main.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2012 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include "alert.h"
#include "checkpoints.h"
#include "db.h"
#include "txdb.h"
#include "net.h"
#include "init.h"
#include "ui_interface.h"
#include "checkqueue.h"
#include "kernel.h"
#include <boost/algorithm/string/replace.hpp>
#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>

#include "main.h"

using namespace std;
using namespace boost;



CCriticalSection cs_setpwalletRegistered;
set<CWallet*> setpwalletRegistered;

CCriticalSection cs_main;

CTxMemPool mempool;
unsigned int nTransactionsUpdated = 0;

map<uint256, CBlockIndex*> mapBlockIndex;
set<pair<COutPoint, unsigned int> > setStakeSeen;

CBigNum bnProofOfWorkLimit(~uint256(0) >> 20); // "standard" scrypt target limit for proof of work, results with 0,000244140625 proof-of-work difficulty
CBigNum bnProofOfStakeLegacyLimit(~uint256(0) >> 20); // proof of stake target limit from block #15000 and until 20 June 2013, results with 0,00390625 proof of stake difficulty
CBigNum bnProofOfStakeLimit(~uint256(0) >> 20); // proof of stake target limit since 20 June 2013, equal to 0.03125  proof of stake difficulty
CBigNum bnProofOfStakeHardLimit(~uint256(0) >> 20); // disabled temporarily, will be used in the future to fix minimal proof of stake difficulty at 0.25
uint256 nPoWBase = uint256("0x00000000ffff0000000000000000000000000000000000000000000000000000"); // difficulty-1 target

CBigNum bnProofOfWorkLimitTestNet(~uint256(0) >> 16);

unsigned int nStakeMinAge = 2 * 24 * nOneHour; //
unsigned int nStakeMaxAge = 30 * 24 * nOneHour; // 
unsigned int nStakeTargetSpacing = 6 * 60; // 6-minute stakes spacing
int64_t nTargetSpacing = 6 * 60;  // Same as the above
unsigned int nModifierInterval = 1 * nOneHour; // time to elapse before new modifier is computed

int nCoinbaseMaturity = 20;

CBlockIndex* pindexGenesisBlock = NULL;
int nBestHeight = -1;

uint256 nBestChainTrust = 0;
uint256 nBestInvalidTrust = 0;

uint256 hashBestChain = 0;
CBlockIndex* pindexBest = NULL;
int64_t nTimeBestReceived = 0;
int nScriptCheckThreads = 0;

CMedianFilter<int> cPeerBlockCounts(5, 0); // Amount of blocks that other nodes claim to have

map<uint256, CBlock*> mapOrphanBlocks;
multimap<uint256, CBlock*> mapOrphanBlocksByPrev;
set<pair<COutPoint, unsigned int> > setStakeSeenOrphan;
map<uint256, uint256> mapProofOfStake;

map<uint256, CTransaction> mapOrphanTransactions;
map<uint256, set<uint256> > mapOrphanTransactionsByPrev;

// Constant stuff for coinbase transactions we create:
CScript COINBASE_FLAGS;

const string strMessageMagic = "iWalletCoin Signed Message:\n";

// Settings
int64_t nTransactionFee = MIN_TX_FEE;
int64_t nMinimumInputValue = MIN_TXOUT_AMOUNT;

// Ping and address broadcast intervals
int64_t nPingInterval = 30 * 60;
int64_t nBroadcastInterval = nOneDay;

extern enum Checkpoints::CPMode CheckpointsMode;

//////////////////////////////////////////////////////////////////////////////
//
// dispatching functions
//

// These functions dispatch to one or all registered wallets


void RegisterWallet(CWallet* pwalletIn)
{
    {
        LOCK(cs_setpwalletRegistered);
        setpwalletRegistered.insert(pwalletIn);
    }
}

void UnregisterWallet(CWallet* pwalletIn)
{
    {
        LOCK(cs_setpwalletRegistered);
        setpwalletRegistered.erase(pwalletIn);
    }
}

// check whether the passed transaction is from us
bool static IsFromMe(CTransaction& tx)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        if (pwallet->IsFromMe(tx))
            return true;
    return false;
}

// get the wallet transaction with the given hash (if it exists)
bool static GetTransaction(const uint256& hashTx, CWalletTx& wtx)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        if (pwallet->GetTransaction(hashTx,wtx))
            return true;
    return false;
}

// erases transaction with the given hash from all wallets
void static EraseFromWallets(uint256 hash)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->EraseFromWallet(hash);
}

// make sure all wallets know about the given transaction, in the given block
void SyncWithWallets(const CTransaction& tx, const CBlock* pblock, bool fUpdate, bool fConnect)
{
    if (!fConnect)
    {
        // wallets need to refund inputs when disconnecting coinstake
        if (tx.IsCoinStake())
        {
            BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
                if (pwallet->IsFromMe(tx))
                    pwallet->DisableTransaction(tx);
        }
        return;
    }

    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->AddToWalletIfInvolvingMe(tx, pblock, fUpdate);
}

// notify wallets about a new best chain
void static SetBestChain(const CBlockLocator& loc)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->SetBestChain(loc);
}

// notify wallets about an updated transaction
void static UpdatedTransaction(const uint256& hashTx)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->UpdatedTransaction(hashTx);
}

// dump all wallets
void static PrintWallets(const CBlock& block)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->PrintWallet(block);
}

// notify wallets about an incoming inventory (for request counts)
void static Inventory(const uint256& hash)
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->Inventory(hash);
}

// ask wallets to resend their transactions
void ResendWalletTransactions()
{
    BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
        pwallet->ResendWalletTransactions();
}







//////////////////////////////////////////////////////////////////////////////
//
// mapOrphanTransactions
//

bool AddOrphanTx(const CTransaction& tx)
{
    uint256 hash = tx.GetHash();
    if (mapOrphanTransactions.count(hash))
        return false;

    // Ignore big transactions, to avoid a
    // send-big-orphans memory exhaustion attack. If a peer has a legitimate
    // large transaction with a missing parent then we assume
    // it will rebroadcast it later, after the parent transaction(s)
    // have been mined or received.
    // 10,000 orphans, each of which is at most 5,000 bytes big is
    // at most 500 megabytes of orphans:

    size_t nSize = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);

    if (nSize > 5000)
    {
        printf("ignoring large orphan tx (size: %" PRIszu ", hash: %s)\n", nSize, hash.ToString().substr(0,10).c_str());
        return false;
    }

    mapOrphanTransactions[hash] = tx;
    BOOST_FOREACH(const CTxIn& txin, tx.vin)
        mapOrphanTransactionsByPrev[txin.prevout.hash].insert(hash);

    printf("stored orphan tx %s (mapsz %" PRIszu ")\n", hash.ToString().substr(0,10).c_str(),
        mapOrphanTransactions.size());
    return true;
}

void static EraseOrphanTx(uint256 hash)
{
    if (!mapOrphanTransactions.count(hash))
        return;
    const CTransaction& tx = mapOrphanTransactions[hash];
    BOOST_FOREACH(const CTxIn& txin, tx.vin)
    {
        mapOrphanTransactionsByPrev[txin.prevout.hash].erase(hash);
        if (mapOrphanTransactionsByPrev[txin.prevout.hash].empty())
            mapOrphanTransactionsByPrev.erase(txin.prevout.hash);
    }
    mapOrphanTransactions.erase(hash);
}

unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
{
    unsigned int nEvicted = 0;
    while (mapOrphanTransactions.size() > nMaxOrphans)
    {
        // Evict a random orphan:
        uint256 randomhash = GetRandHash();
        map<uint256, CTransaction>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
        if (it == mapOrphanTransactions.end())
            it = mapOrphanTransactions.begin();
        EraseOrphanTx(it->first);
        ++nEvicted;
    }
    return nEvicted;
}







//////////////////////////////////////////////////////////////////////////////
//
// CTransaction and CTxIndex
//

bool CTransaction::ReadFromDisk(CTxDB& txdb, const uint256& hash, CTxIndex& txindexRet)
{
    SetNull();
    if (!txdb.ReadTxIndex(hash, txindexRet))
         return false;
    if (!ReadFromDisk(txindexRet.pos))
         return false;
    return true;
}

bool CTransaction::ReadFromDisk(CTxDB& txdb, COutPoint prevout, CTxIndex& txindexRet)
{
    if (!ReadFromDisk(txdb, prevout.hash, txindexRet))
        return false;
    if (prevout.n >= vout.size())
    {
        SetNull();
        return false;
    }
    return true;
}

bool CTransaction::ReadFromDisk(CTxDB& txdb, COutPoint prevout)
{
    CTxIndex txindex;
    return ReadFromDisk(txdb, prevout, txindex);
}

bool CTransaction::ReadFromDisk(COutPoint prevout)
{
    CTxDB txdb("r");
    CTxIndex txindex;
    return ReadFromDisk(txdb, prevout, txindex);
}

bool CTransaction::IsStandard(string& strReason) const
{
    if (nVersion > CTransaction::CURRENT_VERSION)
    {
        strReason = "version";
        return false;
    }

    unsigned int nDataOut = 0;
    txnouttype whichType;
    BOOST_FOREACH(const CTxIn& txin, vin)
    {
        // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
        // keys. (remember the 520 byte limit on redeemScript size) That works
        // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)=1624
        // bytes of scriptSig, which we round off to 1650 bytes for some minor
        // future-proofing. That's also enough to spend a 20-of-20
        // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
        // considered standard)
        if (txin.scriptSig.size() > 1650)
        {
            strReason = "scriptsig-size";
            return false;
        }
        if (!txin.scriptSig.IsPushOnly())
        {
            strReason = "scriptsig-not-pushonly";
            return false;
        }
        if (!txin.scriptSig.HasCanonicalPushes()) {
            strReason = "txin-scriptsig-not-canonicalpushes";
            return false;
        }
    }
    BOOST_FOREACH(const CTxOut& txout, vout) {
        if (!::IsStandard(txout.scriptPubKey, whichType)) {
            strReason = "scriptpubkey";
            return false;
        }
        if (whichType == TX_NULL_DATA)
            nDataOut++;
        else {
            if (txout.nValue == 0) {
                strReason = "txout-value=0";
                return false;
            }
            if (!txout.scriptPubKey.HasCanonicalPushes()) {
                strReason = "txout-scriptsig-not-canonicalpushes";
                return false;
            }
        }
    }

    // only one OP_RETURN txout is permitted
    if (nDataOut > 1) {
        strReason = "multi-op-return";
        return false;
    }

    return true;
}

//
// Check transaction inputs, and make sure any
// pay-to-script-hash transactions are evaluating IsStandard scripts
//
// Why bother? To avoid denial-of-service attacks; an attacker
// can submit a standard HASH... OP_EQUAL transaction,
// which will get accepted into blocks. The redemption
// script can be anything; an attacker could use a very
// expensive-to-check-upon-redemption script like:
//   DUP CHECKSIG DROP ... repeated 100 times... OP_1
//
bool CTransaction::AreInputsStandard(const MapPrevTx& mapInputs) const
{
    if (IsCoinBase())
        return true; // Coinbases don't use vin normally

    for (unsigned int i = 0; i < vin.size(); i++)
    {
        const CTxOut& prev = GetOutputFor(vin[i], mapInputs);

        vector<vector<unsigned char> > vSolutions;
        txnouttype whichType;
        // get the scriptPubKey corresponding to this input:
        const CScript& prevScript = prev.scriptPubKey;
        if (!Solver(prevScript, whichType, vSolutions))
            return false;
        int nArgsExpected = ScriptSigArgsExpected(whichType, vSolutions);
        if (nArgsExpected < 0)
            return false;

        // Transactions with extra stuff in their scriptSigs are
        // non-standard. Note that this EvalScript() call will
        // be quick, because if there are any operations
        // beside "push data" in the scriptSig the
        // IsStandard() call returns false
        vector<vector<unsigned char> > stack;
        if (!EvalScript(stack, vin[i].scriptSig, *this, i, false, 0))
            return false;

        if (whichType == TX_SCRIPTHASH)
        {
            if (stack.empty())
                return false;
            CScript subscript(stack.back().begin(), stack.back().end());
            vector<vector<unsigned char> > vSolutions2;
            txnouttype whichType2;
            if (!Solver(subscript, whichType2, vSolutions2))
                return false;
            if (whichType2 == TX_SCRIPTHASH)
                return false;

            int tmpExpected;
            tmpExpected = ScriptSigArgsExpected(whichType2, vSolutions2);
            if (tmpExpected < 0)
                return false;
            nArgsExpected += tmpExpected;
        }

        if (stack.size() != (unsigned int)nArgsExpected)
            return false;
    }

    return true;
}

unsigned int
CTransaction::GetLegacySigOpCount() const
{
    unsigned int nSigOps = 0;
    if (!IsCoinBase() || nTime < COINBASE_SIGOPS_SWITCH_TIME)
    {
        // Coinbase scriptsigs are never executed, so there is 
        //    no sense in calculation of sigops.
        BOOST_FOREACH(const CTxIn& txin, vin)
        {
            nSigOps += txin.scriptSig.GetSigOpCount(false);
        }
    }
    BOOST_FOREACH(const CTxOut& txout, vout)
    {
        nSigOps += txout.scriptPubKey.GetSigOpCount(false);
    }
    return nSigOps;
}


int CMerkleTx::SetMerkleBranch(const CBlock* pblock)
{
    if (fClient)
    {
        if (hashBlock == 0)
            return 0;
    }
    else
    {
        CBlock blockTmp;
        if (pblock == NULL)
        {
            // Load the block this tx is in
            CTxIndex txindex;
            if (!CTxDB("r").ReadTxIndex(GetHash(), txindex))
                return 0;
            if (!blockTmp.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos))
                return 0;
            pblock = &blockTmp;
        }

        // Update the tx's hashBlock
        hashBlock = pblock->GetHash();

        // Locate the transaction
        for (nIndex = 0; nIndex < (int)pblock->vtx.size(); nIndex++)
            if (pblock->vtx[nIndex] == *(CTransaction*)this)
                break;
        if (nIndex == (int)pblock->vtx.size())
        {
            vMerkleBranch.clear();
            nIndex = -1;
            printf("ERROR: SetMerkleBranch() : couldn't find tx in block\n");
            return 0;
        }

        // Fill in merkle branch
        vMerkleBranch = pblock->GetMerkleBranch(nIndex);
    }

    // Is the tx in a block that's in the main chain
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashBlock);
    if (mi == mapBlockIndex.end())
        return 0;
    CBlockIndex* pindex = (*mi).second;
    if (!pindex || !pindex->IsInMainChain())
        return 0;

    return pindexBest->nHeight - pindex->nHeight + 1;
}







bool CTransaction::CheckTransaction() const
{
    // Basic checks that don't depend on any context
    if (vin.empty())
        return DoS(10, error("CTransaction::CheckTransaction() : vin empty"));
    if (vout.empty())
        return DoS(10, error("CTransaction::CheckTransaction() : vout empty"));
    // Time (prevent mempool memory exhaustion attack)
	if (nTime > FutureDrift(GetAdjustedTime()))
        return DoS(10, error("CTransaction::CheckTransaction() : timestamp is too far into the future"));
    // Size limits
    if (::GetSerializeSize(*this, SER_NETWORK, PROTOCOL_VERSION) > MAX_BLOCK_SIZE)
        return DoS(100, error("CTransaction::CheckTransaction() : size limits failed"));

    // Check for negative or overflow output values
    int64_t nValueOut = 0;
    for (unsigned int i = 0; i < vout.size(); i++)
    {
        const CTxOut& txout = vout[i];
        if (txout.IsEmpty() && !IsCoinBase() && !IsCoinStake())
            return DoS(100, error("CTransaction::CheckTransaction() : txout empty for user transaction"));

        if (txout.nValue < 0)
            return DoS(100, error("CTransaction::CheckTransaction() : txout.nValue is negative"));
        if (txout.nValue > MAX_MONEY)
            return DoS(100, error("CTransaction::CheckTransaction() : txout.nValue too high"));
        nValueOut += txout.nValue;
        if (!MoneyRange(nValueOut))
            return DoS(100, error("CTransaction::CheckTransaction() : txout total out of range"));
    }

    // Check for duplicate inputs
    set<COutPoint> vInOutPoints;
    BOOST_FOREACH(const CTxIn& txin, vin)
    {
        if (vInOutPoints.count(txin.prevout))
            return false;
        vInOutPoints.insert(txin.prevout);
    }

    if (IsCoinBase())
    {
        if (vin[0].scriptSig.size() < 2 || vin[0].scriptSig.size() > 100)
            return DoS(100, error("CTransaction::CheckTransaction() : coinbase script size is invalid"));
    }
    else
    {
        BOOST_FOREACH(const CTxIn& txin, vin)
            if (txin.prevout.IsNull())
                return DoS(10, error("CTransaction::CheckTransaction() : prevout is null"));
    }

    return true;
}

int64_t CTransaction::GetMinFee(unsigned int nBlockSize, bool fAllowFree, enum GetMinFee_mode mode, unsigned int nBytes) const
{
    int64_t nMinTxFee = MIN_TX_FEE, nMinRelayTxFee = MIN_RELAY_TX_FEE;

    if(IsCoinStake())
    {
        // Enforce 0.01 as minimum fee for coinstake
        nMinTxFee = CENT;
        nMinRelayTxFee = CENT;
    }

    // Base fee is either nMinTxFee or nMinRelayTxFee
    int64_t nBaseFee = (mode == GMF_RELAY) ? nMinRelayTxFee : nMinTxFee;

    unsigned int nNewBlockSize = nBlockSize + nBytes;
    int64_t nMinFee = (1 + (int64_t)nBytes / 1000) * nBaseFee;

    if (fAllowFree)
    {
        if (nBlockSize == 1)
        {
            // Transactions under 1K are free
            if (nBytes < 1000)
                nMinFee = 0;
        }
        else
        {
            // Free transaction area
            if (nNewBlockSize < 27000)
                nMinFee = 0;
        }
    }

