coins.cpp

// Copyright (c) 2012-2013 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 "coins.h"

#include "random.h"

#include <assert.h>

// calculate number of bytes for the bitmask, and its number of non-zero bytes
// each bit in the bitmask represents the availability of one output, but the
// availabilities of the first two outputs are encoded separately
void CCoins::CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const {
    unsigned int nLastUsedByte = 0;
    for (unsigned int b = 0; 2+b*8 < vout.size(); b++) {
        bool fZero = true;
        for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++) {
            if (!vout[2+b*8+i].IsNull()) {
                fZero = false;
                continue;
            }
        }
        if (!fZero) {
            nLastUsedByte = b + 1;
            nNonzeroBytes++;
        }
    }
    nBytes += nLastUsedByte;
}

bool CCoins::Spend(const COutPoint &out, CTxInUndo &undo) {
    if (out.n >= vout.size())
        return false;
    if (vout[out.n].IsNull())
        return false;
    undo = CTxInUndo(vout[out.n]);
    vout[out.n].SetNull();
    Cleanup();
    if (vout.size() == 0) {
        undo.nHeight = nHeight;
        undo.fCoinBase = fCoinBase;
        undo.nVersion = this->nVersion;
    }
    return true;
}

bool CCoins::Spend(int nPos) {
    CTxInUndo undo;
    COutPoint out(0, nPos);
    return Spend(out, undo);
}


bool CCoinsView::GetCoins(const uint256 &txid, CCoins &coins) const { return false; }
bool CCoinsView::SetCoins(const uint256 &txid, const CCoins &coins) { return false; }
bool CCoinsView::HaveCoins(const uint256 &txid) const { return false; }
uint256 CCoinsView::GetBestBlock() const { return uint256(0); }
bool CCoinsView::SetBestBlock(const uint256 &hashBlock) { return false; }
bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
bool CCoinsView::GetStats(CCoinsStats &stats) const { return false; }


CCoinsViewBacked::CCoinsViewBacked(CCoinsView &viewIn) : base(&viewIn) { }
bool CCoinsViewBacked::GetCoins(const uint256 &txid, CCoins &coins) const { return base->GetCoins(txid, coins); }
bool CCoinsViewBacked::SetCoins(const uint256 &txid, const CCoins &coins) { return base->SetCoins(txid, coins); }
bool CCoinsViewBacked::HaveCoins(const uint256 &txid) const { return base->HaveCoins(txid); }
uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
bool CCoinsViewBacked::SetBestBlock(const uint256 &hashBlock) { return base->SetBestBlock(hashBlock); }
void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
bool CCoinsViewBacked::GetStats(CCoinsStats &stats) const { return base->GetStats(stats); }

CCoinsKeyHasher::CCoinsKeyHasher() : salt(GetRandHash()) {}

CCoinsViewCache::CCoinsViewCache(CCoinsView &baseIn, bool fDummy) : CCoinsViewBacked(baseIn), hashBlock(0) { }

bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
    if (cacheCoins.count(txid)) {
        coins = cacheCoins[txid];
        return true;
    }
    if (base->GetCoins(txid, coins)) {
        cacheCoins[txid] = coins;
        return true;
    }
    return false;
}

CCoinsMap::iterator CCoinsViewCache::FetchCoins(const uint256 &txid) {
    CCoinsMap::iterator it = cacheCoins.find(txid);
    if (it != cacheCoins.end())
        return it;
    CCoins tmp;
    if (!base->GetCoins(txid,tmp))
        return cacheCoins.end();
    CCoinsMap::iterator ret = cacheCoins.insert(it, std::make_pair(txid, CCoins()));
    tmp.swap(ret->second);
    return ret;
}

CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
    /* Avoid redundant implementation with the const-cast.  */
    return const_cast<CCoinsViewCache*>(this)->FetchCoins(txid);
}

CCoins &CCoinsViewCache::GetCoins(const uint256 &txid) {
    CCoinsMap::iterator it = FetchCoins(txid);
    assert(it != cacheCoins.end());
    return it->second;
}

const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
    CCoinsMap::const_iterator it = FetchCoins(txid);
    if (it == cacheCoins.end()) {
        return NULL;
    } else {
        return &it->second;
    }
}

bool CCoinsViewCache::SetCoins(const uint256 &txid, const CCoins &coins) {
    cacheCoins[txid] = coins;
    return true;
}

bool CCoinsViewCache::HaveCoins(const uint256 &txid) const {
    CCoinsMap::const_iterator it = FetchCoins(txid);
    // We're using vtx.empty() instead of IsPruned here for performance reasons,
    // as we only care about the case where an transaction was replaced entirely
    // in a reorganization (which wipes vout entirely, as opposed to spending
    // which just cleans individual outputs).
    return (it != cacheCoins.end() && !it->second.vout.empty());
}

uint256 CCoinsViewCache::GetBestBlock() const {
    if (hashBlock == uint256(0))
        hashBlock = base->GetBestBlock();
    return hashBlock;
}

bool CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
    hashBlock = hashBlockIn;
    return true;
}

bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
    for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
        cacheCoins[it->first].swap(it->second);
        CCoinsMap::iterator itOld = it++;
        mapCoins.erase(itOld);
    }
    hashBlock = hashBlockIn;
    return true;
}

bool CCoinsViewCache::Flush() {
    bool fOk = base->BatchWrite(cacheCoins, hashBlock);
    cacheCoins.clear();
    return fOk;
}

unsigned int CCoinsViewCache::GetCacheSize() const {
    return cacheCoins.size();
}

const CTxOut &CCoinsViewCache::GetOutputFor(const CTxIn& input) const
{
    const CCoins* coins = AccessCoins(input.prevout.hash);
    assert(coins && coins->IsAvailable(input.prevout.n));
    return coins->vout[input.prevout.n];
}

int64_t CCoinsViewCache::GetValueIn(const CTransaction& tx) const
{
    if (tx.IsCoinBase())
        return 0;

    int64_t nResult = 0;
    for (unsigned int i = 0; i < tx.vin.size(); i++)
        nResult += GetOutputFor(tx.vin[i]).nValue;

    return nResult;
}

bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
{
    if (!tx.IsCoinBase()) {
        for (unsigned int i = 0; i < tx.vin.size(); i++) {
            const COutPoint &prevout = tx.vin[i].prevout;
            const CCoins* coins = AccessCoins(prevout.hash);
            if (!coins || !coins->IsAvailable(prevout.n)) {
                return false;
            }
        }
    }
    return true;
}

double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight) const
{
    if (tx.IsCoinBase())
        return 0.0;
    double dResult = 0.0;
    BOOST_FOREACH(const CTxIn& txin, tx.vin)
    {
        const CCoins* coins = AccessCoins(txin.prevout.hash);
        assert(coins);
        if (!coins->IsAvailable(txin.prevout.n)) continue;
        if (coins->nHeight < nHeight) {
            dResult += coins->vout[txin.prevout.n].nValue * (nHeight-coins->nHeight);
        }
    }
    return tx.ComputePriority(dResult);
}