coins.h

Go to the documentation of this file.

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2018 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 <primitives/transaction.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 <unordered_map>

class Coin
{
public:
    CTxOut out;

    unsigned int fCoinBase : 1;

    uint32_t nHeight : 31;

    Coin(CTxOut&& outIn, int nHeightIn, bool fCoinBaseIn) : out(std::move(outIn)), fCoinBase(fCoinBaseIn), nHeight(nHeightIn) {}
    Coin(const CTxOut& outIn, int nHeightIn, bool fCoinBaseIn) : out(outIn), fCoinBase(fCoinBaseIn),nHeight(nHeightIn) {}

    void Clear() {
        out.SetNull();
        fCoinBase = false;
        nHeight = 0;
    }

    Coin() : fCoinBase(false), nHeight(0) { }

    bool IsCoinBase() const {
        return fCoinBase;
    }

    template<typename Stream>
    void Serialize(Stream &s) const {
        assert(!IsSpent());
        uint32_t code = nHeight * 2 + fCoinBase;
        ::Serialize(s, VARINT(code));
        ::Serialize(s, CTxOutCompressor(REF(out)));
    }

    template<typename Stream>
    void Unserialize(Stream &s) {
        uint32_t code = 0;
        ::Unserialize(s, VARINT(code));
        nHeight = code >> 1;
        fCoinBase = code & 1;
        ::Unserialize(s, CTxOutCompressor(out));
    }

    bool IsSpent() const {
        return out.IsNull();
    }

    size_t DynamicMemoryUsage() const {
        return memusage::DynamicUsage(out.scriptPubKey);
    }
};

class SaltedOutpointHasher
{
private:
    const uint64_t k0, k1;

public:
    SaltedOutpointHasher();

    size_t operator()(const COutPoint& id) const {
        return SipHashUint256Extra(k0, k1, id.hash, id.n);
    }
};

struct CCoinsCacheEntry
{
    Coin coin; // 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() : flags(0) {}
    explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
};

typedef std::unordered_map<COutPoint, CCoinsCacheEntry, SaltedOutpointHasher> CCoinsMap;

class CCoinsViewCursor
{
public:
    CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
    virtual ~CCoinsViewCursor() {}

    virtual bool GetKey(COutPoint &key) const = 0;
    virtual bool GetValue(Coin &coin) const = 0;
    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 GetCoin(const COutPoint &outpoint, Coin &coin) const;

    virtual bool HaveCoin(const COutPoint &outpoint) const;

    virtual uint256 GetBestBlock() const;

    virtual std::vector<uint256> GetHeadBlocks() const;

    virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);

    virtual CCoinsViewCursor *Cursor() const;

    virtual ~CCoinsView() {}

    virtual size_t EstimateSize() const { return 0; }
};


class CCoinsViewBacked : public CCoinsView
{
protected:
    CCoinsView *base;

public:
    CCoinsViewBacked(CCoinsView *viewIn);
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    bool HaveCoin(const COutPoint &outpoint) const override;
    uint256 GetBestBlock() const override;
    std::vector<uint256> GetHeadBlocks() const override;
    void SetBackend(CCoinsView &viewIn);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
    CCoinsViewCursor *Cursor() const override;
    size_t EstimateSize() const override;
};


class CCoinsViewCache : public CCoinsViewBacked
{
protected:
    mutable uint256 hashBlock;
    mutable CCoinsMap cacheCoins;

    /* Cached dynamic memory usage for the inner Coin objects. */
    mutable size_t cachedCoinsUsage;

public:
    CCoinsViewCache(CCoinsView *baseIn);

    CCoinsViewCache(const CCoinsViewCache &) = delete;

    // Standard CCoinsView methods
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    bool HaveCoin(const COutPoint &outpoint) const override;
    uint256 GetBestBlock() const override;
    void SetBestBlock(const uint256 &hashBlock);
    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
    CCoinsViewCursor* Cursor() const override {
        throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
    }

    bool HaveCoinInCache(const COutPoint &outpoint) const;

    const Coin& AccessCoin(const COutPoint &output) const;

    void AddCoin(const COutPoint& outpoint, Coin&& coin, bool potential_overwrite);

    bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr);

    bool Flush();

    void Uncache(const COutPoint &outpoint);

    unsigned int GetCacheSize() const;

    size_t DynamicMemoryUsage() const;

    CAmount GetValueIn(const CTransaction& tx) const;

    bool HaveInputs(const CTransaction& tx) const;

private:
    CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
};

// When check is false, this assumes that overwrites are only possible for coinbase transactions.
// When check is true, the underlying view may be queried to determine whether an addition is
// an overwrite.
// TODO: pass in a boolean to limit these possible overwrites to known
// (pre-BIP34) cases.
void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);

// This function can be quite expensive because in the event of a transaction
// which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
// lookups to database, so it should be used with care.
const Coin& AccessByTxid(const CCoinsViewCache& cache, const uint256& txid);

#endif // BITCOIN_COINS_H