    // To limit dust spam, require additional MIN_TX_FEE/MIN_RELAY_TX_FEE for
    //    each non empty output which is less than 0.01
    //
    // It's safe to ignore empty outputs here, because these inputs are allowed
    //     only for coinbase and coinstake transactions.
    BOOST_FOREACH(const CTxOut& txout, vout)
        if (txout.nValue < CENT && !txout.IsEmpty())
            nMinFee += nBaseFee;

    // Raise the price as the block approaches full
    if (nBlockSize != 1 && nNewBlockSize >= MAX_BLOCK_SIZE_GEN/2)
    {
        if (nNewBlockSize >= MAX_BLOCK_SIZE_GEN)
            return MAX_MONEY;
        nMinFee *= MAX_BLOCK_SIZE_GEN / (MAX_BLOCK_SIZE_GEN - nNewBlockSize);
    }

    if (!MoneyRange(nMinFee))
        nMinFee = MAX_MONEY;

    return nMinFee;
}


bool CTxMemPool::accept(CTxDB& txdb, CTransaction &tx, bool fCheckInputs,
                        bool* pfMissingInputs)
{
    if (pfMissingInputs)
        *pfMissingInputs = false;

    if (!tx.CheckTransaction())
        return error("CTxMemPool::accept() : CheckTransaction failed");

    // Coinbase is only valid in a block, not as a loose transaction
    if (tx.IsCoinBase())
        return tx.DoS(100, error("CTxMemPool::accept() : coinbase as individual tx"));

    // ppcoin: coinstake is also only valid in a block, not as a loose transaction
    if (tx.IsCoinStake())
        return tx.DoS(100, error("CTxMemPool::accept() : coinstake as individual tx"));

    // To help v0.1.5 clients who would see it as a negative number
    if ((int64_t)tx.nLockTime > std::numeric_limits<int>::max())
        return error("CTxMemPool::accept() : not accepting nLockTime beyond 2038 yet");

    // Rather not work on nonstandard transactions (unless -testnet)
    string strNonStd;
    if (!fTestNet && !tx.IsStandard(strNonStd))
        return error("CTxMemPool::accept() : nonstandard transaction (%s)", strNonStd.c_str());

    // Do we already have it?
    uint256 hash = tx.GetHash();
    {
        LOCK(cs);
        if (mapTx.count(hash))
            return false;
    }
    if (fCheckInputs)
        if (txdb.ContainsTx(hash))
            return false;

    // Check for conflicts with in-memory transactions
    CTransaction* ptxOld = NULL;
    for (unsigned int i = 0; i < tx.vin.size(); i++)
    {
        COutPoint outpoint = tx.vin[i].prevout;
        if (mapNextTx.count(outpoint))
        {
            // Disable replacement feature for now
            return false;

            // Allow replacing with a newer version of the same transaction
            if (i != 0)
                return false;
            ptxOld = mapNextTx[outpoint].ptx;
            if (ptxOld->IsFinal())
                return false;
            if (!tx.IsNewerThan(*ptxOld))
                return false;
            for (unsigned int i = 0; i < tx.vin.size(); i++)
            {
                COutPoint outpoint = tx.vin[i].prevout;
                if (!mapNextTx.count(outpoint) || mapNextTx[outpoint].ptx != ptxOld)
                    return false;
            }
            break;
        }
    }

    if (fCheckInputs)
    {
        MapPrevTx mapInputs;
        map<uint256, CTxIndex> mapUnused;
        bool fInvalid = false;
        if (!tx.FetchInputs(txdb, mapUnused, false, false, mapInputs, fInvalid))
        {
            if (fInvalid)
                return error("CTxMemPool::accept() : FetchInputs found invalid tx %s", hash.ToString().substr(0,10).c_str());
            if (pfMissingInputs)
                *pfMissingInputs = true;
            return false;
        }

        // Check for non-standard pay-to-script-hash in inputs
        if (!tx.AreInputsStandard(mapInputs) && !fTestNet)
            return error("CTxMemPool::accept() : nonstandard transaction input");

        // Note: if you modify this code to accept non-standard transactions, then
        // you should add code here to check that the transaction does a
        // reasonable number of ECDSA signature verifications.

        int64_t nFees = tx.GetValueIn(mapInputs)-tx.GetValueOut();
        unsigned int nSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);

        // Don't accept it if it can't get into a block
        int64_t txMinFee = tx.GetMinFee(1000, true, GMF_RELAY, nSize);
        if (nFees < txMinFee)
            return error("CTxMemPool::accept() : not enough fees %s, %" PRId64 " < %" PRId64,
                         hash.ToString().c_str(),
                         nFees, txMinFee);

        // Continuously rate-limit free transactions
        // This mitigates 'penny-flooding' -- sending thousands of free transactions just to
        // be annoying or make others' transactions take longer to confirm.
        if (nFees < MIN_RELAY_TX_FEE)
        {
            static CCriticalSection cs;
            static double dFreeCount;
            static int64_t nLastTime;
            int64_t nNow = GetTime();

            {
                LOCK(cs);
                // Use an exponentially decaying ~10-minute window:
                dFreeCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime));
                nLastTime = nNow;
                // -limitfreerelay unit is thousand-bytes-per-minute
                // At default rate it would take over a month to fill 1GB
                if (dFreeCount > GetArg("-limitfreerelay", 15)*10*1000 && !IsFromMe(tx))
                    return error("CTxMemPool::accept() : free transaction rejected by rate limiter");
                if (fDebug)
                    printf("Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
                dFreeCount += nSize;
            }
        }

        // Check against previous transactions
        // This is done last to help prevent CPU exhaustion denial-of-service attacks.
        if (!tx.ConnectInputs(txdb, mapInputs, mapUnused, CDiskTxPos(1,1,1), pindexBest, false, false, true, STRICT_FLAGS))
        {
            return error("CTxMemPool::accept() : ConnectInputs failed %s", hash.ToString().substr(0,10).c_str());
        }
    }

    // Store transaction in memory
    {
        LOCK(cs);
        if (ptxOld)
        {
            printf("CTxMemPool::accept() : replacing tx %s with new version\n", ptxOld->GetHash().ToString().c_str());
            remove(*ptxOld);
        }
        addUnchecked(hash, tx);
    }

    ///// are we sure this is ok when loading transactions or restoring block txes
    // If updated, erase old tx from wallet
    if (ptxOld)
        EraseFromWallets(ptxOld->GetHash());

    printf("CTxMemPool::accept() : accepted %s (poolsz %" PRIszu ")\n",
           hash.ToString().substr(0,10).c_str(),
           mapTx.size());
    return true;
}

bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMissingInputs)
{
    return mempool.accept(txdb, *this, fCheckInputs, pfMissingInputs);
}

bool CTxMemPool::addUnchecked(const uint256& hash, CTransaction &tx)
{
    // Add to memory pool without checking anything.  Don't call this directly,
    // call CTxMemPool::accept to properly check the transaction first.
    {
        mapTx[hash] = tx;
        for (unsigned int i = 0; i < tx.vin.size(); i++)
            mapNextTx[tx.vin[i].prevout] = CInPoint(&mapTx[hash], i);
        nTransactionsUpdated++;
    }
    return true;
}


bool CTxMemPool::remove(CTransaction &tx)
{
    // Remove transaction from memory pool
    {
        LOCK(cs);
        uint256 hash = tx.GetHash();
        if (mapTx.count(hash))
        {
            BOOST_FOREACH(const CTxIn& txin, tx.vin)
                mapNextTx.erase(txin.prevout);
            mapTx.erase(hash);
            nTransactionsUpdated++;
        }
    }
    return true;
}

void CTxMemPool::clear()
{
    LOCK(cs);
    mapTx.clear();
    mapNextTx.clear();
    ++nTransactionsUpdated;
}

void CTxMemPool::queryHashes(std::vector<uint256>& vtxid)
{
    vtxid.clear();

    LOCK(cs);
    vtxid.reserve(mapTx.size());
    for (map<uint256, CTransaction>::iterator mi = mapTx.begin(); mi != mapTx.end(); ++mi)
        vtxid.push_back((*mi).first);
}




int CMerkleTx::GetDepthInMainChain(CBlockIndex* &pindexRet) const
{
    if (hashBlock == 0 || nIndex == -1)
        return 0;

    // Find the block it claims to be in
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashBlock);
    if (mi == mapBlockIndex.end())
        return 0;
    CBlockIndex* pindex = (*mi).second;
    if (!pindex || !pindex->IsInMainChain())
        return 0;

    // Make sure the merkle branch connects to this block
    if (!fMerkleVerified)
    {
        if (CBlock::CheckMerkleBranch(GetHash(), vMerkleBranch, nIndex) != pindex->hashMerkleRoot)
            return 0;
        fMerkleVerified = true;
    }

    pindexRet = pindex;
    return pindexBest->nHeight - pindex->nHeight + 1;
}


int CMerkleTx::GetBlocksToMaturity() const
{
    if (!(IsCoinBase() || IsCoinStake()))
        return 0;
    return max(0, (nCoinbaseMaturity+20) - GetDepthInMainChain());
}


bool CMerkleTx::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs)
{
    if (fClient)
    {
        if (!IsInMainChain() && !ClientConnectInputs())
            return false;
        return CTransaction::AcceptToMemoryPool(txdb, false);
    }
    else
    {
        return CTransaction::AcceptToMemoryPool(txdb, fCheckInputs);
    }
}

bool CMerkleTx::AcceptToMemoryPool()
{
    CTxDB txdb("r");
    return AcceptToMemoryPool(txdb);
}



bool CWalletTx::AcceptWalletTransaction(CTxDB& txdb, bool fCheckInputs)
{

    {
        LOCK(mempool.cs);
        // Add previous supporting transactions first
        BOOST_FOREACH(CMerkleTx& tx, vtxPrev)
        {
            if (!(tx.IsCoinBase() || tx.IsCoinStake()))
            {
                uint256 hash = tx.GetHash();
                if (!mempool.exists(hash) && !txdb.ContainsTx(hash))
                    tx.AcceptToMemoryPool(txdb, fCheckInputs);
            }
        }
        return AcceptToMemoryPool(txdb, fCheckInputs);
    }
    return false;
}

bool CWalletTx::AcceptWalletTransaction()
{
    CTxDB txdb("r");
    return AcceptWalletTransaction(txdb);
}

int CTxIndex::GetDepthInMainChain() const
{
    // Read block header
    CBlock block;
    if (!block.ReadFromDisk(pos.nFile, pos.nBlockPos, false))
        return 0;
    // Find the block in the index
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(block.GetHash());
    if (mi == mapBlockIndex.end())
        return 0;
    CBlockIndex* pindex = (*mi).second;
    if (!pindex || !pindex->IsInMainChain())
        return 0;
    return 1 + nBestHeight - pindex->nHeight;
}

// Return transaction in tx, and if it was found inside a block, its hash is placed in hashBlock
bool GetTransaction(const uint256 &hash, CTransaction &tx, uint256 &hashBlock)
{
    {
        LOCK(cs_main);
        {
            LOCK(mempool.cs);
            if (mempool.exists(hash))
            {
                tx = mempool.lookup(hash);
                return true;
            }
        }
        CTxDB txdb("r");
        CTxIndex txindex;
        if (tx.ReadFromDisk(txdb, hash, txindex))
        {
            CBlock block;
            if (block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
                hashBlock = block.GetHash();
            return true;
        }
        // look for transaction in disconnected blocks to find orphaned CoinBase and CoinStake transactions
        BOOST_FOREACH(PAIRTYPE(const uint256, CBlockIndex*)& item, mapBlockIndex)
        {
            CBlockIndex* pindex = item.second;
            if (pindex == pindexBest || pindex->pnext != 0)
                continue;
            CBlock block;
            if (!block.ReadFromDisk(pindex))
                continue;
            BOOST_FOREACH(const CTransaction& txOrphan, block.vtx)
            {
                if (txOrphan.GetHash() == hash)
                {
                    tx = txOrphan;
                    return true;
                }
            }
        }
    }
    return false;
}








//////////////////////////////////////////////////////////////////////////////
//
// CBlock and CBlockIndex
//

static CBlockIndex* pblockindexFBBHLast;
CBlockIndex* FindBlockByHeight(int nHeight)
{
    CBlockIndex *pblockindex;
    if (nHeight < nBestHeight / 2)
        pblockindex = pindexGenesisBlock;
    else
        pblockindex = pindexBest;
    if (pblockindexFBBHLast && abs(nHeight - pblockindex->nHeight) > abs(nHeight - pblockindexFBBHLast->nHeight))
        pblockindex = pblockindexFBBHLast;
    while (pblockindex->nHeight > nHeight)
        pblockindex = pblockindex->pprev;
    while (pblockindex->nHeight < nHeight)
        pblockindex = pblockindex->pnext;
    pblockindexFBBHLast = pblockindex;
    return pblockindex;
}

bool CBlock::ReadFromDisk(const CBlockIndex* pindex, bool fReadTransactions)
{
    if (!fReadTransactions)
    {
        *this = pindex->GetBlockHeader();
        return true;
    }
    if (!ReadFromDisk(pindex->nFile, pindex->nBlockPos, fReadTransactions))
        return false;
    if (GetHash() != pindex->GetBlockHash())
        return error("CBlock::ReadFromDisk() : GetHash() doesn't match index");
    return true;
}

uint256 static GetOrphanRoot(const CBlock* pblock)
{
    // Work back to the first block in the orphan chain
    while (mapOrphanBlocks.count(pblock->hashPrevBlock))
        pblock = mapOrphanBlocks[pblock->hashPrevBlock];
    return pblock->GetHash();
}

// ppcoin: find block wanted by given orphan block
uint256 WantedByOrphan(const CBlock* pblockOrphan)
{
    // Work back to the first block in the orphan chain
    while (mapOrphanBlocks.count(pblockOrphan->hashPrevBlock))
        pblockOrphan = mapOrphanBlocks[pblockOrphan->hashPrevBlock];
    return pblockOrphan->hashPrevBlock;
}

// select stake target limit according to hard-coded conditions
CBigNum inline GetProofOfStakeLimit(int nHeight, unsigned int nTime)
{
    if(fTestNet) // separate proof of stake target limit for testnet
        return bnProofOfStakeLimit;
    if(nTime > TARGETS_SWITCH_TIME) // 27 bits since 20 July 2013
        return bnProofOfStakeLimit;
    if(nHeight + 1 > 15000) // 24 bits since block 15000
        return bnProofOfStakeLegacyLimit;
    if(nHeight + 1 > 14060) // 31 bits since block 14060 until 15000
        return bnProofOfStakeHardLimit;

    return bnProofOfWorkLimit; // return bnProofOfWorkLimit of none matched
}

// miner's coin base reward based on nBits
int64_t GetProofOfWorkReward(unsigned int nBits, int64_t nFees, int nHeight)
{
    int64_t nSubsidy = 900 * COIN;
	
	if (nHeight == 1)
		return 300000000 * COIN;
    
	// Force block reward to zero when right shift is undefined.
    int halvings = nHeight / 1000000;
    if (halvings >= 64)
        return nFees;
		
	nSubsidy >>= halvings;
	
    if (fDebug && GetBoolArg("-printcreation"))
        printf("GetProofOfWorkReward() : create=%s nBits=0x%08x nSubsidy=%" PRId64 "\n", FormatMoney(nSubsidy).c_str(), nBits, nSubsidy);

    return nSubsidy + nFees;
}

// miner's coin stake reward based on nBits and coin age spent (coin-days)
int64_t GetProofOfStakeReward(int64_t nCoinAge, unsigned int nBits, int64_t nTime, bool bCoinYearOnly)
{
    int64_t nRewardCoinYear = 40 * CENT;

    int64_t nSubsidy = nCoinAge * nRewardCoinYear / 365;

    if (fDebug && GetBoolArg("-printcreation"))
        printf("GetProofOfStakeReward(): create=%s nCoinAge=%"PRId64"\n", FormatMoney(nSubsidy).c_str(), nCoinAge);

    return nSubsidy; // + nFees;
}

static const int64_t nTargetTimespan = 6 * 15 * 60;

// Get proof of work blocks max spacing according to hard-coded conditions
// Not in use right now!
int64_t inline GetTargetSpacingWorkMax(int nHeight, unsigned int nTime)
{
    if(nTime > TARGETS_SWITCH_TIME)
        return 3 * nStakeTargetSpacing; // 30 minutes on mainNet since 20 Jul 2013 00:00:00

    if(fTestNet)
        return 3 * nStakeTargetSpacing; // 15 minutes on testNet

    return 12 * nStakeTargetSpacing; // 2 hours otherwise
}

//
// maximum nBits value could possible be required nTime after
//
unsigned int ComputeMaxBits(CBigNum bnTargetLimit, unsigned int nBase, int64_t nTime)
{
    CBigNum bnResult;
    bnResult.SetCompact(nBase);
    bnResult *= 2;
    while (nTime > 0 && bnResult < bnTargetLimit)
    {
        // Maximum 200% adjustment per day...
        bnResult *= 2;
        nTime -= nOneDay;
    }
    if (bnResult > bnTargetLimit)
        bnResult = bnTargetLimit;
    return bnResult.GetCompact();
}

//
// minimum amount of work that could possibly be required nTime after
// minimum proof-of-work required was nBase
//
unsigned int ComputeMinWork(unsigned int nBase, int64_t nTime)
{
    return ComputeMaxBits(bnProofOfWorkLimit, nBase, nTime);
}

//
// minimum amount of stake that could possibly be required nTime after
// minimum proof-of-stake required was nBase
//
unsigned int ComputeMinStake(unsigned int nBase, int64_t nTime, unsigned int nBlockTime)
{
    return ComputeMaxBits(GetProofOfStakeLimit(0, nBlockTime), nBase, nTime);
}


