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base / allocator / partition_allocator / src / partition_alloc / reverse_bytes.h [blame]
// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef PARTITION_ALLOC_REVERSE_BYTES_H_
#define PARTITION_ALLOC_REVERSE_BYTES_H_
// This header defines drop-in constexpr replacements for the
// byte-reversing routines that we used from `//base/sys_byteorder.h`.
// They will be made moot by C++23's <endian> header or by C++20's
// <bit> header.
#include <cstdint>
#include "partition_alloc/build_config.h"
#include "partition_alloc/partition_alloc_config.h"
namespace partition_alloc::internal {
constexpr uint32_t ReverseFourBytes(uint32_t value) {
#if PA_CONFIG(IS_NONCLANG_MSVC)
return value >> 24 | (value >> 8 & 0xff00) | (value & 0xff00) << 8 |
value << 24;
#else
return __builtin_bswap32(value);
#endif // PA_CONFIG(IS_NONCLANG_MSVC)
}
constexpr uint64_t ReverseEightBytes(uint64_t value) {
#if PA_CONFIG(IS_NONCLANG_MSVC)
return value >> 56 | (value >> 40 & 0xff00) | (value >> 24 & 0xff0000) |
(value >> 8 & 0xff000000) | (value & 0xff000000) << 8 |
(value & 0xff0000) << 24 | (value & 0xff00) << 40 |
(value & 0xff) << 56;
#else
return __builtin_bswap64(value);
#endif // PA_CONFIG(IS_NONCLANG_MSVC)
}
constexpr uintptr_t ReverseBytes(uintptr_t value) {
if (sizeof(uintptr_t) == 4) {
return ReverseFourBytes(static_cast<uint32_t>(value));
}
return ReverseEightBytes(static_cast<uint64_t>(value));
}
} // namespace partition_alloc::internal
#endif // PARTITION_ALLOC_REVERSE_BYTES_H_