-class AddressTableModel;
 class BanTableModel;
 class OptionsModel;
 class PeerTableModel;
-class TransactionTableModel;
 
-class CWallet;
 class CBlockIndex;
 
 QT_BEGIN_NAMESPACE
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index f6c47e025fdc..ef5068348bb6 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -478,7 +478,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     CAmount nPayAmount = 0;
     bool fDust = false;
     CMutableTransaction txDummy;
-    Q_FOREACH(const CAmount &amount, CoinControlDialog::payAmounts)
+    for (const CAmount &amount : CoinControlDialog::payAmounts)
     {
         nPayAmount += amount;
 
@@ -504,7 +504,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     coinControl->ListSelected(vCoinControl);
     model->getOutputs(vCoinControl, vOutputs);
 
-    BOOST_FOREACH(const COutput& out, vOutputs) {
+    for (const COutput& out : vOutputs) {
         // unselect already spent, very unlikely scenario, this could happen
         // when selected are spent elsewhere, like rpc or another computer
         uint256 txhash = out.tx->GetHash();
@@ -549,7 +549,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
                 nBytes -= 34;
 
         // Fee
-        nPayFee = CWallet::GetMinimumFee(nBytes, nTxConfirmTarget, ::mempool, ::feeEstimator);
+        nPayFee = CWallet::GetMinimumFee(nBytes, coinControl->nConfirmTarget, ::mempool, ::feeEstimator);
 
         if (nPayAmount > 0)
         {
@@ -633,7 +633,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     if (payTxFee.GetFeePerK() > 0)
         dFeeVary = (double)std::max(CWallet::GetRequiredFee(1000), payTxFee.GetFeePerK()) / 1000;
     else {
-        dFeeVary = (double)std::max(CWallet::GetRequiredFee(1000), ::feeEstimator.estimateSmartFee(nTxConfirmTarget, NULL, ::mempool).GetFeePerK()) / 1000;
+        dFeeVary = (double)std::max(CWallet::GetRequiredFee(1000), ::feeEstimator.estimateSmartFee(coinControl->nConfirmTarget, NULL, ::mempool).GetFeePerK()) / 1000;
     }
     QString toolTip4 = tr("Can vary +/- %1 duff(s) per input.").arg(dFeeVary);
 
@@ -672,7 +672,7 @@ void CoinControlDialog::updateView()
     std::map<QString, std::vector<COutput> > mapCoins;
     model->listCoins(mapCoins);
 
-    BOOST_FOREACH(const PAIRTYPE(QString, std::vector<COutput>)& coins, mapCoins) {
+    for (const std::pair<QString, std::vector<COutput>>& coins : mapCoins) {
         CCoinControlWidgetItem *itemWalletAddress = new CCoinControlWidgetItem();
         itemWalletAddress->setCheckState(COLUMN_CHECKBOX, Qt::Unchecked);
         QString sWalletAddress = coins.first;
@@ -699,7 +699,7 @@ void CoinControlDialog::updateView()
 
         CAmount nSum = 0;
         int nChildren = 0;
-        BOOST_FOREACH(const COutput& out, coins.second) {
+        for (const COutput& out : coins.second) {
             nSum += out.tx->tx->vout[out.i].nValue;
             nChildren++;
 
diff --git a/src/qt/coincontroldialog.h b/src/qt/coincontroldialog.h
index 594a68fee897..2940ab3bd24a 100644
--- a/src/qt/coincontroldialog.h
+++ b/src/qt/coincontroldialog.h
@@ -20,7 +20,6 @@ class PlatformStyle;
 class WalletModel;
 
 class CCoinControl;
-class CTxMemPool;
 
 namespace Ui {
     class CoinControlDialog;
diff --git a/src/qt/intro.cpp b/src/qt/intro.cpp
index 1c7251f3c747..6ec5da6d03a9 100644
--- a/src/qt/intro.cpp
+++ b/src/qt/intro.cpp
@@ -217,7 +217,7 @@ bool Intro::pickDataDirectory()
             }
             dataDir = intro.getDataDirectory();
             try {
-                TryCreateDirectory(GUIUtil::qstringToBoostPath(dataDir));
+                TryCreateDirectories(GUIUtil::qstringToBoostPath(dataDir));
                 break;
             } catch (const fs::filesystem_error&) {
                 QMessageBox::critical(0, tr(PACKAGE_NAME),
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index da3789742064..83cbe5186d30 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -106,7 +106,7 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
 
     ui->lang->setToolTip(ui->lang->toolTip().arg(tr(PACKAGE_NAME)));
     ui->lang->addItem(QString("(") + tr("default") + QString(")"), QVariant(""));
-    Q_FOREACH(const QString &langStr, translations.entryList())
+    for (const QString &langStr : translations.entryList())
     {
         QLocale locale(langStr);
 
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 22eff5dcfe5f..436df9f67d3a 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -145,7 +145,7 @@ void PaymentServer::LoadRootCAs(X509_STORE* _store)
     int nRootCerts = 0;
     const QDateTime currentTime = QDateTime::currentDateTime();
 
-    Q_FOREACH (const QSslCertificate& cert, certList) {
+    for (const QSslCertificate& cert : certList) {
         // Don't log NULL certificates
         if (cert.isNull())
             continue;
@@ -268,7 +268,7 @@ void PaymentServer::ipcParseCommandLine(int argc, char* argv[])
 bool PaymentServer::ipcSendCommandLine()
 {
     bool fResult = false;
-    Q_FOREACH (const QString& r, savedPaymentRequests)
+    for (const QString& r : savedPaymentRequests)
     {
         QLocalSocket* socket = new QLocalSocket();
         socket->connectToServer(ipcServerName(), QIODevice::WriteOnly);
@@ -393,7 +393,7 @@ void PaymentServer::uiReady()
     initNetManager();
 
     saveURIs = false;
-    Q_FOREACH (const QString& s, savedPaymentRequests)
+    for (const QString& s : savedPaymentRequests)
     {
         handleURIOrFile(s);
     }
@@ -556,7 +556,7 @@ bool PaymentServer::processPaymentRequest(const PaymentRequestPlus& request, Sen
     QList<std::pair<CScript, CAmount> > sendingTos = request.getPayTo();
     QStringList addresses;
 
-    Q_FOREACH(const PAIRTYPE(CScript, CAmount)& sendingTo, sendingTos) {
+    for (const std::pair<CScript, CAmount>& sendingTo : sendingTos) {
         // Extract and check destination addresses
         CTxDestination dest;
         if (ExtractDestination(sendingTo.first, dest)) {
@@ -743,7 +743,7 @@ void PaymentServer::reportSslErrors(QNetworkReply* reply, const QList<QSslError>
     Q_UNUSED(reply);
 
     QString errString;
-    Q_FOREACH (const QSslError& err, errs) {
+    for (const QSslError& err : errs) {
         qWarning() << "PaymentServer::reportSslErrors: " << err;
         errString += err.errorString() + "\n";
     }
diff --git a/src/qt/peertablemodel.cpp b/src/qt/peertablemodel.cpp
index 33b1f611f86f..b81b644da98d 100644
--- a/src/qt/peertablemodel.cpp
+++ b/src/qt/peertablemodel.cpp
@@ -62,7 +62,7 @@ class PeerTablePriv
 #if QT_VERSION >= 0x040700
             cachedNodeStats.reserve(vstats.size());
 #endif
-            Q_FOREACH (const CNodeStats& nodestats, vstats)
+            for (const CNodeStats& nodestats : vstats)
             {
                 CNodeCombinedStats stats;
                 stats.nodeStateStats.nMisbehavior = 0;
@@ -79,7 +79,7 @@ class PeerTablePriv
             TRY_LOCK(cs_main, lockMain);
             if (lockMain)
             {
-                BOOST_FOREACH(CNodeCombinedStats &stats, cachedNodeStats)
+                for (CNodeCombinedStats &stats : cachedNodeStats)
                     stats.fNodeStateStatsAvailable = GetNodeStateStats(stats.nodeStats.nodeid, stats.nodeStateStats);
             }
         }
@@ -91,7 +91,7 @@ class PeerTablePriv
         // build index map
         mapNodeRows.clear();
         int row = 0;
-        Q_FOREACH (const CNodeCombinedStats& stats, cachedNodeStats)
+        for (const CNodeCombinedStats& stats : cachedNodeStats)
             mapNodeRows.insert(std::pair<NodeId, int>(stats.nodeStats.nodeid, row++));
     }
 
diff --git a/src/qt/platformstyle.cpp b/src/qt/platformstyle.cpp
index 06ecd38d260a..4d66e8d5f247 100644
--- a/src/qt/platformstyle.cpp
+++ b/src/qt/platformstyle.cpp
@@ -48,8 +48,7 @@ void MakeSingleColorImage(QImage& img, const QColor& colorbase)
 QIcon ColorizeIcon(const QIcon& ico, const QColor& colorbase)
 {
     QIcon new_ico;
-    QSize sz;
-    Q_FOREACH(sz, ico.availableSizes())
+    for (const QSize sz : ico.availableSizes())
     {
         QImage img(ico.pixmap(sz).toImage());
         MakeSingleColorImage(img, colorbase);
diff --git a/src/qt/receivecoinsdialog.cpp b/src/qt/receivecoinsdialog.cpp
index 11a105cb5661..d9b566e3ebb9 100644
--- a/src/qt/receivecoinsdialog.cpp
+++ b/src/qt/receivecoinsdialog.cpp
@@ -192,7 +192,7 @@ void ReceiveCoinsDialog::on_showRequestButton_clicked()
         return;
     QModelIndexList selection = ui->recentRequestsView->selectionModel()->selectedRows();
 
-    Q_FOREACH (const QModelIndex& index, selection) {
+    for (const QModelIndex& index : selection) {
         on_recentRequestsView_doubleClicked(index);
     }
 }
diff --git a/src/qt/receivecoinsdialog.h b/src/qt/receivecoinsdialog.h
index ac85c50f4d18..488741d654c2 100644
--- a/src/qt/receivecoinsdialog.h
+++ b/src/qt/receivecoinsdialog.h
@@ -15,7 +15,6 @@
 #include <QPoint>
 #include <QVariant>
 
-class OptionsModel;
 class PlatformStyle;
 class WalletModel;
 
diff --git a/src/qt/recentrequeststablemodel.cpp b/src/qt/recentrequeststablemodel.cpp
index fd57b494abd6..e1850983535a 100644
--- a/src/qt/recentrequeststablemodel.cpp
+++ b/src/qt/recentrequeststablemodel.cpp
@@ -22,7 +22,7 @@ RecentRequestsTableModel::RecentRequestsTableModel(CWallet *wallet, WalletModel
     // Load entries from wallet
     std::vector<std::string> vReceiveRequests;
     parent->loadReceiveRequests(vReceiveRequests);
-    BOOST_FOREACH(const std::string& request, vReceiveRequests)
+    for (const std::string& request : vReceiveRequests)
         addNewRequest(request);
 
     /* These columns must match the indices in the ColumnIndex enumeration */
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index bc9e57137024..9de6a0d0ddd1 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -329,7 +329,7 @@ void SendCoinsDialog::send(QList<SendCoinsRecipient> recipients, QString strFee,
 
     // Format confirmation message
     QStringList formatted;
-    Q_FOREACH(const SendCoinsRecipient &rcp, currentTransaction.getRecipients())
+    for (const SendCoinsRecipient &rcp : currentTransaction.getRecipients())
     {
         // generate bold amount string
         QString amount = "<b>" + BitcoinUnits::formatHtmlWithUnit(model->getOptionsModel()->getDisplayUnit(), rcp.amount);
@@ -386,7 +386,7 @@ void SendCoinsDialog::send(QList<SendCoinsRecipient> recipients, QString strFee,
     questionString.append("<hr />");
     CAmount totalAmount = currentTransaction.getTotalTransactionAmount() + txFee;
     QStringList alternativeUnits;
-    Q_FOREACH(BitcoinUnits::Unit u, BitcoinUnits::availableUnits())
+    for (BitcoinUnits::Unit u : BitcoinUnits::availableUnits())
     {
         if(u != model->getOptionsModel()->getDisplayUnit())
             alternativeUnits.append(BitcoinUnits::formatHtmlWithUnit(u, totalAmount));
@@ -912,6 +912,12 @@ void SendCoinsDialog::coinControlUpdateLabels()
     // set pay amounts
     CoinControlDialog::payAmounts.clear();
     CoinControlDialog::fSubtractFeeFromAmount = false;
+    if (ui->radioSmartFee->isChecked()) {
+        CoinControlDialog::coinControl->nConfirmTarget = ui->sliderSmartFee->maximum() - ui->sliderSmartFee->value() + 2;
+    } else {
+        CoinControlDialog::coinControl->nConfirmTarget = model->getDefaultConfirmTarget();
+    }
+
     for(int i = 0; i < ui->entries->count(); ++i)
     {
         SendCoinsEntry *entry = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(i)->widget());
diff --git a/src/qt/sendcoinsdialog.h b/src/qt/sendcoinsdialog.h
index ae34d1e6a93b..403d90bc5f8b 100644
--- a/src/qt/sendcoinsdialog.h
+++ b/src/qt/sendcoinsdialog.h
@@ -15,7 +15,6 @@
 static const int MAX_SEND_POPUP_ENTRIES = 10;
 
 class ClientModel;
-class OptionsModel;
 class PlatformStyle;
 class SendCoinsEntry;
 class SendCoinsRecipient;
diff --git a/src/qt/splashscreen.cpp b/src/qt/splashscreen.cpp
index d90f32483aea..1d37fa49a7ce 100644
--- a/src/qt/splashscreen.cpp
+++ b/src/qt/splashscreen.cpp
@@ -192,7 +192,7 @@ void SplashScreen::unsubscribeFromCoreSignals()
     uiInterface.InitMessage.disconnect(boost::bind(InitMessage, this, _1));
     uiInterface.ShowProgress.disconnect(boost::bind(ShowProgress, this, _1, _2));
 #ifdef ENABLE_WALLET
-    Q_FOREACH(CWallet* const & pwallet, connectedWallets) {
+    for (CWallet* const & pwallet : connectedWallets) {
         pwallet->ShowProgress.disconnect(boost::bind(ShowProgress, this, _1, _2));
     }
 #endif
diff --git a/src/qt/test/paymentservertests.cpp b/src/qt/test/paymentservertests.cpp
index 08a76c7d4963..b9a8ad6e280d 100644
--- a/src/qt/test/paymentservertests.cpp
+++ b/src/qt/test/paymentservertests.cpp
@@ -196,7 +196,7 @@ void PaymentServerTests::paymentServerTests()
     QVERIFY(r.paymentRequest.IsInitialized());
     // Extract address and amount from the request
     QList<std::pair<CScript, CAmount> > sendingTos = r.paymentRequest.getPayTo();
-    Q_FOREACH (const PAIRTYPE(CScript, CAmount)& sendingTo, sendingTos) {
+    for (const std::pair<CScript, CAmount>& sendingTo : sendingTos) {
         CTxDestination dest;
         if (ExtractDestination(sendingTo.first, dest))
             QCOMPARE(PaymentServer::verifyAmount(sendingTo.second), false);
diff --git a/src/qt/trafficgraphwidget.cpp b/src/qt/trafficgraphwidget.cpp
index 8266f553c6dd..05029bc1f2d1 100644
--- a/src/qt/trafficgraphwidget.cpp
+++ b/src/qt/trafficgraphwidget.cpp
@@ -155,7 +155,7 @@ void TrafficGraphWidget::updateRates()
 
     if (updated){
         float tmax = DEFAULT_SAMPLE_HEIGHT;
-        Q_FOREACH(const TrafficSample& sample, trafficGraphData.getCurrentRangeQueueWithAverageBandwidth()) {
+        for (const TrafficSample& sample : trafficGraphData.getCurrentRangeQueueWithAverageBandwidth()) {
             if(sample.in > tmax) tmax = sample.in;
             if(sample.out > tmax) tmax = sample.out;
         }
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index 8a495eddc1a7..a3d8706c78a7 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -149,7 +149,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
         // Coinbase
         //
         CAmount nUnmatured = 0;
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
             nUnmatured += wallet->GetCredit(txout, ISMINE_ALL);
         strHTML += "<b>" + tr("Credit") + ":</b> ";
         if (wtx.IsInMainChain())
@@ -168,14 +168,14 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
     else
     {
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+        for (const CTxIn& txin : wtx.tx->vin)
         {
             isminetype mine = wallet->IsMine(txin);
             if(fAllFromMe > mine) fAllFromMe = mine;
         }
 
         isminetype fAllToMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
         {
             isminetype mine = wallet->IsMine(txout);
             if(fAllToMe > mine) fAllToMe = mine;
@@ -189,7 +189,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
             //
             // Debit
             //
-            BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+            for (const CTxOut& txout : wtx.tx->vout)
             {
                 // Ignore change
                 isminetype toSelf = wallet->IsMine(txout);
@@ -237,10 +237,10 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
             //
             // Mixed debit transaction
             //
-            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+            for (const CTxIn& txin : wtx.tx->vin)
                 if (wallet->IsMine(txin))
                     strHTML += "<b>" + tr("Debit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, -wallet->GetDebit(txin, ISMINE_ALL)) + "<br>";
-            BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+            for (const CTxOut& txout : wtx.tx->vout)
                 if (wallet->IsMine(txout))
                     strHTML += "<b>" + tr("Credit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, wallet->GetCredit(txout, ISMINE_ALL)) + "<br>";
         }
@@ -261,14 +261,14 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
     strHTML += "<b>" + tr("Transaction total size") + ":</b> " + QString::number(wtx.tx->GetTotalSize()) + " bytes<br>";
 
     // Message from normal dash:URI (dash:XyZ...?message=example)
-    Q_FOREACH (const PAIRTYPE(std::string, std::string)& r, wtx.vOrderForm)
+    for (const std::pair<std::string, std::string>& r : wtx.vOrderForm)
         if (r.first == "Message")
             strHTML += "<br><b>" + tr("Message") + ":</b><br>" + GUIUtil::HtmlEscape(r.second, true) + "<br>";
 
     //
     // PaymentRequest info:
     //
-    Q_FOREACH (const PAIRTYPE(std::string, std::string)& r, wtx.vOrderForm)
+    for (const std::pair<std::string, std::string>& r : wtx.vOrderForm)
     {
         if (r.first == "PaymentRequest")
         {
@@ -292,10 +292,10 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
     if (logCategories != BCLog::NONE)
     {
         strHTML += "<hr><br>" + tr("Debug information") + "<br><br>";
-        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+        for (const CTxIn& txin : wtx.tx->vin)
             if(wallet->IsMine(txin))
                 strHTML += "<b>" + tr("Debit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, -wallet->GetDebit(txin, ISMINE_ALL)) + "<br>";
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
             if(wallet->IsMine(txout))
                 strHTML += "<b>" + tr("Credit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, wallet->GetCredit(txout, ISMINE_ALL)) + "<br>";
 