// ppcoin: find last block index up to pindex
const CBlockIndex* GetLastBlockIndex(const CBlockIndex* pindex, bool fProofOfStake)
{
    while (pindex && pindex->pprev && (pindex->IsProofOfStake() != fProofOfStake))
        pindex = pindex->pprev;
    return pindex;
}

unsigned int GetNextTargetRequired(const CBlockIndex* pindexLast, bool fProofOfStake)
{
    CBigNum bnTargetLimit = !fProofOfStake ? bnProofOfWorkLimit : GetProofOfStakeLimit(pindexLast->nHeight, pindexLast->nTime);

    if (pindexLast == NULL)
        return bnTargetLimit.GetCompact(); // genesis block

    const CBlockIndex* pindexPrev = GetLastBlockIndex(pindexLast, fProofOfStake);
    if (pindexPrev->pprev == NULL)
        return bnTargetLimit.GetCompact(); // first block
    const CBlockIndex* pindexPrevPrev = GetLastBlockIndex(pindexPrev->pprev, fProofOfStake);
    if (pindexPrevPrev->pprev == NULL)
        return bnTargetLimit.GetCompact(); // second block

    int64_t nActualSpacing = pindexPrev->GetBlockTime() - pindexPrevPrev->GetBlockTime();

	// Don't allow zero or negative values.
	if (nActualSpacing < 1)
		nActualSpacing = 1;
	
	// Limit the impact of blocks that are unusually far in the future
	if (nActualSpacing > 3 * nTargetSpacing)
		nActualSpacing = 3 * nTargetSpacing;
	
    // ppcoin: target change every block
    // ppcoin: retarget with exponential moving toward target spacing
    CBigNum bnNew;
    bnNew.SetCompact(pindexPrev->nBits);
	// The below is intentionally commented out. We use the same time for POW and POS.
    // int64_t nTargetSpacing = fProofOfStake? nStakeTargetSpacing : min(GetTargetSpacingWorkMax(pindexLast->nHeight, pindexLast->nTime), (int64_t) nStakeTargetSpacing * (1 + pindexLast->nHeight - pindexPrev->nHeight));
    int64_t nInterval = nTargetTimespan / nTargetSpacing;
    bnNew *= ((nInterval - 1) * nTargetSpacing + nActualSpacing + nActualSpacing);
    bnNew /= ((nInterval + 1) * nTargetSpacing);

    if (bnNew > bnTargetLimit)
        bnNew = bnTargetLimit;

    return bnNew.GetCompact();
}

bool CheckProofOfWork(uint256 hash, unsigned int nBits)
{
    CBigNum bnTarget;
    bnTarget.SetCompact(nBits);

    // Check range
    if (bnTarget <= 0 || bnTarget > bnProofOfWorkLimit)
        return error("CheckProofOfWork() : nBits below minimum work");

    // Check proof of work matches claimed amount
    if (hash > bnTarget.getuint256())
        return error("CheckProofOfWork() : hash doesn't match nBits");

    return true;
}

// Return maximum amount of blocks that other nodes claim to have
int GetNumBlocksOfPeers()
{
    return std::max(cPeerBlockCounts.median(), Checkpoints::GetTotalBlocksEstimate());
}

bool IsInitialBlockDownload()
{
    if (pindexBest == NULL || nBestHeight < Checkpoints::GetTotalBlocksEstimate())
        return true;
    static int64_t nLastUpdate;
    static CBlockIndex* pindexLastBest;
    int64_t nCurrentTime = GetTime();
    if (pindexBest != pindexLastBest)
    {
        pindexLastBest = pindexBest;
        nLastUpdate = nCurrentTime;
    }
    return (nCurrentTime - nLastUpdate < 10 &&
            pindexBest->GetBlockTime() < nCurrentTime - nOneDay);
}

void static InvalidChainFound(CBlockIndex* pindexNew)
{
    if (pindexNew->nChainTrust > nBestInvalidTrust)
    {
        nBestInvalidTrust = pindexNew->nChainTrust;
        CTxDB().WriteBestInvalidTrust(CBigNum(nBestInvalidTrust));
        uiInterface.NotifyBlocksChanged();
    }

    uint256 nBestInvalidBlockTrust = pindexNew->nChainTrust - pindexNew->pprev->nChainTrust;
    uint256 nBestBlockTrust = pindexBest->nHeight != 0 ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust) : pindexBest->nChainTrust;

    printf("InvalidChainFound: invalid block=%s  height=%d  trust=%s  blocktrust=%" PRId64 "  date=%s\n",
      pindexNew->GetBlockHash().ToString().substr(0,20).c_str(), pindexNew->nHeight,
      CBigNum(pindexNew->nChainTrust).ToString().c_str(), nBestInvalidBlockTrust.Get64(),
      DateTimeStrFormat("%x %H:%M:%S", pindexNew->GetBlockTime()).c_str());
    printf("InvalidChainFound:  current best=%s  height=%d  trust=%s  blocktrust=%" PRId64 "  date=%s\n",
      hashBestChain.ToString().substr(0,20).c_str(), nBestHeight,
      CBigNum(pindexBest->nChainTrust).ToString().c_str(),
      nBestBlockTrust.Get64(),
      DateTimeStrFormat("%x %H:%M:%S", pindexBest->GetBlockTime()).c_str());
}


void CBlock::UpdateTime(const CBlockIndex* pindexPrev)
{
    nTime = max(GetBlockTime(), GetAdjustedTime());
}











bool CTransaction::DisconnectInputs(CTxDB& txdb)
{
    // Relinquish previous transactions' spent pointers
    if (!IsCoinBase())
    {
        BOOST_FOREACH(const CTxIn& txin, vin)
        {
            COutPoint prevout = txin.prevout;

            // Get prev txindex from disk
            CTxIndex txindex;
            if (!txdb.ReadTxIndex(prevout.hash, txindex))
                return error("DisconnectInputs() : ReadTxIndex failed");

            if (prevout.n >= txindex.vSpent.size())
                return error("DisconnectInputs() : prevout.n out of range");

            // Mark outpoint as not spent
            txindex.vSpent[prevout.n].SetNull();

            // Write back
            if (!txdb.UpdateTxIndex(prevout.hash, txindex))
                return error("DisconnectInputs() : UpdateTxIndex failed");
        }
    }

    // Remove transaction from index
    // This can fail if a duplicate of this transaction was in a chain that got
    // reorganized away. This is only possible if this transaction was completely
    // spent, so erasing it would be a no-op anyway.
    txdb.EraseTxIndex(*this);

    return true;
}


bool CTransaction::FetchInputs(CTxDB& txdb, const map<uint256, CTxIndex>& mapTestPool,
                               bool fBlock, bool fMiner, MapPrevTx& inputsRet, bool& fInvalid)
{
    // FetchInputs can return false either because we just haven't seen some inputs
    // (in which case the transaction should be stored as an orphan)
    // or because the transaction is malformed (in which case the transaction should
    // be dropped).  If tx is definitely invalid, fInvalid will be set to true.
    fInvalid = false;

    if (IsCoinBase())
        return true; // Coinbase transactions have no inputs to fetch.

    for (unsigned int i = 0; i < vin.size(); i++)
    {
        COutPoint prevout = vin[i].prevout;
        if (inputsRet.count(prevout.hash))
            continue; // Got it already

        // Read txindex
        CTxIndex& txindex = inputsRet[prevout.hash].first;
        bool fFound = true;
        if ((fBlock || fMiner) && mapTestPool.count(prevout.hash))
        {
            // Get txindex from current proposed changes
            txindex = mapTestPool.find(prevout.hash)->second;
        }
        else
        {
            // Read txindex from txdb
            fFound = txdb.ReadTxIndex(prevout.hash, txindex);
        }
        if (!fFound && (fBlock || fMiner))
            return fMiner ? false : error("FetchInputs() : %s prev tx %s index entry not found", GetHash().ToString().substr(0,10).c_str(),  prevout.hash.ToString().substr(0,10).c_str());

        // Read txPrev
        CTransaction& txPrev = inputsRet[prevout.hash].second;
        if (!fFound || txindex.pos == CDiskTxPos(1,1,1))
        {
            // Get prev tx from single transactions in memory
            {
                LOCK(mempool.cs);
                if (!mempool.exists(prevout.hash))
                    return error("FetchInputs() : %s mempool Tx prev not found %s", GetHash().ToString().substr(0,10).c_str(),  prevout.hash.ToString().substr(0,10).c_str());
                txPrev = mempool.lookup(prevout.hash);
            }
            if (!fFound)
                txindex.vSpent.resize(txPrev.vout.size());
        }
        else
        {
            // Get prev tx from disk
            if (!txPrev.ReadFromDisk(txindex.pos))
                return error("FetchInputs() : %s ReadFromDisk prev tx %s failed", GetHash().ToString().substr(0,10).c_str(),  prevout.hash.ToString().substr(0,10).c_str());
        }
    }

    // Make sure all prevout.n indexes are valid:
    for (unsigned int i = 0; i < vin.size(); i++)
    {
        const COutPoint prevout = vin[i].prevout;
        assert(inputsRet.count(prevout.hash) != 0);
        const CTxIndex& txindex = inputsRet[prevout.hash].first;
        const CTransaction& txPrev = inputsRet[prevout.hash].second;
        if (prevout.n >= txPrev.vout.size() || prevout.n >= txindex.vSpent.size())
        {
            // Revisit this if/when transaction replacement is implemented and allows
            // adding inputs:
            fInvalid = true;
            return DoS(100, error("FetchInputs() : %s prevout.n out of range %d %" PRIszu " %" PRIszu " prev tx %s\n%s", GetHash().ToString().substr(0,10).c_str(), prevout.n, txPrev.vout.size(), txindex.vSpent.size(), prevout.hash.ToString().substr(0,10).c_str(), txPrev.ToString().c_str()));
        }
    }

    return true;
}

const CTxOut& CTransaction::GetOutputFor(const CTxIn& input, const MapPrevTx& inputs) const
{
    MapPrevTx::const_iterator mi = inputs.find(input.prevout.hash);
    if (mi == inputs.end())
        throw std::runtime_error("CTransaction::GetOutputFor() : prevout.hash not found");

    const CTransaction& txPrev = (mi->second).second;
    if (input.prevout.n >= txPrev.vout.size())
        throw std::runtime_error("CTransaction::GetOutputFor() : prevout.n out of range");

    return txPrev.vout[input.prevout.n];
}

int64_t CTransaction::GetValueIn(const MapPrevTx& inputs) const
{
    if (IsCoinBase())
        return 0;

    int64_t nResult = 0;
    for (unsigned int i = 0; i < vin.size(); i++)
    {
        nResult += GetOutputFor(vin[i], inputs).nValue;
    }
    return nResult;

}

unsigned int CTransaction::GetP2SHSigOpCount(const MapPrevTx& inputs) const
{
    if (IsCoinBase())
        return 0;

    unsigned int nSigOps = 0;
    for (unsigned int i = 0; i < vin.size(); i++)
    {
        const CTxOut& prevout = GetOutputFor(vin[i], inputs);
        if (prevout.scriptPubKey.IsPayToScriptHash())
            nSigOps += prevout.scriptPubKey.GetSigOpCount(vin[i].scriptSig);
    }
    return nSigOps;
}

bool CScriptCheck::operator()() const {
    const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
    if (!VerifyScript(scriptSig, scriptPubKey, *ptxTo, nIn, nFlags, nHashType))
        return error("CScriptCheck() : %s VerifySignature failed", ptxTo->GetHash().ToString().substr(0,10).c_str());
    return true;
}

bool VerifySignature(const CTransaction& txFrom, const CTransaction& txTo, unsigned int nIn, unsigned int flags, int nHashType)
{
    return CScriptCheck(txFrom, txTo, nIn, flags, nHashType)();
}

bool CTransaction::ConnectInputs(CTxDB& txdb, MapPrevTx inputs, map<uint256, CTxIndex>& mapTestPool, const CDiskTxPos& posThisTx,
    const CBlockIndex* pindexBlock, bool fBlock, bool fMiner, bool fScriptChecks, unsigned int flags, std::vector<CScriptCheck> *pvChecks)
{
    // Take over previous transactions' spent pointers
    // fBlock is true when this is called from AcceptBlock when a new best-block is added to the blockchain
    // fMiner is true when called from the internal bitcoin miner
    // ... both are false when called from CTransaction::AcceptToMemoryPool

    if (!IsCoinBase())
    {
        int64_t nValueIn = 0;
        int64_t nFees = 0;
        for (unsigned int i = 0; i < vin.size(); i++)
        {
            COutPoint prevout = vin[i].prevout;
            assert(inputs.count(prevout.hash) > 0);
            CTxIndex& txindex = inputs[prevout.hash].first;
            CTransaction& txPrev = inputs[prevout.hash].second;

            if (prevout.n >= txPrev.vout.size() || prevout.n >= txindex.vSpent.size())
                return DoS(100, error("ConnectInputs() : %s prevout.n out of range %d %" PRIszu " %" PRIszu " prev tx %s\n%s", GetHash().ToString().substr(0,10).c_str(), prevout.n, txPrev.vout.size(), txindex.vSpent.size(), prevout.hash.ToString().substr(0,10).c_str(), txPrev.ToString().c_str()));

            // If prev is coinbase or coinstake, check that it's matured
            if (txPrev.IsCoinBase() || txPrev.IsCoinStake())
                for (const CBlockIndex* pindex = pindexBlock; pindex && pindexBlock->nHeight - pindex->nHeight < nCoinbaseMaturity; pindex = pindex->pprev)
                    if (pindex->nBlockPos == txindex.pos.nBlockPos && pindex->nFile == txindex.pos.nFile)
                        return error("ConnectInputs() : tried to spend %s at depth %d", txPrev.IsCoinBase() ? "coinbase" : "coinstake", pindexBlock->nHeight - pindex->nHeight);

            // ppcoin: check transaction timestamp
            if (txPrev.nTime > nTime)
                return DoS(100, error("ConnectInputs() : transaction timestamp earlier than input transaction"));

            // Check for negative or overflow input values
            nValueIn += txPrev.vout[prevout.n].nValue;
            if (!MoneyRange(txPrev.vout[prevout.n].nValue) || !MoneyRange(nValueIn))
                return DoS(100, error("ConnectInputs() : txin values out of range"));

        }

        if (pvChecks)
            pvChecks->reserve(vin.size());

        // The first loop above does all the inexpensive checks.
        // Only if ALL inputs pass do we perform expensive ECDSA signature checks.
        // Helps prevent CPU exhaustion attacks.
        for (unsigned int i = 0; i < vin.size(); i++)
        {
            COutPoint prevout = vin[i].prevout;
            assert(inputs.count(prevout.hash) > 0);
            CTxIndex& txindex = inputs[prevout.hash].first;
            CTransaction& txPrev = inputs[prevout.hash].second;

            // Check for conflicts (double-spend)
            // This doesn't trigger the DoS code on purpose; if it did, it would make it easier
            // for an attacker to attempt to split the network.
            if (!txindex.vSpent[prevout.n].IsNull())
                return fMiner ? false : error("ConnectInputs() : %s prev tx already used at %s", GetHash().ToString().substr(0,10).c_str(), txindex.vSpent[prevout.n].ToString().c_str());

            // Skip ECDSA signature verification when connecting blocks (fBlock=true)
            // before the last blockchain checkpoint. This is safe because block merkle hashes are
            // still computed and checked, and any change will be caught at the next checkpoint.
            if (fScriptChecks)
            {
                // Verify signature
                CScriptCheck check(txPrev, *this, i, flags, 0);
                if (pvChecks)
                {
                    pvChecks->push_back(CScriptCheck());
                    check.swap(pvChecks->back());
                }
                else if (!check())
                {
                    if (flags & STRICT_FLAGS)
                    {
                        // Don't trigger DoS code in case of STRICT_FLAGS caused failure.
                        CScriptCheck check(txPrev, *this, i, flags & ~STRICT_FLAGS, 0);
                        if (check())
                            return error("ConnectInputs() : %s strict VerifySignature failed", GetHash().ToString().substr(0,10).c_str());
                    }
                    return DoS(100,error("ConnectInputs() : %s VerifySignature failed", GetHash().ToString().substr(0,10).c_str()));
                }
            }

            // Mark outpoints as spent
            txindex.vSpent[prevout.n] = posThisTx;

            // Write back
            if (fBlock || fMiner)
            {
                mapTestPool[prevout.hash] = txindex;
            }
        }

        if (IsCoinStake())
        {
            if (nTime >  Checkpoints::GetLastCheckpointTime())
            {
                unsigned int nTxSize = GetSerializeSize(SER_NETWORK, PROTOCOL_VERSION);

                // coin stake tx earns reward instead of paying fee
                uint64_t nCoinAge;
                if (!GetCoinAge(txdb, nCoinAge))
                    return error("ConnectInputs() : %s unable to get coin age for coinstake", GetHash().ToString().substr(0,10).c_str());

                int64_t nReward = GetValueOut() - nValueIn;
                int64_t nCalculatedReward = GetProofOfStakeReward(nCoinAge, pindexBlock->nBits, nTime) - GetMinFee(1, false, GMF_BLOCK, nTxSize) + CENT;

                if (nReward > nCalculatedReward)
                    return DoS(100, error("ConnectInputs() : coinstake pays too much(actual=%" PRId64 " vs calculated=%" PRId64 ")", nReward, nCalculatedReward));
            }
        }
        else
        {
            if (nValueIn < GetValueOut())
                return DoS(100, error("ConnectInputs() : %s value in < value out", GetHash().ToString().substr(0,10).c_str()));

            // Tally transaction fees
            int64_t nTxFee = nValueIn - GetValueOut();
            if (nTxFee < 0)
                return DoS(100, error("ConnectInputs() : %s nTxFee < 0", GetHash().ToString().substr(0,10).c_str()));

            nFees += nTxFee;
            if (!MoneyRange(nFees))
                return DoS(100, error("ConnectInputs() : nFees out of range"));
        }
    }

    return true;
}


bool CTransaction::ClientConnectInputs()
{
    if (IsCoinBase())
        return false;

