Adapt to system min block version, add get_block/get_header from locator.

include/bitcoin/database/impl/query/height.ipp

@@ -19,6 +19,7 @@
 #ifndef LIBBITCOIN_DATABASE_QUERY_HEIGHT_IPP
 #define LIBBITCOIN_DATABASE_QUERY_HEIGHT_IPP
 
+#include <algorithm>
 #include <bitcoin/system.hpp>
 #include <bitcoin/database/define.hpp>
 
@@ -59,6 +60,98 @@ size_t CLASS::get_confirmed_size(size_t top) const NOEXCEPT
     return wire;
 }
 
+// locator readers
+// ----------------------------------------------------------------------------
+// These do not require strict consistency.
+
+TEMPLATE
+CLASS::headers CLASS::get_headers(const hashes& locator,
+    const hash_digest& stop, size_t limit) const NOEXCEPT
+{
+    headers out{};
+    const auto span = get_locator_span(locator, stop, limit);
+    out.reserve(span.size());
+
+    for (auto height = span.begin; height < span.end; ++height)
+    {
+        // Terminal implies intervening reorganization.
+        const auto link = to_confirmed(height);
+        if (link.is_terminal())
+            return {};
+
+        out.push_back(get_header(link));
+        BC_ASSERT(!is_null(out.back()));
+    }
+
+    return out;
+}
+
+TEMPLATE
+hashes CLASS::get_blocks(const hashes& locator,
+    const hash_digest& stop, size_t limit) const NOEXCEPT
+{
+    hashes out{};
+    const auto span = get_locator_span(locator, stop, limit);
+    out.reserve(span.size());
+
+    for (auto height = span.begin; height < span.end; ++height)
+    {
+        // Terminal implies intervening reorganization.
+        const auto link = to_confirmed(height);
+        if (link.is_terminal())
+            return {};
+
+        out.push_back(get_header_key(link));
+        BC_ASSERT(out.back() != system::null_hash);
+    }
+
+    return out;
+}
+
+TEMPLATE
+CLASS::span CLASS::get_locator_span(const hashes& locator,
+    const hash_digest& stop, size_t limit) const NOEXCEPT
+{
+    using namespace system;
+    span out{};
+
+    // Start at fork point, stop at given header (both excluded).
+    const auto start = add1(get_fork(locator));
+    const auto last1 = (stop == null_hash) ? max_uint32 :
+        get_height(to_header(stop)).value;
+
+    // Determine number of headers requested, limited by max allowed.
+    const auto request = floored_subtract<size_t>(last1, start);
+    const auto allowed = std::min(request, limit);
+
+    // Set end to (start + allowed), limited by (top + 1).
+    const auto top1 = ceilinged_add(get_top_confirmed(), one);
+    const auto end = std::min(ceilinged_add(start, allowed), top1);
+
+    // Convert negative range to empty.
+    out.end = std::max(start, end);
+    return out;
+}
+
+// protected
+TEMPLATE
+size_t CLASS::get_fork(const hashes& locator) const NOEXCEPT
+{
+    // Locator is presumed (by convention) to be in order by height.
+    for (const auto& hash: locator)
+    {
+        const auto link = to_header(hash);
+        const auto height = get_height(link);
+
+        table::height::record confirmed{};
+        if (store_.confirmed.get(height, confirmed) &&
+            confirmed.header_fk == link)
+                return height;
+    }
+
+    return zero;
+}
+
 // shared_lock readers
 // ----------------------------------------------------------------------------
 // Protected against index pop (low contention) to ensure branch consistency.

include/bitcoin/database/query.hpp

@@ -67,6 +67,7 @@ class query
     using script = system::chain::script;
     using output = system::chain::output;
     using header = system::chain::header;
+    using headers = system::chain::header_cptrs;
     using transaction = system::chain::transaction;
     using transactions = system::chain::transaction_cptrs;
     using inputs_ptr = system::chain::inputs_ptr;
@@ -534,6 +535,12 @@ class query
     bool pop_candidate() NOEXCEPT;
     bool pop_confirmed() NOEXCEPT;
 
+    /// Populate message payloads from locator.
+    headers get_headers(const hashes& locator, const hash_digest& stop,
+        size_t limit) const NOEXCEPT;
+    hashes get_blocks(const hashes& locator, const hash_digest& stop,
+        size_t limit) const NOEXCEPT;
+
     /// Optional Tables.
     /// -----------------------------------------------------------------------
 
@@ -557,6 +564,23 @@ class query
         const hash_digest& head) NOEXCEPT;
 
 protected:
+    struct span
+    {
+        size_t size() const NOEXCEPT { return end - begin; }
+        size_t begin;
+        size_t end;
+    };
+
+    /// Network
+    /// -----------------------------------------------------------------------
+
+    /// Height of highest confirmed block (assumes locator descending).
+    size_t get_fork(const hashes& locator) const NOEXCEPT;
+
+    /// Height of highest confirmed block (assumes locator descending).
+    span get_locator_span(const hashes& locator, const hash_digest& stop,
+        size_t limit) const NOEXCEPT;
+
     /// Translate.
     /// -----------------------------------------------------------------------
     uint32_t to_input_index(const tx_link& parent_fk,

test/query/context.cpp

@@ -51,7 +51,7 @@ BOOST_AUTO_TEST_CASE(query_context__get_candidate_chain_state__genesis__expected
         test::genesis.header().timestamp(),
         0u,
         0u,
-        1u,
+        0u,
         0u
     };
 
@@ -83,7 +83,7 @@ BOOST_AUTO_TEST_CASE(query_context__get_candidate_chain_state__block1__expected)
         test::block1.header().timestamp(),  // timestamp
         test::genesis.header().timestamp(), // mtp
         1u,                                 // height
-        1u,                                 // minimum_block_version
+        0u,                                 // minimum_block_version
         486604799u                          // work_required
     };