@@ -305,7 +305,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
         strHTML += "<br><b>" + tr("Inputs") + ":</b>";
         strHTML += "<ul>";
 
-        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+        for (const CTxIn& txin : wtx.tx->vin)
         {
             COutPoint prevout = txin.prevout;
 
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index fb78a17f9c26..7fde2aa4349e 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -83,7 +83,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
         int nFromMe = 0;
         bool involvesWatchAddress = false;
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+        for (const CTxIn& txin : wtx.tx->vin)
         {
             if(wallet->IsMine(txin)) {
                 fAllFromMeDenom = fAllFromMeDenom && wallet->IsDenominated(txin.prevout);
@@ -97,7 +97,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
         isminetype fAllToMe = ISMINE_SPENDABLE;
         bool fAllToMeDenom = true;
         int nToMe = 0;
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout) {
+        for (const CTxOut& txout : wtx.tx->vout) {
             if(wallet->IsMine(txout)) {
                 fAllToMeDenom = fAllToMeDenom && CPrivateSend::IsDenominatedAmount(txout.nValue);
                 nToMe++;
diff --git a/src/qt/transactiontablemodel.cpp b/src/qt/transactiontablemodel.cpp
index 96fa10bdfb65..954b92860be2 100644
--- a/src/qt/transactiontablemodel.cpp
+++ b/src/qt/transactiontablemodel.cpp
@@ -144,7 +144,7 @@ class TransactionTablePriv
                 {
                     parent->beginInsertRows(QModelIndex(), lowerIndex, lowerIndex+toInsert.size()-1);
                     int insert_idx = lowerIndex;
-                    Q_FOREACH(const TransactionRecord &rec, toInsert)
+                    for (const TransactionRecord &rec : toInsert)
                     {
                         cachedWallet.insert(insert_idx, rec);
                         insert_idx += 1;
diff --git a/src/qt/transactionview.cpp b/src/qt/transactionview.cpp
index 7f2be564b502..84e796b97dc4 100644
--- a/src/qt/transactionview.cpp
+++ b/src/qt/transactionview.cpp
@@ -574,7 +574,7 @@ void TransactionView::computeSum()
         return;
     QModelIndexList selection = transactionView->selectionModel()->selectedRows();
 
-    Q_FOREACH (QModelIndex index, selection){
+    for (QModelIndex index : selection){
         amount += index.data(TransactionTableModel::AmountRole).toLongLong();
     }
     QString strAmount(BitcoinUnits::formatWithUnit(nDisplayUnit, amount, true, BitcoinUnits::separatorAlways));
diff --git a/src/qt/utilitydialog.cpp b/src/qt/utilitydialog.cpp
index e5e729df54a5..d8fc1c943c36 100644
--- a/src/qt/utilitydialog.cpp
+++ b/src/qt/utilitydialog.cpp
@@ -108,7 +108,7 @@ HelpMessageDialog::HelpMessageDialog(QWidget *parent, HelpMode helpMode) :
         QTextCharFormat bold;
         bold.setFontWeight(QFont::Bold);
 
-        Q_FOREACH (const QString &line, coreOptions.split("\n")) {
+        for (const QString &line : coreOptions.split("\n")) {
             if (line.startsWith("  -"))
             {
                 cursor.currentTable()->appendRows(1);
diff --git a/src/qt/utilitydialog.h b/src/qt/utilitydialog.h
index c3493ac28bb8..c1c95dcb55c4 100644
--- a/src/qt/utilitydialog.h
+++ b/src/qt/utilitydialog.h
@@ -9,7 +9,6 @@
 #include <QObject>
 
 class BitcoinGUI;
-class ClientModel;
 
 namespace Ui {
     class HelpMessageDialog;
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 71b3b37b2a3d..4d2ef994ad26 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -79,7 +79,7 @@ CAmount WalletModel::getBalance(const CCoinControl *coinControl) const
         CAmount nBalance = 0;
         std::vector<COutput> vCoins;
         wallet->AvailableCoins(vCoins, true, coinControl);
-        BOOST_FOREACH(const COutput& out, vCoins)
+        for (const COutput& out : vCoins)
             if(out.fSpendable)
                 nBalance += out.tx->tx->vout[out.i].nValue;
 
@@ -256,7 +256,7 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
     int nAddresses = 0;
 
     // Pre-check input data for validity
-    Q_FOREACH(const SendCoinsRecipient &rcp, recipients)
+    for (const SendCoinsRecipient &rcp : recipients)
     {
         if (rcp.fSubtractFeeFromAmount)
             fSubtractFeeFromAmount = true;
@@ -367,7 +367,7 @@ WalletModel::SendCoinsReturn WalletModel::sendCoins(WalletModelTransaction &tran
         CWalletTx *newTx = transaction.getTransaction();
         QList<SendCoinsRecipient> recipients = transaction.getRecipients();
 
-        Q_FOREACH(const SendCoinsRecipient &rcp, recipients)
+        for (const SendCoinsRecipient &rcp : recipients)
         {
             if (rcp.paymentRequest.IsInitialized())
             {
@@ -400,7 +400,7 @@ WalletModel::SendCoinsReturn WalletModel::sendCoins(WalletModelTransaction &tran
 
     // Add addresses / update labels that we've sent to to the address book,
     // and emit coinsSent signal for each recipient
-    Q_FOREACH(const SendCoinsRecipient &rcp, transaction.getRecipients())
+    for (const SendCoinsRecipient &rcp : transaction.getRecipients())
     {
         // Don't touch the address book when we have a payment request
         if (!rcp.paymentRequest.IsInitialized())
@@ -681,7 +681,7 @@ bool WalletModel::getPrivKey(const CKeyID &address, CKey& vchPrivKeyOut) const
 void WalletModel::getOutputs(const std::vector<COutPoint>& vOutpoints, std::vector<COutput>& vOutputs)
 {
     LOCK2(cs_main, wallet->cs_wallet);
-    BOOST_FOREACH(const COutPoint& outpoint, vOutpoints)
+    for (const COutPoint& outpoint : vOutpoints)
     {
         if (!wallet->mapWallet.count(outpoint.hash)) continue;
         int nDepth = wallet->mapWallet[outpoint.hash].GetDepthInMainChain();
@@ -708,7 +708,7 @@ void WalletModel::listCoins(std::map<QString, std::vector<COutput> >& mapCoins)
     wallet->ListLockedCoins(vLockedCoins);
 
     // add locked coins
-    BOOST_FOREACH(const COutPoint& outpoint, vLockedCoins)
+    for (const COutPoint& outpoint : vLockedCoins)
     {
         if (!wallet->mapWallet.count(outpoint.hash)) continue;
         int nDepth = wallet->mapWallet[outpoint.hash].GetDepthInMainChain();
@@ -718,7 +718,7 @@ void WalletModel::listCoins(std::map<QString, std::vector<COutput> >& mapCoins)
             vCoins.push_back(out);
     }
 
-    BOOST_FOREACH(const COutput& out, vCoins)
+    for (const COutput& out : vCoins)
     {
         COutput cout = out;
 
@@ -768,8 +768,8 @@ void WalletModel::listProTxCoins(std::vector<COutPoint>& vOutpts)
 void WalletModel::loadReceiveRequests(std::vector<std::string>& vReceiveRequests)
 {
     LOCK(wallet->cs_wallet);
-    BOOST_FOREACH(const PAIRTYPE(CTxDestination, CAddressBookData)& item, wallet->mapAddressBook)
-        BOOST_FOREACH(const PAIRTYPE(std::string, std::string)& item2, item.second.destdata)
+    for (const std::pair<CTxDestination, CAddressBookData>& item : wallet->mapAddressBook)
+        for (const std::pair<std::string, std::string>& item2 : item.second.destdata)
             if (item2.first.size() > 2 && item2.first.substr(0,2) == "rr") // receive request
                 vReceiveRequests.push_back(item2.second);
 }
diff --git a/src/qt/walletmodeltransaction.cpp b/src/qt/walletmodeltransaction.cpp
index 8077156d9e3e..a8a9feb4d08d 100644
--- a/src/qt/walletmodeltransaction.cpp
+++ b/src/qt/walletmodeltransaction.cpp
@@ -88,7 +88,7 @@ void WalletModelTransaction::reassignAmounts()
 CAmount WalletModelTransaction::getTotalTransactionAmount()
 {
     CAmount totalTransactionAmount = 0;
-    Q_FOREACH(const SendCoinsRecipient &rcp, recipients)
+    for (const SendCoinsRecipient &rcp : recipients)
     {
         totalTransactionAmount += rcp.amount;
     }
diff --git a/src/random.cpp b/src/random.cpp
index 0668966756f0..b171b3dabfed 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -65,6 +65,70 @@ static inline int64_t GetPerformanceCounter()
 #endif
 }
 
+
+#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+static std::atomic<bool> hwrand_initialized{false};
+static bool rdrand_supported = false;
+static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
+static void RDRandInit()
+{
+    uint32_t eax, ecx, edx;
+#if defined(__i386__) && ( defined(__PIC__) || defined(__PIE__))
+    // Avoid clobbering ebx, as that is used for PIC on x86.
+    uint32_t tmp;
+    __asm__ ("mov %%ebx, %1; cpuid; mov %1, %%ebx": "=a"(eax), "=g"(tmp), "=c"(ecx), "=d"(edx) : "a"(1));
+#else
+    uint32_t ebx;
+    __asm__ ("cpuid": "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx) : "a"(1));
+#endif
+    //! When calling cpuid function #1, ecx register will have this set if RDRAND is available.
+    if (ecx & CPUID_F1_ECX_RDRAND) {
+        LogPrintf("Using RdRand as entropy source\n");
+        rdrand_supported = true;
+    }
+    hwrand_initialized.store(true);
+}
+#else
+static void RDRandInit() {}
+#endif
+
+static bool GetHWRand(unsigned char* ent32) {
+#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+    assert(hwrand_initialized.load(std::memory_order_relaxed));
+    if (rdrand_supported) {
+        uint8_t ok;
+        // Not all assemblers support the rdrand instruction, write it in hex.
+#ifdef __i386__
+        for (int iter = 0; iter < 4; ++iter) {
+            uint32_t r1, r2;
+            __asm__ volatile (".byte 0x0f, 0xc7, 0xf0;" // rdrand %eax
+                              ".byte 0x0f, 0xc7, 0xf2;" // rdrand %edx
+                              "setc %2" :
+                              "=a"(r1), "=d"(r2), "=q"(ok) :: "cc");
+            if (!ok) return false;
+            WriteLE32(ent32 + 8 * iter, r1);
+            WriteLE32(ent32 + 8 * iter + 4, r2);
+        }
+#else
+        uint64_t r1, r2, r3, r4;
+        __asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0, " // rdrand %rax
+                                "0x48, 0x0f, 0xc7, 0xf3, " // rdrand %rbx
+                                "0x48, 0x0f, 0xc7, 0xf1, " // rdrand %rcx
+                                "0x48, 0x0f, 0xc7, 0xf2; " // rdrand %rdx
+                          "setc %4" :
+                          "=a"(r1), "=b"(r2), "=c"(r3), "=d"(r4), "=q"(ok) :: "cc");
+        if (!ok) return false;
+        WriteLE64(ent32, r1);
+        WriteLE64(ent32 + 8, r2);
+        WriteLE64(ent32 + 16, r3);
+        WriteLE64(ent32 + 24, r4);
+#endif
+        return true;
+    }
+#endif
+    return false;
+}
+
 void RandAddSeed()
 {
     // Seed with CPU performance counter
@@ -255,6 +319,11 @@ void GetStrongRandBytes(unsigned char* out, int num)
     GetOSRand(buf);
     hasher.Write(buf, 32);
 
+    // Third source: HW RNG, if available.
+    if (GetHWRand(buf)) {
+        hasher.Write(buf, 32);
+    }
+
     // Combine with and update state
     {
         std::unique_lock<std::mutex> lock(cs_rng_state);
@@ -392,3 +461,8 @@ FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDete
     uint256 seed;
     rng.SetKey(seed.begin(), 32);
 }
+
+void RandomInit()
+{
+    RDRandInit();
+}
diff --git a/src/random.h b/src/random.h
index 306c9355830b..72659e12b115 100644
--- a/src/random.h
+++ b/src/random.h
@@ -150,4 +150,7 @@ void GetOSRand(unsigned char *ent32);
  */
 bool Random_SanityCheck();
 
+/** Initialize the RNG. */
+void RandomInit();
+
 #endif // BITCOIN_RANDOM_H
diff --git a/src/rest.cpp b/src/rest.cpp
index 7bca7488e95c..69220579269d 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -158,7 +158,7 @@ static bool rest_headers(HTTPRequest* req,
     }
 
     CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
-    BOOST_FOREACH(const CBlockIndex *pindex, headers) {
+    for (const CBlockIndex *pindex : headers) {
         ssHeader << pindex->GetBlockHeader();
     }
 
@@ -178,7 +178,7 @@ static bool rest_headers(HTTPRequest* req,
     }
     case RF_JSON: {
         UniValue jsonHeaders(UniValue::VARR);
-        BOOST_FOREACH(const CBlockIndex *pindex, headers) {
+        for (const CBlockIndex *pindex : headers) {
             jsonHeaders.push_back(blockheaderToJSON(pindex));
         }
         std::string strJSON = jsonHeaders.write() + "\n";
@@ -558,7 +558,7 @@ static bool rest_getutxos(HTTPRequest* req, const std::string& strURIPart)
         objGetUTXOResponse.push_back(Pair("bitmap", bitmapStringRepresentation));
 
         UniValue utxos(UniValue::VARR);
-        BOOST_FOREACH (const CCoin& coin, outs) {
+        for (const CCoin& coin : outs) {
             UniValue utxo(UniValue::VOBJ);
             utxo.push_back(Pair("height", (int32_t)coin.nHeight));
             utxo.push_back(Pair("value", ValueFromAmount(coin.out.nValue)));
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 7806f425ae3a..73ce295ea418 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -387,14 +387,14 @@ void entryToJSON(UniValue &info, const CTxMemPoolEntry &e)
     info.push_back(Pair("ancestorfees", e.GetModFeesWithAncestors()));
     const CTransaction& tx = e.GetTx();
     std::set<std::string> setDepends;
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         if (mempool.exists(txin.prevout.hash))
             setDepends.insert(txin.prevout.hash.ToString());
     }
 
     UniValue depends(UniValue::VARR);
-    BOOST_FOREACH(const std::string& dep, setDepends)
+    for (const std::string& dep : setDepends)
     {
         depends.push_back(dep);
     }
@@ -409,7 +409,7 @@ UniValue mempoolToJSON(bool fVerbose)
     {
         LOCK(mempool.cs);
         UniValue o(UniValue::VOBJ);
-        BOOST_FOREACH(const CTxMemPoolEntry& e, mempool.mapTx)
+        for (const CTxMemPoolEntry& e : mempool.mapTx)
         {
             const uint256& hash = e.GetTx().GetHash();
             UniValue info(UniValue::VOBJ);
@@ -424,7 +424,7 @@ UniValue mempoolToJSON(bool fVerbose)
         mempool.queryHashes(vtxid);
 
         UniValue a(UniValue::VARR);
-        BOOST_FOREACH(const uint256& hash, vtxid)
+        for (const uint256& hash : vtxid)
             a.push_back(hash.ToString());
 
         return a;
@@ -509,14 +509,14 @@ UniValue getmempoolancestors(const JSONRPCRequest& request)
 
     if (!fVerbose) {
         UniValue o(UniValue::VARR);
-        BOOST_FOREACH(CTxMemPool::txiter ancestorIt, setAncestors) {
+        for (CTxMemPool::txiter ancestorIt : setAncestors) {
             o.push_back(ancestorIt->GetTx().GetHash().ToString());
         }
 
         return o;
     } else {
         UniValue o(UniValue::VOBJ);
-        BOOST_FOREACH(CTxMemPool::txiter ancestorIt, setAncestors) {
+        for (CTxMemPool::txiter ancestorIt : setAncestors) {
             const CTxMemPoolEntry &e = *ancestorIt;
             const uint256& _hash = e.GetTx().GetHash();
             UniValue info(UniValue::VOBJ);
@@ -573,14 +573,14 @@ UniValue getmempooldescendants(const JSONRPCRequest& request)
 
     if (!fVerbose) {
         UniValue o(UniValue::VARR);
-        BOOST_FOREACH(CTxMemPool::txiter descendantIt, setDescendants) {
+        for (CTxMemPool::txiter descendantIt : setDescendants) {
             o.push_back(descendantIt->GetTx().GetHash().ToString());
         }
 
         return o;
     } else {
         UniValue o(UniValue::VOBJ);
-        BOOST_FOREACH(CTxMemPool::txiter descendantIt, setDescendants) {
+        for (CTxMemPool::txiter descendantIt : setDescendants) {
             const CTxMemPoolEntry &e = *descendantIt;
             const uint256& _hash = e.GetTx().GetHash();
             UniValue info(UniValue::VOBJ);
@@ -1512,7 +1512,7 @@ UniValue getchaintips(const JSONRPCRequest& request)
     std::set<const CBlockIndex*> setOrphans;
     std::set<const CBlockIndex*> setPrevs;
 
-    BOOST_FOREACH(const PAIRTYPE(const uint256, CBlockIndex*)& item, mapBlockIndex)
+    for (const std::pair<const uint256, CBlockIndex*>& item : mapBlockIndex)
     {
         if (!chainActive.Contains(item.second)) {
             setOrphans.insert(item.second);
@@ -1541,7 +1541,7 @@ UniValue getchaintips(const JSONRPCRequest& request)
 
     /* Construct the output array.  */
     UniValue res(UniValue::VARR);
-    BOOST_FOREACH(const CBlockIndex* block, setTips)
+    for (const CBlockIndex* block : setTips)
     {
         const CBlockIndex* pindexFork = chainActive.FindFork(block);
         const int branchLen = block->nHeight - pindexFork->nHeight;
diff --git a/src/rpc/blockchain.h b/src/rpc/blockchain.h
index c021441b0a73..960edfd56f5b 100644
--- a/src/rpc/blockchain.h
+++ b/src/rpc/blockchain.h
@@ -7,9 +7,6 @@
 
 class CBlock;
 class CBlockIndex;
-class CScript;
-class CTransaction;
-class uint256;
 class UniValue;
 
 /**
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 00ae7a059350..f4ef6cebd593 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -601,7 +601,7 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
         entry.push_back(Pair("hash", txHash.GetHex()));
 