    // Take over previous transactions' spent pointers
    {
        LOCK(mempool.cs);
        int64_t nValueIn = 0;
        for (unsigned int i = 0; i < vin.size(); i++)
        {
            // Get prev tx from single transactions in memory
            COutPoint prevout = vin[i].prevout;
            if (!mempool.exists(prevout.hash))
                return false;
            CTransaction& txPrev = mempool.lookup(prevout.hash);

            if (prevout.n >= txPrev.vout.size())
                return false;

            // Verify signature
            if (!VerifySignature(txPrev, *this, i, SCRIPT_VERIFY_NOCACHE | SCRIPT_VERIFY_P2SH, 0))
                return error("ClientConnectInputs() : VerifySignature failed");

            ///// this is redundant with the mempool.mapNextTx stuff,
            ///// not sure which I want to get rid of
            ///// this has to go away now that posNext is gone
            // // Check for conflicts
            // if (!txPrev.vout[prevout.n].posNext.IsNull())
            //     return error("ConnectInputs() : prev tx already used");
            //
            // // Flag outpoints as used
            // txPrev.vout[prevout.n].posNext = posThisTx;

            nValueIn += txPrev.vout[prevout.n].nValue;

            if (!MoneyRange(txPrev.vout[prevout.n].nValue) || !MoneyRange(nValueIn))
                return error("ClientConnectInputs() : txin values out of range");
        }
        if (GetValueOut() > nValueIn)
            return false;
    }

    return true;
}




bool CBlock::DisconnectBlock(CTxDB& txdb, CBlockIndex* pindex)
{
    // Disconnect in reverse order
    for (int i = vtx.size()-1; i >= 0; i--)
        if (!vtx[i].DisconnectInputs(txdb))
            return false;

    // Update block index on disk without changing it in memory.
    // The memory index structure will be changed after the db commits.
    if (pindex->pprev)
    {
        CDiskBlockIndex blockindexPrev(pindex->pprev);
        blockindexPrev.hashNext = 0;
        if (!txdb.WriteBlockIndex(blockindexPrev))
            return error("DisconnectBlock() : WriteBlockIndex failed");
    }

    // ppcoin: clean up wallet after disconnecting coinstake
    BOOST_FOREACH(CTransaction& tx, vtx)
        SyncWithWallets(tx, this, false, false);

    return true;
}

static CCheckQueue<CScriptCheck> scriptcheckqueue(128);

void ThreadScriptCheck(void*) {
    vnThreadsRunning[THREAD_SCRIPTCHECK]++;
    RenameThread("iWalletCoin-scriptch");
    scriptcheckqueue.Thread();
    vnThreadsRunning[THREAD_SCRIPTCHECK]--;
}

void ThreadScriptCheckQuit() {
    scriptcheckqueue.Quit();
}

bool CBlock::ConnectBlock(CTxDB& txdb, CBlockIndex* pindex, bool fJustCheck)
{
    // Check it again in case a previous version let a bad block in, but skip BlockSig checking
    if (!CheckBlock(!fJustCheck, !fJustCheck, false))
        return false;

    // Do not allow blocks that contain transactions which 'overwrite' older transactions,
    // unless those are already completely spent.
    // If such overwrites are allowed, coinbases and transactions depending upon those
    // can be duplicated to remove the ability to spend the first instance -- even after
    // being sent to another address.
    // See BIP30 and http://r6.ca/blog/20120206T005236Z.html for more information.
    // This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
    // already refuses previously-known transaction ids entirely.
    // This rule was originally applied all blocks whose timestamp was after March 15, 2012, 0:00 UTC.
    // Now that the whole chain is irreversibly beyond that time it is applied to all blocks except the
    // two in the chain that violate it. This prevents exploiting the issue against nodes in their
    // initial block download.
    bool fEnforceBIP30 = true; // Always active in iWalletCoin
    bool fScriptChecks = pindex->nHeight >= Checkpoints::GetTotalBlocksEstimate();

    //// issue here: it doesn't know the version
    unsigned int nTxPos;
    if (fJustCheck)
        // FetchInputs treats CDiskTxPos(1,1,1) as a special "refer to memorypool" indicator
        // Since we're just checking the block and not actually connecting it, it might not (and probably shouldn't) be on the disk to get the transaction from
        nTxPos = 1;
    else
        nTxPos = pindex->nBlockPos + ::GetSerializeSize(CBlock(), SER_DISK, CLIENT_VERSION) - (2 * GetSizeOfCompactSize(0)) + GetSizeOfCompactSize(vtx.size());

    map<uint256, CTxIndex> mapQueuedChanges;
    CCheckQueueControl<CScriptCheck> control(fScriptChecks && nScriptCheckThreads ? &scriptcheckqueue : NULL);

    int64_t nFees = 0;
    int64_t nValueIn = 0;
    int64_t nValueOut = 0;
    unsigned int nSigOps = 0;
    BOOST_FOREACH(CTransaction& tx, vtx)
    {
        uint256 hashTx = tx.GetHash();

        if (fEnforceBIP30) {
            CTxIndex txindexOld;
            if (txdb.ReadTxIndex(hashTx, txindexOld)) {
                BOOST_FOREACH(CDiskTxPos &pos, txindexOld.vSpent)
                    if (pos.IsNull())
                        return false;
            }
        }

        nSigOps += tx.GetLegacySigOpCount();
        if (nSigOps > MAX_BLOCK_SIGOPS)
            return DoS(100, error("ConnectBlock() : too many sigops"));

        CDiskTxPos posThisTx(pindex->nFile, pindex->nBlockPos, nTxPos);
        if (!fJustCheck)
            nTxPos += ::GetSerializeSize(tx, SER_DISK, CLIENT_VERSION);

        MapPrevTx mapInputs;
        if (tx.IsCoinBase())
            nValueOut += tx.GetValueOut();
        else
        {
            bool fInvalid;
            if (!tx.FetchInputs(txdb, mapQueuedChanges, true, false, mapInputs, fInvalid))
                return false;

            // Add in sigops done by pay-to-script-hash inputs;
            // this is to prevent a "rogue miner" from creating
            // an incredibly-expensive-to-validate block.
            nSigOps += tx.GetP2SHSigOpCount(mapInputs);
            if (nSigOps > MAX_BLOCK_SIGOPS)
                return DoS(100, error("ConnectBlock() : too many sigops"));

            int64_t nTxValueIn = tx.GetValueIn(mapInputs);
            int64_t nTxValueOut = tx.GetValueOut();
            nValueIn += nTxValueIn;
            nValueOut += nTxValueOut;
            if (!tx.IsCoinStake())
                nFees += nTxValueIn - nTxValueOut;

            std::vector<CScriptCheck> vChecks;
            if (!tx.ConnectInputs(txdb, mapInputs, mapQueuedChanges, posThisTx, pindex, true, false, fScriptChecks, SCRIPT_VERIFY_NOCACHE | SCRIPT_VERIFY_P2SH, nScriptCheckThreads ? &vChecks : NULL))
                return false;
            control.Add(vChecks);
        }

        mapQueuedChanges[hashTx] = CTxIndex(posThisTx, tx.vout.size());
    }

    if (!control.Wait())
        return DoS(100, false);

    if (IsProofOfWork())
    {
        int64_t nBlockReward = GetProofOfWorkReward(nBits, nFees, pindex->pprev->nHeight + 1);

        // Check coinbase reward
        if (vtx[0].GetValueOut() > nBlockReward)
            return error("CheckBlock() : coinbase reward exceeded (actual=%" PRId64 " vs calculated=%" PRId64 ")",
                   vtx[0].GetValueOut(),
                   nBlockReward);
    }

    // track money supply and mint amount info
    pindex->nMint = nValueOut - nValueIn + nFees;
    pindex->nMoneySupply = (pindex->pprev? pindex->pprev->nMoneySupply : 0) + nValueOut - nValueIn;
    if (!txdb.WriteBlockIndex(CDiskBlockIndex(pindex)))
        return error("Connect() : WriteBlockIndex for pindex failed");

    // fees are not collected by proof-of-stake miners
    // fees are destroyed to compensate the entire network
    if (fDebug && IsProofOfStake() && GetBoolArg("-printcreation"))
        printf("ConnectBlock() : destroy=%s nFees=%" PRId64 "\n", FormatMoney(nFees).c_str(), nFees);

    if (fJustCheck)
        return true;

    // Write queued txindex changes
    for (map<uint256, CTxIndex>::iterator mi = mapQueuedChanges.begin(); mi != mapQueuedChanges.end(); ++mi)
    {
        if (!txdb.UpdateTxIndex((*mi).first, (*mi).second))
            return error("ConnectBlock() : UpdateTxIndex failed");
    }

    // Update block index on disk without changing it in memory.
    // The memory index structure will be changed after the db commits.
    if (pindex->pprev)
    {
        CDiskBlockIndex blockindexPrev(pindex->pprev);
        blockindexPrev.hashNext = pindex->GetBlockHash();
        if (!txdb.WriteBlockIndex(blockindexPrev))
            return error("ConnectBlock() : WriteBlockIndex failed");
    }

    // Watch for transactions paying to me
    BOOST_FOREACH(CTransaction& tx, vtx)
        SyncWithWallets(tx, this, true);


    return true;
}

bool static Reorganize(CTxDB& txdb, CBlockIndex* pindexNew)
{
    printf("REORGANIZE\n");

    // Find the fork
    CBlockIndex* pfork = pindexBest;
    CBlockIndex* plonger = pindexNew;
    while (pfork != plonger)
    {
        while (plonger->nHeight > pfork->nHeight)
            if (!(plonger = plonger->pprev))
                return error("Reorganize() : plonger->pprev is null");
        if (pfork == plonger)
            break;
        if (!(pfork = pfork->pprev))
            return error("Reorganize() : pfork->pprev is null");
    }

    // List of what to disconnect
    vector<CBlockIndex*> vDisconnect;
    for (CBlockIndex* pindex = pindexBest; pindex != pfork; pindex = pindex->pprev)
        vDisconnect.push_back(pindex);

    // List of what to connect
    vector<CBlockIndex*> vConnect;
    for (CBlockIndex* pindex = pindexNew; pindex != pfork; pindex = pindex->pprev)
        vConnect.push_back(pindex);
    reverse(vConnect.begin(), vConnect.end());

    printf("REORGANIZE: Disconnect %" PRIszu " blocks; %s..%s\n", vDisconnect.size(), pfork->GetBlockHash().ToString().substr(0,20).c_str(), pindexBest->GetBlockHash().ToString().substr(0,20).c_str());
    printf("REORGANIZE: Connect %" PRIszu " blocks; %s..%s\n", vConnect.size(), pfork->GetBlockHash().ToString().substr(0,20).c_str(), pindexNew->GetBlockHash().ToString().substr(0,20).c_str());

    // Disconnect shorter branch
    vector<CTransaction> vResurrect;
    BOOST_FOREACH(CBlockIndex* pindex, vDisconnect)
    {
        CBlock block;
        if (!block.ReadFromDisk(pindex))
            return error("Reorganize() : ReadFromDisk for disconnect failed");
        if (!block.DisconnectBlock(txdb, pindex))
            return error("Reorganize() : DisconnectBlock %s failed", pindex->GetBlockHash().ToString().substr(0,20).c_str());

        // Queue memory transactions to resurrect
        BOOST_FOREACH(const CTransaction& tx, block.vtx)
            if (!(tx.IsCoinBase() || tx.IsCoinStake()))
                vResurrect.push_back(tx);
    }

    // Connect longer branch
    vector<CTransaction> vDelete;
    for (unsigned int i = 0; i < vConnect.size(); i++)
    {
        CBlockIndex* pindex = vConnect[i];
        CBlock block;
        if (!block.ReadFromDisk(pindex))
            return error("Reorganize() : ReadFromDisk for connect failed");
        if (!block.ConnectBlock(txdb, pindex))
        {
            // Invalid block
            return error("Reorganize() : ConnectBlock %s failed", pindex->GetBlockHash().ToString().substr(0,20).c_str());
        }

        // Queue memory transactions to delete
        BOOST_FOREACH(const CTransaction& tx, block.vtx)
            vDelete.push_back(tx);
    }
    if (!txdb.WriteHashBestChain(pindexNew->GetBlockHash()))
        return error("Reorganize() : WriteHashBestChain failed");

    // Make sure it's successfully written to disk before changing memory structure
    if (!txdb.TxnCommit())
        return error("Reorganize() : TxnCommit failed");

    // Disconnect shorter branch
    BOOST_FOREACH(CBlockIndex* pindex, vDisconnect)
        if (pindex->pprev)
            pindex->pprev->pnext = NULL;

    // Connect longer branch
    BOOST_FOREACH(CBlockIndex* pindex, vConnect)
        if (pindex->pprev)
            pindex->pprev->pnext = pindex;

    // Resurrect memory transactions that were in the disconnected branch
    BOOST_FOREACH(CTransaction& tx, vResurrect)
        tx.AcceptToMemoryPool(txdb, false);

    // Delete redundant memory transactions that are in the connected branch
    BOOST_FOREACH(CTransaction& tx, vDelete)
        mempool.remove(tx);

    printf("REORGANIZE: done\n");

    return true;
}


// Called from inside SetBestChain: attaches a block to the new best chain being built
bool CBlock::SetBestChainInner(CTxDB& txdb, CBlockIndex *pindexNew)
{
    uint256 hash = GetHash();

    // Adding to current best branch
    if (!ConnectBlock(txdb, pindexNew) || !txdb.WriteHashBestChain(hash))
    {
        txdb.TxnAbort();
        InvalidChainFound(pindexNew);
        return false;
    }
    if (!txdb.TxnCommit())
        return error("SetBestChain() : TxnCommit failed");

    // Add to current best branch
    pindexNew->pprev->pnext = pindexNew;

    // Delete redundant memory transactions
    BOOST_FOREACH(CTransaction& tx, vtx)
        mempool.remove(tx);

    return true;
}

bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
{
    uint256 hash = GetHash();

    if (!txdb.TxnBegin())
        return error("SetBestChain() : TxnBegin failed");

    if (pindexGenesisBlock == NULL && hash == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet))
    {
        txdb.WriteHashBestChain(hash);
        if (!txdb.TxnCommit())
            return error("SetBestChain() : TxnCommit failed");
        pindexGenesisBlock = pindexNew;
    }
    else if (hashPrevBlock == hashBestChain)
    {
        if (!SetBestChainInner(txdb, pindexNew))
            return error("SetBestChain() : SetBestChainInner failed");
    }
    else
    {
        // the first block in the new chain that will cause it to become the new best chain
        CBlockIndex *pindexIntermediate = pindexNew;

        // list of blocks that need to be connected afterwards
        std::vector<CBlockIndex*> vpindexSecondary;

        // Reorganize is costly in terms of db load, as it works in a single db transaction.
        // Try to limit how much needs to be done inside
        while (pindexIntermediate->pprev && pindexIntermediate->pprev->nChainTrust > pindexBest->nChainTrust)
        {
            vpindexSecondary.push_back(pindexIntermediate);
            pindexIntermediate = pindexIntermediate->pprev;
        }

        if (!vpindexSecondary.empty())
            printf("Postponing %" PRIszu " reconnects\n", vpindexSecondary.size());

        // Switch to new best branch
        if (!Reorganize(txdb, pindexIntermediate))
        {
            txdb.TxnAbort();
            InvalidChainFound(pindexNew);
            return error("SetBestChain() : Reorganize failed");
        }

        // Connect further blocks
        BOOST_REVERSE_FOREACH(CBlockIndex *pindex, vpindexSecondary)
        {
            CBlock block;
            if (!block.ReadFromDisk(pindex))
            {
                printf("SetBestChain() : ReadFromDisk failed\n");
                break;
            }
            if (!txdb.TxnBegin()) {
                printf("SetBestChain() : TxnBegin 2 failed\n");
                break;
            }
            // errors now are not fatal, we still did a reorganisation to a new chain in a valid way
            if (!block.SetBestChainInner(txdb, pindex))
                break;
        }
    }

    // Update best block in wallet (so we can detect restored wallets)
    bool fIsInitialDownload = IsInitialBlockDownload();
    if (!fIsInitialDownload)
    {
        const CBlockLocator locator(pindexNew);
        ::SetBestChain(locator);
    }

    // New best block
    hashBestChain = hash;
    pindexBest = pindexNew;
    pblockindexFBBHLast = NULL;
    nBestHeight = pindexBest->nHeight;
    nBestChainTrust = pindexNew->nChainTrust;
    nTimeBestReceived = GetTime();
    nTransactionsUpdated++;

    uint256 nBestBlockTrust = pindexBest->nHeight != 0 ? (pindexBest->nChainTrust - pindexBest->pprev->nChainTrust) : pindexBest->nChainTrust;

    printf("SetBestChain: new best=%s  height=%d  trust=%s  blocktrust=%" PRId64 "  date=%s\n",
      hashBestChain.ToString().substr(0,20).c_str(), nBestHeight,
      CBigNum(nBestChainTrust).ToString().c_str(),
      nBestBlockTrust.Get64(),
      DateTimeStrFormat("%x %H:%M:%S", pindexBest->GetBlockTime()).c_str());

    // Check the version of the last 100 blocks to see if we need to upgrade:
    if (!fIsInitialDownload)
    {
        int nUpgraded = 0;
        const CBlockIndex* pindex = pindexBest;
        for (int i = 0; i < 100 && pindex != NULL; i++)
        {
            if (pindex->nVersion > CBlock::CURRENT_VERSION)
                ++nUpgraded;
            pindex = pindex->pprev;
        }
        if (nUpgraded > 0)
            printf("SetBestChain: %d of last 100 blocks above version %d\n", nUpgraded, CBlock::CURRENT_VERSION);
        if (nUpgraded > 100/2)
            // strMiscWarning is read by GetWarnings(), called by Qt and the JSON-RPC code to warn the user:
            strMiscWarning = _("Warning: This version is obsolete, upgrade required!");
    }

    std::string strCmd = GetArg("-blocknotify", "");

    if (!fIsInitialDownload && !strCmd.empty())
    {
        boost::replace_all(strCmd, "%s", hashBestChain.GetHex());
        boost::thread t(runCommand, strCmd); // thread runs free
    }

    return true;
}

// ppcoin: total coin age spent in transaction, in the unit of coin-days.
// Only those coins meeting minimum age requirement counts. As those
// transactions not in main chain are not currently indexed so we
// might not find out about their coin age. Older transactions are 
// guaranteed to be in main chain by sync-checkpoint. This rule is
// introduced to help nodes establish a consistent view of the coin
// age (trust score) of competing branches.
bool CTransaction::GetCoinAge(CTxDB& txdb, uint64_t& nCoinAge) const
{
    CBigNum bnCentSecond = 0;  // coin age in the unit of cent-seconds
    nCoinAge = 0;

    if (IsCoinBase())
        return true;

