1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___BIT_BYTESWAP_H
11#define _LIBCPP___BIT_BYTESWAP_H
12
13#include <__concepts/arithmetic.h>
14#include <__config>
15#include <cstdint>
16
17#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18# pragma GCC system_header
19#endif
20
21_LIBCPP_BEGIN_NAMESPACE_STD
22
23#if _LIBCPP_STD_VER >= 23
24
25template <integral _Tp>
26[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp byteswap(_Tp __val) noexcept {
27 if constexpr (sizeof(_Tp) == 1) {
28 return __val;
29 } else if constexpr (sizeof(_Tp) == 2) {
30 return __builtin_bswap16(__val);
31 } else if constexpr (sizeof(_Tp) == 4) {
32 return __builtin_bswap32(__val);
33 } else if constexpr (sizeof(_Tp) == 8) {
34 return __builtin_bswap64(__val);
35# if _LIBCPP_HAS_INT128
36 } else if constexpr (sizeof(_Tp) == 16) {
37# if __has_builtin(__builtin_bswap128)
38 return __builtin_bswap128(__val);
39# else
40 return static_cast<_Tp>(byteswap(val: static_cast<uint64_t>(__val))) << 64 |
41 static_cast<_Tp>(byteswap(val: static_cast<uint64_t>(__val >> 64)));
42# endif // __has_builtin(__builtin_bswap128)
43# endif // _LIBCPP_HAS_INT128
44 } else {
45 static_assert(sizeof(_Tp) == 0, "byteswap is unimplemented for integral types of this size");
46 }
47}
48
49#endif // _LIBCPP_STD_VER >= 23
50
51_LIBCPP_END_NAMESPACE_STD
52
53#endif // _LIBCPP___BIT_BYTESWAP_H
54