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(static_cast<uint64_t>(__val))) << 64 |
41           static_cast<_Tp>(byteswap(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