bits/byteswap.h

   1 /* Macros and inline functions to swap the order of bytes in integer values.
   2    Copyright (C) 1997-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H && !defined _ENDIAN_H
  20 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
  21 #endif
  22
  23 #ifndef _BITS_BYTESWAP_H
  24 #define _BITS_BYTESWAP_H 1
  25
  26 #include <features.h>
  27 #include <bits/types.h>
  28
  29 /* Swap bytes in 16-bit value.  */
  30 #define __bswap_constant_16(x)                                  \
  31   ((__uint16_t) ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8)))
  32
  33 static __inline __uint16_t
  34 __bswap_16 (__uint16_t __bsx)
  35 {
  36 #if __GNUC_PREREQ (4, 8)
  37   return __builtin_bswap16 (__bsx);
  38 #else
  39   return __bswap_constant_16 (__bsx);
  40 #endif
  41 }
  42
  43 /* Swap bytes in 32-bit value.  */
  44 #define __bswap_constant_32(x)                                  \
  45   ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >> 8)     \
  46    | (((x) & 0x0000ff00u) << 8) | (((x) & 0x000000ffu) << 24))
  47
  48 static __inline __uint32_t
  49 __bswap_32 (__uint32_t __bsx)
  50 {
  51 #if __GNUC_PREREQ (4, 3)
  52   return __builtin_bswap32 (__bsx);
  53 #else
  54   return __bswap_constant_32 (__bsx);
  55 #endif
  56 }
  57
  58 /* Swap bytes in 64-bit value.  */
  59 #define __bswap_constant_64(x)                  \
  60   ((((x) & 0xff00000000000000ull) >> 56)        \
  61    | (((x) & 0x00ff000000000000ull) >> 40)      \
  62    | (((x) & 0x0000ff0000000000ull) >> 24)      \
  63    | (((x) & 0x000000ff00000000ull) >> 8)       \
  64    | (((x) & 0x00000000ff000000ull) << 8)       \
  65    | (((x) & 0x0000000000ff0000ull) << 24)      \
  66    | (((x) & 0x000000000000ff00ull) << 40)      \
  67    | (((x) & 0x00000000000000ffull) << 56))
  68
  69 __extension__ static __inline __uint64_t
  70 __bswap_64 (__uint64_t __bsx)
  71 {
  72 #if __GNUC_PREREQ (4, 3)
  73   return __builtin_bswap64 (__bsx);
  74 #else
  75   return __bswap_constant_64 (__bsx);
  76 #endif
  77 }
  78
  79 #endif /* _BITS_BYTESWAP_H */