         UniValue deps(UniValue::VARR);
-        BOOST_FOREACH (const CTxIn &in, tx.vin)
+        for (const CTxIn &in : tx.vin)
         {
             if (setTxIndex.count(in.prevout.hash))
                 deps.push_back(setTxIndex[in.prevout.hash]);
diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index c8d6ef003a42..ef886dbc1b7c 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -232,7 +232,7 @@ class DescribeAddressVisitor : public boost::static_visitor<UniValue>
             obj.push_back(Pair("script", GetTxnOutputType(whichType)));
             obj.push_back(Pair("hex", HexStr(subscript.begin(), subscript.end())));
             UniValue a(UniValue::VARR);
-            BOOST_FOREACH(const CTxDestination& addr, addresses)
+            for (const CTxDestination& addr : addresses)
                 a.push_back(CBitcoinAddress(addr).ToString());
             obj.push_back(Pair("addresses", a));
             if (whichType == TX_MULTISIG)
@@ -371,8 +371,8 @@ UniValue validateaddress(const JSONRPCRequest& request)
 
 #ifdef ENABLE_WALLET
         isminetype mine = pwallet ? IsMine(*pwallet, dest) : ISMINE_NO;
-        ret.push_back(Pair("ismine", (mine & ISMINE_SPENDABLE) ? true : false));
-        ret.push_back(Pair("iswatchonly", (mine & ISMINE_WATCH_ONLY) ? true: false));
+        ret.push_back(Pair("ismine", bool(mine & ISMINE_SPENDABLE)));
+        ret.push_back(Pair("iswatchonly", bool(mine & ISMINE_WATCH_ONLY)));
         UniValue detail = boost::apply_visitor(DescribeAddressVisitor(pwallet), dest);
         ret.pushKVs(detail);
         if (pwallet && pwallet->mapAddressBook.count(dest)) {
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index 3d31b52d5091..5396e548c97d 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -127,7 +127,7 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
 
     UniValue ret(UniValue::VARR);
 
-    BOOST_FOREACH(const CNodeStats& stats, vstats) {
+    for (const CNodeStats& stats : vstats) {
         UniValue obj(UniValue::VOBJ);
         CNodeStateStats statestats;
         bool fStateStats = GetNodeStateStats(stats.nodeid, statestats);
@@ -164,7 +164,7 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
             obj.push_back(Pair("synced_headers", statestats.nSyncHeight));
             obj.push_back(Pair("synced_blocks", statestats.nCommonHeight));
             UniValue heights(UniValue::VARR);
-            BOOST_FOREACH(int height, statestats.vHeightInFlight) {
+            for (int height : statestats.vHeightInFlight) {
                 heights.push_back(height);
             }
             obj.push_back(Pair("inflight", heights));
@@ -172,14 +172,14 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
         obj.push_back(Pair("whitelisted", stats.fWhitelisted));
 
         UniValue sendPerMsgCmd(UniValue::VOBJ);
-        BOOST_FOREACH(const mapMsgCmdSize::value_type &i, stats.mapSendBytesPerMsgCmd) {
+        for (const mapMsgCmdSize::value_type &i : stats.mapSendBytesPerMsgCmd) {
             if (i.second > 0)
                 sendPerMsgCmd.push_back(Pair(i.first, i.second));
         }
         obj.push_back(Pair("bytessent_per_msg", sendPerMsgCmd));
 
         UniValue recvPerMsgCmd(UniValue::VOBJ);
-        BOOST_FOREACH(const mapMsgCmdSize::value_type &i, stats.mapRecvBytesPerMsgCmd) {
+        for (const mapMsgCmdSize::value_type &i : stats.mapRecvBytesPerMsgCmd) {
             if (i.second > 0)
                 recvPerMsgCmd.push_back(Pair(i.first, i.second));
         }
@@ -475,7 +475,7 @@ UniValue getnetworkinfo(const JSONRPCRequest& request)
     UniValue localAddresses(UniValue::VARR);
     {
         LOCK(cs_mapLocalHost);
-        BOOST_FOREACH(const PAIRTYPE(CNetAddr, LocalServiceInfo) &item, mapLocalHost)
+        for (const std::pair<CNetAddr, LocalServiceInfo> &item : mapLocalHost)
         {
             UniValue rec(UniValue::VOBJ);
             rec.push_back(Pair("address", item.first.ToString()));
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index e5b7d64a06ec..318b601c1b0e 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -265,9 +265,13 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         pblockindex = mapBlockIndex[hashBlock];
     } else {
-        const Coin& coin = AccessByTxid(*pcoinsTip, oneTxid);
-        if (!coin.IsSpent() && coin.nHeight > 0 && coin.nHeight <= chainActive.Height()) {
-            pblockindex = chainActive[coin.nHeight];
+        // Loop through txids and try to find which block they're in. Exit loop once a block is found.
+        for (const auto& tx : setTxids) {
+            const Coin& coin = AccessByTxid(*pcoinsTip, tx);
+            if (!coin.IsSpent()) {
+                pblockindex = chainActive[coin.nHeight];
+                break;
+            }
         }
     }
 
@@ -290,7 +294,7 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
         if (setTxids.count(tx->GetHash()))
             ntxFound++;
     if (ntxFound != setTxids.size())
-        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "(Not all) transactions not found in specified block");
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Not all transactions found in specified or retrieved block");
 
     CDataStream ssMB(SER_NETWORK, PROTOCOL_VERSION);
     CMerkleBlock mb(block, setTxids);
@@ -332,7 +336,7 @@ UniValue verifytxoutproof(const JSONRPCRequest& request)
     if (!mapBlockIndex.count(merkleBlock.header.GetHash()) || !chainActive.Contains(mapBlockIndex[merkleBlock.header.GetHash()]))
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
 
-    BOOST_FOREACH(const uint256& hash, vMatch)
+    for (const uint256& hash : vMatch)
         res.push_back(hash.GetHex());
     return res;
 }
@@ -423,7 +427,7 @@ UniValue createrawtransaction(const JSONRPCRequest& request)
 
     std::set<CBitcoinAddress> setAddress;
     std::vector<std::string> addrList = sendTo.getKeys();
-    BOOST_FOREACH(const std::string& name_, addrList) {
+    for (const std::string& name_ : addrList) {
 
         if (name_ == "data") {
             std::vector<unsigned char> data = ParseHexV(sendTo[name_].getValStr(),"Data");
@@ -682,7 +686,7 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
         CCoinsViewMemPool viewMempool(&viewChain, mempool);
         view.SetBackend(viewMempool); // temporarily switch cache backend to db+mempool view
 
-        BOOST_FOREACH(const CTxIn& txin, mergedTx.vin) {
+        for (const CTxIn& txin : mergedTx.vin) {
             view.AccessCoin(txin.prevout); // Load entries from viewChain into view; can fail.
         }
 
@@ -821,7 +825,7 @@ UniValue signrawtransaction(const JSONRPCRequest& request)
             SignSignature(keystore, prevPubKey, mergedTx, i, nHashType);
 
         // ... and merge in other signatures:
-        BOOST_FOREACH(const CMutableTransaction& txv, txVariants) {
+        for (const CMutableTransaction& txv : txVariants) {
             if (txv.vin.size() > i) {
                 txin.scriptSig = CombineSignatures(prevPubKey, txConst, i, txin.scriptSig, txv.vin[i].scriptSig);
             }
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index 8eb15d315319..241c456f344c 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -64,7 +64,7 @@ void RPCTypeCheck(const UniValue& params,
                   bool fAllowNull)
 {
     unsigned int i = 0;
-    BOOST_FOREACH(UniValue::VType t, typesExpected)
+    for (UniValue::VType t : typesExpected)
     {
         if (params.size() <= i)
             break;
@@ -103,7 +103,7 @@ void RPCTypeCheckObj(const UniValue& o,
 
     if (fStrict)
     {
-        BOOST_FOREACH(const std::string& k, o.getKeys())
+        for (const std::string& k : o.getKeys())
         {
             if (typesExpected.count(k) == 0)
             {
@@ -233,7 +233,7 @@ std::string CRPCTable::help(const std::string& strCommand, const std::string& st
     jreq.fHelp = true;
     jreq.params = UniValue();
 
-    BOOST_FOREACH(const PAIRTYPE(std::string, const CRPCCommand*)& command, vCommands)
+    for (const std::pair<std::string, const CRPCCommand*>& command : vCommands)
     {
         const CRPCCommand *pcmd = command.second;
         std::string strMethod = pcmd->name;
diff --git a/src/rpc/server.h b/src/rpc/server.h
index de3b74ead22d..f2f1dd2a9270 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -26,9 +26,6 @@ namespace RPCServer
     void OnPreCommand(std::function<void (const CRPCCommand&)> slot);
 }
 
-class CBlockIndex;
-class CNetAddr;
-
 /** Wrapper for UniValue::VType, which includes typeAny:
  * Used to denote don't care type. Only used by RPCTypeCheckObj */
 struct UniValueType {
diff --git a/src/script/ismine.cpp b/src/script/ismine.cpp
index a66e79bef17f..fe9215c67da2 100644
--- a/src/script/ismine.cpp
+++ b/src/script/ismine.cpp
@@ -18,7 +18,7 @@ typedef std::vector<unsigned char> valtype;
 unsigned int HaveKeys(const std::vector<valtype>& pubkeys, const CKeyStore& keystore)
 {
     unsigned int nResult = 0;
-    BOOST_FOREACH(const valtype& pubkey, pubkeys)
+    for (const valtype& pubkey : pubkeys)
     {
         CKeyID keyID = CPubKey(pubkey).GetID();
         if (keystore.HaveKey(keyID))
diff --git a/src/script/script.h b/src/script/script.h
index 9a276ed3fe1b..77eb896503bc 100644
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -645,8 +645,9 @@ class CScript : public CScriptBase
 
     void clear()
     {
-        // The default std::vector::clear() does not release memory.
-        CScriptBase().swap(*this);
+        // The default prevector::clear() does not release memory
+        CScriptBase::clear();
+        shrink_to_fit();
     }
 
     template<typename Stream>
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index c945972a44fa..9e4424e7c8a9 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -148,7 +148,7 @@ bool SignSignature(const CKeyStore &keystore, const CTransaction& txFrom, CMutab
 static CScript PushAll(const std::vector<valtype>& values)
 {
     CScript result;
-    BOOST_FOREACH(const valtype& v, values)
+    for (const valtype& v : values)
         result << v;
     return result;
 }
@@ -159,12 +159,12 @@ static CScript CombineMultisig(const CScript& scriptPubKey, const BaseSignatureC
 {
     // Combine all the signatures we've got:
     std::set<valtype> allsigs;
-    BOOST_FOREACH(const valtype& v, sigs1)
+    for (const valtype& v : sigs1)
     {
         if (!v.empty())
             allsigs.insert(v);
     }
-    BOOST_FOREACH(const valtype& v, sigs2)
+    for (const valtype& v : sigs2)
     {
         if (!v.empty())
             allsigs.insert(v);
@@ -175,7 +175,7 @@ static CScript CombineMultisig(const CScript& scriptPubKey, const BaseSignatureC
     unsigned int nSigsRequired = vSolutions.front()[0];
     unsigned int nPubKeys = vSolutions.size()-2;
     std::map<valtype, valtype> sigs;
-    BOOST_FOREACH(const valtype& sig, allsigs)
+    for (const valtype& sig : allsigs)
     {
         for (unsigned int i = 0; i < nPubKeys; i++)
         {
diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index 616b30cca948..470bdb4c6c23 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -76,7 +76,7 @@ bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, std::vector<std::v
 
     // Scan templates
     const CScript& script1 = scriptPubKey;
-    BOOST_FOREACH(const PAIRTYPE(txnouttype, CScript)& tplate, mTemplates)
+    for (const std::pair<txnouttype, CScript>& tplate : mTemplates)
     {
         const CScript& script2 = tplate.second;
         vSolutionsRet.clear();
@@ -275,7 +275,7 @@ CScript GetScriptForMultisig(int nRequired, const std::vector<CPubKey>& keys)
     CScript script;
 
     script << CScript::EncodeOP_N(nRequired);
-    BOOST_FOREACH(const CPubKey& key, keys)
+    for (const CPubKey& key : keys)
         script << ToByteVector(key);
     script << CScript::EncodeOP_N(keys.size()) << OP_CHECKMULTISIG;
     return script;
diff --git a/src/sync.cpp b/src/sync.cpp
index 924223630ee8..785b4f07cfd4 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -77,7 +77,7 @@ static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch,
     std::string strOutput = "";
     strOutput += "POTENTIAL DEADLOCK DETECTED\n";
     strOutput += "Previous lock order was:\n";
-    BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s2) {
+    for (const std::pair<void*, CLockLocation> & i : s2) {
         if (i.first == mismatch.first) {
             strOutput += " (1)";
         }
@@ -87,7 +87,7 @@ static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch,
         strOutput += strprintf(" %s\n", i.second.ToString().c_str());
     }
     strOutput += "Current lock order is:\n";
-    BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, s1) {
+    for (const std::pair<void*, CLockLocation> & i : s1) {
         if (i.first == mismatch.first) {
             strOutput += " (1)";
         }
@@ -112,7 +112,7 @@ static void push_lock(void* c, const CLockLocation& locklocation, bool fTry)
 
     (*lockstack).push_back(std::make_pair(c, locklocation));
 
-    BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, (*lockstack)) {
+    for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
         if (i.first == c)
             break;
 
@@ -146,14 +146,14 @@ void LeaveCritical()
 std::string LocksHeld()
 {
     std::string result;
-    BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, *lockstack)
+    for (const std::pair<void*, CLockLocation> & i : *lockstack)
         result += i.second.ToString() + std::string("\n");
     return result;
 }
 
 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 {
-    BOOST_FOREACH (const PAIRTYPE(void*, CLockLocation) & i, *lockstack)
+    for (const std::pair<void*, CLockLocation> & i : *lockstack)
         if (i.first == cs)
             return;
     fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
diff --git a/src/test/bip32_tests.cpp b/src/test/bip32_tests.cpp
index 402aef27a0e6..ab040c5cc7f4 100644
--- a/src/test/bip32_tests.cpp
+++ b/src/test/bip32_tests.cpp
@@ -93,7 +93,7 @@ void RunTest(const TestVector &test) {
     CExtPubKey pubkey;
     key.SetMaster(&seed[0], seed.size());
     pubkey = key.Neuter();
-    BOOST_FOREACH(const TestDerivation &derive, test.vDerive) {
+    for (const TestDerivation &derive : test.vDerive) {
         unsigned char data[74];
         key.Encode(data);
         pubkey.Encode(data);
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index f6e8adab802c..58f77731b4e9 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -201,7 +201,7 @@ BOOST_AUTO_TEST_CASE(coins_cache_simulation_test)
                     found_an_entry = true;
                 }
             }
-            BOOST_FOREACH(const CCoinsViewCacheTest *test, stack) {
+            for (const CCoinsViewCacheTest *test : stack) {
                 test->SelfTest();
             }
         }
diff --git a/src/test/getarg_tests.cpp b/src/test/getarg_tests.cpp
index b9ce280d047b..28bec6374a29 100644
--- a/src/test/getarg_tests.cpp
+++ b/src/test/getarg_tests.cpp
@@ -25,7 +25,7 @@ static void ResetArgs(const std::string& strArg)
 
     // Convert to char*:
     std::vector<const char*> vecChar;
-    BOOST_FOREACH(std::string& s, vecArg)
+    for (std::string& s : vecArg)
         vecChar.push_back(s.c_str());
 
     gArgs.ParseParameters(vecChar.size(), &vecChar[0]);
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index 3f860cffdaec..dcab00ca5a95 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -279,7 +279,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     {
         tx.vout[0].nValue -= LOWFEE;
         hash = tx.GetHash();
-        bool spendsCoinbase = (i == 0) ? true : false; // only first tx spends coinbase
+        bool spendsCoinbase = i == 0; // only first tx spends coinbase
         // If we don't set the # of sig ops in the CTxMemPoolEntry, template creation fails
         mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(spendsCoinbase).FromTx(tx));
         tx.vin[0].prevout.hash = hash;
@@ -293,7 +293,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     {
         tx.vout[0].nValue -= LOWFEE;
         hash = tx.GetHash();
-        bool spendsCoinbase = (i == 0) ? true : false; // only first tx spends coinbase
+        bool spendsCoinbase = i == 0; // only first tx spends coinbase
         // If we do set the # of sig ops in the CTxMemPoolEntry, template creation passes
         mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(spendsCoinbase).SigOps(20).FromTx(tx));
         tx.vin[0].prevout.hash = hash;
@@ -314,7 +314,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     {
         tx.vout[0].nValue -= LOWFEE;
         hash = tx.GetHash();
-        bool spendsCoinbase = (i == 0) ? true : false; // only first tx spends coinbase
+        bool spendsCoinbase = i == 0; // only first tx spends coinbase
         mempool.addUnchecked(hash, entry.Fee(LOWFEE).Time(GetTime()).SpendsCoinbase(spendsCoinbase).FromTx(tx));
         tx.vin[0].prevout.hash = hash;
     }
diff --git a/src/test/multisig_tests.cpp b/src/test/multisig_tests.cpp
index 2c2f76323813..d1dc6ed8058b 100644
--- a/src/test/multisig_tests.cpp
+++ b/src/test/multisig_tests.cpp
@@ -28,7 +28,7 @@ sign_multisig(CScript scriptPubKey, std::vector<CKey> keys, CTransaction transac
 
     CScript result;
     result << OP_0; // CHECKMULTISIG bug workaround
-    BOOST_FOREACH(const CKey &key, keys)
+    for (const CKey &key : keys)
     {
         std::vector<unsigned char> vchSig;
         BOOST_CHECK(key.Sign(hash, vchSig));
diff --git a/src/test/prevector_tests.cpp b/src/test/prevector_tests.cpp
index 2c36f12389ee..01308cbbb312 100644
--- a/src/test/prevector_tests.cpp
+++ b/src/test/prevector_tests.cpp
@@ -53,13 +53,13 @@ class prevector_tester {
         local_check(pretype(real_vector.begin(), real_vector.end()) == pre_vector);
         local_check(pretype(pre_vector.begin(), pre_vector.end()) == pre_vector);
         size_t pos = 0;
-        BOOST_FOREACH(const T& v, pre_vector) {
+        for (const T& v : pre_vector) {
              local_check(v == real_vector[pos++]);
         }
         BOOST_REVERSE_FOREACH(const T& v, pre_vector) {
              local_check(v == real_vector[--pos]);
         }
-        BOOST_FOREACH(const T& v, const_pre_vector) {
+        for (const T& v : const_pre_vector) {
              local_check(v == real_vector[pos++]);
         }
         BOOST_REVERSE_FOREACH(const T& v, const_pre_vector) {
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 13a996499be1..623dbf0efa20 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -676,7 +676,7 @@ BOOST_AUTO_TEST_CASE(script_build)
 
     std::string strGen;
 