    BOOST_FOREACH(const CTxIn& txin, vin)
    {
        // First try finding the previous transaction in database
        CTransaction txPrev;
        CTxIndex txindex;
        if (!txPrev.ReadFromDisk(txdb, txin.prevout, txindex))
            continue;  // previous transaction not in main chain
        if (nTime < txPrev.nTime)
            return false;  // Transaction timestamp violation

        // Read block header
        CBlock block;
        if (!block.ReadFromDisk(txindex.pos.nFile, txindex.pos.nBlockPos, false))
            return false; // unable to read block of previous transaction
        if (block.GetBlockTime() + nStakeMinAge > nTime)
            continue; // only count coins meeting min age requirement

        int64_t nValueIn = txPrev.vout[txin.prevout.n].nValue;
        bnCentSecond += CBigNum(nValueIn) * (nTime-txPrev.nTime) / CENT;

        if (fDebug && GetBoolArg("-printcoinage"))
            printf("coin age nValueIn=%" PRId64 " nTimeDiff=%d bnCentSecond=%s\n", nValueIn, nTime - txPrev.nTime, bnCentSecond.ToString().c_str());
    }

    CBigNum bnCoinDay = bnCentSecond * CENT / COIN / nOneDay;
    if (fDebug && GetBoolArg("-printcoinage"))
        printf("coin age bnCoinDay=%s\n", bnCoinDay.ToString().c_str());
    nCoinAge = bnCoinDay.getuint64();
    return true;
}

// ppcoin: total coin age spent in block, in the unit of coin-days.
bool CBlock::GetCoinAge(uint64_t& nCoinAge) const
{
    nCoinAge = 0;

    CTxDB txdb("r");
    BOOST_FOREACH(const CTransaction& tx, vtx)
    {
        uint64_t nTxCoinAge;
        if (tx.GetCoinAge(txdb, nTxCoinAge))
            nCoinAge += nTxCoinAge;
        else
            return false;
    }

    if (nCoinAge == 0) // block coin age minimum 1 coin-day
        nCoinAge = 1;
    if (fDebug && GetBoolArg("-printcoinage"))
        printf("block coin age total nCoinDays=%" PRId64 "\n", nCoinAge);
    return true;
}

bool CBlock::AddToBlockIndex(unsigned int nFile, unsigned int nBlockPos)
{
    // Check for duplicate
    uint256 hash = GetHash();
    if (mapBlockIndex.count(hash))
        return error("AddToBlockIndex() : %s already exists", hash.ToString().substr(0,20).c_str());

    // Construct new block index object
    CBlockIndex* pindexNew = new CBlockIndex(nFile, nBlockPos, *this);
    if (!pindexNew)
        return error("AddToBlockIndex() : new CBlockIndex failed");
    pindexNew->phashBlock = &hash;
    map<uint256, CBlockIndex*>::iterator miPrev = mapBlockIndex.find(hashPrevBlock);
    if (miPrev != mapBlockIndex.end())
    {
        pindexNew->pprev = (*miPrev).second;
        pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
    }

    // ppcoin: compute chain trust score
    pindexNew->nChainTrust = (pindexNew->pprev ? pindexNew->pprev->nChainTrust : 0) + pindexNew->GetBlockTrust();

    // ppcoin: compute stake entropy bit for stake modifier
    if (!pindexNew->SetStakeEntropyBit(GetStakeEntropyBit(pindexNew->nHeight)))
        return error("AddToBlockIndex() : SetStakeEntropyBit() failed");

    // ppcoin: record proof-of-stake hash value
    if (pindexNew->IsProofOfStake())
    {
        if (!mapProofOfStake.count(hash))
            return error("AddToBlockIndex() : hashProofOfStake not found in map");
        pindexNew->hashProofOfStake = mapProofOfStake[hash];
    }

    // ppcoin: compute stake modifier
    uint64_t nStakeModifier = 0;
    bool fGeneratedStakeModifier = false;
    if (!ComputeNextStakeModifier(pindexNew, nStakeModifier, fGeneratedStakeModifier))
        return error("AddToBlockIndex() : ComputeNextStakeModifier() failed");
    pindexNew->SetStakeModifier(nStakeModifier, fGeneratedStakeModifier);
    pindexNew->nStakeModifierChecksum = GetStakeModifierChecksum(pindexNew);
    if (!CheckStakeModifierCheckpoints(pindexNew->nHeight, pindexNew->nStakeModifierChecksum))
        return error("AddToBlockIndex() : Rejected by stake modifier checkpoint height=%d, modifier=0x%016" PRIx64, pindexNew->nHeight, nStakeModifier);

    // Add to mapBlockIndex
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.insert(make_pair(hash, pindexNew)).first;
    if (pindexNew->IsProofOfStake())
        setStakeSeen.insert(make_pair(pindexNew->prevoutStake, pindexNew->nStakeTime));
    pindexNew->phashBlock = &((*mi).first);

    // Write to disk block index
    CTxDB txdb;
    if (!txdb.TxnBegin())
        return false;
    txdb.WriteBlockIndex(CDiskBlockIndex(pindexNew));
    if (!txdb.TxnCommit())
        return false;

    // New best
    if (pindexNew->nChainTrust > nBestChainTrust)
        if (!SetBestChain(txdb, pindexNew))
            return false;

    if (pindexNew == pindexBest)
    {
        // Notify UI to display prev block's coinbase if it was ours
        static uint256 hashPrevBestCoinBase;
        UpdatedTransaction(hashPrevBestCoinBase);
        hashPrevBestCoinBase = vtx[0].GetHash();
    }

    static int8_t counter = 0;
    if( (++counter & 0x0F) == 0 || !IsInitialBlockDownload()) // repaint every 16 blocks if not in initial block download
        uiInterface.NotifyBlocksChanged();
    return true;
}




bool CBlock::CheckBlock(bool fCheckPOW, bool fCheckMerkleRoot, bool fCheckSig) const
{
    // These are checks that are independent of context
    // that can be verified before saving an orphan block.

    set<uint256> uniqueTx; // tx hashes
    unsigned int nSigOps = 0; // total sigops

    // Size limits
    if (vtx.empty() || vtx.size() > MAX_BLOCK_SIZE || ::GetSerializeSize(*this, SER_NETWORK, PROTOCOL_VERSION) > MAX_BLOCK_SIZE)
        return DoS(100, error("CheckBlock() : size limits failed"));

    bool fProofOfStake = IsProofOfStake();

    // First transaction must be coinbase, the rest must not be
    if (!vtx[0].IsCoinBase())
        return DoS(100, error("CheckBlock() : first tx is not coinbase"));

    if (!vtx[0].CheckTransaction())
        return DoS(vtx[0].nDoS, error("CheckBlock() : CheckTransaction failed on coinbase"));

    uniqueTx.insert(vtx[0].GetHash());
    nSigOps += vtx[0].GetLegacySigOpCount();

    if (fProofOfStake)
    {
        // Proof-of-STake related checkings. Note that we know here that 1st transactions is coinstake. We don't need 
        //   check the type of 1st transaction because it's performed earlier by IsProofOfStake()

        // nNonce must be zero for proof-of-stake blocks
        if (nNonce != 0)
            return DoS(100, error("CheckBlock() : non-zero nonce in proof-of-stake block"));

        // Coinbase output should be empty if proof-of-stake block
        if (vtx[0].vout.size() != 1 || !vtx[0].vout[0].IsEmpty())
            return DoS(100, error("CheckBlock() : coinbase output not empty for proof-of-stake block"));

        // Check coinstake timestamp
        if (GetBlockTime() != (int64_t)vtx[1].nTime)
            return DoS(50, error("CheckBlock() : coinstake timestamp violation nTimeBlock=%" PRId64 " nTimeTx=%u", GetBlockTime(), vtx[1].nTime));

        // iWalletCoin: check proof-of-stake block signature
        if (fCheckSig && !CheckBlockSignature())
            return DoS(100, error("CheckBlock() : bad proof-of-stake block signature"));

        if (!vtx[1].CheckTransaction())
            return DoS(vtx[1].nDoS, error("CheckBlock() : CheckTransaction failed on coinstake"));

        uniqueTx.insert(vtx[1].GetHash());
        nSigOps += vtx[1].GetLegacySigOpCount();
    }
    else
    {
        // Check proof of work matches claimed amount
        if (fCheckPOW && !CheckProofOfWork(GetHash(), nBits))
            return DoS(50, error("CheckBlock() : proof of work failed"));

        // Check timestamp
        if (GetBlockTime() > FutureDrift(GetAdjustedTime()))
            return error("CheckBlock() : block timestamp too far in the future");

        // Check coinbase timestamp
        if (GetBlockTime() < PastDrift((int64_t)vtx[0].nTime))
            return DoS(50, error("CheckBlock() : coinbase timestamp is too late"));
    }

    // Iterate all transactions starting from second for proof-of-stake block 
    //    or first for proof-of-work block
    for (unsigned int i = fProofOfStake ? 2 : 1; i < vtx.size(); i++)
    {
        const CTransaction& tx = vtx[i];

        // Reject coinbase transactions at non-zero index
        if (tx.IsCoinBase())
            return DoS(100, error("CheckBlock() : coinbase at wrong index"));

        // Reject coinstake transactions at index != 1
        if (tx.IsCoinStake())
            return DoS(100, error("CheckBlock() : coinstake at wrong index"));

        // Check transaction timestamp
        if (GetBlockTime() < (int64_t)tx.nTime)
            return DoS(50, error("CheckBlock() : block timestamp earlier than transaction timestamp"));

        // Check transaction consistency
        if (!tx.CheckTransaction())
            return DoS(tx.nDoS, error("CheckBlock() : CheckTransaction failed"));

        // Add transaction hash into list of unique transaction IDs
        uniqueTx.insert(tx.GetHash());

        // Calculate sigops count
        nSigOps += tx.GetLegacySigOpCount();
    }

    // Check for duplicate txids. This is caught by ConnectInputs(),
    // but catching it earlier avoids a potential DoS attack:
    if (uniqueTx.size() != vtx.size())
        return DoS(100, error("CheckBlock() : duplicate transaction"));

    // Reject block if validation would consume too much resources.
    if (nSigOps > MAX_BLOCK_SIGOPS)
        return DoS(100, error("CheckBlock() : out-of-bounds SigOpCount"));

    // Check merkle root
    if (fCheckMerkleRoot && hashMerkleRoot != BuildMerkleTree())
        return DoS(100, error("CheckBlock() : hashMerkleRoot mismatch"));

    return true;
}

bool CBlock::AcceptBlock()
{
    // Check for duplicate
    uint256 hash = GetHash();
    if (mapBlockIndex.count(hash))
        return error("AcceptBlock() : block already in mapBlockIndex");

    // Get prev block index
    map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashPrevBlock);
    if (mi == mapBlockIndex.end())
        return DoS(10, error("AcceptBlock() : prev block not found"));
    CBlockIndex* pindexPrev = (*mi).second;
    int nHeight = pindexPrev->nHeight+1;

    if (IsProofOfWork() && nHeight > LAST_POW_BLOCK)
        return DoS(100, error("AcceptBlock() : reject proof-of-work at height %d", nHeight));

    // Check proof-of-work or proof-of-stake
    if (nBits != GetNextTargetRequired(pindexPrev, IsProofOfStake()))
        return DoS(100, error("AcceptBlock() : incorrect %s", IsProofOfWork() ? "proof-of-work" : "proof-of-stake"));

    int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
    int64_t nMaxOffset = 4 * 86400; // Four days

    // Check timestamp against prev
    if (GetBlockTime() <= nMedianTimePast || FutureDrift(GetBlockTime()) < pindexPrev->GetBlockTime())
        return error("AcceptBlock() : block's timestamp is too early");

    // Don't accept blocks with future timestamps
     if (pindexPrev->nHeight > 50000 && nMedianTimePast  + nMaxOffset < GetBlockTime())
        return error("AcceptBlock() : block's timestamp is too far in the future");

    // Check that all transactions are finalized
    BOOST_FOREACH(const CTransaction& tx, vtx)
        if (!tx.IsFinal(nHeight, GetBlockTime()))
            return DoS(10, error("AcceptBlock() : contains a non-final transaction"));

    // Check that the block chain matches the known block chain up to a checkpoint
    if (!Checkpoints::CheckHardened(nHeight, hash))
        return DoS(100, error("AcceptBlock() : rejected by hardened checkpoint lock-in at %d", nHeight));

    bool cpSatisfies = Checkpoints::CheckSync(hash, pindexPrev);

    // Check that the block satisfies synchronized checkpoint
    if (CheckpointsMode == Checkpoints::STRICT && !cpSatisfies)
        return error("AcceptBlock() : rejected by synchronized checkpoint");

    if (CheckpointsMode == Checkpoints::ADVISORY && !cpSatisfies)
        strMiscWarning = _("WARNING: syncronized checkpoint violation detected, but skipped!");

    // Enforce rule that the coinbase starts with serialized block height
    CScript expect = CScript() << nHeight;
    if (vtx[0].vin[0].scriptSig.size() < expect.size() ||
        !std::equal(expect.begin(), expect.end(), vtx[0].vin[0].scriptSig.begin()))
        return DoS(100, error("AcceptBlock() : block height mismatch in coinbase"));

    // Write block to history file
    if (!CheckDiskSpace(::GetSerializeSize(*this, SER_DISK, CLIENT_VERSION)))
        return error("AcceptBlock() : out of disk space");
    unsigned int nFile = std::numeric_limits<unsigned int>::max();
    unsigned int nBlockPos = 0;
    if (!WriteToDisk(nFile, nBlockPos))
        return error("AcceptBlock() : WriteToDisk failed");
    if (!AddToBlockIndex(nFile, nBlockPos))
        return error("AcceptBlock() : AddToBlockIndex failed");

    // Relay inventory, but don't relay old inventory during initial block download
    int nBlockEstimate = Checkpoints::GetTotalBlocksEstimate();
    if (hashBestChain == hash)
    {
        LOCK(cs_vNodes);
        BOOST_FOREACH(CNode* pnode, vNodes)
            if (nBestHeight > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate))
                pnode->PushInventory(CInv(MSG_BLOCK, hash));
    }

    // ppcoin: check pending sync-checkpoint
    Checkpoints::AcceptPendingSyncCheckpoint();

    return true;
}

uint256 CBlockIndex::GetBlockTrust() const
{
    CBigNum bnTarget;
    bnTarget.SetCompact(nBits);

    if (bnTarget <= 0)
        return 0;

    // Return 1 for the first 12 blocks
    if (pprev == NULL || pprev->nHeight < 12)
        return 1;

    const CBlockIndex* currentIndex = pprev;

    if(IsProofOfStake())
    {
        CBigNum bnNewTrust = (CBigNum(1)<<256) / (bnTarget+1);

        // Return 1/3 of score if parent block is not the PoW block
        if (!pprev->IsProofOfWork())
            return (bnNewTrust / 3).getuint256();

        int nPoWCount = 0;

        // Check last 12 blocks type
        while (pprev->nHeight - currentIndex->nHeight < 12)
        {
            if (currentIndex->IsProofOfWork())
                nPoWCount++;
            currentIndex = currentIndex->pprev;
        }

        // Return 1/3 of score if less than 3 PoW blocks found
        if (nPoWCount < 3)
            return (bnNewTrust / 3).getuint256();

        return bnNewTrust.getuint256();
    }
    else
    {
        // Calculate work amount for block
        CBigNum bnPoWTrust = CBigNum(nPoWBase) / (bnTarget+1);

        // Set nPowTrust to 1 if PoW difficulty is too low
        if (bnPoWTrust < 1)
            bnPoWTrust = 1;

        CBigNum bnLastBlockTrust = CBigNum(pprev->nChainTrust - pprev->pprev->nChainTrust);

        // Return nPoWTrust + 2/3 of previous block score if two parent blocks are not PoS blocks
        if (!(pprev->IsProofOfStake() && pprev->pprev->IsProofOfStake()))
            return (bnPoWTrust + 2 * bnLastBlockTrust / 3).getuint256();

        int nPoSCount = 0;

        // Check last 12 blocks type
        while (pprev->nHeight - currentIndex->nHeight < 12)
        {
            if (currentIndex->IsProofOfStake())
                nPoSCount++;
            currentIndex = currentIndex->pprev;
        }

        // Return nPoWTrust + 2/3 of previous block score if less than 7 PoS blocks found
        if (nPoSCount < 7)
            return (bnPoWTrust + 2 * bnLastBlockTrust / 3).getuint256();

        bnTarget.SetCompact(pprev->nBits);

        if (bnTarget <= 0)
            return 0;

        CBigNum bnNewTrust = (CBigNum(1)<<256) / (bnTarget+1);

