| // Copyright 2012 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // This header defines cross-platform ByteSwap() implementations for 16, 32 and |
| // 64-bit values, and NetToHostXX() / HostToNextXX() functions equivalent to |
| // the traditional ntohX() and htonX() functions. |
| // Use the functions defined here rather than using the platform-specific |
| // functions directly. |
| |
| #ifndef BASE_SYS_BYTEORDER_H_ |
| #define BASE_SYS_BYTEORDER_H_ |
| |
| #include <stdint.h> |
| |
| #include "build/build_config.h" |
| |
| #if defined(COMPILER_MSVC) |
| #include <stdlib.h> |
| #endif |
| |
| #if defined(COMPILER_MSVC) && !defined(__clang__) |
| // TODO(pkasting): See |
| // https://developercommunity.visualstudio.com/t/Mark-some-built-in-functions-as-constexp/362558 |
| // https://developercommunity.visualstudio.com/t/constexpr-byte-swapping-optimization/983963 |
| #define BASE_BYTESWAPS_CONSTEXPR |
| #else |
| #define BASE_BYTESWAPS_CONSTEXPR constexpr |
| #endif |
| |
| namespace base { |
| |
| // Returns a value with all bytes in |x| swapped, i.e. reverses the endianness. |
| // TODO(pkasting): Once C++23 is available, replace with std::byteswap. |
| inline BASE_BYTESWAPS_CONSTEXPR uint16_t ByteSwap(uint16_t x) { |
| #if defined(COMPILER_MSVC) && !defined(__clang__) |
| return _byteswap_ushort(x); |
| #else |
| return __builtin_bswap16(x); |
| #endif |
| } |
| |
| inline BASE_BYTESWAPS_CONSTEXPR uint32_t ByteSwap(uint32_t x) { |
| #if defined(COMPILER_MSVC) && !defined(__clang__) |
| return _byteswap_ulong(x); |
| #else |
| return __builtin_bswap32(x); |
| #endif |
| } |
| |
| inline BASE_BYTESWAPS_CONSTEXPR uint64_t ByteSwap(uint64_t x) { |
| // Per build/build_config.h, clang masquerades as MSVC on Windows. If we are |
| // actually using clang, we can rely on the builtin. |
| // |
| // This matters in practice, because on x86(_64), this is a single "bswap" |
| // instruction. MSVC correctly replaces the call with an inlined bswap at /O2 |
| // as of 2021, but clang as we use it in Chromium doesn't, keeping a function |
| // call for a single instruction. |
| #if defined(COMPILER_MSVC) && !defined(__clang__) |
| return _byteswap_uint64(x); |
| #else |
| return __builtin_bswap64(x); |
| #endif |
| } |
| |
| inline BASE_BYTESWAPS_CONSTEXPR uintptr_t ByteSwapUintPtrT(uintptr_t x) { |
| // We do it this way because some build configurations are ILP32 even when |
| // defined(ARCH_CPU_64_BITS). Unfortunately, we can't use sizeof in #ifs. But, |
| // because these conditionals are constexprs, the irrelevant branches will |
| // likely be optimized away, so this construction should not result in code |
| // bloat. |
| static_assert(sizeof(uintptr_t) == 4 || sizeof(uintptr_t) == 8, |
| "Unsupported uintptr_t size"); |
| if (sizeof(uintptr_t) == 4) |
| return ByteSwap(static_cast<uint32_t>(x)); |
| return ByteSwap(static_cast<uint64_t>(x)); |
| } |
| |
| // Converts the bytes in |x| from host order (endianness) to little endian, and |
| // returns the result. |
| inline BASE_BYTESWAPS_CONSTEXPR uint16_t ByteSwapToLE16(uint16_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return x; |
| #else |
| return ByteSwap(x); |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint32_t ByteSwapToLE32(uint32_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return x; |
| #else |
| return ByteSwap(x); |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint64_t ByteSwapToLE64(uint64_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return x; |
| #else |
| return ByteSwap(x); |
| #endif |
| } |
| |
| // Converts the bytes in |x| from network to host order (endianness), and |
| // returns the result. |
| inline BASE_BYTESWAPS_CONSTEXPR uint16_t NetToHost16(uint16_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint32_t NetToHost32(uint32_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint64_t NetToHost64(uint64_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| |
| // Converts the bytes in |x| from host to network order (endianness), and |
| // returns the result. |
| inline BASE_BYTESWAPS_CONSTEXPR uint16_t HostToNet16(uint16_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint32_t HostToNet32(uint32_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| inline BASE_BYTESWAPS_CONSTEXPR uint64_t HostToNet64(uint64_t x) { |
| #if defined(ARCH_CPU_LITTLE_ENDIAN) |
| return ByteSwap(x); |
| #else |
| return x; |
| #endif |
| } |
| |
| } // namespace base |
| |
| #undef BASE_BYTESWAPS_CONSTEXPR |
| |
| #endif // BASE_SYS_BYTEORDER_H_ |