-    BOOST_FOREACH(TestBuilder& test, tests) {
+    for (TestBuilder& test : tests) {
         test.Test();
         std::string str = JSONPrettyPrint(test.GetJSON());
 #ifndef UPDATE_JSON_TESTS
@@ -769,7 +769,7 @@ sign_multisig(CScript scriptPubKey, std::vector<CKey> keys, CTransaction transac
     // and vice-versa)
     //
     result << OP_0;
-    BOOST_FOREACH(const CKey &key, keys)
+    for (const CKey &key : keys)
     {
         std::vector<unsigned char> vchSig;
         BOOST_CHECK(key.Sign(hash, vchSig));
diff --git a/src/test/test_dash.cpp b/src/test/test_dash.cpp
index a99b6ac498fb..a440feee6cef 100644
--- a/src/test/test_dash.cpp
+++ b/src/test/test_dash.cpp
@@ -38,6 +38,7 @@ extern void noui_connect();
 
 BasicTestingSetup::BasicTestingSetup(const std::string& chainName)
 {
+        RandomInit();
         ECC_Start();
         BLSInit();
         SetupEnvironment();
@@ -159,7 +160,7 @@ CBlock TestChainSetup::CreateBlock(const std::vector<CMutableTransaction>& txns,
     block.vtx.resize(1);
     // Re-add quorum commitments
     block.vtx.insert(block.vtx.end(), llmqCommitments.begin(), llmqCommitments.end());
-    BOOST_FOREACH(const CMutableTransaction& tx, txns)
+    for (const CMutableTransaction& tx : txns)
         block.vtx.push_back(MakeTransactionRef(tx));
 
     // Manually update CbTx as we modified the block here
diff --git a/src/test/test_dash.h b/src/test/test_dash.h
index c5babca70c91..be3a0c94d8a2 100644
--- a/src/test/test_dash.h
+++ b/src/test/test_dash.h
@@ -34,7 +34,6 @@ static inline uint256 InsecureRand256() { return insecure_rand_ctx.rand256(); }
 static inline uint64_t InsecureRandBits(int bits) { return insecure_rand_ctx.randbits(bits); }
 static inline uint64_t InsecureRandRange(uint64_t range) { return insecure_rand_ctx.randrange(range); }
 static inline bool InsecureRandBool() { return insecure_rand_ctx.randbool(); }
-static inline std::vector<unsigned char> InsecureRandBytes(size_t len) { return insecure_rand_ctx.randbytes(len); }
 
 /** Basic testing setup.
  * This just configures logging and chain parameters.
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index 9681111828e1..dddeacf2d7b6 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -55,7 +55,7 @@ unsigned int ParseScriptFlags(std::string strFlags)
     std::vector<std::string> words;
     boost::algorithm::split(words, strFlags, boost::algorithm::is_any_of(","));
 
-    BOOST_FOREACH(std::string word, words)
+    for (std::string word : words)
     {
         if (!mapFlagNames.count(word))
             BOOST_ERROR("Bad test: unknown verification flag '" << word << "'");
diff --git a/src/timedata.cpp b/src/timedata.cpp
index e5cdd5497dd3..6549ecd53e12 100644
--- a/src/timedata.cpp
+++ b/src/timedata.cpp
@@ -95,7 +95,7 @@ void AddTimeData(const CNetAddr& ip, int64_t nOffsetSample)
             {
                 // If nobody has a time different than ours but within 5 minutes of ours, give a warning
                 bool fMatch = false;
-                BOOST_FOREACH(int64_t nOffset, vSorted)
+                for (int64_t nOffset : vSorted)
                     if (nOffset != 0 && abs64(nOffset) < 5 * 60)
                         fMatch = true;
 
@@ -110,7 +110,7 @@ void AddTimeData(const CNetAddr& ip, int64_t nOffsetSample)
         }
 
         if (LogAcceptCategory(BCLog::NET)) {
-            BOOST_FOREACH(int64_t n, vSorted) {
+            for (int64_t n : vSorted) {
                 LogPrint(BCLog::NET, "%+d  ", n);
             }
             LogPrint(BCLog::NET, "|  ");
diff --git a/src/torcontrol.cpp b/src/torcontrol.cpp
index e2ba2209b1df..3f460ae8c71e 100644
--- a/src/torcontrol.cpp
+++ b/src/torcontrol.cpp
@@ -376,8 +376,10 @@ static std::pair<bool,std::string> ReadBinaryFile(const fs::path &filename, size
     while ((n=fread(buffer, 1, sizeof(buffer), f)) > 0) {
         // Check for reading errors so we don't return any data if we couldn't
         // read the entire file (or up to maxsize)
-        if (ferror(f))
+        if (ferror(f)) {
+            fclose(f);
             return std::make_pair(false,"");
+        }
         retval.append(buffer, buffer+n);
         if (retval.size() > maxsize)
             break;
@@ -486,7 +488,7 @@ void TorController::add_onion_cb(TorControlConnection& _conn, const TorControlRe
 {
     if (reply.code == 250) {
         LogPrint(BCLog::TOR, "tor: ADD_ONION successful\n");
-        BOOST_FOREACH(const std::string &s, reply.lines) {
+        for (const std::string &s : reply.lines) {
             std::map<std::string,std::string> m = ParseTorReplyMapping(s);
             std::map<std::string,std::string>::iterator i;
             if ((i = m.find("ServiceID")) != m.end())
@@ -616,7 +618,7 @@ void TorController::protocolinfo_cb(TorControlConnection& _conn, const TorContro
          * 250-AUTH METHODS=NULL
          * 250-AUTH METHODS=HASHEDPASSWORD
          */
-        BOOST_FOREACH(const std::string &s, reply.lines) {
+        for (const std::string &s : reply.lines) {
             std::pair<std::string,std::string> l = SplitTorReplyLine(s);
             if (l.first == "AUTH") {
                 std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
@@ -633,7 +635,7 @@ void TorController::protocolinfo_cb(TorControlConnection& _conn, const TorContro
                 }
             }
         }
-        BOOST_FOREACH(const std::string &s, methods) {
+        for (const std::string &s : methods) {
             LogPrint(BCLog::TOR, "tor: Supported authentication method: %s\n", s);
         }
         // Prefer NULL, otherwise SAFECOOKIE. If a password is provided, use HASHEDPASSWORD
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 2542091c51d2..e5c8c5664ac3 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -74,12 +74,12 @@ void CTxMemPool::UpdateForDescendants(txiter updateIt, cacheMap &cachedDescendan
         setAllDescendants.insert(cit);
         stageEntries.erase(cit);
         const setEntries &setChildren = GetMemPoolChildren(cit);
-        BOOST_FOREACH(const txiter childEntry, setChildren) {
+        for (const txiter childEntry : setChildren) {
             cacheMap::iterator cacheIt = cachedDescendants.find(childEntry);
             if (cacheIt != cachedDescendants.end()) {
                 // We've already calculated this one, just add the entries for this set
                 // but don't traverse again.
-                BOOST_FOREACH(const txiter cacheEntry, cacheIt->second) {
+                for (const txiter cacheEntry : cacheIt->second) {
                     setAllDescendants.insert(cacheEntry);
                 }
             } else if (!setAllDescendants.count(childEntry)) {
@@ -93,7 +93,7 @@ void CTxMemPool::UpdateForDescendants(txiter updateIt, cacheMap &cachedDescendan
     int64_t modifySize = 0;
     CAmount modifyFee = 0;
     int64_t modifyCount = 0;
-    BOOST_FOREACH(txiter cit, setAllDescendants) {
+    for (txiter cit : setAllDescendants) {
         if (!setExclude.count(cit->GetTx().GetHash())) {
             modifySize += cit->GetTxSize();
             modifyFee += cit->GetModifiedFee();
@@ -203,7 +203,7 @@ bool CTxMemPool::CalculateMemPoolAncestors(const CTxMemPoolEntry &entry, setEntr
         }
 
         const setEntries & setMemPoolParents = GetMemPoolParents(stageit);
-        BOOST_FOREACH(const txiter &phash, setMemPoolParents) {
+        for (const txiter &phash : setMemPoolParents) {
             // If this is a new ancestor, add it.
             if (setAncestors.count(phash) == 0) {
                 parentHashes.insert(phash);
@@ -222,13 +222,13 @@ void CTxMemPool::UpdateAncestorsOf(bool add, txiter it, setEntries &setAncestors
 {
     setEntries parentIters = GetMemPoolParents(it);
     // add or remove this tx as a child of each parent
-    BOOST_FOREACH(txiter piter, parentIters) {
+    for (txiter piter : parentIters) {
         UpdateChild(piter, it, add);
     }
     const int64_t updateCount = (add ? 1 : -1);
     const int64_t updateSize = updateCount * it->GetTxSize();
     const CAmount updateFee = updateCount * it->GetModifiedFee();
-    BOOST_FOREACH(txiter ancestorIt, setAncestors) {
+    for (txiter ancestorIt : setAncestors) {
         mapTx.modify(ancestorIt, update_descendant_state(updateSize, updateFee, updateCount));
     }
 }
@@ -239,7 +239,7 @@ void CTxMemPool::UpdateEntryForAncestors(txiter it, const setEntries &setAncesto
     int64_t updateSize = 0;
     CAmount updateFee = 0;
     int updateSigOps = 0;
-    BOOST_FOREACH(txiter ancestorIt, setAncestors) {
+    for (txiter ancestorIt : setAncestors) {
         updateSize += ancestorIt->GetTxSize();
         updateFee += ancestorIt->GetModifiedFee();
         updateSigOps += ancestorIt->GetSigOpCount();
@@ -250,7 +250,7 @@ void CTxMemPool::UpdateEntryForAncestors(txiter it, const setEntries &setAncesto
 void CTxMemPool::UpdateChildrenForRemoval(txiter it)
 {
     const setEntries &setMemPoolChildren = GetMemPoolChildren(it);
-    BOOST_FOREACH(txiter updateIt, setMemPoolChildren) {
+    for (txiter updateIt : setMemPoolChildren) {
         UpdateParent(updateIt, it, false);
     }
 }
@@ -267,19 +267,19 @@ void CTxMemPool::UpdateForRemoveFromMempool(const setEntries &entriesToRemove, b
         // Here we only update statistics and not data in mapLinks (which
         // we need to preserve until we're finished with all operations that
         // need to traverse the mempool).
-        BOOST_FOREACH(txiter removeIt, entriesToRemove) {
+        for (txiter removeIt : entriesToRemove) {
             setEntries setDescendants;
             CalculateDescendants(removeIt, setDescendants);
             setDescendants.erase(removeIt); // don't update state for self
             int64_t modifySize = -((int64_t)removeIt->GetTxSize());
             CAmount modifyFee = -removeIt->GetModifiedFee();
             int modifySigOps = -removeIt->GetSigOpCount();
-            BOOST_FOREACH(txiter dit, setDescendants) {
+            for (txiter dit : setDescendants) {
                 mapTx.modify(dit, update_ancestor_state(modifySize, modifyFee, -1, modifySigOps));
             }
         }
     }
-    BOOST_FOREACH(txiter removeIt, entriesToRemove) {
+    for (txiter removeIt : entriesToRemove) {
         setEntries setAncestors;
         const CTxMemPoolEntry &entry = *removeIt;
         std::string dummy;
@@ -308,7 +308,7 @@ void CTxMemPool::UpdateForRemoveFromMempool(const setEntries &entriesToRemove, b
     // After updating all the ancestor sizes, we can now sever the link between each
     // transaction being removed and any mempool children (ie, update setMemPoolParents
     // for each direct child of a transaction being removed).
-    BOOST_FOREACH(txiter removeIt, entriesToRemove) {
+    for (txiter removeIt : entriesToRemove) {
         UpdateChildrenForRemoval(removeIt);
     }
 }
@@ -402,7 +402,7 @@ bool CTxMemPool::addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry,
     // to clean up the mess we're leaving here.
 
     // Update ancestors with information about this tx
-    BOOST_FOREACH (const uint256 &phash, setParentTransactions) {
+    for (const uint256 &phash : setParentTransactions) {
         txiter pit = mapTx.find(phash);
         if (pit != mapTx.end()) {
             UpdateParent(newit, pit, true);
@@ -628,7 +628,7 @@ void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason)
 {
     NotifyEntryRemoved(it->GetSharedTx(), reason);
     const uint256 hash = it->GetTx().GetHash();
-    BOOST_FOREACH(const CTxIn& txin, it->GetTx().vin)
+    for (const CTxIn& txin : it->GetTx().vin)
         mapNextTx.erase(txin.prevout);
 
     if (vTxHashes.size() > 1) {
@@ -717,7 +717,7 @@ void CTxMemPool::CalculateDescendants(txiter entryit, setEntries &setDescendants
         stage.erase(it);
 
         const setEntries &setChildren = GetMemPoolChildren(it);
-        BOOST_FOREACH(const txiter &childiter, setChildren) {
+        for (const txiter &childiter : setChildren) {
             if (!setDescendants.count(childiter)) {
                 stage.insert(childiter);
             }
@@ -749,7 +749,7 @@ void CTxMemPool::removeRecursive(const CTransaction &origTx, MemPoolRemovalReaso
             }
         }
         setEntries setAllRemoves;
-        BOOST_FOREACH(txiter it, txToRemove) {
+        for (txiter it : txToRemove) {
             CalculateDescendants(it, setAllRemoves);
         }
 
@@ -771,7 +771,7 @@ void CTxMemPool::removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMem
             // So it's critical that we remove the tx and not depend on the LockPoints.
             txToRemove.insert(it);
         } else if (it->GetSpendsCoinbase()) {
-            BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+            for (const CTxIn& txin : tx.vin) {
                 indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
                 if (it2 != mapTx.end())
                     continue;
@@ -798,7 +798,7 @@ void CTxMemPool::removeConflicts(const CTransaction &tx)
 {
     // Remove transactions which depend on inputs of tx, recursively
     LOCK(cs);
-    BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+    for (const CTxIn &txin : tx.vin) {
         auto it = mapNextTx.find(txin.prevout);
         if (it != mapNextTx.end()) {
             const CTransaction &txConflict = *it->second;
@@ -1035,7 +1035,7 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
         setEntries setParentCheck;
         int64_t parentSizes = 0;
         unsigned int parentSigOpCount = 0;
-        BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+        for (const CTxIn &txin : tx.vin) {
             // Check that every mempool transaction's inputs refer to available coins, or other mempool tx's.
             indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
             if (it2 != mapTx.end()) {
@@ -1067,7 +1067,7 @@ void CTxMemPool::check(const CCoinsViewCache *pcoins) const
         CAmount nFeesCheck = it->GetModifiedFee();
         unsigned int nSigOpCheck = it->GetSigOpCount();
 
-        BOOST_FOREACH(txiter ancestorIt, setAncestors) {
+        for (txiter ancestorIt : setAncestors) {
             nSizeCheck += ancestorIt->GetTxSize();
             nFeesCheck += ancestorIt->GetModifiedFee();
             nSigOpCheck += ancestorIt->GetSigOpCount();
@@ -1329,14 +1329,14 @@ void CTxMemPool::PrioritiseTransaction(const uint256& hash, const CAmount& nFeeD
             uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
             std::string dummy;
             CalculateMemPoolAncestors(*it, setAncestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
-            BOOST_FOREACH(txiter ancestorIt, setAncestors) {
+            for (txiter ancestorIt : setAncestors) {
                 mapTx.modify(ancestorIt, update_descendant_state(0, nFeeDelta, 0));
             }
             // Now update all descendants' modified fees with ancestors
             setEntries setDescendants;
             CalculateDescendants(it, setDescendants);
             setDescendants.erase(it);
-            BOOST_FOREACH(txiter descendantIt, setDescendants) {
+            for (txiter descendantIt : setDescendants) {
                 mapTx.modify(descendantIt, update_ancestor_state(0, nFeeDelta, 0, 0));
             }
             ++nTransactionsUpdated;
@@ -1396,7 +1396,7 @@ size_t CTxMemPool::DynamicMemoryUsage() const {
 void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants, MemPoolRemovalReason reason) {
     AssertLockHeld(cs);
     UpdateForRemoveFromMempool(stage, updateDescendants);
-    BOOST_FOREACH(const txiter& it, stage) {
+    for (const txiter& it : stage) {
         removeUnchecked(it, reason);
     }
 }
@@ -1415,7 +1415,7 @@ int CTxMemPool::Expire(int64_t time) {
         it++;
     }
     setEntries stage;
-    BOOST_FOREACH(txiter removeit, toremove) {
+    for (txiter removeit : toremove) {
         CalculateDescendants(removeit, stage);
     }
     RemoveStaged(stage, false, MemPoolRemovalReason::EXPIRY);
@@ -1524,13 +1524,13 @@ void CTxMemPool::TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpends
         std::vector<CTransaction> txn;
         if (pvNoSpendsRemaining) {
             txn.reserve(stage.size());
-            BOOST_FOREACH(txiter iter, stage)
+            for (txiter iter : stage)
                 txn.push_back(iter->GetTx());
         }
         RemoveStaged(stage, false, MemPoolRemovalReason::SIZELIMIT);
         if (pvNoSpendsRemaining) {
-            BOOST_FOREACH(const CTransaction& tx, txn) {
-                BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+            for (const CTransaction& tx : txn) {
+                for (const CTxIn& txin : tx.vin) {
                     if (exists(txin.prevout.hash)) continue;
                     pvNoSpendsRemaining->push_back(txin.prevout);
                 }
diff --git a/src/txmempool.h b/src/txmempool.h
index 04b6587bd03d..64f032534eaa 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -33,7 +33,6 @@
 
 #include <boost/signals2/signal.hpp>
 
-class CAutoFile;
 class CBlockIndex;
 
 /** Fake height value used in Coin to signify they are only in the memory pool (since 0.8) */
diff --git a/src/ui_interface.h b/src/ui_interface.h
index cb07bc0c867c..bbe25b5caaae 100644
--- a/src/ui_interface.h
+++ b/src/ui_interface.h
@@ -12,9 +12,7 @@
 #include <boost/signals2/last_value.hpp>
 #include <boost/signals2/signal.hpp>
 
-class CBasicKeyStore;
 class CWallet;
-class uint256;
 class CBlockIndex;
 class CDeterministicMNList;
 
diff --git a/src/util.cpp b/src/util.cpp
index 581b1faf48d2..16976cf6c357 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -757,21 +757,21 @@ bool RenameOver(fs::path src, fs::path dest)
 }
 