        // Return nPoWTrust + full trust score for previous block nBits
        return (bnPoWTrust + bnNewTrust).getuint256();
    }
}

bool CBlockIndex::IsSuperMajority(int minVersion, const CBlockIndex* pstart, unsigned int nRequired, unsigned int nToCheck)
{
    unsigned int nFound = 0;
    for (unsigned int i = 0; i < nToCheck && nFound < nRequired && pstart != NULL; i++)
    {
        if (pstart->nVersion >= minVersion)
            ++nFound;
        pstart = pstart->pprev;
    }
    return (nFound >= nRequired);
}

bool static ReserealizeBlockSignature(CBlock* pblock)
{
    if (pblock->IsProofOfWork())
    {
        pblock->vchBlockSig.clear();
        return true;
    }

    return CKey::ReserealizeSignature(pblock->vchBlockSig);
}

bool static IsCanonicalBlockSignature(CBlock* pblock)
{
    if (pblock->IsProofOfWork())
        return pblock->vchBlockSig.empty();

    return IsDERSignature(pblock->vchBlockSig);
}

bool ProcessBlock(CNode* pfrom, CBlock* pblock)
{
    // Check for duplicate
    uint256 hash = pblock->GetHash();
    if (mapBlockIndex.count(hash))
        return error("ProcessBlock() : already have block %d %s", mapBlockIndex[hash]->nHeight, hash.ToString().substr(0,20).c_str());
    if (mapOrphanBlocks.count(hash))
        return error("ProcessBlock() : already have block (orphan) %s", hash.ToString().substr(0,20).c_str());

    // Check proof-of-stake
    // Limited duplicity on stake: prevents block flood attack
    // Duplicate stake allowed only when there is orphan child block
    if (pblock->IsProofOfStake() && setStakeSeen.count(pblock->GetProofOfStake()) && !mapOrphanBlocksByPrev.count(hash) && !Checkpoints::WantedByPendingSyncCheckpoint(hash))
        return error("ProcessBlock() : duplicate proof-of-stake (%s, %d) for block %s", pblock->GetProofOfStake().first.ToString().c_str(), pblock->GetProofOfStake().second, hash.ToString().c_str());

    // Strip the garbage from newly received blocks, if we found some
    if (!IsCanonicalBlockSignature(pblock)) {
        if (!ReserealizeBlockSignature(pblock))
            printf("WARNING: ProcessBlock() : ReserealizeBlockSignature FAILED\n");
    }

    // Preliminary checks
    if (!pblock->CheckBlock(true, true, (pblock->nTime > Checkpoints::GetLastCheckpointTime())))
        return error("ProcessBlock() : CheckBlock FAILED");

    // ppcoin: verify hash target and signature of coinstake tx
    if (pblock->IsProofOfStake())
    {
        uint256 hashProofOfStake = 0, targetProofOfStake = 0;
        if (!CheckProofOfStake(pblock->vtx[1], pblock->nBits, hashProofOfStake, targetProofOfStake))
        {
            printf("WARNING: ProcessBlock(): check proof-of-stake failed for block %s\n", hash.ToString().c_str());
            return false; // do not error here as we expect this during initial block download
        }
        if (!mapProofOfStake.count(hash)) // add to mapProofOfStake
            mapProofOfStake.insert(make_pair(hash, hashProofOfStake));
    }

    CBlockIndex* pcheckpoint = Checkpoints::GetLastSyncCheckpoint();
    if (pcheckpoint && pblock->hashPrevBlock != hashBestChain && !Checkpoints::WantedByPendingSyncCheckpoint(hash))
    {
        // Extra checks to prevent "fill up memory by spamming with bogus blocks"
        int64_t deltaTime = pblock->GetBlockTime() - pcheckpoint->nTime;
        CBigNum bnNewBlock;
        bnNewBlock.SetCompact(pblock->nBits);
        CBigNum bnRequired;

        if (pblock->IsProofOfStake())
            bnRequired.SetCompact(ComputeMinStake(GetLastBlockIndex(pcheckpoint, true)->nBits, deltaTime, pblock->nTime));
        else
            bnRequired.SetCompact(ComputeMinWork(GetLastBlockIndex(pcheckpoint, false)->nBits, deltaTime));

        if (bnNewBlock > bnRequired)
        {
            if (pfrom)
                pfrom->Misbehaving(100);
            return error("ProcessBlock() : block with too little %s", pblock->IsProofOfStake()? "proof-of-stake" : "proof-of-work");
        }
    }

    // ppcoin: ask for pending sync-checkpoint if any
    if (!IsInitialBlockDownload())
        Checkpoints::AskForPendingSyncCheckpoint(pfrom);

    // If don't already have its previous block, shunt it off to holding area until we get it
    if (!mapBlockIndex.count(pblock->hashPrevBlock))
    {
        printf("ProcessBlock: ORPHAN BLOCK, prev=%s\n", pblock->hashPrevBlock.ToString().substr(0,20).c_str());
        // ppcoin: check proof-of-stake
        if (pblock->IsProofOfStake())
        {
            // Limited duplicity on stake: prevents block flood attack
            // Duplicate stake allowed only when there is orphan child block
            if (setStakeSeenOrphan.count(pblock->GetProofOfStake()) && !mapOrphanBlocksByPrev.count(hash) && !Checkpoints::WantedByPendingSyncCheckpoint(hash))
                return error("ProcessBlock() : duplicate proof-of-stake (%s, %d) for orphan block %s", pblock->GetProofOfStake().first.ToString().c_str(), pblock->GetProofOfStake().second, hash.ToString().c_str());
            else
                setStakeSeenOrphan.insert(pblock->GetProofOfStake());
        }
        CBlock* pblock2 = new CBlock(*pblock);
        mapOrphanBlocks.insert(make_pair(hash, pblock2));
        mapOrphanBlocksByPrev.insert(make_pair(pblock2->hashPrevBlock, pblock2));

        // Ask this guy to fill in what we're missing
        if (pfrom)
        {
            pfrom->PushGetBlocks(pindexBest, GetOrphanRoot(pblock2));
            // ppcoin: getblocks may not obtain the ancestor block rejected
            // earlier by duplicate-stake check so we ask for it again directly
            if (!IsInitialBlockDownload())
                pfrom->AskFor(CInv(MSG_BLOCK, WantedByOrphan(pblock2)));
        }
        return true;
    }

    // Store to disk
    if (!pblock->AcceptBlock())
        return error("ProcessBlock() : AcceptBlock FAILED");

    // Recursively process any orphan blocks that depended on this one
    vector<uint256> vWorkQueue;
    vWorkQueue.push_back(hash);
    for (unsigned int i = 0; i < vWorkQueue.size(); i++)
    {
        uint256 hashPrev = vWorkQueue[i];
        for (multimap<uint256, CBlock*>::iterator mi = mapOrphanBlocksByPrev.lower_bound(hashPrev);
             mi != mapOrphanBlocksByPrev.upper_bound(hashPrev);
             ++mi)
        {
            CBlock* pblockOrphan = (*mi).second;
            if (pblockOrphan->AcceptBlock())
                vWorkQueue.push_back(pblockOrphan->GetHash());
            mapOrphanBlocks.erase(pblockOrphan->GetHash());
            setStakeSeenOrphan.erase(pblockOrphan->GetProofOfStake());
            delete pblockOrphan;
        }
        mapOrphanBlocksByPrev.erase(hashPrev);
    }

    printf("ProcessBlock: ACCEPTED\n");

    // ppcoin: if responsible for sync-checkpoint send it
    if (pfrom && !CSyncCheckpoint::strMasterPrivKey.empty())
        Checkpoints::SendSyncCheckpoint(Checkpoints::AutoSelectSyncCheckpoint());

    return true;
}

// ppcoin: check block signature
bool CBlock::CheckBlockSignature() const
{
    if (vchBlockSig.empty())
        return false;

    txnouttype whichType;
    vector<valtype> vSolutions;
    if (!Solver(vtx[1].vout[1].scriptPubKey, whichType, vSolutions))
        return false;

    if (whichType == TX_PUBKEY)
    {
        valtype& vchPubKey = vSolutions[0];
        CKey key;
        if (!key.SetPubKey(vchPubKey))
            return false;
        return key.Verify(GetHash(), vchBlockSig);
    }

    return false;
}

bool CheckDiskSpace(uint64_t nAdditionalBytes)
{
    uint64_t nFreeBytesAvailable = filesystem::space(GetDataDir()).available;

    // Check for nMinDiskSpace bytes (currently 50MB)
    if (nFreeBytesAvailable < nMinDiskSpace + nAdditionalBytes)
    {
        fShutdown = true;
        string strMessage = _("Warning: Disk space is low!");
        strMiscWarning = strMessage;
        printf("*** %s\n", strMessage.c_str());
        uiInterface.ThreadSafeMessageBox(strMessage, "iWalletCoin", CClientUIInterface::OK | CClientUIInterface::ICON_EXCLAMATION | CClientUIInterface::MODAL);
        StartShutdown();
        return false;
    }
    return true;
}

static filesystem::path BlockFilePath(unsigned int nFile)
{
    string strBlockFn = strprintf("blk%04u.dat", nFile);
    return GetDataDir() / strBlockFn;
}

FILE* OpenBlockFile(unsigned int nFile, unsigned int nBlockPos, const char* pszMode)
{
    if ((nFile < 1) || (nFile == std::numeric_limits<uint32_t>::max()))
        return NULL;
    FILE* file = fopen(BlockFilePath(nFile).string().c_str(), pszMode);
    if (!file)
        return NULL;
    if (nBlockPos != 0 && !strchr(pszMode, 'a') && !strchr(pszMode, 'w'))
    {
        if (fseek(file, nBlockPos, SEEK_SET) != 0)
        {
            fclose(file);
            return NULL;
        }
    }
    return file;
}

static unsigned int nCurrentBlockFile = 1;

FILE* AppendBlockFile(unsigned int& nFileRet)
{
    nFileRet = 0;
    while (true)
    {
        FILE* file = OpenBlockFile(nCurrentBlockFile, 0, "ab");
        if (!file)
            return NULL;
        if (fseek(file, 0, SEEK_END) != 0)
            return NULL;
        // FAT32 file size max 4GB, fseek and ftell max 2GB, so we must stay under 2GB
        if (ftell(file) < (long)(0x7F000000 - MAX_SIZE))
        {
            nFileRet = nCurrentBlockFile;
            return file;
        }
        fclose(file);
        nCurrentBlockFile++;
    }
}

void UnloadBlockIndex()
{
    mapBlockIndex.clear();
    setStakeSeen.clear();
    pindexGenesisBlock = NULL;
    nBestHeight = 0;
    nBestChainTrust = 0;
    nBestInvalidTrust = 0;
    hashBestChain = 0;
    pindexBest = NULL;
}

bool LoadBlockIndex(bool fAllowNew)
{
    if (fTestNet)
    {
        pchMessageStart[0] = 0xcd;
        pchMessageStart[1] = 0xf2;
        pchMessageStart[2] = 0xc0;
        pchMessageStart[3] = 0xef;

        bnProofOfWorkLimit = bnProofOfWorkLimitTestNet; // 16 bits PoW target limit for testnet
        nStakeMinAge = 2 * nOneHour; // test net min age is 2 hours
        nModifierInterval = 20 * 60; // test modifier interval is 20 minutes
        nCoinbaseMaturity = 10; // test maturity is 10 blocks
        nStakeTargetSpacing = 5 * 60; // test block spacing is 5 minutes
    }

    //
    // Load block index
    //
    CTxDB txdb("cr+");
    if (!txdb.LoadBlockIndex())
        return false;

    //
    // Init with genesis block
    //
    if (mapBlockIndex.empty())
    {
        if (!fAllowNew)
            return false;

        const char* pszTimestamp = "IW Genesis";
        CTransaction txNew;
        txNew.nTime = 1470105017;
        txNew.vin.resize(1);
        txNew.vout.resize(1);
        txNew.vin[0].scriptSig = CScript() << 486604799 << CBigNum(9999) << vector<unsigned char>((const unsigned char*)pszTimestamp, (const unsigned char*)pszTimestamp + strlen(pszTimestamp));
        txNew.vout[0].SetEmpty();
        CBlock block;
        block.vtx.push_back(txNew);
        block.hashPrevBlock = 0;
        block.hashMerkleRoot = block.BuildMerkleTree();
        block.nVersion = 1;
        block.nTime    = 1470105017;
        block.nBits    = bnProofOfWorkLimit.GetCompact();
        block.nNonce   = 3038487; // !fTestNet ? 1575379 : 46534;
		
       if (true && (block.GetHash() != hashGenesisBlock)) {

        // This will figure out a valid hash and Nonce if you're
        // creating a different genesis block:
            uint256 hashTarget = CBigNum().SetCompact(block.nBits).getuint256();
            while (block.GetHash() > hashTarget)
               {
                   ++block.nNonce;
                   if (block.nNonce == 0)
                   {
                       printf("NONCE WRAPPED, incrementing time");
                       ++block.nTime;
                   }
               }
        }
        block.print();

        //// debug print
        // assert(block.hashMerkleRoot == uint256("0x4cb33b3b6a861dcbc685d3e614a9cafb945738d6833f182855679f2fad02057b"));
        assert(block.GetHash() == (!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet));
        assert(block.CheckBlock());

        // Start new block file
        unsigned int nFile;
        unsigned int nBlockPos;
        if (!block.WriteToDisk(nFile, nBlockPos))
            return error("LoadBlockIndex() : writing genesis block to disk failed");
        if (!block.AddToBlockIndex(nFile, nBlockPos))
            return error("LoadBlockIndex() : genesis block not accepted");

        // initialize synchronized checkpoint
        if (!Checkpoints::WriteSyncCheckpoint((!fTestNet ? hashGenesisBlock : hashGenesisBlockTestNet)))
            return error("LoadBlockIndex() : failed to init sync checkpoint");

        // upgrade time set to zero if txdb initialized
        {
            if (!txdb.WriteModifierUpgradeTime(0))
                return error("LoadBlockIndex() : failed to init upgrade info");
            printf(" Upgrade Info: ModifierUpgradeTime txdb initialization\n");
        }
    }

    {
        CTxDB txdb("r+");
        string strPubKey = "";
        if (!txdb.ReadCheckpointPubKey(strPubKey) || strPubKey != CSyncCheckpoint::strMasterPubKey)
        {
            // write checkpoint master key to db
            txdb.TxnBegin();
            if (!txdb.WriteCheckpointPubKey(CSyncCheckpoint::strMasterPubKey))
                return error("LoadBlockIndex() : failed to write new checkpoint master key to db");
            if (!txdb.TxnCommit())
                return error("LoadBlockIndex() : failed to commit new checkpoint master key to db");
            if ((!fTestNet) && !Checkpoints::ResetSyncCheckpoint())
                return error("LoadBlockIndex() : failed to reset sync-checkpoint");
        }

        // upgrade time set to zero if blocktreedb initialized
        if (txdb.ReadModifierUpgradeTime(nModifierUpgradeTime))
        {
            if (nModifierUpgradeTime)
                printf(" Upgrade Info: blocktreedb upgrade detected at timestamp %d\n", nModifierUpgradeTime);
            else
                printf(" Upgrade Info: no blocktreedb upgrade detected.\n");
        }
        else
        {
            nModifierUpgradeTime = GetTime();
            printf(" Upgrade Info: upgrading blocktreedb at timestamp %u\n", nModifierUpgradeTime);
            if (!txdb.WriteModifierUpgradeTime(nModifierUpgradeTime))
                return error("LoadBlockIndex() : failed to write upgrade info");
        }

#ifndef USE_LEVELDB
        txdb.Close();
#endif
    }

    return true;
}



void PrintBlockTree()
{
    // pre-compute tree structure
    map<CBlockIndex*, vector<CBlockIndex*> > mapNext;
    for (map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.begin(); mi != mapBlockIndex.end(); ++mi)
    {
        CBlockIndex* pindex = (*mi).second;
        mapNext[pindex->pprev].push_back(pindex);
        // test
        //while (rand() % 3 == 0)
        //    mapNext[pindex->pprev].push_back(pindex);
    }

    vector<pair<int, CBlockIndex*> > vStack;
    vStack.push_back(make_pair(0, pindexGenesisBlock));

    int nPrevCol = 0;
    while (!vStack.empty())
    {
        int nCol = vStack.back().first;
        CBlockIndex* pindex = vStack.back().second;
        vStack.pop_back();

        // print split or gap
        if (nCol > nPrevCol)
        {
            for (int i = 0; i < nCol-1; i++)
                printf("| ");
            printf("|\\\n");
        }
        else if (nCol < nPrevCol)
        {
            for (int i = 0; i < nCol; i++)
                printf("| ");
            printf("|\n");
       }
        nPrevCol = nCol;

        // print columns
        for (int i = 0; i < nCol; i++)
            printf("| ");

        // print item
        CBlock block;
        block.ReadFromDisk(pindex);
        printf("%d (%u,%u) %s  %08x  %s  mint %7s  tx %" PRIszu "",
            pindex->nHeight,
            pindex->nFile,
            pindex->nBlockPos,
            block.GetHash().ToString().c_str(),
            block.nBits,
            DateTimeStrFormat("%x %H:%M:%S", block.GetBlockTime()).c_str(),
            FormatMoney(pindex->nMint).c_str(),
            block.vtx.size());

        PrintWallets(block);

        // put the main time-chain first
        vector<CBlockIndex*>& vNext = mapNext[pindex];
        for (unsigned int i = 0; i < vNext.size(); i++)
        {
            if (vNext[i]->pnext)
            {
                swap(vNext[0], vNext[i]);
                break;
            }
        }

