coins.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_COINS_H
#define BITCOIN_COINS_H
 
#include "compressor.h"
#include "core_memusage.h"
#include "hash.h"
#include "memusage.h"
#include "serialize.h"
#include "uint256.h"
 
#include <assert.h>
#include <stdint.h>
 
#include <boost/foreach.hpp>
#include <boost/unordered_map.hpp>
 
class CCoins
{
public:
    bool fCoinBase;
 
    std::vector<CTxOut> vout;
 
    int nHeight;
 
    int nVersion;
 
    void FromTx(const CTransaction &tx, int nHeightIn) {
        fCoinBase = tx.IsCoinBase();
        vout = tx.vout;
        nHeight = nHeightIn;
        nVersion = tx.nVersion;
        ClearUnspendable();
    }
 
    CCoins(const CTransaction &tx, int nHeightIn) {
        FromTx(tx, nHeightIn);
    }
 
    void Clear() {
        fCoinBase = false;
        std::vector<CTxOut>().swap(vout);
        nHeight = 0;
        nVersion = 0;
    }
 
    CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }
 
    void Cleanup() {
        while (vout.size() > 0 && vout.back().IsNull())
            vout.pop_back();
        if (vout.empty())
            std::vector<CTxOut>().swap(vout);
    }
 
    void ClearUnspendable() {
        BOOST_FOREACH(CTxOut &txout, vout) {
            if (txout.scriptPubKey.IsUnspendable())
                txout.SetNull();
        }
        Cleanup();
    }
 
    void swap(CCoins &to) {
        std::swap(to.fCoinBase, fCoinBase);
        to.vout.swap(vout);
        std::swap(to.nHeight, nHeight);
        std::swap(to.nVersion, nVersion);
    }
 
    friend bool operator==(const CCoins &a, const CCoins &b) {
         // Empty CCoins objects are always equal.
         if (a.IsPruned() && b.IsPruned())
             return true;
         return a.fCoinBase == b.fCoinBase &&
                a.nHeight == b.nHeight &&
                a.nVersion == b.nVersion &&
                a.vout == b.vout;
    }
    friend bool operator!=(const CCoins &a, const CCoins &b) {
        return !(a == b);
    }
 
    void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const;
 
    bool IsCoinBase() const {
        return fCoinBase;
    }
 
    template<typename Stream>
    void Serialize(Stream &s) const {
        unsigned int nMaskSize = 0, nMaskCode = 0;
        CalcMaskSize(nMaskSize, nMaskCode);
        bool fFirst = vout.size() > 0 && !vout[0].IsNull();
        bool fSecond = vout.size() > 1 && !vout[1].IsNull();
        assert(fFirst || fSecond || nMaskCode);
        unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
        // version
        ::Serialize(s, VARINT(this->nVersion));
        // header code
        ::Serialize(s, VARINT(nCode));
        // spentness bitmask
        for (unsigned int b = 0; b<nMaskSize; b++) {
            unsigned char chAvail = 0;
            for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
                if (!vout[2+b*8+i].IsNull())
                    chAvail |= (1 << i);
            ::Serialize(s, chAvail);
        }
        // txouts themself
        for (unsigned int i = 0; i < vout.size(); i++) {
            if (!vout[i].IsNull())
                ::Serialize(s, CTxOutCompressor(REF(vout[i])));
        }
        // coinbase height
        ::Serialize(s, VARINT(nHeight));
    }
 
    template<typename Stream>
    void Unserialize(Stream &s) {
        unsigned int nCode = 0;
        // version
        ::Unserialize(s, VARINT(this->nVersion));
        // header code
        ::Unserialize(s, VARINT(nCode));
        fCoinBase = nCode & 1;
        std::vector<bool> vAvail(2, false);
        vAvail[0] = (nCode & 2) != 0;
        vAvail[1] = (nCode & 4) != 0;
        unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
        // spentness bitmask
        while (nMaskCode > 0) {
            unsigned char chAvail = 0;
            ::Unserialize(s, chAvail);
            for (unsigned int p = 0; p < 8; p++) {
                bool f = (chAvail & (1 << p)) != 0;
                vAvail.push_back(f);
            }
            if (chAvail != 0)
                nMaskCode--;
        }
        // txouts themself
        vout.assign(vAvail.size(), CTxOut());
        for (unsigned int i = 0; i < vAvail.size(); i++) {
            if (vAvail[i])
                ::Unserialize(s, REF(CTxOutCompressor(vout[i])));
        }
        // coinbase height
        ::Unserialize(s, VARINT(nHeight));
        Cleanup();
    }
 
    bool Spend(uint32_t nPos);
 
    bool IsAvailable(unsigned int nPos) const {
        return (nPos < vout.size() && !vout[nPos].IsNull());
    }
 