 /**
- * Ignores exceptions thrown by Boost's create_directory if the requested directory exists.
+ * Ignores exceptions thrown by Boost's create_directories if the requested directory exists.
  * Specifically handles case where path p exists, but it wasn't possible for the user to
  * write to the parent directory.
  */
-bool TryCreateDirectory(const fs::path& p)
+bool TryCreateDirectories(const fs::path& p)
 {
     try
     {
-        return fs::create_directory(p);
+        return fs::create_directories(p);
     } catch (const fs::filesystem_error&) {
         if (!fs::exists(p) || !fs::is_directory(p))
             throw;
     }
 
-    // create_directory didn't create the directory, it had to have existed already
+    // create_directories didn't create the directory, it had to have existed already
     return false;
 }
 
diff --git a/src/util.h b/src/util.h
index a38c010efbc9..034f6205a1c9 100644
--- a/src/util.h
+++ b/src/util.h
@@ -205,7 +205,7 @@ bool TruncateFile(FILE *file, unsigned int length);
 int RaiseFileDescriptorLimit(int nMinFD);
 void AllocateFileRange(FILE *file, unsigned int offset, unsigned int length);
 bool RenameOver(fs::path src, fs::path dest);
-bool TryCreateDirectory(const fs::path& p);
+bool TryCreateDirectories(const fs::path& p);
 fs::path GetDefaultDataDir();
 const fs::path &GetDataDir(bool fNetSpecific = true);
 fs::path GetBackupsDir();
@@ -241,64 +241,65 @@ class ArgsManager
     void ParseParameters(int argc, const char*const argv[]);
     void ReadConfigFile(const std::string& confPath);
     std::vector<std::string> GetArgs(const std::string& strArg);
-/**
- * Return true if the given argument has been manually set
- *
- * @param strArg Argument to get (e.g. "-foo")
- * @return true if the argument has been set
- */
-bool IsArgSet(const std::string& strArg);
-
-/**
- * Return string argument or default value
- *
- * @param strArg Argument to get (e.g. "-foo")
- * @param default (e.g. "1")
- * @return command-line argument or default value
- */
-std::string GetArg(const std::string& strArg, const std::string& strDefault);
-
-/**
- * Return integer argument or default value
- *
- * @param strArg Argument to get (e.g. "-foo")
- * @param default (e.g. 1)
- * @return command-line argument (0 if invalid number) or default value
- */
-int64_t GetArg(const std::string& strArg, int64_t nDefault);
-
-/**
- * Return boolean argument or default value
- *
- * @param strArg Argument to get (e.g. "-foo")
- * @param default (true or false)
- * @return command-line argument or default value
- */
-bool GetBoolArg(const std::string& strArg, bool fDefault);
-
-/**
- * Set an argument if it doesn't already have a value
- *
- * @param strArg Argument to set (e.g. "-foo")
- * @param strValue Value (e.g. "1")
- * @return true if argument gets set, false if it already had a value
- */
-bool SoftSetArg(const std::string& strArg, const std::string& strValue);
-
-/**
- * Set a boolean argument if it doesn't already have a value
- *
- * @param strArg Argument to set (e.g. "-foo")
- * @param fValue Value (e.g. false)
- * @return true if argument gets set, false if it already had a value
- */
-bool SoftSetBoolArg(const std::string& strArg, bool fValue);
 
-// Forces an arg setting. Called by SoftSetArg() if the arg hasn't already
-// been set. Also called directly in testing.
-void ForceSetArg(const std::string& strArg, const std::string& strValue);
-void ForceSetMultiArgs(const std::string& strArg, const std::vector<std::string>& values);
-void ForceRemoveArg(const std::string& strArg);
+    /**
+     * Return true if the given argument has been manually set
+     *
+     * @param strArg Argument to get (e.g. "-foo")
+     * @return true if the argument has been set
+     */
+    bool IsArgSet(const std::string& strArg);
+
+    /**
+     * Return string argument or default value
+     *
+     * @param strArg Argument to get (e.g. "-foo")
+     * @param default (e.g. "1")
+     * @return command-line argument or default value
+     */
+    std::string GetArg(const std::string& strArg, const std::string& strDefault);
+
+    /**
+     * Return integer argument or default value
+     *
+     * @param strArg Argument to get (e.g. "-foo")
+     * @param default (e.g. 1)
+     * @return command-line argument (0 if invalid number) or default value
+     */
+    int64_t GetArg(const std::string& strArg, int64_t nDefault);
+
+    /**
+     * Return boolean argument or default value
+     *
+     * @param strArg Argument to get (e.g. "-foo")
+     * @param default (true or false)
+     * @return command-line argument or default value
+     */
+    bool GetBoolArg(const std::string& strArg, bool fDefault);
+
+    /**
+     * Set an argument if it doesn't already have a value
+     *
+     * @param strArg Argument to set (e.g. "-foo")
+     * @param strValue Value (e.g. "1")
+     * @return true if argument gets set, false if it already had a value
+     */
+    bool SoftSetArg(const std::string& strArg, const std::string& strValue);
+
+    /**
+     * Set a boolean argument if it doesn't already have a value
+     *
+     * @param strArg Argument to set (e.g. "-foo")
+     * @param fValue Value (e.g. false)
+     * @return true if argument gets set, false if it already had a value
+     */
+    bool SoftSetBoolArg(const std::string& strArg, bool fValue);
+
+    // Forces an arg setting. Called by SoftSetArg() if the arg hasn't already
+    // been set. Also called directly in testing.
+    void ForceSetArg(const std::string& strArg, const std::string& strValue);
+    void ForceSetMultiArgs(const std::string& strArg, const std::vector<std::string>& values);
+    void ForceRemoveArg(const std::string& strArg);
 };
 
 extern ArgsManager gArgs;
diff --git a/src/utilstrencodings.h b/src/utilstrencodings.h
index e4b6d6cf7cb1..a35cea289caf 100644
--- a/src/utilstrencodings.h
+++ b/src/utilstrencodings.h
@@ -19,9 +19,6 @@
 #define UEND(a)             ((unsigned char*)&((&(a))[1]))
 #define ARRAYLEN(array)     (sizeof(array)/sizeof((array)[0]))
 
-/** This is needed because the foreach macro can't get over the comma in pair<t1, t2> */
-#define PAIRTYPE(t1, t2)    std::pair<t1, t2>
-
 /** Used by SanitizeString() */
 enum SafeChars
 {
diff --git a/src/validation.cpp b/src/validation.cpp
index 969d242119b6..6f96fb56894e 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -177,7 +177,7 @@ namespace {
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
 {
     // Find the first block the caller has in the main chain
-    BOOST_FOREACH(const uint256& hash, locator.vHave) {
+    for (const uint256& hash : locator.vHave) {
         BlockMap::iterator mi = mapBlockIndex.find(hash);
         if (mi != mapBlockIndex.end())
         {
@@ -411,7 +411,7 @@ bool CheckSequenceLocks(const CTransaction &tx, int flags, LockPoints* lp, bool
             // lock on a mempool input, so we can use the return value of
             // CheckSequenceLocks to indicate the LockPoints validity
             int maxInputHeight = 0;
-            BOOST_FOREACH(int height, prevheights) {
+            for (int height : prevheights) {
                 // Can ignore mempool inputs since we'll fail if they had non-zero locks
                 if (height != tip->nHeight+1) {
                     maxInputHeight = std::max(maxInputHeight, height);
@@ -579,7 +579,7 @@ static void LimitMempoolSize(CTxMemPool& pool, size_t limit, unsigned long age)
 
     std::vector<COutPoint> vNoSpendsRemaining;
     pool.TrimToSize(limit, &vNoSpendsRemaining);
-    BOOST_FOREACH(const COutPoint& removed, vNoSpendsRemaining)
+    for (const COutPoint& removed : vNoSpendsRemaining)
         pcoinsTip->Uncache(removed);
 }
 
@@ -691,8 +691,9 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         return state.DoS(0, false, REJECT_NONSTANDARD, "non-final");
 
     // is it already in the memory pool?
-    if (pool.exists(hash))
-        return state.Invalid(false, REJECT_ALREADY_KNOWN, "txn-already-in-mempool");
+    if (pool.exists(hash)) {
+        return state.Invalid(false, REJECT_DUPLICATE, "txn-already-in-mempool");
+    }
 
     llmq::CInstantSendLockPtr conflictLock = llmq::quorumInstantSendManager->GetConflictingLock(tx);
     if (conflictLock) {
@@ -709,7 +710,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
     // Check for conflicts with in-memory transactions
     {
     LOCK(pool.cs); // protect pool.mapNextTx
-    BOOST_FOREACH(const CTxIn &txin, tx.vin)
+    for (const CTxIn &txin : tx.vin)
     {
         auto itConflicting = pool.mapNextTx.find(txin.prevout);
         if (itConflicting != pool.mapNextTx.end())
@@ -717,7 +718,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
             const CTransaction *ptxConflicting = itConflicting->second;
 
             // Transaction conflicts with mempool and RBF doesn't exist in Dash
-            return state.Invalid(false, REJECT_CONFLICT, "txn-mempool-conflict");
+            return state.Invalid(false, REJECT_DUPLICATE, "txn-mempool-conflict");
         }
     }
     }
@@ -741,12 +742,12 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
                 if (!had_coin_in_cache) {
                     coins_to_uncache.push_back(outpoint);
                 }
-                return state.Invalid(false, REJECT_ALREADY_KNOWN, "txn-already-known");
+                return state.Invalid(false, REJECT_DUPLICATE, "txn-already-known");
             }
         }
 
         // do all inputs exist?
-        BOOST_FOREACH(const CTxIn txin, tx.vin) {
+        for (const CTxIn txin : tx.vin) {
             if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
                 coins_to_uncache.push_back(txin.prevout);
             }
@@ -791,7 +792,7 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
         // Keep track of transactions that spend a coinbase, which we re-scan
         // during reorgs to ensure COINBASE_MATURITY is still met.
         bool fSpendsCoinbase = false;
-        BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+        for (const CTxIn &txin : tx.vin) {
             const Coin &coin = view.AccessCoin(txin.prevout);
             if (coin.IsCoinBase()) {
                 fSpendsCoinbase = true;
@@ -913,7 +914,7 @@ static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPo
     bool res = AcceptToMemoryPoolWorker(chainparams, pool, state, tx, fLimitFree, pfMissingInputs, nAcceptTime, fOverrideMempoolLimit, nAbsurdFee, coins_to_uncache, fDryRun);
     if (!res || fDryRun) {
         if(!res) LogPrint(BCLog::MEMPOOL, "%s: %s %s (%s)\n", __func__, tx->GetHash().ToString(), state.GetRejectReason(), state.GetDebugMessage());
-        BOOST_FOREACH(const COutPoint& hashTx, coins_to_uncache)
+        for (const COutPoint& hashTx : coins_to_uncache)
             pcoinsTip->Uncache(hashTx);
     }
     // After we've (potentially) uncached entries, ensure our coins cache is still within its size limits
@@ -1355,7 +1356,7 @@ void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, CTxUndo &txund
     // mark inputs spent
     if (!tx.IsCoinBase()) {
         txundo.vprevout.reserve(tx.vin.size());
-        BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+        for (const CTxIn &txin : tx.vin) {
             txundo.vprevout.emplace_back();
             bool is_spent = inputs.SpendCoin(txin.prevout, &txundo.vprevout.back());
             assert(is_spent);
@@ -3710,7 +3711,7 @@ bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams,
 static uint64_t CalculateCurrentUsage()
 {
     uint64_t retval = 0;
-    BOOST_FOREACH(const CBlockFileInfo &file, vinfoBlockFile) {
+    for (const CBlockFileInfo &file : vinfoBlockFile) {
         retval += file.nSize + file.nUndoSize;
     }
     return retval;
@@ -3929,7 +3930,7 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
     // Calculate nChainWork
     std::vector<std::pair<int, CBlockIndex*> > vSortedByHeight;
     vSortedByHeight.reserve(mapBlockIndex.size());
-    BOOST_FOREACH(const PAIRTYPE(uint256, CBlockIndex*)& item, mapBlockIndex)
+    for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
     {
         CBlockIndex* pindex = item.second;
         vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
@@ -3940,7 +3941,7 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
         }
     }
     sort(vSortedByHeight.begin(), vSortedByHeight.end());
-    BOOST_FOREACH(const PAIRTYPE(int, CBlockIndex*)& item, vSortedByHeight)
+    for (const std::pair<int, CBlockIndex*>& item : vSortedByHeight)
     {
         CBlockIndex* pindex = item.second;
         pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) + GetBlockProof(*pindex);
@@ -3989,7 +3990,7 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
     // Check presence of blk files
     LogPrintf("Checking all blk files are present...\n");
     std::set<int> setBlkDataFiles;
-    BOOST_FOREACH(const PAIRTYPE(uint256, CBlockIndex*)& item, mapBlockIndex)
+    for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
     {
         CBlockIndex* pindex = item.second;
         if (pindex->nStatus & BLOCK_HAVE_DATA) {
@@ -4176,7 +4177,7 @@ void UnloadBlockIndex()
         warningcache[b].clear();
     }
 
-    BOOST_FOREACH(BlockMap::value_type& entry, mapBlockIndex) {
+    for (BlockMap::value_type& entry : mapBlockIndex) {
         delete entry.second;
     }
     mapBlockIndex.clear();
diff --git a/src/validation.h b/src/validation.h
index ade1a3cd3fc9..db4da5a7ed66 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -34,7 +34,6 @@
 
 class CBlockIndex;
 class CBlockTreeDB;
-class CBloomFilter;
 class CChainParams;
 class CCoinsViewDB;
 class CInv;
@@ -42,7 +41,6 @@ class CConnman;
 class CScriptCheck;
 class CBlockPolicyEstimator;
 class CTxMemPool;
-class CValidationInterface;
 class CValidationState;
 class PrecomputedTransactionData;
 struct ChainTxData;
@@ -524,10 +522,6 @@ bool GetBlockHash(uint256& hashRet, int nBlockHeight = -1);
 static const unsigned int REJECT_INTERNAL = 0x100;
 /** Too high fee. Can not be triggered by P2P transactions */
 static const unsigned int REJECT_HIGHFEE = 0x100;
-/** Transaction is already known (either in mempool or blockchain) */
-static const unsigned int REJECT_ALREADY_KNOWN = 0x101;
-/** Transaction conflicts with a transaction already known */
-static const unsigned int REJECT_CONFLICT = 0x102;
 
 /** Get block file info entry for one block file */
 CBlockFileInfo* GetBlockFileInfo(size_t n);
diff --git a/src/wallet/crypter.cpp b/src/wallet/crypter.cpp
index 3e50059e6dd3..1f54d7430444 100644
--- a/src/wallet/crypter.cpp
+++ b/src/wallet/crypter.cpp
@@ -348,7 +348,7 @@ bool CCryptoKeyStore::EncryptKeys(CKeyingMaterial& vMasterKeyIn)
             return false;
 
         fUseCrypto = true;
-        BOOST_FOREACH(KeyMap::value_type& mKey, mapKeys)
+        for (KeyMap::value_type& mKey : mapKeys)
         {
             const CKey &key = mKey.second;
             CPubKey vchPubKey = key.GetPubKey();
diff --git a/src/wallet/crypter.h b/src/wallet/crypter.h
index 1b5cdbcffcb8..d8012537db1d 100644
--- a/src/wallet/crypter.h
+++ b/src/wallet/crypter.h
@@ -9,8 +9,6 @@
 #include "serialize.h"
 #include "support/allocators/secure.h"
 
-class uint256;
-
 const unsigned int WALLET_CRYPTO_KEY_SIZE = 32;
 const unsigned int WALLET_CRYPTO_SALT_SIZE = 8;
 const unsigned int WALLET_CRYPTO_IV_SIZE = 16;
diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index 67f9f223f01d..1ccae839253e 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -74,7 +74,7 @@ bool CDBEnv::Open(const fs::path& pathIn)
 
     strPath = pathIn.string();
     fs::path pathLogDir = pathIn / "database";
-    TryCreateDirectory(pathLogDir);
+    TryCreateDirectories(pathLogDir);
     fs::path pathErrorFile = pathIn / "db.log";
     LogPrintf("CDBEnv::Open: LogDir=%s ErrorFile=%s\n", pathLogDir.string(), pathErrorFile.string());
 
@@ -204,7 +204,7 @@ bool CDB::Recover(const std::string& filename, void *callbackDataIn, bool (*reco
     }
 
     DbTxn* ptxn = bitdb.TxnBegin();
-    BOOST_FOREACH(CDBEnv::KeyValPair& row, salvagedData)
+    for (CDBEnv::KeyValPair& row : salvagedData)
     {
         if (recoverKVcallback)
         {
diff --git a/src/wallet/db.h b/src/wallet/db.h
index e4d8a5154d13..d5ff62d18790 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -13,6 +13,7 @@
 #include "sync.h"
 #include "version.h"
 
+#include <atomic>
 #include <map>
 #include <string>
 #include <vector>
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 8b5ccb97cd1e..05af581dc032 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -48,7 +48,7 @@ int64_t static DecodeDumpTime(const std::string &str) {
 
 std::string static EncodeDumpString(const std::string &str) {
     std::stringstream ret;
-    BOOST_FOREACH(unsigned char c, str) {
+    for (unsigned char c : str) {
         if (c <= 32 || c >= 128 || c == '%') {
             ret << '%' << HexStr(&c, &c + 1);
         } else {
@@ -1311,7 +1311,7 @@ UniValue importmulti(const JSONRPCRequest& mainRequest)
 
     UniValue response(UniValue::VARR);
 
-    BOOST_FOREACH (const UniValue& data, requests.getValues()) {
+    for (const UniValue& data : requests.getValues()) {
         const int64_t timestamp = std::max(GetImportTimestamp(data, now), minimumTimestamp);
         const UniValue result = ProcessImport(pwallet, data, timestamp);
         response.push_back(result);
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 39a8267c81e0..9b9b31fc93ae 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -86,13 +86,13 @@ void WalletTxToJSON(const CWalletTx& wtx, UniValue& entry)
     uint256 hash = wtx.GetHash();
     entry.push_back(Pair("txid", hash.GetHex()));
     UniValue conflicts(UniValue::VARR);
-    BOOST_FOREACH(const uint256& conflict, wtx.GetConflicts())
+    for (const uint256& conflict : wtx.GetConflicts())
         conflicts.push_back(conflict.GetHex());
     entry.push_back(Pair("walletconflicts", conflicts));
     entry.push_back(Pair("time", wtx.GetTxTime()));
     entry.push_back(Pair("timereceived", (int64_t)wtx.nTimeReceived));
 
-    BOOST_FOREACH(const PAIRTYPE(std::string, std::string)& item, wtx.mapValue)
+    for (const std::pair<std::string, std::string>& item : wtx.mapValue)
         entry.push_back(Pair(item.first, item.second));
 }
 
