1 files changed, 68 insertions, 0 deletions
diff --git a/src/util/transaction_identifier.h b/src/util/transaction_identifier.h
new file mode 100644
index 0000000000..4fb9b49966
--- /dev/null
+++ b/src/util/transaction_identifier.h
@@ -0,0 +1,68 @@
+#ifndef BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H
+#define BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H
+
+#include <attributes.h>
+#include <uint256.h>
+#include <util/types.h>
+
+/** transaction_identifier represents the two canonical transaction identifier
+ * types (txid, wtxid).*/
+template <bool has_witness>
+class transaction_identifier
+{
+    uint256 m_wrapped;
+
+    // Note: Use FromUint256 externally instead.
+    transaction_identifier(const uint256& wrapped) : m_wrapped{wrapped} {}
+
+    // TODO: Comparisons with uint256 should be disallowed once we have
+    // converted most of the code to using the new txid types.
+    constexpr int Compare(const uint256& other) const { return m_wrapped.Compare(other); }
+    constexpr int Compare(const transaction_identifier<has_witness>& other) const { return m_wrapped.Compare(other.m_wrapped); }
+    template <typename Other>
+    constexpr int Compare(const Other& other) const
+    {
+        static_assert(ALWAYS_FALSE<Other>, "Forbidden comparison type");
+        return 0;
+    }
+
+public:
+    transaction_identifier() : m_wrapped{} {}
+
+    template <typename Other>
+    bool operator==(const Other& other) const { return Compare(other) == 0; }
+    template <typename Other>
+    bool operator!=(const Other& other) const { return Compare(other) != 0; }
+    template <typename Other>
+    bool operator<(const Other& other) const { return Compare(other) < 0; }
+
+    const uint256& ToUint256() const LIFETIMEBOUND { return m_wrapped; }
+    static transaction_identifier FromUint256(const uint256& id) { return {id}; }
+
+    /** Wrapped `uint256` methods. */
+    constexpr bool IsNull() const { return m_wrapped.IsNull(); }
+    constexpr void SetNull() { m_wrapped.SetNull(); }
+    std::string GetHex() const { return m_wrapped.GetHex(); }
+    std::string ToString() const { return m_wrapped.ToString(); }
+    constexpr const std::byte* data() const { return reinterpret_cast<const std::byte*>(m_wrapped.data()); }
+    constexpr const std::byte* begin() const { return reinterpret_cast<const std::byte*>(m_wrapped.begin()); }
+    constexpr const std::byte* end() const { return reinterpret_cast<const std::byte*>(m_wrapped.end()); }
+    template <typename Stream> void Serialize(Stream& s) const { m_wrapped.Serialize(s); }
+    template <typename Stream> void Unserialize(Stream& s) { m_wrapped.Unserialize(s); }
+
+    /** Conversion function to `uint256`.
+     *
+     * Note: new code should use `ToUint256`.
+     *
+     * TODO: This should be removed once the majority of the code has switched
+     * to using the Txid and Wtxid types. Until then it makes for a smoother
+     * transition to allow this conversion. */
+    operator const uint256&() const LIFETIMEBOUND { return m_wrapped; }
+};
+
+/** Txid commits to all transaction fields except the witness. */
+using Txid = transaction_identifier<false>;
+/** Wtxid commits to all transaction fields including the witness. */
+using Wtxid = transaction_identifier<true>;
+
+#endif // BITCOIN_UTIL_TRANSACTION_IDENTIFIER_H