        // iterate children
        for (unsigned int i = 0; i < vNext.size(); i++)
            vStack.push_back(make_pair(nCol+i, vNext[i]));
    }
}

bool LoadExternalBlockFile(FILE* fileIn)
{
    int64_t nStart = GetTimeMillis();

    int nLoaded = 0;
    {
        LOCK(cs_main);
        try {
            CAutoFile blkdat(fileIn, SER_DISK, CLIENT_VERSION);
            unsigned int nPos = 0;
            while (nPos != std::numeric_limits<uint32_t>::max() && blkdat.good() && !fRequestShutdown)
            {
                unsigned char pchData[65536];
                do {
                    fseek(blkdat, nPos, SEEK_SET);
                    int nRead = fread(pchData, 1, sizeof(pchData), blkdat);
                    if (nRead <= 8)
                    {
                        nPos = std::numeric_limits<uint32_t>::max();
                        break;
                    }
                    void* nFind = memchr(pchData, pchMessageStart[0], nRead+1-sizeof(pchMessageStart));
                    if (nFind)
                    {
                        if (memcmp(nFind, pchMessageStart, sizeof(pchMessageStart))==0)
                        {
                            nPos += ((unsigned char*)nFind - pchData) + sizeof(pchMessageStart);
                            break;
                        }
                        nPos += ((unsigned char*)nFind - pchData) + 1;
                    }
                    else
                        nPos += sizeof(pchData) - sizeof(pchMessageStart) + 1;
                } while(!fRequestShutdown);
                if (nPos == std::numeric_limits<uint32_t>::max())
                    break;
                fseek(blkdat, nPos, SEEK_SET);
                unsigned int nSize;
                blkdat >> nSize;
                if (nSize > 0 && nSize <= MAX_BLOCK_SIZE)
                {
                    CBlock block;
                    blkdat >> block;
                    if (ProcessBlock(NULL,&block))
                    {
                        nLoaded++;
                        nPos += 4 + nSize;
                    }
                }
            }
        }
        catch (const std::exception&) {
            printf("%s() : Deserialize or I/O error caught during load\n",
                   BOOST_CURRENT_FUNCTION);
        }
    }
    printf("Loaded %i blocks from external file in %" PRId64 "ms\n", nLoaded, GetTimeMillis() - nStart);
    return nLoaded > 0;
}

//////////////////////////////////////////////////////////////////////////////
//
// CAlert
//

extern map<uint256, CAlert> mapAlerts;
extern CCriticalSection cs_mapAlerts;

string GetWarnings(string strFor)
{
    int nPriority = 0;
    string strStatusBar;
    string strRPC;

    if (GetBoolArg("-testsafemode"))
        strRPC = "test";

    // Misc warnings like out of disk space and clock is wrong
    if (strMiscWarning != "")
    {
        nPriority = 1000;
        strStatusBar = strMiscWarning;
    }

    // if detected unmet upgrade requirement enter safe mode
    // Note: Modifier upgrade requires blockchain redownload if past protocol switch
    if (IsFixedModifierInterval(nModifierUpgradeTime + nOneDay)) // 1 day margin
    {
        nPriority = 5000;
        strStatusBar = strRPC = "WARNING: Blockchain redownload required approaching or past v.0.4.4.6u4 upgrade deadline.";
    }

    // if detected invalid checkpoint enter safe mode
    if (Checkpoints::hashInvalidCheckpoint != 0)
    {
        nPriority = 3000;
        strStatusBar = strRPC = _("WARNING: Invalid checkpoint found! Displayed transactions may not be correct! You may need to upgrade, or notify developers.");
    }

    // Alerts
    {
        LOCK(cs_mapAlerts);
        BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
        {
            const CAlert& alert = item.second;
            if (alert.AppliesToMe() && alert.nPriority > nPriority)
            {
                nPriority = alert.nPriority;
                strStatusBar = alert.strStatusBar;
                if (nPriority > 1000)
                    strRPC = strStatusBar;
            }
        }
    }

    if (strFor == "statusbar")
        return strStatusBar;
    else if (strFor == "rpc")
        return strRPC;
    assert(!"GetWarnings() : invalid parameter");
    return "error";
}








//////////////////////////////////////////////////////////////////////////////
//
// Messages
//


bool static AlreadyHave(CTxDB& txdb, const CInv& inv)
{
    switch (inv.type)
    {
    case MSG_TX:
        {
        bool txInMap = false;
            {
            LOCK(mempool.cs);
            txInMap = (mempool.exists(inv.hash));
            }
        return txInMap ||
               mapOrphanTransactions.count(inv.hash) ||
               txdb.ContainsTx(inv.hash);
        }

    case MSG_BLOCK:
        return mapBlockIndex.count(inv.hash) ||
               mapOrphanBlocks.count(inv.hash);
    }
    // Don't know what it is, just say we already got one
    return true;
}




// The message start string is designed to be unlikely to occur in normal data.
// The characters are rarely used upper ASCII, not valid as UTF-8, and produce
// a large 4-byte int at any alignment.
unsigned char pchMessageStart[4] = { 0xb7, 0xf8, 0xe2, 0xe5 };

bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
{
    static map<CService, CPubKey> mapReuseKey;
    RandAddSeedPerfmon();
    if (fDebug)
        printf("received: %s (%" PRIszu " bytes)\n", strCommand.c_str(), vRecv.size());
    if (mapArgs.count("-dropmessagestest") && GetRand(atoi(mapArgs["-dropmessagestest"])) == 0)
    {
        printf("dropmessagestest DROPPING RECV MESSAGE\n");
        return true;
    }

    if (strCommand == "version")
    {
        // Each connection can only send one version message
        if (pfrom->nVersion != 0)
        {
            pfrom->Misbehaving(1);
            return false;
        }

        int64_t nTime;
        CAddress addrMe;
        CAddress addrFrom;
        uint64_t nNonce = 1;
        vRecv >> pfrom->nVersion >> pfrom->nServices >> nTime >> addrMe;
        if (pfrom->nVersion < MIN_PROTO_VERSION)
        {
            // Since February 20, 2012, the protocol is initiated at version 209,
            // and earlier versions are no longer supported
            printf("partner %s using obsolete version %i; disconnecting\n", pfrom->addr.ToString().c_str(), pfrom->nVersion);
            pfrom->fDisconnect = true;
            return false;
        }

        if (pfrom->nVersion == 10300)
            pfrom->nVersion = 300;
        if (!vRecv.empty())
            vRecv >> addrFrom >> nNonce;
        if (!vRecv.empty())
            vRecv >> pfrom->strSubVer;
        if (!vRecv.empty())
            vRecv >> pfrom->nStartingHeight;

        if (pfrom->fInbound && addrMe.IsRoutable())
        {
            pfrom->addrLocal = addrMe;
            SeenLocal(addrMe);
        }

        // Disconnect if we connected to ourself
        if (nNonce == nLocalHostNonce && nNonce > 1)
        {
            printf("connected to self at %s, disconnecting\n", pfrom->addr.ToString().c_str());
            pfrom->fDisconnect = true;
            return true;
        }

        if (pfrom->nVersion < 60010)
        {
            printf("partner %s using a buggy client %d, disconnecting\n", pfrom->addr.ToString().c_str(), pfrom->nVersion);
            pfrom->fDisconnect = true;
            return true;
        }

        // record my external IP reported by peer
        if (addrFrom.IsRoutable() && addrMe.IsRoutable())
            addrSeenByPeer = addrMe;

        // Be shy and don't send version until we hear
        if (pfrom->fInbound)
            pfrom->PushVersion();

        pfrom->fClient = !(pfrom->nServices & NODE_NETWORK);

        AddTimeData(pfrom->addr, nTime);

        // Change version
        pfrom->PushMessage("verack");
        pfrom->vSend.SetVersion(min(pfrom->nVersion, PROTOCOL_VERSION));

        if (!pfrom->fInbound)
        {
            // Advertise our address
            if (!fNoListen && !IsInitialBlockDownload())
            {
                CAddress addr = GetLocalAddress(&pfrom->addr);
                if (addr.IsRoutable())
                    pfrom->PushAddress(addr);
            }

            // Get recent addresses
            if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || addrman.size() < 1000)
            {
                pfrom->PushMessage("getaddr");
                pfrom->fGetAddr = true;
            }
            addrman.Good(pfrom->addr);
        } else {
            if (((CNetAddr)pfrom->addr) == (CNetAddr)addrFrom)
            {
                addrman.Add(addrFrom, addrFrom);
                addrman.Good(addrFrom);
            }
        }

        // Ask the first connected node for block updates
        static int nAskedForBlocks = 0;
        if (!pfrom->fClient && !pfrom->fOneShot &&
            (pfrom->nStartingHeight > (nBestHeight - 144)) &&
            (pfrom->nVersion < NOBLKS_VERSION_START ||
             pfrom->nVersion >= NOBLKS_VERSION_END) &&
             (nAskedForBlocks < 1 || vNodes.size() <= 1))
        {
            nAskedForBlocks++;
            pfrom->PushGetBlocks(pindexBest, uint256(0));
        }

        // Relay alerts
        {
            LOCK(cs_mapAlerts);
            BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
                item.second.RelayTo(pfrom);
        }

        // Relay sync-checkpoint
        {
            LOCK(Checkpoints::cs_hashSyncCheckpoint);
            if (!Checkpoints::checkpointMessage.IsNull())
                Checkpoints::checkpointMessage.RelayTo(pfrom);
        }

        pfrom->fSuccessfullyConnected = true;

        printf("receive version message: version %d, blocks=%d, us=%s, them=%s, peer=%s\n", pfrom->nVersion, pfrom->nStartingHeight, addrMe.ToString().c_str(), addrFrom.ToString().c_str(), pfrom->addr.ToString().c_str());

        cPeerBlockCounts.input(pfrom->nStartingHeight);

        // ppcoin: ask for pending sync-checkpoint if any
        if (!IsInitialBlockDownload())
            Checkpoints::AskForPendingSyncCheckpoint(pfrom);
    }


    else if (pfrom->nVersion == 0)
    {
        // Must have a version message before anything else
        pfrom->Misbehaving(1);
        return false;
    }


    else if (strCommand == "verack")
    {
        pfrom->vRecv.SetVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
    }


    else if (strCommand == "addr")
    {
        vector<CAddress> vAddr;
        vRecv >> vAddr;

        // Don't want addr from older versions unless seeding
        if (pfrom->nVersion < CADDR_TIME_VERSION && addrman.size() > 1000)
            return true;
        if (vAddr.size() > 1000)
        {
            pfrom->Misbehaving(20);
            return error("message addr size() = %" PRIszu "", vAddr.size());
        }

        // Store the new addresses
        vector<CAddress> vAddrOk;
        int64_t nNow = GetAdjustedTime();
        int64_t nSince = nNow - 10 * 60;
        BOOST_FOREACH(CAddress& addr, vAddr)
        {
            if (fShutdown)
                return true;
            if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
                addr.nTime = nNow - 5 * nOneDay;
            pfrom->AddAddressKnown(addr);
            bool fReachable = IsReachable(addr);
            if (addr.nTime > nSince && !pfrom->fGetAddr && vAddr.size() <= 10 && addr.IsRoutable())
            {
                // Relay to a limited number of other nodes
                {
                    LOCK(cs_vNodes);
                    // Use deterministic randomness to send to the same nodes for 24 hours
                    // at a time so the setAddrKnowns of the chosen nodes prevent repeats
                    static uint256 hashSalt;
                    if (hashSalt == 0)
                        hashSalt = GetRandHash();
                    uint64_t hashAddr = addr.GetHash();
                    uint256 hashRand = hashSalt ^ (hashAddr<<32) ^ ((GetTime()+hashAddr)/nOneDay);
                    hashRand = Hash(BEGIN(hashRand), END(hashRand));
                    multimap<uint256, CNode*> mapMix;
                    BOOST_FOREACH(CNode* pnode, vNodes)
                    {
                        if (pnode->nVersion < CADDR_TIME_VERSION)
                            continue;
                        unsigned int nPointer;
                        memcpy(&nPointer, &pnode, sizeof(nPointer));
                        uint256 hashKey = hashRand ^ nPointer;
                        hashKey = Hash(BEGIN(hashKey), END(hashKey));
                        mapMix.insert(make_pair(hashKey, pnode));
                    }
                    int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
                    for (multimap<uint256, CNode*>::iterator mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
                        ((*mi).second)->PushAddress(addr);
                }
            }
            // Do not store addresses outside our network
            if (fReachable)
                vAddrOk.push_back(addr);
        }
        addrman.Add(vAddrOk, pfrom->addr, 2 * nOneHour);
        if (vAddr.size() < 1000)
            pfrom->fGetAddr = false;
        if (pfrom->fOneShot)
            pfrom->fDisconnect = true;
    }

    else if (strCommand == "inv")
    {
        vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ)
        {
            pfrom->Misbehaving(20);
            return error("message inv size() = %" PRIszu "", vInv.size());
        }

        // find last block in inv vector
        unsigned int nLastBlock = std::numeric_limits<uint32_t>::max();
        for (unsigned int nInv = 0; nInv < vInv.size(); nInv++) {
            if (vInv[vInv.size() - 1 - nInv].type == MSG_BLOCK) {
                nLastBlock = vInv.size() - 1 - nInv;
                break;
            }
        }
        CTxDB txdb("r");
        for (unsigned int nInv = 0; nInv < vInv.size(); nInv++)
        {
            const CInv &inv = vInv[nInv];

            if (fShutdown)
                return true;
            pfrom->AddInventoryKnown(inv);

            bool fAlreadyHave = AlreadyHave(txdb, inv);
            if (fDebug)
                printf("  got inventory: %s  %s\n", inv.ToString().c_str(), fAlreadyHave ? "have" : "new");

            if (!fAlreadyHave)
                pfrom->AskFor(inv);
            else if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) {
                pfrom->PushGetBlocks(pindexBest, GetOrphanRoot(mapOrphanBlocks[inv.hash]));
            } else if (nInv == nLastBlock) {
                // In case we are on a very long side-chain, it is possible that we already have
                // the last block in an inv bundle sent in response to getblocks. Try to detect
                // this situation and push another getblocks to continue.
                pfrom->PushGetBlocks(mapBlockIndex[inv.hash], uint256(0));
                if (fDebug)
                    printf("force request: %s\n", inv.ToString().c_str());
            }

            // Track requests for our stuff
            Inventory(inv.hash);
        }
    }


    else if (strCommand == "getdata")
    {
        vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ)
        {
            pfrom->Misbehaving(20);
            return error("message getdata size() = %" PRIszu "", vInv.size());
        }

        if (fDebugNet || (vInv.size() != 1))
            printf("received getdata (%" PRIszu " invsz)\n", vInv.size());

        BOOST_FOREACH(const CInv& inv, vInv)
        {
            if (fShutdown)
                return true;
            if (fDebugNet || (vInv.size() == 1))
                printf("received getdata for: %s\n", inv.ToString().c_str());

            if (inv.type == MSG_BLOCK)
            {
                // Send block from disk
                map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(inv.hash);
                if (mi != mapBlockIndex.end())
                {
                    CBlock block;
                    block.ReadFromDisk((*mi).second);
                    pfrom->PushMessage("block", block);

                    // Trigger them to send a getblocks request for the next batch of inventory
                    if (inv.hash == pfrom->hashContinue)
                    {
                        // ppcoin: send latest proof-of-work block to allow the
                        // download node to accept as orphan (proof-of-stake 
                        // block might be rejected by stake connection check)
                        vector<CInv> vInv;
                        vInv.push_back(CInv(MSG_BLOCK, GetLastBlockIndex(pindexBest, false)->GetBlockHash()));
                        pfrom->PushMessage("inv", vInv);
                        pfrom->hashContinue = 0;
                    }
                }
            }
            else if (inv.IsKnownType())
            {
                // Send stream from relay memory
                bool pushed = false;
                {
                    LOCK(cs_mapRelay);
                    map<CInv, CDataStream>::iterator mi = mapRelay.find(inv);
                    if (mi != mapRelay.end()) {
                        pfrom->PushMessage(inv.GetCommand(), (*mi).second);
                        pushed = true;
                    }
                }
                if (!pushed && inv.type == MSG_TX) {
                    LOCK(mempool.cs);
                    if (mempool.exists(inv.hash)) {
                        CTransaction tx = mempool.lookup(inv.hash);
                        CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                        ss.reserve(1000);
                        ss << tx;
                        pfrom->PushMessage("tx", ss);
                    }
                }
            }

            // Track requests for our stuff
            Inventory(inv.hash);
        }
    }


    else if (strCommand == "getblocks")
    {
        CBlockLocator locator;
        uint256 hashStop;
        vRecv >> locator >> hashStop;

        // Find the last block the caller has in the main chain
        CBlockIndex* pindex = locator.GetBlockIndex();

        // Send the rest of the chain
        if (pindex)
            pindex = pindex->pnext;
        int nLimit = 500;
        printf("getblocks %d to %s limit %d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().substr(0,20).c_str(), nLimit);
        for (; pindex; pindex = pindex->pnext)
        {
            if (pindex->GetBlockHash() == hashStop)
            {
                printf("  getblocks stopping at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString().substr(0,20).c_str());
                // ppcoin: tell downloading node about the latest block if it's
                // without risk being rejected due to stake connection check
                if (hashStop != hashBestChain && pindex->GetBlockTime() + nStakeMinAge > pindexBest->GetBlockTime())
                    pfrom->PushInventory(CInv(MSG_BLOCK, hashBestChain));
                break;
            }
            pfrom->PushInventory(CInv(MSG_BLOCK, pindex->GetBlockHash()));
            if (--nLimit <= 0)
            {
                // When this block is requested, we'll send an inv that'll make them
                // getblocks the next batch of inventory.
                printf("  getblocks stopping at limit %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString().substr(0,20).c_str());
                pfrom->hashContinue = pindex->GetBlockHash();
                break;
            }
        }
    }
    else if (strCommand == "checkpoint")
    {
        CSyncCheckpoint checkpoint;
        vRecv >> checkpoint;

        if (checkpoint.ProcessSyncCheckpoint(pfrom))
        {
            // Relay
            pfrom->hashCheckpointKnown = checkpoint.hashCheckpoint;
            LOCK(cs_vNodes);
            BOOST_FOREACH(CNode* pnode, vNodes)
                checkpoint.RelayTo(pnode);
        }
    }

    else if (strCommand == "getheaders")
    {
        CBlockLocator locator;
        uint256 hashStop;
        vRecv >> locator >> hashStop;