@@ -503,7 +503,7 @@ UniValue listaddressgroupings(const JSONRPCRequest& request)
     std::map<CTxDestination, CAmount> balances = pwallet->GetAddressBalances();
     for (std::set<CTxDestination> grouping : pwallet->GetAddressGroupings()) {
         UniValue jsonGrouping(UniValue::VARR);
-        BOOST_FOREACH(CTxDestination address, grouping)
+        for (CTxDestination address : grouping)
         {
             UniValue addressInfo(UniValue::VARR);
             addressInfo.push_back(CBitcoinAddress(address).ToString());
@@ -673,7 +673,7 @@ UniValue getreceivedbyaddress(const JSONRPCRequest& request)
         if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
             if (txout.scriptPubKey == scriptPubKey)
                 if ((wtx.GetDepthInMainChain() >= nMinDepth) || (fAddLocked && wtx.IsLockedByInstantSend()))
                     nAmount += txout.nValue;
@@ -730,7 +730,7 @@ UniValue getreceivedbyaccount(const JSONRPCRequest& request)
         if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
         {
             CTxDestination address;
             if (ExtractDestination(txout.scriptPubKey, address) && IsMine(*pwallet, address) && setAddress.count(address)) {
@@ -1004,7 +1004,7 @@ UniValue sendmany(const JSONRPCRequest& request)
 
     CAmount totalAmount = 0;
     std::vector<std::string> keys = sendTo.getKeys();
-    BOOST_FOREACH(const std::string& name_, keys)
+    for (const std::string& name_ : keys)
     {
         CBitcoinAddress address(name_);
         if (!address.IsValid())
@@ -1158,7 +1158,7 @@ UniValue ListReceived(CWallet * const pwallet, const UniValue& params, bool fByA
         if ((nDepth < nMinDepth) && !(fAddLocked && wtx.IsLockedByInstantSend()))
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
+        for (const CTxOut& txout : wtx.tx->vout)
         {
             CTxDestination address;
             if (!ExtractDestination(txout.scriptPubKey, address))
@@ -1222,7 +1222,7 @@ UniValue ListReceived(CWallet * const pwallet, const UniValue& params, bool fByA
             UniValue transactions(UniValue::VARR);
             if (it != mapTally.end())
             {
-                BOOST_FOREACH(const uint256& _item, (*it).second.txids)
+                for (const uint256& _item : (*it).second.txids)
                 {
                     transactions.push_back(_item.GetHex());
                 }
@@ -1360,7 +1360,7 @@ void ListTransactions(CWallet * const pwallet, const CWalletTx& wtx, const std::
     // Sent
     if ((!listSent.empty() || nFee != 0) && (fAllAccounts || strAccount == strSentAccount))
     {
-        BOOST_FOREACH(const COutputEntry& s, listSent)
+        for (const COutputEntry& s : listSent)
         {
             UniValue entry(UniValue::VOBJ);
             if (involvesWatchonly || (::IsMine(*pwallet, s.destination) & ISMINE_WATCH_ONLY)) {
@@ -1386,7 +1386,7 @@ void ListTransactions(CWallet * const pwallet, const CWalletTx& wtx, const std::
     // Received
     if (listReceived.size() > 0 && ((wtx.GetDepthInMainChain() >= nMinDepth) || wtx.IsLockedByInstantSend()))
     {
-        BOOST_FOREACH(const COutputEntry& r, listReceived)
+        for (const COutputEntry& r : listReceived)
         {
             std::string account;
             if (pwallet->mapAddressBook.count(r.destination)) {
@@ -1634,11 +1634,11 @@ UniValue listaccounts(const JSONRPCRequest& request)
             continue;
         wtx.GetAmounts(listReceived, listSent, nFee, strSentAccount, includeWatchonly);
         mapAccountBalances[strSentAccount] -= nFee;
-        BOOST_FOREACH(const COutputEntry& s, listSent)
+        for (const COutputEntry& s : listSent)
             mapAccountBalances[strSentAccount] -= s.amount;
         if ((nDepth >= nMinDepth) || (fAddLocked && wtx.IsLockedByInstantSend()))
         {
-            BOOST_FOREACH(const COutputEntry& r, listReceived)
+            for (const COutputEntry& r : listReceived)
                 if (pwallet->mapAddressBook.count(r.destination)) {
                     mapAccountBalances[pwallet->mapAddressBook[r.destination].name] += r.amount;
                 }
@@ -1648,11 +1648,11 @@ UniValue listaccounts(const JSONRPCRequest& request)
     }
 
     const std::list<CAccountingEntry> & acentries = pwallet->laccentries;
-    BOOST_FOREACH(const CAccountingEntry& entry, acentries)
+    for (const CAccountingEntry& entry : acentries)
         mapAccountBalances[entry.strAccount] += entry.nCreditDebit;
 
     UniValue ret(UniValue::VOBJ);
-    BOOST_FOREACH(const PAIRTYPE(std::string, CAmount)& accountBalance, mapAccountBalances) {
+    for (const std::pair<std::string, CAmount>& accountBalance : mapAccountBalances) {
         ret.push_back(Pair(accountBalance.first, ValueFromAmount(accountBalance.second)));
     }
     return ret;
@@ -2327,7 +2327,7 @@ UniValue listlockunspent(const JSONRPCRequest& request)
 
     UniValue ret(UniValue::VARR);
 
-    BOOST_FOREACH(COutPoint &outpt, vOutpts) {
+    for (COutPoint &outpt : vOutpts) {
         UniValue o(UniValue::VOBJ);
 
         o.push_back(Pair("txid", outpt.hash.GetHex()));
@@ -2583,7 +2583,7 @@ UniValue resendwallettransactions(const JSONRPCRequest& request)
 
     std::vector<uint256> txids = pwallet->ResendWalletTransactionsBefore(GetTime(), g_connman.get());
     UniValue result(UniValue::VARR);
-    BOOST_FOREACH(const uint256& txid, txids)
+    for (const uint256& txid : txids)
     {
         result.push_back(txid.ToString());
     }
@@ -2709,7 +2709,7 @@ UniValue listunspent(const JSONRPCRequest& request)
     LOCK2(cs_main, pwallet->cs_wallet);
 
     pwallet->AvailableCoins(vecOutputs, !include_unsafe, NULL, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount, nMinDepth, nMaxDepth);
-    BOOST_FOREACH(const COutput& out, vecOutputs) {
+    for (const COutput& out : vecOutputs) {
         CTxDestination address;
         const CScript& scriptPubKey = out.tx->tx->vout[out.i].scriptPubKey;
         bool fValidAddress = ExtractDestination(scriptPubKey, address);
diff --git a/src/wallet/test/accounting_tests.cpp b/src/wallet/test/accounting_tests.cpp
index eb14d176bd70..927aa980c198 100644
--- a/src/wallet/test/accounting_tests.cpp
+++ b/src/wallet/test/accounting_tests.cpp
@@ -23,7 +23,7 @@ GetResults(std::map<CAmount, CAccountingEntry>& results)
     results.clear();
     BOOST_CHECK(pwalletMain->ReorderTransactions() == DB_LOAD_OK);
     pwalletMain->ListAccountCreditDebit("", aes);
-    BOOST_FOREACH(CAccountingEntry& ae, aes)
+    for (CAccountingEntry& ae : aes)
     {
         results[ae.nOrderPos] = ae;
     }
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 976d55f7b5c0..9c613ff9fd05 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -436,7 +436,7 @@ bool CWallet::Unlock(const SecureString& strWalletPassphrase, bool fForMixingOnl
 
     {
         LOCK(cs_wallet);
-        BOOST_FOREACH(const MasterKeyMap::value_type& pMasterKey, mapMasterKeys)
+        for (const MasterKeyMap::value_type& pMasterKey : mapMasterKeys)
         {
             if (!crypter.SetKeyFromPassphrase(strWalletPassphraseFinal, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod))
                 return false;
@@ -481,7 +481,7 @@ bool CWallet::ChangeWalletPassphrase(const SecureString& strOldWalletPassphrase,
 
         CCrypter crypter;
         CKeyingMaterial _vMasterKey;
-        BOOST_FOREACH(MasterKeyMap::value_type& pMasterKey, mapMasterKeys)
+        for (MasterKeyMap::value_type& pMasterKey : mapMasterKeys)
         {
             if(!crypter.SetKeyFromPassphrase(strOldWalletPassphraseFinal, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod))
                 return false;
@@ -585,7 +585,7 @@ std::set<uint256> CWallet::GetConflicts(const uint256& txid) const
 
     std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range;
 
-    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+    for (const CTxIn& txin : wtx.tx->vin)
     {
         if (mapTxSpends.count(txin.prevout) <= 1)
             continue;  // No conflict if zero or one spends
@@ -711,7 +711,7 @@ void CWallet::AddToSpends(const uint256& wtxid)
     if (thisTx.IsCoinBase()) // Coinbases don't spend anything!
         return;
 
-    BOOST_FOREACH(const CTxIn& txin, thisTx.tx->vin)
+    for (const CTxIn& txin : thisTx.tx->vin)
         AddToSpends(txin.prevout, wtxid);
 }
 
@@ -858,7 +858,7 @@ DBErrors CWallet::ReorderTransactions()
     }
     std::list<CAccountingEntry> acentries;
     walletdb.ListAccountCreditDebit("", acentries);
-    BOOST_FOREACH(CAccountingEntry& entry, acentries)
+    for (CAccountingEntry& entry : acentries)
     {
         txByTime.insert(std::make_pair(entry.nTime, TxPair((CWalletTx*)0, &entry)));
     }
@@ -888,7 +888,7 @@ DBErrors CWallet::ReorderTransactions()
         else
         {
             int64_t nOrderPosOff = 0;
-            BOOST_FOREACH(const int64_t& nOffsetStart, nOrderPosOffsets)
+            for (const int64_t& nOffsetStart : nOrderPosOffsets)
             {
                 if (nOrderPos >= nOffsetStart)
                     ++nOrderPosOff;
@@ -977,7 +977,7 @@ bool CWallet::GetAccountPubkey(CPubKey &pubKey, std::string strAccount, bool bFo
             for (std::map<uint256, CWalletTx>::iterator it = mapWallet.begin();
                  it != mapWallet.end() && account.vchPubKey.IsValid();
                  ++it)
-                BOOST_FOREACH(const CTxOut& txout, (*it).second.tx->vout)
+                for (const CTxOut& txout : (*it).second.tx->vout)
                     if (txout.scriptPubKey == scriptPubKey) {
                         bForceNew = true;
                         break;
@@ -1003,7 +1003,7 @@ void CWallet::MarkDirty()
 {
     {
         LOCK(cs_wallet);
-        BOOST_FOREACH(PAIRTYPE(const uint256, CWalletTx)& item, mapWallet)
+        for (std::pair<const uint256, CWalletTx>& item : mapWallet)
             item.second.MarkDirty();
     }
 
@@ -1108,7 +1108,7 @@ bool CWallet::LoadToWallet(const CWalletTx& wtxIn)
     wtx.BindWallet(this);
     wtxOrdered.insert(std::make_pair(wtx.nOrderPos, TxPair(&wtx, (CAccountingEntry*)0)));
     AddToSpends(hash);
-    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin) {
+    for (const CTxIn& txin : wtx.tx->vin) {
         if (mapWallet.count(txin.prevout.hash)) {
             CWalletTx& prevtx = mapWallet[txin.prevout.hash];
             if (prevtx.nIndex == -1 && !prevtx.hashUnset()) {
@@ -1140,7 +1140,7 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const CBlockI
         AssertLockHeld(cs_wallet);
 
         if (pIndex != NULL) {
-            BOOST_FOREACH(const CTxIn& txin, tx.vin) {
+            for (const CTxIn& txin : tx.vin) {
                 std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(txin.prevout);
                 while (range.first != range.second) {
                     if (range.first->second != tx.GetHash()) {
@@ -1214,7 +1214,7 @@ bool CWallet::AbandonTransaction(const uint256& hashTx)
             }
             // If a transaction changes 'conflicted' state, that changes the balance
             // available of the outputs it spends. So force those to be recomputed
-            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+            for (const CTxIn& txin : wtx.tx->vin)
             {
                 if (mapWallet.count(txin.prevout.hash))
                     mapWallet[txin.prevout.hash].MarkDirty();
@@ -1278,7 +1278,7 @@ void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
             }
             // If a transaction changes 'conflicted' state, that changes the balance
             // available of the outputs it spends. So force those to be recomputed
-            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+            for (const CTxIn& txin : wtx.tx->vin)
             {
                 if (mapWallet.count(txin.prevout.hash))
                     mapWallet[txin.prevout.hash].MarkDirty();
@@ -1299,7 +1299,7 @@ void CWallet::SyncTransaction(const CTransactionRef& ptx, const CBlockIndex *pin
     // If a transaction changes 'conflicted' state, that changes the balance
     // available of the outputs it spends. So force those to be
     // recomputed, also:
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         if (mapWallet.count(txin.prevout.hash))
             mapWallet[txin.prevout.hash].MarkDirty();
@@ -1649,7 +1649,7 @@ bool CWallet::IsHDEnabled() const
 
 bool CWallet::IsMine(const CTransaction& tx) const
 {
-    BOOST_FOREACH(const CTxOut& txout, tx.vout)
+    for (const CTxOut& txout : tx.vout)
         if (IsMine(txout))
             return true;
     return false;
@@ -1663,7 +1663,7 @@ bool CWallet::IsFromMe(const CTransaction& tx) const
 CAmount CWallet::GetDebit(const CTransaction& tx, const isminefilter& filter) const
 {
     CAmount nDebit = 0;
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         nDebit += GetDebit(txin, filter);
         if (!MoneyRange(nDebit))
@@ -1676,7 +1676,7 @@ bool CWallet::IsAllFromMe(const CTransaction& tx, const isminefilter& filter) co
 {
     LOCK(cs_wallet);
 
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
     {
         auto mi = mapWallet.find(txin.prevout.hash);
         if (mi == mapWallet.end())
@@ -1696,7 +1696,7 @@ bool CWallet::IsAllFromMe(const CTransaction& tx, const isminefilter& filter) co
 CAmount CWallet::GetCredit(const CTransaction& tx, const isminefilter& filter) const
 {
     CAmount nCredit = 0;
-    BOOST_FOREACH(const CTxOut& txout, tx.vout)
+    for (const CTxOut& txout : tx.vout)
     {
         nCredit += GetCredit(txout, filter);
         if (!MoneyRange(nCredit))
@@ -1708,7 +1708,7 @@ CAmount CWallet::GetCredit(const CTransaction& tx, const isminefilter& filter) c
 CAmount CWallet::GetChange(const CTransaction& tx) const
 {
     CAmount nChange = 0;
-    BOOST_FOREACH(const CTxOut& txout, tx.vout)
+    for (const CTxOut& txout : tx.vout)
     {
         nChange += GetChange(txout);
         if (!MoneyRange(nChange))
@@ -1885,7 +1885,7 @@ void CWallet::ReacceptWalletTransactions()
     std::map<int64_t, CWalletTx*> mapSorted;
 
     // Sort pending wallet transactions based on their initial wallet insertion order
-    BOOST_FOREACH(PAIRTYPE(const uint256, CWalletTx)& item, mapWallet)
+    for (std::pair<const uint256, CWalletTx>& item : mapWallet)
     {
         const uint256& wtxid = item.first;
         CWalletTx& wtx = item.second;
@@ -1899,7 +1899,7 @@ void CWallet::ReacceptWalletTransactions()
     }
 
     // Try to add wallet transactions to memory pool
-    BOOST_FOREACH(PAIRTYPE(const int64_t, CWalletTx*)& item, mapSorted)
+    for (std::pair<const int64_t, CWalletTx*>& item : mapSorted)
     {
         CWalletTx& wtx = *(item.second);
 
@@ -2206,7 +2206,7 @@ bool CWalletTx::IsTrusted() const
         return false;
 
     // Trusted if all inputs are from us and are in the mempool:
-    BOOST_FOREACH(const CTxIn& txin, tx->vin)
+    for (const CTxIn& txin : tx->vin)
     {
         // Transactions not sent by us: not trusted
         const CWalletTx* parent = pwallet->GetWalletTx(txin.prevout.hash);
@@ -2235,7 +2235,7 @@ std::vector<uint256> CWallet::ResendWalletTransactionsBefore(int64_t nTime, CCon
     LOCK(cs_wallet);
     // Sort them in chronological order
     std::multimap<unsigned int, CWalletTx*> mapSorted;
-    BOOST_FOREACH(PAIRTYPE(const uint256, CWalletTx)& item, mapWallet)
+    for (std::pair<const uint256, CWalletTx>& item : mapWallet)
     {
         CWalletTx& wtx = item.second;
         // Don't rebroadcast if newer than nTime:
@@ -2243,7 +2243,7 @@ std::vector<uint256> CWallet::ResendWalletTransactionsBefore(int64_t nTime, CCon
             continue;
         mapSorted.insert(std::make_pair(wtx.nTimeReceived, &wtx));
     }
-    BOOST_FOREACH(PAIRTYPE(const unsigned int, CWalletTx*)& item, mapSorted)
+    for (std::pair<const unsigned int, CWalletTx*>& item : mapSorted)
     {
         CWalletTx& wtx = *item.second;
         if (wtx.RelayWalletTransaction(connman))
@@ -2729,7 +2729,7 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const int nConfMin
         LogPrint(BCLog::SELECTCOINS, "tryDenom: %d\n", tryDenom);
         vValue.clear();
         nTotalLower = 0;
-        BOOST_FOREACH(const COutput &output, vCoins)
+        for (const COutput &output : vCoins)
         {
             if (!output.fSpendable)
                 continue;
@@ -2851,7 +2851,7 @@ bool CWallet::SelectCoins(const std::vector<COutput>& vAvailableCoins, const CAm
     // coin control -> return all selected outputs (we want all selected to go into the transaction for sure)
     if (coinControl && coinControl->HasSelected() && !coinControl->fAllowOtherInputs)
     {
-        BOOST_FOREACH(const COutput& out, vCoins)
+        for (const COutput& out : vCoins)
         {
             if(!out.fSpendable)
                 continue;
@@ -2881,7 +2881,7 @@ bool CWallet::SelectCoins(const std::vector<COutput>& vAvailableCoins, const CAm
     std::vector<COutPoint> vPresetInputs;
     if (coinControl)
         coinControl->ListSelected(vPresetInputs);
-    BOOST_FOREACH(const COutPoint& outpoint, vPresetInputs)
+    for (const COutPoint& outpoint : vPresetInputs)
     {
         std::map<uint256, CWalletTx>::const_iterator it = mapWallet.find(outpoint.hash);
         if (it != mapWallet.end())
@@ -2951,7 +2951,7 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool ov
     coinControl.fOverrideFeeRate = overrideEstimatedFeeRate;
     coinControl.nFeeRate = specificFeeRate;
 
