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432b18ca8d
Rather than a complicated set of tests to decide which bswap functions to use, always prefer the compiler built-ins when available. These builtins and fallbacks can all be removed once we're using c++23, which adds std::byteswap.
79 lines
2.2 KiB
C++
79 lines
2.2 KiB
C++
// Copyright (c) 2014-2022 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_COMPAT_BYTESWAP_H
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#define BITCOIN_COMPAT_BYTESWAP_H
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#include <cstdint>
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#ifdef _MSC_VER
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#include <cstdlib>
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#endif
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// All internal_bswap_* functions can be replaced with std::byteswap once we
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// require c++23. Both libstdc++ and libc++ implement std::byteswap via these
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// builtins.
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#ifndef DISABLE_BUILTIN_BSWAPS
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# if defined __has_builtin
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# if __has_builtin(__builtin_bswap16)
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# define bitcoin_builtin_bswap16(x) __builtin_bswap16(x)
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# endif
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# if __has_builtin(__builtin_bswap32)
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# define bitcoin_builtin_bswap32(x) __builtin_bswap32(x)
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# endif
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# if __has_builtin(__builtin_bswap64)
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# define bitcoin_builtin_bswap64(x) __builtin_bswap64(x)
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# endif
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# elif defined(_MSC_VER)
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# define bitcoin_builtin_bswap16(x) _byteswap_ushort(x)
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# define bitcoin_builtin_bswap32(x) _byteswap_ulong(x)
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# define bitcoin_builtin_bswap64(x) _byteswap_uint64(x)
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# endif
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#endif
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// MSVC's _byteswap_* functions are not constexpr
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#ifndef _MSC_VER
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#define BSWAP_CONSTEXPR constexpr
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#else
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#define BSWAP_CONSTEXPR
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#endif
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inline BSWAP_CONSTEXPR uint16_t internal_bswap_16(uint16_t x)
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{
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#ifdef bitcoin_builtin_bswap16
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return bitcoin_builtin_bswap16(x);
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#else
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return (x >> 8) | (x << 8);
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#endif
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}
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inline BSWAP_CONSTEXPR uint32_t internal_bswap_32(uint32_t x)
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{
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#ifdef bitcoin_builtin_bswap32
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return bitcoin_builtin_bswap32(x);
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#else
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return (((x & 0xff000000U) >> 24) | ((x & 0x00ff0000U) >> 8) |
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((x & 0x0000ff00U) << 8) | ((x & 0x000000ffU) << 24));
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#endif
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}
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inline BSWAP_CONSTEXPR uint64_t internal_bswap_64(uint64_t x)
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{
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#ifdef bitcoin_builtin_bswap64
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return bitcoin_builtin_bswap64(x);
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#else
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return (((x & 0xff00000000000000ull) >> 56)
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| ((x & 0x00ff000000000000ull) >> 40)
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| ((x & 0x0000ff0000000000ull) >> 24)
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| ((x & 0x000000ff00000000ull) >> 8)
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| ((x & 0x00000000ff000000ull) << 8)
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| ((x & 0x0000000000ff0000ull) << 24)
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| ((x & 0x000000000000ff00ull) << 40)
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| ((x & 0x00000000000000ffull) << 56));
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#endif
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}
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#endif // BITCOIN_COMPAT_BYTESWAP_H
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