The transaction-by-ID index interface

1// Copyright (c) 2017-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_INDEX_TXINDEX_H
6#define BITCOIN_INDEX_TXINDEX_H
7
8#include <index/base.h>
9#include <primitives/transaction.h>
10#include <uint256.h>
11
12#include <cstddef>
13#include <memory>
14#include <optional>
15
16namespace interfaces {
17class Chain;
18}
19namespace txindex_tests {
20class TxIndexTest;
21}
22
23inline constexpr bool DEFAULT_TXINDEX{false};
24
25/// A found transaction and the hash of the block that contains it.
26struct TxIndexResult {
27    uint256 block_hash;
28    CTransactionRef tx;
29};
30
31/**
32 * TxIndex is used to look up transactions included in the blockchain by hash.
33 * The index is written to a LevelDB database and records the block sequence
34 * number and serialized block offset of each transaction by transaction hash.
35 */
36class TxIndex final : public BaseIndex
37{
38protected:
39    class DB;
40
41private:
42    friend class txindex_tests::TxIndexTest;
43    const std::unique_ptr<DB> m_db;
44
45    bool AllowPrune() const override { return false; }
46
47    /// Look up a transaction among the legacy (full-txid) entries.
48    std::optional<TxIndexResult> FindLegacyTx(const Txid& tx_hash) const;
49
50protected:
51    bool CustomAppend(const interfaces::BlockInfo& block) override;
52
53    BaseIndex::DB& GetDB() const override;
54
55public:
56    /// Constructs the index, which becomes available to be queried.
57    explicit TxIndex(std::unique_ptr<interfaces::Chain> chain, size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
58
59    // Destructor is declared because this class contains a unique_ptr to an incomplete type.
60    virtual ~TxIndex() override;
61
62    /// Look up a transaction by hash.
63    ///
64    /// @param[in]   tx_hash  The hash of the transaction to be returned.
65    /// @return  the transaction and containing block hash, or nullopt if it is not found
66    std::optional<TxIndexResult> FindTx(const Txid& tx_hash) const;
67};
68
69/// The global transaction index, used in GetTransaction. May be null.
70extern std::unique_ptr<TxIndex> g_txindex;
71
72#endif // BITCOIN_INDEX_TXINDEX_H
73