-    BOOST_FOREACH(const CTxIn& txin, tx.vin)
+    for (const CTxIn& txin : tx.vin)
         coinControl.Select(txin.prevout);
 
     int nExtraPayloadSize = 0;
@@ -2971,7 +2971,7 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool ov
         tx.vout[idx].nValue = wtx.tx->vout[idx].nValue;
 
     // Add new txins (keeping original txin scriptSig/order)
-    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
+    for (const CTxIn& txin : wtx.tx->vin)
     {
         if (!coinControl.IsSelected(txin.prevout))
         {
@@ -3614,7 +3614,7 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT
                 // If there was change output added before, we must update its position now
                 if (nChangePosInOut != -1) {
                     int i = 0;
-                    BOOST_FOREACH(const CTxOut& txOut, txNew.vout)
+                    for (const CTxOut& txOut : txNew.vout)
                     {
                         if (txOut == newTxOut)
                         {
@@ -3773,7 +3773,7 @@ bool CWallet::CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey, CCon
 
             // Notify that old coins are spent
             std::set<uint256> updated_hahes;
-            BOOST_FOREACH(const CTxIn& txin, wtxNew.tx->vin)
+            for (const CTxIn& txin : wtxNew.tx->vin)
             {
                 // notify only once
                 if(updated_hahes.find(txin.prevout.hash) != updated_hahes.end()) continue;
@@ -3987,7 +3987,7 @@ bool CWallet::DelAddressBook(const CTxDestination& address)
 
         // Delete destdata tuples associated with address
         std::string strAddress = CBitcoinAddress(address).ToString();
-        BOOST_FOREACH(const PAIRTYPE(std::string, std::string) &item, mapAddressBook[address].destdata)
+        for (const std::pair<std::string, std::string> &item : mapAddressBook[address].destdata)
         {
             CWalletDB(*dbw).EraseDestData(strAddress, item.first);
         }
@@ -4032,11 +4032,11 @@ bool CWallet::NewKeyPool()
     {
         LOCK(cs_wallet);
         CWalletDB walletdb(*dbw);
-        BOOST_FOREACH(int64_t nIndex, setInternalKeyPool) {
+        for (int64_t nIndex : setInternalKeyPool) {
             walletdb.ErasePool(nIndex);
         }
         setInternalKeyPool.clear();
-        BOOST_FOREACH(int64_t nIndex, setExternalKeyPool) {
+        for (int64_t nIndex : setExternalKeyPool) {
             walletdb.ErasePool(nIndex);
         }
         setExternalKeyPool.clear();
@@ -4291,7 +4291,7 @@ std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
         {
             bool any_mine = false;
             // group all input addresses with each other
-            BOOST_FOREACH(CTxIn txin, pcoin->tx->vin)
+            for (CTxIn txin : pcoin->tx->vin)
             {
                 CTxDestination address;
                 if(!IsMine(txin)) /* If this input isn't mine, ignore it */
@@ -4305,7 +4305,7 @@ std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
             // group change with input addresses
             if (any_mine)
             {
-               BOOST_FOREACH(CTxOut txout, pcoin->tx->vout)
+               for (CTxOut txout : pcoin->tx->vout)
                    if (IsChange(txout))
                    {
                        CTxDestination txoutAddr;
@@ -4336,18 +4336,18 @@ std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
 
     std::set< std::set<CTxDestination>* > uniqueGroupings; // a set of pointers to groups of addresses
     std::map< CTxDestination, std::set<CTxDestination>* > setmap;  // map addresses to the unique group containing it
-    BOOST_FOREACH(std::set<CTxDestination> _grouping, groupings)
+    for (std::set<CTxDestination> _grouping : groupings)
     {
         // make a set of all the groups hit by this new group
         std::set< std::set<CTxDestination>* > hits;
         std::map< CTxDestination, std::set<CTxDestination>* >::iterator it;
-        BOOST_FOREACH(CTxDestination address, _grouping)
+        for (CTxDestination address : _grouping)
             if ((it = setmap.find(address)) != setmap.end())
                 hits.insert((*it).second);
 
         // merge all hit groups into a new single group and delete old groups
         std::set<CTxDestination>* merged = new std::set<CTxDestination>(_grouping);
-        BOOST_FOREACH(std::set<CTxDestination>* hit, hits)
+        for (std::set<CTxDestination>* hit : hits)
         {
             merged->insert(hit->begin(), hit->end());
             uniqueGroupings.erase(hit);
@@ -4356,12 +4356,12 @@ std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
         uniqueGroupings.insert(merged);
 
         // update setmap
-        BOOST_FOREACH(CTxDestination element, *merged)
+        for (CTxDestination element : *merged)
             setmap[element] = merged;
     }
 
     std::set< std::set<CTxDestination> > ret;
-    BOOST_FOREACH(std::set<CTxDestination>* uniqueGrouping, uniqueGroupings)
+    for (std::set<CTxDestination>* uniqueGrouping : uniqueGroupings)
     {
         ret.insert(*uniqueGrouping);
         delete uniqueGrouping;
@@ -4374,7 +4374,7 @@ std::set<CTxDestination> CWallet::GetAccountAddresses(const std::string& strAcco
 {
     LOCK(cs_wallet);
     std::set<CTxDestination> result;
-    BOOST_FOREACH(const PAIRTYPE(CTxDestination, CAddressBookData)& item, mapAddressBook)
+    for (const std::pair<CTxDestination, CAddressBookData>& item : mapAddressBook)
     {
         const CTxDestination& address = item.first;
         const std::string& strName = item.second.name;
@@ -4423,7 +4423,7 @@ void CReserveKey::ReturnKey()
 
 static void LoadReserveKeysToSet(std::set<CKeyID>& setAddress, const std::set<int64_t>& setKeyPool, CWalletDB& walletdb)
 {
-    BOOST_FOREACH(const int64_t& id, setKeyPool)
+    for (const int64_t& id : setKeyPool)
     {
         CKeyPool keypool;
         if (!walletdb.ReadPool(id, keypool))
@@ -4444,7 +4444,7 @@ void CWallet::GetAllReserveKeys(std::set<CKeyID>& setAddress) const
     LoadReserveKeysToSet(setAddress, setInternalKeyPool, walletdb);
     LoadReserveKeysToSet(setAddress, setExternalKeyPool, walletdb);
 
-    BOOST_FOREACH (const CKeyID& keyID, setAddress) {
+    for (const CKeyID& keyID : setAddress) {
         if (!HaveKey(keyID)) {
             throw std::runtime_error(std::string(__func__) + ": unknown key in key pool");
         }
@@ -4538,7 +4538,7 @@ class CAffectedKeysVisitor : public boost::static_visitor<void> {
         std::vector<CTxDestination> vDest;
         int nRequired;
         if (ExtractDestinations(script, type, vDest, nRequired)) {
-            BOOST_FOREACH(const CTxDestination &dest, vDest)
+            for (const CTxDestination &dest : vDest)
                 boost::apply_visitor(*this, dest);
         }
     }
@@ -4573,7 +4573,7 @@ void CWallet::GetKeyBirthTimes(std::map<CTxDestination, int64_t> &mapKeyBirth) c
     std::map<CKeyID, CBlockIndex*> mapKeyFirstBlock;
     std::set<CKeyID> setKeys;
     GetKeys(setKeys);
-    BOOST_FOREACH(const CKeyID &keyid, setKeys) {
+    for (const CKeyID &keyid : setKeys) {
         if (mapKeyBirth.count(keyid) == 0)
             mapKeyFirstBlock[keyid] = pindexMax;
     }
@@ -4592,10 +4592,10 @@ void CWallet::GetKeyBirthTimes(std::map<CTxDestination, int64_t> &mapKeyBirth) c
         if (blit != mapBlockIndex.end() && chainActive.Contains(blit->second)) {
             // ... which are already in a block
             int nHeight = blit->second->nHeight;
-            BOOST_FOREACH(const CTxOut &txout, wtx.tx->vout) {
+            for (const CTxOut &txout : wtx.tx->vout) {
                 // iterate over all their outputs
                 CAffectedKeysVisitor(*this, vAffected).Process(txout.scriptPubKey);
-                BOOST_FOREACH(const CKeyID &keyid, vAffected) {
+                for (const CKeyID &keyid : vAffected) {
                     // ... and all their affected keys
                     std::map<CKeyID, CBlockIndex*>::iterator rit = mapKeyFirstBlock.find(keyid);
                     if (rit != mapKeyFirstBlock.end() && nHeight < rit->second->nHeight)
@@ -4934,7 +4934,7 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         {
             CWalletDB walletdb(*walletInstance->dbw);
 
-            BOOST_FOREACH(const CWalletTx& wtxOld, vWtx)
+            for (const CWalletTx& wtxOld : vWtx)
             {
                 uint256 hash = wtxOld.GetHash();
                 std::map<uint256, CWalletTx>::iterator mi = walletInstance->mapWallet.find(hash);
@@ -5232,8 +5232,8 @@ bool AutoBackupWallet(CWallet* wallet, const std::string& strWalletFile_, std::s
 
     // Loop backward through backup files and keep the N newest ones (1 <= N <= 10)
     int counter = 0;
-    BOOST_REVERSE_FOREACH(PAIRTYPE(const std::time_t, fs::path) file, folder_set)
-    {
+    for(auto it = folder_set.rbegin(); it != folder_set.rend(); ++it) {
+        std::pair<const std::time_t, fs::path> file = *it;
         counter++;
         if (counter > nWalletBackups)
         {
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index ec6871036470..a2d0a2fc080b 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -208,7 +208,7 @@ CAmount CWalletDB::GetAccountCreditDebit(const std::string& strAccount)
     ListAccountCreditDebit(strAccount, entries);
 
     CAmount nCreditDebit = 0;
-    BOOST_FOREACH (const CAccountingEntry& entry, entries)
+    for (const CAccountingEntry& entry : entries)
         nCreditDebit += entry.nCreditDebit;
 
     return nCreditDebit;
@@ -668,7 +668,7 @@ DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
     if ((wss.nKeys + wss.nCKeys + wss.nWatchKeys) != wss.nKeyMeta)
         pwallet->UpdateTimeFirstKey(1);
 
-    BOOST_FOREACH(uint256 hash, wss.vWalletUpgrade)
+    for (uint256 hash : wss.vWalletUpgrade)
         WriteTx(pwallet->mapWallet[hash]);
 
     // Rewrite encrypted wallets of versions 0.4.0 and 0.5.0rc:
@@ -683,7 +683,7 @@ DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
 
     pwallet->laccentries.clear();
     ListAccountCreditDebit("*", pwallet->laccentries);
-    BOOST_FOREACH(CAccountingEntry& entry, pwallet->laccentries) {
+    for (CAccountingEntry& entry : pwallet->laccentries) {
         pwallet->wtxOrdered.insert(make_pair(entry.nOrderPos, CWallet::TxPair((CWalletTx*)0, &entry)));
     }
 
@@ -769,7 +769,7 @@ DBErrors CWalletDB::ZapSelectTx(std::vector<uint256>& vTxHashIn, std::vector<uin
     // erase each matching wallet TX
     bool delerror = false;
     std::vector<uint256>::iterator it = vTxHashIn.begin();
-    BOOST_FOREACH (uint256 hash, vTxHash) {
+    for (uint256 hash : vTxHash) {
         while (it < vTxHashIn.end() && (*it) < hash) {
             it++;
         }
@@ -800,7 +800,7 @@ DBErrors CWalletDB::ZapWalletTx(std::vector<CWalletTx>& vWtx)
         return err;
 
     // erase each wallet TX
-    BOOST_FOREACH (uint256& hash, vTxHash) {
+    for (uint256& hash : vTxHash) {
         if (!EraseTx(hash))
             return DB_CORRUPT;
     }
diff --git a/test/functional/merkle_blocks.py b/test/functional/merkle_blocks.py
index 564a4b5b0130..d9d3e17f9472 100755
--- a/test/functional/merkle_blocks.py
+++ b/test/functional/merkle_blocks.py
@@ -40,7 +40,8 @@ def run_test(self):
         txid1 = self.nodes[0].sendrawtransaction(self.nodes[0].signrawtransaction(tx1)["hex"])
         tx2 = self.nodes[0].createrawtransaction([node0utxos.pop()], {self.nodes[1].getnewaddress(): 500 - tx_fee})
         txid2 = self.nodes[0].sendrawtransaction(self.nodes[0].signrawtransaction(tx2)["hex"])
-        assert_raises(JSONRPCException, self.nodes[0].gettxoutproof, [txid1])
+        # This will raise an exception because the transaction is not yet in a block
+        assert_raises_jsonrpc(-5, "Transaction not yet in block", self.nodes[0].gettxoutproof, [txid1])
 
         self.nodes[0].generate(1)
         blockhash = self.nodes[0].getblockhash(chain_height + 1)
@@ -57,7 +58,7 @@ def run_test(self):
 
         txin_spent = self.nodes[1].listunspent(1).pop()
         tx3 = self.nodes[1].createrawtransaction([txin_spent], {self.nodes[0].getnewaddress(): 500 - tx_fee*2})
-        self.nodes[0].sendrawtransaction(self.nodes[1].signrawtransaction(tx3)["hex"])
+        txid3 = self.nodes[0].sendrawtransaction(self.nodes[1].signrawtransaction(tx3)["hex"])
         self.nodes[0].generate(1)
         self.sync_all()
 
@@ -66,17 +67,21 @@ def run_test(self):
 
         # We can't find the block from a fully-spent tx
         # Doesn't apply to Dash Core - we have txindex always on
-        # assert_raises(JSONRPCException, self.nodes[2].gettxoutproof, [txid_spent])
-        # ...but we can if we specify the block
+        # assert_raises_jsonrpc(-5, "Transaction not yet in block", self.nodes[2].gettxoutproof, [txid_spent])
+        # We can get the proof if we specify the block
         assert_equal(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid_spent], blockhash)), [txid_spent])
-        # ...or if the first tx is not fully-spent
+        # We can't get the proof if we specify a non-existent block
+        assert_raises_jsonrpc(-5, "Block not found", self.nodes[2].gettxoutproof, [txid_spent], "00000000000000000000000000000000")
+        # We can get the proof if the transaction is unspent
         assert_equal(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid_unspent])), [txid_unspent])
-        try:
-            assert_equal(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid1, txid2])), txlist)
-        except JSONRPCException:
-            assert_equal(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid2, txid1])), txlist)
-        # ...or if we have a -txindex
+        # We can get the proof if we provide a list of transactions and one of them is unspent. The ordering of the list should not matter.
+        assert_equal(sorted(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid1, txid2]))), sorted(txlist))
+        assert_equal(sorted(self.nodes[2].verifytxoutproof(self.nodes[2].gettxoutproof([txid2, txid1]))), sorted(txlist))
+        # We can always get a proof if we have a -txindex
         assert_equal(self.nodes[2].verifytxoutproof(self.nodes[3].gettxoutproof([txid_spent])), [txid_spent])
+        # We can't get a proof if we specify transactions from different blocks
+        assert_raises_jsonrpc(-5, "Not all transactions found in specified or retrieved block", self.nodes[2].gettxoutproof, [txid1, txid3])
+
 
 if __name__ == '__main__':
     MerkleBlockTest().main()
diff --git a/test/functional/multi_rpc.py b/test/functional/multi_rpc.py
index 9e51810a8883..891184ca6e82 100755
--- a/test/functional/multi_rpc.py
+++ b/test/functional/multi_rpc.py
@@ -16,16 +16,21 @@ class HTTPBasicsTest (BitcoinTestFramework):
     def __init__(self):
         super().__init__()
         self.setup_clean_chain = False
-        self.num_nodes = 1
+        self.num_nodes = 2
 
     def setup_chain(self):
         super().setup_chain()
         #Append rpcauth to dash.conf before initialization
         rpcauth = "rpcauth=rt:93648e835a54c573682c2eb19f882535$7681e9c5b74bdd85e78166031d2058e1069b3ed7ed967c93fc63abba06f31144"
         rpcauth2 = "rpcauth=rt2:f8607b1a88861fac29dfccf9b52ff9f$ff36a0c23c8c62b4846112e50fa888416e94c17bfd4c42f88fd8f55ec6a3137e"
+        rpcuser = "rpcuser=rpcuser💻"
+        rpcpassword = "rpcpassword=rpcpassword🔑"
         with open(os.path.join(self.options.tmpdir+"/node0", "dash.conf"), 'a', encoding='utf8') as f:
             f.write(rpcauth+"\n")
             f.write(rpcauth2+"\n")
+        with open(os.path.join(self.options.tmpdir+"/node1", "dash.conf"), 'a', encoding='utf8') as f:
+            f.write(rpcuser+"\n")
+            f.write(rpcpassword+"\n")
 
     def run_test(self):
 
@@ -50,7 +55,7 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, False)
+        assert_equal(resp.status, 200)
         conn.close()
         
         #Use new authpair to confirm both work
@@ -60,7 +65,7 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, False)
+        assert_equal(resp.status, 200)
         conn.close()
 
         #Wrong login name with rt's password
@@ -71,7 +76,7 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, True)
+        assert_equal(resp.status, 401)
         conn.close()
 
         #Wrong password for rt
@@ -82,7 +87,7 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, True)
+        assert_equal(resp.status, 401)
         conn.close()
 
         #Correct for rt2
@@ -93,7 +98,7 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, False)
+        assert_equal(resp.status, 200)
         conn.close()
 