        CBlockIndex* pindex = NULL;
        if (locator.IsNull())
        {
            // If locator is null, return the hashStop block
            map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashStop);
            if (mi == mapBlockIndex.end())
                return true;
            pindex = (*mi).second;
        }
        else
        {
            // Find the last block the caller has in the main chain
            pindex = locator.GetBlockIndex();
            if (pindex)
                pindex = pindex->pnext;
        }

        vector<CBlock> vHeaders;
        int nLimit = 2000;
        printf("getheaders %d to %s\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().substr(0,20).c_str());
        for (; pindex; pindex = pindex->pnext)
        {
            vHeaders.push_back(pindex->GetBlockHeader());
            if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                break;
        }
        pfrom->PushMessage("headers", vHeaders);
    }


    else if (strCommand == "tx")
    {
        vector<uint256> vWorkQueue;
        vector<uint256> vEraseQueue;
        CDataStream vMsg(vRecv);
        CTxDB txdb("r");
        CTransaction tx;
        vRecv >> tx;

        CInv inv(MSG_TX, tx.GetHash());
        pfrom->AddInventoryKnown(inv);

        bool fMissingInputs = false;
        if (tx.AcceptToMemoryPool(txdb, true, &fMissingInputs))
        {
            SyncWithWallets(tx, NULL, true);
            RelayTransaction(tx, inv.hash);
            mapAlreadyAskedFor.erase(inv);
            vWorkQueue.push_back(inv.hash);
            vEraseQueue.push_back(inv.hash);

            // Recursively process any orphan transactions that depended on this one
            for (unsigned int i = 0; i < vWorkQueue.size(); i++)
            {
                uint256 hashPrev = vWorkQueue[i];
                for (set<uint256>::iterator mi = mapOrphanTransactionsByPrev[hashPrev].begin();
                     mi != mapOrphanTransactionsByPrev[hashPrev].end();
                     ++mi)
                {
                    const uint256& orphanTxHash = *mi;
                    CTransaction& orphanTx = mapOrphanTransactions[orphanTxHash];
                    bool fMissingInputs2 = false;

                    if (orphanTx.AcceptToMemoryPool(txdb, true, &fMissingInputs2))
                    {
                        printf("   accepted orphan tx %s\n", orphanTxHash.ToString().substr(0,10).c_str());
                        SyncWithWallets(tx, NULL, true);
                        RelayTransaction(orphanTx, orphanTxHash);
                        mapAlreadyAskedFor.erase(CInv(MSG_TX, orphanTxHash));
                        vWorkQueue.push_back(orphanTxHash);
                        vEraseQueue.push_back(orphanTxHash);
                    }
                    else if (!fMissingInputs2)
                    {
                        // invalid orphan
                        vEraseQueue.push_back(orphanTxHash);
                        printf("   removed invalid orphan tx %s\n", orphanTxHash.ToString().substr(0,10).c_str());
                    }
                }
            }

            BOOST_FOREACH(uint256 hash, vEraseQueue)
                EraseOrphanTx(hash);
        }
        else if (fMissingInputs)
        {
            AddOrphanTx(tx);

            // DoS prevention: do not allow mapOrphanTransactions to grow unbounded
            unsigned int nEvicted = LimitOrphanTxSize(MAX_ORPHAN_TRANSACTIONS);
            if (nEvicted > 0)
                printf("mapOrphan overflow, removed %u tx\n", nEvicted);
        }
        if (tx.nDoS) pfrom->Misbehaving(tx.nDoS);
    }


    else if (strCommand == "block")
    {
        CBlock block;
        vRecv >> block;
        uint256 hashBlock = block.GetHash();

        printf("received block %s\n", hashBlock.ToString().substr(0,20).c_str());
        // block.print();

        CInv inv(MSG_BLOCK, hashBlock);
        pfrom->AddInventoryKnown(inv);

        if (ProcessBlock(pfrom, &block))
            mapAlreadyAskedFor.erase(inv);
        if (block.nDoS) pfrom->Misbehaving(block.nDoS);
    }


    // This asymmetric behavior for inbound and outbound connections was introduced
    // to prevent a fingerprinting attack: an attacker can send specific fake addresses
    // to users' AddrMan and later request them by sending getaddr messages. 
    // Making users (which are behind NAT and can only make outgoing connections) ignore 
    // getaddr message mitigates the attack.
    else if ((strCommand == "getaddr") && (pfrom->fInbound))
    {
        // Don't return addresses older than nCutOff timestamp
        int64_t nCutOff = GetTime() - (nNodeLifespan * nOneDay);
        pfrom->vAddrToSend.clear();
        vector<CAddress> vAddr = addrman.GetAddr();
        BOOST_FOREACH(const CAddress &addr, vAddr)
            if(addr.nTime > nCutOff)
                pfrom->PushAddress(addr);
    }


    else if (strCommand == "mempool")
    {
        std::vector<uint256> vtxid;
        mempool.queryHashes(vtxid);
        vector<CInv> vInv;
        for (unsigned int i = 0; i < vtxid.size(); i++) {
            CInv inv(MSG_TX, vtxid[i]);
            vInv.push_back(inv);
            if (i == (MAX_INV_SZ - 1))
                    break;
        }
        if (vInv.size() > 0)
            pfrom->PushMessage("inv", vInv);
    }


    else if (strCommand == "checkorder")
    {
        uint256 hashReply;
        vRecv >> hashReply;

        if (!GetBoolArg("-allowreceivebyip"))
        {
            pfrom->PushMessage("reply", hashReply, (int)2, string(""));
            return true;
        }

        CWalletTx order;
        vRecv >> order;

        /// we have a chance to check the order here

        // Keep giving the same key to the same ip until they use it
        if (!mapReuseKey.count(pfrom->addr))
            pwalletMain->GetKeyFromPool(mapReuseKey[pfrom->addr], true);

        // Send back approval of order and pubkey to use
        CScript scriptPubKey;
        scriptPubKey << mapReuseKey[pfrom->addr] << OP_CHECKSIG;
        pfrom->PushMessage("reply", hashReply, (int)0, scriptPubKey);
    }


    else if (strCommand == "reply")
    {
        uint256 hashReply;
        vRecv >> hashReply;

        CRequestTracker tracker;
        {
            LOCK(pfrom->cs_mapRequests);
            map<uint256, CRequestTracker>::iterator mi = pfrom->mapRequests.find(hashReply);
            if (mi != pfrom->mapRequests.end())
            {
                tracker = (*mi).second;
                pfrom->mapRequests.erase(mi);
            }
        }
        if (!tracker.IsNull())
            tracker.fn(tracker.param1, vRecv);
    }


    else if (strCommand == "ping")
    {
        if (pfrom->nVersion > BIP0031_VERSION)
        {
            uint64_t nonce = 0;
            vRecv >> nonce;
            // Echo the message back with the nonce. This allows for two useful features:
            //
            // 1) A remote node can quickly check if the connection is operational
            // 2) Remote nodes can measure the latency of the network thread. If this node
            //    is overloaded it won't respond to pings quickly and the remote node can
            //    avoid sending us more work, like chain download requests.
            //
            // The nonce stops the remote getting confused between different pings: without
            // it, if the remote node sends a ping once per second and this node takes 5
            // seconds to respond to each, the 5th ping the remote sends would appear to
            // return very quickly.
            pfrom->PushMessage("pong", nonce);
        }
    }


    else if (strCommand == "alert")
    {
        CAlert alert;
        vRecv >> alert;

        uint256 alertHash = alert.GetHash();
        if (pfrom->setKnown.count(alertHash) == 0)
        {
            if (alert.ProcessAlert())
            {
                // Relay
                pfrom->setKnown.insert(alertHash);
                {
                    LOCK(cs_vNodes);
                    BOOST_FOREACH(CNode* pnode, vNodes)
                        alert.RelayTo(pnode);
                }
            }
            else {
                // Small DoS penalty so peers that send us lots of
                // duplicate/expired/invalid-signature/whatever alerts
                // eventually get banned.
                // This isn't a Misbehaving(100) (immediate ban) because the
                // peer might be an older or different implementation with
                // a different signature key, etc.
                pfrom->Misbehaving(10);
            }
        }
    }


    else
    {
        // Ignore unknown commands for extensibility
    }


    // Update the last seen time for this node's address
    if (pfrom->fNetworkNode)
        if (strCommand == "version" || strCommand == "addr" || strCommand == "inv" || strCommand == "getdata" || strCommand == "ping")
            AddressCurrentlyConnected(pfrom->addr);


    return true;
}

bool ProcessMessages(CNode* pfrom)
{
    CDataStream& vRecv = pfrom->vRecv;
    if (vRecv.empty())
        return true;
    //if (fDebug)
    //    printf("ProcessMessages(%u bytes)\n", vRecv.size());

    //
    // Message format
    //  (4) message start
    //  (12) command
    //  (4) size
    //  (4) checksum
    //  (x) data
    //

    while (true)
    {
        // Don't bother if send buffer is too full to respond anyway
        if (pfrom->vSend.size() >= SendBufferSize())
            break;

        // Scan for message start
        CDataStream::iterator pstart = search(vRecv.begin(), vRecv.end(), BEGIN(pchMessageStart), END(pchMessageStart));
        int nHeaderSize = vRecv.GetSerializeSize(CMessageHeader());
        if (vRecv.end() - pstart < nHeaderSize)
        {
            if ((int)vRecv.size() > nHeaderSize)
            {
                printf("\n\nPROCESSMESSAGE MESSAGESTART NOT FOUND\n\n");
                vRecv.erase(vRecv.begin(), vRecv.end() - nHeaderSize);
            }
            break;
        }
        if (pstart - vRecv.begin() > 0)
            printf("\n\nPROCESSMESSAGE SKIPPED %" PRIpdd " BYTES\n\n", pstart - vRecv.begin());
        vRecv.erase(vRecv.begin(), pstart);

        // Read header
        vector<char> vHeaderSave(vRecv.begin(), vRecv.begin() + nHeaderSize);
        CMessageHeader hdr;
        vRecv >> hdr;
        if (!hdr.IsValid())
        {
            printf("\n\nPROCESSMESSAGE: ERRORS IN HEADER %s\n\n\n", hdr.GetCommand().c_str());
            continue;
        }
        string strCommand = hdr.GetCommand();

        // Message size
        unsigned int nMessageSize = hdr.nMessageSize;
        if (nMessageSize > MAX_SIZE)
        {
            printf("ProcessMessages(%s, %u bytes) : nMessageSize > MAX_SIZE\n", strCommand.c_str(), nMessageSize);
            continue;
        }
        if (nMessageSize > vRecv.size())
        {
            // Rewind and wait for rest of message
            vRecv.insert(vRecv.begin(), vHeaderSave.begin(), vHeaderSave.end());
            break;
        }

        // Checksum
        uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
        unsigned int nChecksum = 0;
        memcpy(&nChecksum, &hash, sizeof(nChecksum));
        if (nChecksum != hdr.nChecksum)
        {
            printf("ProcessMessages(%s, %u bytes) : CHECKSUM ERROR nChecksum=%08x hdr.nChecksum=%08x\n",
               strCommand.c_str(), nMessageSize, nChecksum, hdr.nChecksum);
            continue;
        }

        // Copy message to its own buffer
        CDataStream vMsg(vRecv.begin(), vRecv.begin() + nMessageSize, vRecv.nType, vRecv.nVersion);
        vRecv.ignore(nMessageSize);

        // Process message
        bool fRet = false;
        try
        {
            {
                LOCK(cs_main);
                fRet = ProcessMessage(pfrom, strCommand, vMsg);
            }
            if (fShutdown)
                return true;
        }
        catch (std::ios_base::failure& e)
        {
            if (strstr(e.what(), "end of data"))
            {
                // Allow exceptions from under-length message on vRecv
                printf("ProcessMessages(%s, %u bytes) : Exception '%s' caught, normally caused by a message being shorter than its stated length\n", strCommand.c_str(), nMessageSize, e.what());
            }
            else if (strstr(e.what(), "size too large"))
            {
                // Allow exceptions from over-long size
                printf("ProcessMessages(%s, %u bytes) : Exception '%s' caught\n", strCommand.c_str(), nMessageSize, e.what());
            }
            else
            {
                PrintExceptionContinue(&e, "ProcessMessages()");
            }
        }
        catch (std::exception& e) {
            PrintExceptionContinue(&e, "ProcessMessages()");
        } catch (...) {
            PrintExceptionContinue(NULL, "ProcessMessages()");
        }

        if (!fRet)
            printf("ProcessMessage(%s, %u bytes) FAILED\n", strCommand.c_str(), nMessageSize);
    }

    vRecv.Compact();
    return true;
}


bool SendMessages(CNode* pto, bool fSendTrickle)
{
    TRY_LOCK(cs_main, lockMain);
    if (lockMain) {
        // Don't send anything until we get their version message
        if (pto->nVersion == 0)
            return true;

        // Keep-alive ping. We send a nonce of zero because we don't use it anywhere
        // right now.
        if (pto->nLastSend && GetTime() - pto->nLastSend > nPingInterval && pto->vSend.empty()) {
            uint64_t nonce = 0;
            if (pto->nVersion > BIP0031_VERSION)
                pto->PushMessage("ping", nonce);
            else
                pto->PushMessage("ping");
        }

        // Start block sync
        if (pto->fStartSync) {
            pto->fStartSync = false;
            pto->PushGetBlocks(pindexBest, uint256(0));
        }

        // Resend wallet transactions that haven't gotten in a block yet
        ResendWalletTransactions();

        // Address refresh broadcast
        static int64_t nLastRebroadcast;
        if (!IsInitialBlockDownload() && (GetTime() - nLastRebroadcast > nBroadcastInterval))
        {
            {
                LOCK(cs_vNodes);
                BOOST_FOREACH(CNode* pnode, vNodes)
                {
                    // Periodically clear setAddrKnown to allow refresh broadcasts
                    if (nLastRebroadcast)
                        pnode->setAddrKnown.clear();

                    // Rebroadcast our address
                    if (!fNoListen)
                    {
                        CAddress addr = GetLocalAddress(&pnode->addr);
                        if (addr.IsRoutable())
                            pnode->PushAddress(addr);
                    }
                }
            }
            nLastRebroadcast = GetTime();
        }

        //
        // Message: addr
        //
        if (fSendTrickle)
        {
            vector<CAddress> vAddr;
            vAddr.reserve(pto->vAddrToSend.size());
            BOOST_FOREACH(const CAddress& addr, pto->vAddrToSend)
            {
                // returns true if wasn't already contained in the set
                if (pto->setAddrKnown.insert(addr).second)
                {
                    vAddr.push_back(addr);
                    // receiver rejects addr messages larger than 1000
                    if (vAddr.size() >= 1000)
                    {
                        pto->PushMessage("addr", vAddr);
                        vAddr.clear();
                    }
                }
            }
            pto->vAddrToSend.clear();
            if (!vAddr.empty())
                pto->PushMessage("addr", vAddr);
        }


        //
        // Message: inventory
        //
        vector<CInv> vInv;
        vector<CInv> vInvWait;
        {
            LOCK(pto->cs_inventory);
            vInv.reserve(pto->vInventoryToSend.size());
            vInvWait.reserve(pto->vInventoryToSend.size());
            BOOST_FOREACH(const CInv& inv, pto->vInventoryToSend)
            {
                if (pto->setInventoryKnown.count(inv))
                    continue;

                // trickle out tx inv to protect privacy
                if (inv.type == MSG_TX && !fSendTrickle)
                {
                    // 1/4 of tx invs blast to all immediately
                    static uint256 hashSalt;
                    if (hashSalt == 0)
                        hashSalt = GetRandHash();
                    uint256 hashRand = inv.hash ^ hashSalt;
                    hashRand = Hash(BEGIN(hashRand), END(hashRand));
                    bool fTrickleWait = ((hashRand & 3) != 0);

                    // always trickle our own transactions
                    if (!fTrickleWait)
                    {
                        CWalletTx wtx;
                        if (GetTransaction(inv.hash, wtx))
                            if (wtx.fFromMe)
                                fTrickleWait = true;
                    }

                    if (fTrickleWait)
                    {
                        vInvWait.push_back(inv);
                        continue;
                    }
                }

                // returns true if wasn't already contained in the set
                if (pto->setInventoryKnown.insert(inv).second)
                {
                    vInv.push_back(inv);
                    if (vInv.size() >= 1000)
                    {
                        pto->PushMessage("inv", vInv);
                        vInv.clear();
                    }
                }
            }
            pto->vInventoryToSend = vInvWait;
        }
        if (!vInv.empty())
            pto->PushMessage("inv", vInv);


        //
        // Message: getdata
        //
        vector<CInv> vGetData;
        int64_t nNow = GetTime() * 1000000;
        CTxDB txdb("r");
        while (!pto->mapAskFor.empty() && (*pto->mapAskFor.begin()).first <= nNow)
        {
            const CInv& inv = (*pto->mapAskFor.begin()).second;
            if (!AlreadyHave(txdb, inv))
            {
                if (fDebugNet)
                    printf("sending getdata: %s\n", inv.ToString().c_str());
                vGetData.push_back(inv);
                if (vGetData.size() >= 1000)
                {
                    pto->PushMessage("getdata", vGetData);
                    vGetData.clear();
                }
                mapAlreadyAskedFor[inv] = nNow;
            }
            pto->mapAskFor.erase(pto->mapAskFor.begin());
        }
        if (!vGetData.empty())
            pto->PushMessage("getdata", vGetData);

    }
    return true;
}


class CMainCleanup
{
public:
    CMainCleanup() {}
    ~CMainCleanup() {
        // block headers
        std::map<uint256, CBlockIndex*>::iterator it1 = mapBlockIndex.begin();
        for (; it1 != mapBlockIndex.end(); it1++)
            delete (*it1).second;
        mapBlockIndex.clear();

        // orphan blocks
        std::map<uint256, CBlock*>::iterator it2 = mapOrphanBlocks.begin();
        for (; it2 != mapOrphanBlocks.end(); it2++)
            delete (*it2).second;
        mapOrphanBlocks.clear();

        // orphan transactions
    }
} instance_of_cmaincleanup;