1// Copyright (c) 2023-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or https://opensource.org/license/mit.
4
5#ifndef BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
6#define BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
7
8#include <attributes.h>
9#include <uint256.h>
10
11#include <compare>
12#include <cstddef>
13#include <optional>
14#include <string>
15#include <string_view>
16#include <tuple>
17#include <type_traits>
18#include <variant>
19
20/** transaction_identifier represents the two canonical transaction identifier
21 * types (txid, wtxid).*/
22template <bool has_witness>
23class transaction_identifier
24{
25    uint256 m_wrapped;
26
27    // Note: Use FromUint256 externally instead.
28    transaction_identifier(const uint256& wrapped) : m_wrapped{wrapped} {}
29
30public:
31    transaction_identifier() : m_wrapped{} {}
32    consteval explicit transaction_identifier(std::string_view hex_str) : m_wrapped{uint256{hex_str}} {}
33
34    constexpr bool operator==(const transaction_identifier&) const = default;
35    constexpr auto operator<=>(const transaction_identifier&) const = default;
36
37    const uint256& ToUint256() const LIFETIMEBOUND { return m_wrapped; }
38    static transaction_identifier FromUint256(const uint256& id) { return {id}; }
39
40    /** Wrapped `uint256` methods. */
41    constexpr bool IsNull() const { return m_wrapped.IsNull(); }
42    constexpr void SetNull() { m_wrapped.SetNull(); }
43    static std::optional<transaction_identifier> FromHex(std::string_view hex)
44    {
45        auto u{uint256::FromHex(hex)};
46        if (!u) return std::nullopt;
47        return FromUint256(*u);
48    }
49    std::string GetHex() const { return m_wrapped.GetHex(); }
50    std::string ToString() const { return m_wrapped.ToString(); }
51    static constexpr auto size() { return decltype(m_wrapped)::size(); }
52    constexpr const std::byte* data() const { return reinterpret_cast<const std::byte*>(m_wrapped.data()); }
53    constexpr const std::byte* begin() const { return reinterpret_cast<const std::byte*>(m_wrapped.begin()); }
54    constexpr const std::byte* end() const { return reinterpret_cast<const std::byte*>(m_wrapped.end()); }
55    template <typename Stream> void Serialize(Stream& s) const { m_wrapped.Serialize(s); }
56    template <typename Stream> void Unserialize(Stream& s) { m_wrapped.Unserialize(s); }
57};
58
59/** Txid commits to all transaction fields except the witness. */
60using Txid = transaction_identifier<false>;
61/** Wtxid commits to all transaction fields including the witness. */
62using Wtxid = transaction_identifier<true>;
63
64template <typename T>
65concept TxidOrWtxid = std::is_same_v<T, Txid> || std::is_same_v<T, Wtxid>;
66
67class GenTxid : public std::variant<Txid, Wtxid>
68{
69public:
70    using variant::variant;
71
72    bool IsWtxid() const { return std::holds_alternative<Wtxid>(*this); }
73
74    const uint256& ToUint256() const LIFETIMEBOUND
75    {
76        return std::visit([](const auto& id) -> const uint256& { return id.ToUint256(); }, *this);
77    }
78
79    friend auto operator<=>(const GenTxid& a, const GenTxid& b)
80    {
81        // Use a reference for read-only access to the hash, avoiding a copy that might not be optimized away.
82        return std::tuple<bool, const uint256&>(a.IsWtxid(), a.ToUint256()) <=> std::tuple<bool, const uint256&>(b.IsWtxid(), b.ToUint256());
83    }
84};
85
86#endif // BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H
87