         #Wrong password for rt2
@@ -104,7 +109,46 @@ def run_test(self):
         conn.connect()
         conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
         resp = conn.getresponse()
-        assert_equal(resp.status==401, True)
+        assert_equal(resp.status, 401)
+        conn.close()
+
+        ###############################################################
+        # Check correctness of the rpcuser/rpcpassword config options #
+        ###############################################################
+        url = urllib.parse.urlparse(self.nodes[1].url)
+
+        # rpcuser and rpcpassword authpair
+        rpcuserauthpair = "rpcuser💻:rpcpassword🔑"
+
+        headers = {"Authorization": "Basic " + str_to_b64str(rpcuserauthpair)}
+
+        conn = http.client.HTTPConnection(url.hostname, url.port)
+        conn.connect()
+        conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
+        resp = conn.getresponse()
+        assert_equal(resp.status, 200)
+        conn.close()
+
+        #Wrong login name with rpcuser's password
+        rpcuserauthpair = "rpcuserwrong:rpcpassword"
+        headers = {"Authorization": "Basic " + str_to_b64str(rpcuserauthpair)}
+
+        conn = http.client.HTTPConnection(url.hostname, url.port)
+        conn.connect()
+        conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
+        resp = conn.getresponse()
+        assert_equal(resp.status, 401)
+        conn.close()
+
+        #Wrong password for rpcuser
+        rpcuserauthpair = "rpcuser:rpcpasswordwrong"
+        headers = {"Authorization": "Basic " + str_to_b64str(rpcuserauthpair)}
+
+        conn = http.client.HTTPConnection(url.hostname, url.port)
+        conn.connect()
+        conn.request('POST', '/', '{"method": "getbestblockhash"}', headers)
+        resp = conn.getresponse()
+        assert_equal(resp.status, 401)
         conn.close()
 
 
diff --git a/test/functional/pruning.py b/test/functional/pruning.py
index 9ee09c1a72a3..501f98ad45bc 100755
--- a/test/functional/pruning.py
+++ b/test/functional/pruning.py
@@ -315,7 +315,7 @@ def wallet_test(self):
         # check that the pruning node's wallet is still in good shape
         self.log.info("Stop and start pruning node to trigger wallet rescan")
         self.stop_node(2)
-        self.start_node(2, self.options.tmpdir, ["-litemode","-txindex=0","-prune=550"], stderr=sys.stdout)
+        self.nodes[2] = self.start_node(2, self.options.tmpdir, ["-litemode","-txindex=0","-prune=550"], stderr=sys.stdout)
         self.log.info("Success")
 
         # check that wallet loads loads successfully when restarting a pruned node after IBD.
@@ -325,7 +325,7 @@ def wallet_test(self):
         nds = [self.nodes[0], self.nodes[5]]
         sync_blocks(nds, wait=5, timeout=300)
         self.stop_node(5) #stop and start to trigger rescan
-        self.start_node(5, self.options.tmpdir, ["-litemode","-txindex=0","-prune=550"], stderr=sys.stdout)
+        self.nodes[5] = self.start_node(5, self.options.tmpdir, ["-litemode","-txindex=0","-prune=550"], stderr=sys.stdout)
         self.log.info("Success")
 
     def run_test(self):
diff --git a/test/functional/rpcbind_test.py b/test/functional/rpcbind_test.py
index 5336cf2ec89f..198599010e41 100755
--- a/test/functional/rpcbind_test.py
+++ b/test/functional/rpcbind_test.py
@@ -49,7 +49,7 @@ def run_allowip_test(self, allow_ips, rpchost, rpcport):
         base_args = ['-disablewallet', '-nolisten'] + ['-rpcallowip='+x for x in allow_ips]
         self.nodes = self.start_nodes(self.num_nodes, self.options.tmpdir, [base_args])
         # connect to node through non-loopback interface
-        node = get_rpc_proxy(rpc_url(0, "%s:%d" % (rpchost, rpcport)), 0)
+        node = get_rpc_proxy(rpc_url(get_datadir_path(self.options.tmpdir, 0), 0, "%s:%d" % (rpchost, rpcport)), 0)
         node.getnetworkinfo()
         self.stop_nodes()
 
diff --git a/test/functional/test_framework/test_framework.py b/test/functional/test_framework/test_framework.py
index a663482eb392..273e9706f9e3 100755
--- a/test/functional/test_framework/test_framework.py
+++ b/test/functional/test_framework/test_framework.py
@@ -33,6 +33,7 @@
     get_mocktime,
     get_rpc_proxy,
     initialize_datadir,
+    get_datadir_path,
     log_filename,
     p2p_port,
     rpc_url,
@@ -319,13 +320,13 @@ def _initialize_chain(self, test_dir, num_nodes, cachedir, extra_args=None, stde
                     args.extend(extra_args)
                 bitcoind_processes[i] = subprocess.Popen(args, stderr=stderr)
                 self.log.debug("initialize_chain: dashd started, waiting for RPC to come up")
-                wait_for_bitcoind_start(bitcoind_processes[i], rpc_url(i), i)
+                wait_for_bitcoind_start(bitcoind_processes[i], datadir, i)
                 self.log.debug("initialize_chain: RPC successfully started")
 
             self.nodes = []
             for i in range(MAX_NODES):
                 try:
-                    self.nodes.append(get_rpc_proxy(rpc_url(i), i))
+                    self.nodes.append(get_rpc_proxy(rpc_url(get_datadir_path(cachedir, i), i), i))
                 except:
                     self.log.exception("Error connecting to node %d" % i)
                     sys.exit(1)
diff --git a/test/functional/test_framework/util.py b/test/functional/test_framework/util.py
index f062e32da22f..f6c326ac8fd7 100644
--- a/test/functional/test_framework/util.py
+++ b/test/functional/test_framework/util.py
@@ -205,21 +205,40 @@ def initialize_datadir(dirname, n):
     datadir = os.path.join(dirname, "node"+str(n))
     if not os.path.isdir(datadir):
         os.makedirs(datadir)
-    rpc_u, rpc_p = rpc_auth_pair(n)
     with open(os.path.join(datadir, "dash.conf"), 'w', encoding='utf8') as f:
         f.write("regtest=1\n")
-        f.write("rpcuser=" + rpc_u + "\n")
-        f.write("rpcpassword=" + rpc_p + "\n")
         f.write("port="+str(p2p_port(n))+"\n")
         f.write("rpcport="+str(rpc_port(n))+"\n")
         f.write("listenonion=0\n")
     return datadir
 
-def rpc_auth_pair(n):
-    return 'rpcuser💻' + str(n), 'rpcpass🔑' + str(n)
-
-def rpc_url(i, rpchost=None):
-    rpc_u, rpc_p = rpc_auth_pair(i)
+def get_datadir_path(dirname, n):
+    return os.path.join(dirname, "node"+str(n))
+
+def get_auth_cookie(datadir, n):
+    user = None
+    password = None
+    if os.path.isfile(os.path.join(datadir, "dash.conf")):
+        with open(os.path.join(datadir, "dash.conf"), 'r', encoding='utf8') as f:
+            for line in f:
+                if line.startswith("rpcuser="):
+                    assert user is None # Ensure that there is only one rpcuser line
+                    user = line.split("=")[1].strip("\n")
+                if line.startswith("rpcpassword="):
+                    assert password is None # Ensure that there is only one rpcpassword line
+                    password = line.split("=")[1].strip("\n")
+    if os.path.isfile(os.path.join(datadir, "regtest", ".cookie")):
+        with open(os.path.join(datadir, "regtest", ".cookie"), 'r') as f:
+            userpass = f.read()
+            split_userpass = userpass.split(':')
+            user = split_userpass[0]
+            password = split_userpass[1]
+    if user is None or password is None:
+        raise ValueError("No RPC credentials")
+    return user, password
+
+def rpc_url(datadir, i, rpchost=None):
+    rpc_u, rpc_p = get_auth_cookie(datadir, i)
     host = '127.0.0.1'
     port = rpc_port(i)
     if rpchost:
@@ -230,7 +249,7 @@ def rpc_url(i, rpchost=None):
             host = rpchost
     return "http://%s:%s@%s:%d" % (rpc_u, rpc_p, host, int(port))
 
-def wait_for_bitcoind_start(process, url, i):
+def wait_for_bitcoind_start(process, datadir, i, rpchost=None):
     '''
     Wait for dashd to start. This means that RPC is accessible and fully initialized.
     Raise an exception if dashd exits during initialization.
@@ -239,7 +258,8 @@ def wait_for_bitcoind_start(process, url, i):
         if process.poll() is not None:
             raise Exception('dashd exited with status %i during initialization' % process.returncode)
         try:
-            rpc = get_rpc_proxy(url, i)
+            # Check if .cookie file to be created
+            rpc = get_rpc_proxy(rpc_url(datadir, i, rpchost), i)
             blocks = rpc.getblockcount()
             break # break out of loop on success
         except IOError as e:
@@ -248,6 +268,9 @@ def wait_for_bitcoind_start(process, url, i):
         except JSONRPCException as e: # Initialization phase
             if e.error['code'] != -28: # RPC in warmup?
                 raise # unknown JSON RPC exception
+        except ValueError as e: # cookie file not found and no rpcuser or rpcassword. dashd still starting
+            if "No RPC credentials" not in str(e):
+                raise
         time.sleep(0.25)
 
 
@@ -266,10 +289,9 @@ def _start_node(i, dirname, extra_args=None, rpchost=None, timewait=None, binary
 
     bitcoind_processes[i] = subprocess.Popen(args, stderr=stderr)
     logger.debug("initialize_chain: dashd started, waiting for RPC to come up")
-    url = rpc_url(i, rpchost)
-    wait_for_bitcoind_start(bitcoind_processes[i], url, i)
+    wait_for_bitcoind_start(bitcoind_processes[i], datadir, i, rpchost)
     logger.debug("initialize_chain: RPC successfully started")
-    proxy = get_rpc_proxy(url, i, timeout=timewait)
+    proxy = get_rpc_proxy(rpc_url(datadir, i, rpchost), i, timeout=timewait)
 
     if COVERAGE_DIR:
         coverage.write_all_rpc_commands(COVERAGE_DIR, proxy)
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 5fabd71e7648..08734e402d08 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -20,6 +20,7 @@
 import os
 import time
 import shutil
+import signal
 import sys
 import subprocess
 import tempfile
@@ -85,7 +86,7 @@
     'rawtransactions.py',
     'reindex.py',
     # vv Tests less than 30s vv
-    "zmq_test.py",
+    'zmq_test.py',
     'mempool_resurrect_test.py',
     'txn_doublespend.py --mineblock',
     'txn_clone.py',
@@ -124,6 +125,7 @@
     'p2p-compactblocks.py',
     'sporks.py',
     'p2p-fingerprint.py',
+    'wallet-encryption.py',
 ]
 
 EXTENDED_SCRIPTS = [
@@ -403,6 +405,10 @@ def get_next(self):
             time.sleep(.5)
             for j in self.jobs:
                 (name, time0, proc, log_out, log_err) = j
+                if os.getenv('TRAVIS') == 'true' and int(time.time() - time0) > 20 * 60:
+                    # In travis, timeout individual tests after 20 minutes (to stop tests hanging and not
+                    # providing useful output.
+                    proc.send_signal(signal.SIGINT)
                 if proc.poll() is not None:
                     log_out.seek(0), log_err.seek(0)
                     [stdout, stderr] = [l.read().decode('utf-8') for l in (log_out, log_err)]
diff --git a/test/functional/wallet-encryption.py b/test/functional/wallet-encryption.py
new file mode 100755
index 000000000000..33872e3c9465
--- /dev/null
+++ b/test/functional/wallet-encryption.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+# Copyright (c) 2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test Wallet encryption"""
+
+import time
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    assert_raises_jsonrpc,
+    bitcoind_processes,
+    BITCOIND_PROC_WAIT_TIMEOUT,
+)
+
+class WalletEncryptionTest(BitcoinTestFramework):
+
+    def __init__(self):
+        super().__init__()
+        self.setup_clean_chain = True
+        self.num_nodes = 1
+
+    def run_test(self):
+        passphrase = "WalletPassphrase"
+        passphrase2 = "SecondWalletPassphrase"
+
+        # Make sure the wallet isn't encrypted first
+        address = self.nodes[0].getnewaddress()
+        privkey = self.nodes[0].dumpprivkey(address)
+        assert_equal(privkey[:1], "c")
+        assert_equal(len(privkey), 52)
+
+        # Encrypt the wallet
+        self.nodes[0].encryptwallet(passphrase)
+        bitcoind_processes[0].wait(timeout=BITCOIND_PROC_WAIT_TIMEOUT)
+        self.nodes[0] = self.start_node(0, self.options.tmpdir)
+
+        # Test that the wallet is encrypted
+        assert_raises_jsonrpc(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)
+
+        # Check that walletpassphrase works
+        self.nodes[0].walletpassphrase(passphrase, 2)
+        assert_equal(privkey, self.nodes[0].dumpprivkey(address))
+
+        # Check that the timeout is right
+        time.sleep(2)
+        assert_raises_jsonrpc(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)
+
+        # Test wrong passphrase
+        assert_raises_jsonrpc(-14, "wallet passphrase entered was incorrect", self.nodes[0].walletpassphrase, passphrase + "wrong", 10)
+
+        # Test walletlock
+        self.nodes[0].walletpassphrase(passphrase, 84600)
+        assert_equal(privkey, self.nodes[0].dumpprivkey(address))
+        self.nodes[0].walletlock()
+        assert_raises_jsonrpc(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)
+
+        # Test passphrase changes
+        self.nodes[0].walletpassphrasechange(passphrase, passphrase2)
+        assert_raises_jsonrpc(-14, "wallet passphrase entered was incorrect", self.nodes[0].walletpassphrase, passphrase, 10)
+        self.nodes[0].walletpassphrase(passphrase2, 10)
+        assert_equal(privkey, self.nodes[0].dumpprivkey(address))
+
+if __name__ == '__main__':
+    WalletEncryptionTest().main()
diff --git a/test/functional/zmq_test.py b/test/functional/zmq_test.py
index cc357372ebc4..c2b93b68ee69 100755
--- a/test/functional/zmq_test.py
+++ b/test/functional/zmq_test.py
@@ -8,15 +8,15 @@
 import struct
 
 from test_framework.test_framework import BitcoinTestFramework, SkipTest
-from test_framework.util import *
+from test_framework.util import (assert_equal,
+                                 bytes_to_hex_str,
+                                 )
 
 class ZMQTest (BitcoinTestFramework):
 
     def __init__(self):
         super().__init__()
-        self.num_nodes = 4
-
-    port = 28332
+        self.num_nodes = 2
 
     def setup_nodes(self):
         # Try to import python3-zmq. Skip this test if the import fails.
@@ -28,7 +28,7 @@ def setup_nodes(self):
         # Check that dash has been built with ZMQ enabled
         config = configparser.ConfigParser()
         if not self.options.configfile:
-            self.options.configfile = os.path.dirname(__file__) + "/config.ini"
+            self.options.configfile = os.path.dirname(__file__) + "/../config.ini"
         config.read_file(open(self.options.configfile))
 
         if not config["components"].getboolean("ENABLE_ZMQ"):
@@ -36,59 +36,66 @@ def setup_nodes(self):
 
         self.zmqContext = zmq.Context()
         self.zmqSubSocket = self.zmqContext.socket(zmq.SUB)
+        self.zmqSubSocket.set(zmq.RCVTIMEO, 60000)
         self.zmqSubSocket.setsockopt(zmq.SUBSCRIBE, b"hashblock")
         self.zmqSubSocket.setsockopt(zmq.SUBSCRIBE, b"hashtx")
-        self.zmqSubSocket.connect("tcp://127.0.0.1:%i" % self.port)
-        self.nodes = self.start_nodes(self.num_nodes, self.options.tmpdir, extra_args=[
-            ['-zmqpubhashtx=tcp://127.0.0.1:'+str(self.port), '-zmqpubhashblock=tcp://127.0.0.1:'+str(self.port)],
-            [],
-            [],
-            []
-            ])
+        ip_address = "tcp://127.0.0.1:28332"
+        self.zmqSubSocket.connect(ip_address)
+        extra_args = [['-zmqpubhashtx=%s' % ip_address, '-zmqpubhashblock=%s' % ip_address], []]
+        self.nodes = self.start_nodes(self.num_nodes, self.options.tmpdir, extra_args)
 
     def run_test(self):
-        self.sync_all()
+        try:
+            self._zmq_test()
+        finally:
+            # Destroy the zmq context
+            self.log.debug("Destroying zmq context")
+            self.zmqContext.destroy(linger=None)
 
+    def _zmq_test(self):
         genhashes = self.nodes[0].generate(1)
         self.sync_all()
 
-        self.log.info("listen...")
+        self.log.info("Wait for tx")
         msg = self.zmqSubSocket.recv_multipart()
         topic = msg[0]
         assert_equal(topic, b"hashtx")
         body = msg[1]
         msgSequence = struct.unpack('<I', msg[-1])[-1]
-        assert_equal(msgSequence, 0) #must be sequence 0 on hashtx
+        assert_equal(msgSequence, 0)  # must be sequence 0 on hashtx
 
+        self.log.info("Wait for block")
         msg = self.zmqSubSocket.recv_multipart()
         topic = msg[0]
         body = msg[1]
         msgSequence = struct.unpack('<I', msg[-1])[-1]
-        assert_equal(msgSequence, 0) #must be sequence 0 on hashblock
+        assert_equal(msgSequence, 0)  # must be sequence 0 on hashblock
         blkhash = bytes_to_hex_str(body)
 
-        assert_equal(genhashes[0], blkhash) #blockhash from generate must be equal to the hash received over zmq
+        assert_equal(genhashes[0], blkhash)  # blockhash from generate must be equal to the hash received over zmq
 
+        self.log.info("Generate 10 blocks (and 10 coinbase txes)")
         n = 10
         genhashes = self.nodes[1].generate(n)
         self.sync_all()
 
         zmqHashes = []
         blockcount = 0
-        for x in range(0,n*2):
+        for x in range(n * 2):
             msg = self.zmqSubSocket.recv_multipart()
             topic = msg[0]
             body = msg[1]
             if topic == b"hashblock":
                 zmqHashes.append(bytes_to_hex_str(body))
                 msgSequence = struct.unpack('<I', msg[-1])[-1]
-                assert_equal(msgSequence, blockcount+1)
+                assert_equal(msgSequence, blockcount + 1)
                 blockcount += 1
 
-        for x in range(0,n):
-            assert_equal(genhashes[x], zmqHashes[x]) #blockhash from generate must be equal to the hash received over zmq
+        for x in range(n):
+            assert_equal(genhashes[x], zmqHashes[x])  # blockhash from generate must be equal to the hash received over zmq
 
-        #test tx from a second node
+        self.log.info("Wait for tx from second node")
+        # test tx from a second node
         hashRPC = self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 1.0)
         self.sync_all()
 
@@ -96,14 +103,12 @@ def run_test(self):
         msg = self.zmqSubSocket.recv_multipart()
         topic = msg[0]
         body = msg[1]
-        hashZMQ = ""
-        if topic == b"hashtx":
-            hashZMQ = bytes_to_hex_str(body)
-            msgSequence = struct.unpack('<I', msg[-1])[-1]
-            assert_equal(msgSequence, blockcount+1)
-
-        assert_equal(hashRPC, hashZMQ) #blockhash from generate must be equal to the hash received over zmq
+        assert_equal(topic, b"hashtx")
+        hashZMQ = bytes_to_hex_str(body)
+        msgSequence = struct.unpack('<I', msg[-1])[-1]
+        assert_equal(msgSequence, blockcount + 1)
 
+        assert_equal(hashRPC, hashZMQ)  # txid from sendtoaddress must be equal to the hash received over zmq
 
 if __name__ == '__main__':
-    ZMQTest ().main ()
+    ZMQTest().main()