A strong type for script verification flag sets

1// Copyright (c) 2009-2010 Satoshi Nakamoto
2// Copyright (c) 2009-present The Bitcoin Core developers
3// Distributed under the MIT software license, see the accompanying
4// file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6#ifndef BITCOIN_SCRIPT_VERIFY_FLAGS_H
7#define BITCOIN_SCRIPT_VERIFY_FLAGS_H
8
9#include <compare>
10#include <cstdint>
11
12enum class script_verify_flag_name : uint8_t;
13
14class script_verify_flags
15{
16public:
17    using value_type = uint64_t;
18
19    consteval script_verify_flags() = default;
20
21    // also allow construction with hard-coded 0 (but not other integers)
22    consteval explicit(false) script_verify_flags(value_type f) : m_value{f} { if (f != 0) throw 0; }
23
24    // implicit construction from a hard-coded SCRIPT_VERIFY_* constant is also okay
25    constexpr explicit(false) script_verify_flags(script_verify_flag_name f) : m_value{value_type{1} << static_cast<uint8_t>(f)} { }
26
27    // rule of 5
28    constexpr script_verify_flags(const script_verify_flags&) = default;
29    constexpr script_verify_flags(script_verify_flags&&) = default;
30    constexpr script_verify_flags& operator=(const script_verify_flags&) = default;
31    constexpr script_verify_flags& operator=(script_verify_flags&&) = default;
32    constexpr ~script_verify_flags() = default;
33
34    // integer conversion needs to be very explicit
35    static constexpr script_verify_flags from_int(value_type f) { script_verify_flags r; r.m_value = f; return r; }
36    constexpr value_type as_int() const { return m_value; }
37
38    // bitwise operations
39    constexpr script_verify_flags operator~() const { return from_int(~m_value); }
40    friend constexpr script_verify_flags operator|(script_verify_flags a, script_verify_flags b) { return from_int(a.m_value | b.m_value); }
41    friend constexpr script_verify_flags operator&(script_verify_flags a, script_verify_flags b) { return from_int(a.m_value & b.m_value); }
42
43    // in-place bitwise operations
44    constexpr script_verify_flags& operator|=(script_verify_flags vf) { m_value |= vf.m_value; return *this; }
45    constexpr script_verify_flags& operator&=(script_verify_flags vf) { m_value &= vf.m_value; return *this; }
46
47    // tests
48    constexpr explicit operator bool() const { return m_value != 0; }
49    constexpr bool operator==(script_verify_flags other) const { return m_value == other.m_value; }
50
51    /** Compare two script_verify_flags. <, >, <=, and >= are auto-generated from this. */
52    friend constexpr std::strong_ordering operator<=>(const script_verify_flags& a, const script_verify_flags& b) noexcept
53    {
54        return a.m_value <=> b.m_value;
55    }
56
57private:
58    value_type m_value{0}; // default value is SCRIPT_VERIFY_NONE
59};
60
61inline constexpr script_verify_flags operator~(script_verify_flag_name f)
62{
63    return ~script_verify_flags{f};
64}
65
66inline constexpr script_verify_flags operator|(script_verify_flag_name f1, script_verify_flag_name f2)
67{
68    return script_verify_flags{f1} | f2;
69}
70
71#endif // BITCOIN_SCRIPT_VERIFY_FLAGS_H
72