xref: /freebsd/contrib/llvm-project/libcxx/include/__bit/byteswap.h (revision f126890ac5386406dadf7c4cfa9566cbb56537c5)
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 
25 template <integral _Tp>
26 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Tp byteswap(_Tp __val) noexcept {
27 
28   if constexpr (sizeof(_Tp) == 1) {
29     return __val;
30   } else if constexpr (sizeof(_Tp) == 2) {
31     return __builtin_bswap16(__val);
32   } else if constexpr (sizeof(_Tp) == 4) {
33     return __builtin_bswap32(__val);
34   } else if constexpr (sizeof(_Tp) == 8) {
35     return __builtin_bswap64(__val);
36 #ifndef _LIBCPP_HAS_NO_INT128
37   } else if constexpr (sizeof(_Tp) == 16) {
38 #if __has_builtin(__builtin_bswap128)
39     return __builtin_bswap128(__val);
40 #else
41     return static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val))) << 64 |
42            static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val >> 64)));
43 #endif // __has_builtin(__builtin_bswap128)
44 #endif // _LIBCPP_HAS_NO_INT128
45   } else {
46     static_assert(sizeof(_Tp) == 0, "byteswap is unimplemented for integral types of this size");
47   }
48 }
49 
50 #endif // _LIBCPP_STD_VER >= 23
51 
52 _LIBCPP_END_NAMESPACE_STD
53 
54 #endif // _LIBCPP___BIT_BYTESWAP_H
55