diff options
Diffstat (limited to 'src/coins.h')
| -rw-r--r-- | src/coins.h | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/src/coins.h b/src/coins.h index dc3210b8ac..efb5ce869c 100644 --- a/src/coins.h +++ b/src/coins.h @@ -145,16 +145,24 @@ private: class CCoinsView { public: - //! Retrieve the Coin (unspent transaction output) for a given outpoint. + /** Retrieve the Coin (unspent transaction output) for a given outpoint. + * Returns true only when an unspent coin was found, which is returned in coin. + * When false is returned, coin's value is unspecified. + */ virtual bool GetCoin(const COutPoint &outpoint, Coin &coin) const; - //! Just check whether we have data for a given outpoint. - //! This may (but cannot always) return true for spent outputs. + //! Just check whether a given outpoint is unspent. virtual bool HaveCoin(const COutPoint &outpoint) const; //! Retrieve the block hash whose state this CCoinsView currently represents virtual uint256 GetBestBlock() const; + //! Retrieve the range of blocks that may have been only partially written. + //! If the database is in a consistent state, the result is the empty vector. + //! Otherwise, a two-element vector is returned consisting of the new and + //! the old block hash, in that order. + virtual std::vector<uint256> GetHeadBlocks() const; + //! Do a bulk modification (multiple Coin changes + BestBlock change). //! The passed mapCoins can be modified. virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock); @@ -181,6 +189,7 @@ public: 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; @@ -224,8 +233,13 @@ public: /** * Return a reference to Coin in the cache, or a pruned one if not found. This is - * more efficient than GetCoin. Modifications to other cache entries are - * allowed while accessing the returned pointer. + * more efficient than GetCoin. + * + * Generally, do not hold the reference returned for more than a short scope. + * While the current implementation allows for modifications to the contents + * of the cache while holding the reference, this behavior should not be relied + * on! To be safe, best to not hold the returned reference through any other + * calls to this cache. */ const Coin& AccessCoin(const COutPoint &output) const; @@ -240,7 +254,7 @@ public: * If no unspent output exists for the passed outpoint, this call * has no effect. */ - void SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr); + bool SpendCoin(const COutPoint &outpoint, Coin* moveto = nullptr); /** * Push the modifications applied to this cache to its base. @@ -284,12 +298,17 @@ private: }; //! Utility function to add all of a transaction's outputs to a cache. -// It assumes that overwrites are only possible for coinbase transactions, +// 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); +void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false); //! Utility function to find any unspent output with a given txid. +// 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 |