Representing unspent outputs and cache state

751    {
752        StopFetching();
753        CCoinsViewCache::Reset();
754    }
755
756public:
757    explicit CoinsViewOverlay(CCoinsView* in_base, std::shared_ptr<ThreadPool> thread_pool,
758                              bool deterministic = false) noexcept
759        : CCoinsViewCache{in_base, deterministic}, m_thread_pool{std::move(thread_pool)}
760    {
761        Assert(m_thread_pool);
762    }
763
764    ~CoinsViewOverlay() noexcept override { StopFetching(); }
765
766    //! Start fetching inputs from block.
767    [[nodiscard]] ResetGuard StartFetching(const CBlock& block LIFETIMEBOUND) noexcept;
768
769    void Flush(bool reallocate_cache = true) override
770    {
771        if (!Assume(AllInputsConsumed())) {
772            LogWarning("Block %s input prevout prefetch queue was not fully consumed; inputs were accessed out of order, so prefetching degraded to serial lookups for this block.", GetBestBlock().ToString());
773        }
774        StopFetching();
775        CCoinsViewCache::Flush(reallocate_cache);
776    }
777
778    //! Swapping the backend or writing through to it with Sync() is not supported while fetching.
779    void SetBackend(CCoinsView&) = delete;
780    void Sync() = delete;
781
782    //! Verify that all parallel fetched input prevouts have been consumed.
783    bool AllInputsConsumed() const noexcept { return m_input_tail == m_inputs.size(); }
784};
785
786//! Utility function to add all of a transaction's outputs to a cache.
787//! When check is false, this assumes that overwrites are only possible for coinbase transactions.
788//! When check is true, the underlying view may be queried to determine whether an addition is
789//! an overwrite.
790// TODO: pass in a boolean to limit these possible overwrites to known
791// (pre-BIP34) cases.
792void AddCoins(CCoinsViewCache& cache, const CTransaction& tx, int nHeight, bool check = false);
793
794//! Utility function to find any unspent output with a given txid.
795//! This function can be quite expensive because in the event of a transaction
796//! which is not found in the cache, it can cause up to MAX_OUTPUTS_PER_BLOCK
797//! lookups to database, so it should be used with care.
798const Coin& AccessByTxid(const CCoinsViewCache& cache, const Txid& txid);
799
800/**
801 * This is a minimally invasive approach to shutdown on LevelDB read errors from the
802 * chainstate, while keeping user interface out of the common library, which is shared
803 * between bitcoind, and bitcoin-qt and non-server tools.
804 *
805 * Writes do not need similar protection, as failure to write is handled by the caller.
806*/
807class CCoinsViewErrorCatcher final : public CCoinsViewBacked
808{
809public:
810    explicit CCoinsViewErrorCatcher(CCoinsView* view) : CCoinsViewBacked(view) {}
811
812    void AddReadErrCallback(std::function<void()> f) {
813        m_err_callbacks.emplace_back(std::move(f));
814    }
815
816    std::optional<Coin> GetCoin(const COutPoint& outpoint) const override;
817    bool HaveCoin(const COutPoint& outpoint) const override;
818    std::optional<Coin> PeekCoin(const COutPoint& outpoint) const override;
819
820private:
821    /** A list of callbacks to execute upon leveldb read error. */
822    std::vector<std::function<void()>> m_err_callbacks;
823
824};
825
826#endif // BITCOIN_COINS_H
827