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  #include <util/types.h>
11  
12  #include <compare>
13  #include <cstddef>
14  #include <optional>
15  #include <string>
16  #include <string_view>
17  #include <tuple>
18  #include <type_traits>
19  #include <variant>
20  
21  /** transaction_identifier represents the two canonical transaction identifier
22   * types (txid, wtxid).*/
23  template <bool has_witness>
24  class transaction_identifier
25  {
26      uint256 m_wrapped;
27  
28      // Note: Use FromUint256 externally instead.
29      transaction_identifier(const uint256& wrapped) : m_wrapped{wrapped} {}
30  
31      constexpr int Compare(const transaction_identifier<has_witness>& other) const { return m_wrapped.Compare(other.m_wrapped); }
32      template <typename Other>
33      constexpr int Compare(const Other& other) const
34      {
35          static_assert(ALWAYS_FALSE<Other>, "Forbidden comparison type");
36          return 0;
37      }
38  
39  public:
40      transaction_identifier() : m_wrapped{} {}
41      consteval explicit transaction_identifier(std::string_view hex_str) : m_wrapped{uint256{hex_str}} {}
42  
43      template <typename Other>
44      bool operator==(const Other& other) const { return Compare(other) == 0; }
45      template <typename Other>
46      std::strong_ordering operator<=>(const Other& other) const { return Compare(other) <=> 0; }
47  
48      const uint256& ToUint256() const LIFETIMEBOUND { return m_wrapped; }
49      static transaction_identifier FromUint256(const uint256& id) { return {id}; }
50  
51      /** Wrapped `uint256` methods. */
52      constexpr bool IsNull() const { return m_wrapped.IsNull(); }
53      constexpr void SetNull() { m_wrapped.SetNull(); }
54      static std::optional<transaction_identifier> FromHex(std::string_view hex)
55      {
56          auto u{uint256::FromHex(hex)};
57          if (!u) return std::nullopt;
58          return FromUint256(*u);
59      }
60      std::string GetHex() const { return m_wrapped.GetHex(); }
61      std::string ToString() const { return m_wrapped.ToString(); }
62      static constexpr auto size() { return decltype(m_wrapped)::size(); }
63      constexpr const std::byte* data() const { return reinterpret_cast<const std::byte*>(m_wrapped.data()); }
64      constexpr const std::byte* begin() const { return reinterpret_cast<const std::byte*>(m_wrapped.begin()); }
65      constexpr const std::byte* end() const { return reinterpret_cast<const std::byte*>(m_wrapped.end()); }
66      template <typename Stream> void Serialize(Stream& s) const { m_wrapped.Serialize(s); }
67      template <typename Stream> void Unserialize(Stream& s) { m_wrapped.Unserialize(s); }
68  };
69  
70  /** Txid commits to all transaction fields except the witness. */
71  using Txid = transaction_identifier<false>;
72  /** Wtxid commits to all transaction fields including the witness. */
73  using Wtxid = transaction_identifier<true>;
74  
75  template <typename T>
76  concept TxidOrWtxid = std::is_same_v<T, Txid> || std::is_same_v<T, Wtxid>;
77  
78  class GenTxid : public std::variant<Txid, Wtxid>
79  {
80  public:
81      using variant::variant;
82  
83      bool IsWtxid() const { return std::holds_alternative<Wtxid>(*this); }
84  
85      const uint256& ToUint256() const LIFETIMEBOUND
86      {
87          return std::visit([](const auto& id) -> const uint256& { return id.ToUint256(); }, *this);
88      }
89  
90      friend auto operator<=>(const GenTxid& a, const GenTxid& b)
91      {
92          // Use a reference for read-only access to the hash, avoiding a copy that might not be optimized away.
93          return std::tuple<bool, const uint256&>(a.IsWtxid(), a.ToUint256()) <=> std::tuple<bool, const uint256&>(b.IsWtxid(), b.ToUint256());
94      }
95  };
96  
97  #endif // BITCOIN_PRIMITIVES_TRANSACTION_IDENTIFIER_H