    bool IsPruned() const {
        BOOST_FOREACH(const CTxOut &out, vout)
            if (!out.IsNull())
                return false;
        return true;
    }
 
    size_t DynamicMemoryUsage() const {
        size_t ret = memusage::DynamicUsage(vout);
        BOOST_FOREACH(const CTxOut &out, vout) {
            ret += RecursiveDynamicUsage(out.scriptPubKey);
        }
        return ret;
    }
};
 
class SaltedTxidHasher
{
private:
    const uint64_t k0, k1;
 
public:
    SaltedTxidHasher();
 
    size_t operator()(const uint256& txid) const {
        return SipHashUint256(k0, k1, txid);
    }
};
 
struct CCoinsCacheEntry
{
    CCoins coins; // The actual cached data.
    unsigned char flags;
 
    enum Flags {
        DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
        FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
        /* Note that FRESH is a performance optimization with which we can
         * erase coins that are fully spent if we know we do not need to
         * flush the changes to the parent cache.  It is always safe to
         * not mark FRESH if that condition is not guaranteed.
         */
    };
 
    CCoinsCacheEntry() : coins(), flags(0) {}
};
 
typedef boost::unordered_map<uint256, CCoinsCacheEntry, SaltedTxidHasher> CCoinsMap;
 
class CCoinsViewCursor
{
public:
    CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
    virtual ~CCoinsViewCursor();
 
    virtual bool GetKey(uint256 &key) const = 0;
    virtual bool GetValue(CCoins &coins) const = 0;
    /* Don't care about GetKeySize here */
    virtual unsigned int GetValueSize() const = 0;
 
    virtual bool Valid() const = 0;
    virtual void Next() = 0;
 
    const uint256 &GetBestBlock() const { return hashBlock; }
private:
    uint256 hashBlock;
};
 
class CCoinsView
{
public:
    virtual bool GetCoins(const uint256 &txid, CCoins &coins) const;
 
    virtual bool HaveCoins(const uint256 &txid) const;
 
    virtual uint256 GetBestBlock() const;
 
    virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 
    virtual CCoinsViewCursor *Cursor() const;
 
    virtual ~CCoinsView() {}
};
 
 
class CCoinsViewBacked : public CCoinsView
{
protected:
    CCoinsView *base;
 
public:
    CCoinsViewBacked(CCoinsView *viewIn);
    bool GetCoins(const uint256 &txid, CCoins &coins) const;
    bool HaveCoins(const uint256 &txid) const;
    uint256 GetBestBlock() const;
    void SetBackend(CCoinsView &viewIn);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
    CCoinsViewCursor *Cursor() const;
};
 
 
class CCoinsViewCache;
 
class CCoinsModifier
{
private:
    CCoinsViewCache& cache;
    CCoinsMap::iterator it;
    size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
    CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);
 
public:
    CCoins* operator->() { return &it->second.coins; }
    CCoins& operator*() { return it->second.coins; }
    ~CCoinsModifier();
    friend class CCoinsViewCache;
};
 
class CCoinsViewCache : public CCoinsViewBacked
{
protected:
    /* Whether this cache has an active modifier. */
    bool hasModifier;
 
 
    mutable uint256 hashBlock;
    mutable CCoinsMap cacheCoins;
 
    /* Cached dynamic memory usage for the inner CCoins objects. */
    mutable size_t cachedCoinsUsage;
 
public:
    CCoinsViewCache(CCoinsView *baseIn);
    ~CCoinsViewCache();
 
    // Standard CCoinsView methods
    bool GetCoins(const uint256 &txid, CCoins &coins) const;
    bool HaveCoins(const uint256 &txid) const;
    uint256 GetBestBlock() const;
    void SetBestBlock(const uint256 &hashBlock);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 
    bool HaveCoinsInCache(const uint256 &txid) const;
 
    const CCoins* AccessCoins(const uint256 &txid) const;
 
    CCoinsModifier ModifyCoins(const uint256 &txid);
 
    CCoinsModifier ModifyNewCoins(const uint256 &txid, bool coinbase);
 
    bool Flush();
 
    void Uncache(const uint256 &txid);
 
    unsigned int GetCacheSize() const;
 
    size_t DynamicMemoryUsage() const;
 
    CAmount GetValueIn(const CTransaction& tx) const;
 
    bool HaveInputs(const CTransaction& tx) const;
 
    double GetPriority(const CTransaction &tx, int nHeight, CAmount &inChainInputValue) const;
 
    const CTxOut &GetOutputFor(const CTxIn& input) const;
 
    friend class CCoinsModifier;
 
private:
    CCoinsMap::const_iterator FetchCoins(const uint256 &txid) const;
 
    CCoinsViewCache(const CCoinsViewCache &);
};
 
#endif // BITCOIN_COINS_H