sysdeps/x86/bits/byteswap-16.h

   1 /* Macros to swap the order of bytes in 16-bit integer values.
   2    Copyright (C) 2012-2014 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _BITS_BYTESWAP_H
  20 # error "Never use <bits/byteswap-16.h> directly; include <byteswap.h> instead."
  21 #endif
  22
  23 #ifdef __GNUC__
  24 # if __GNUC__ >= 2
  25 #  define __bswap_16(x) \
  26      (__extension__                                                           \
  27       ({ unsigned short int __v, __x = (unsigned short int) (x);              \
  28          if (__builtin_constant_p (__x))                                      \
  29            __v = __bswap_constant_16 (__x);                                   \
  30          else                                                                 \
  31            __asm__ ("rorw $8, %w0"                                            \
  32                     : "=r" (__v)                                              \
  33                     : "0" (__x)                                               \
  34                     : "cc");                                                  \
  35          __v; }))
  36 # else
  37 /* This is better than nothing.  */
  38 #  define __bswap_16(x) \
  39      (__extension__                                                           \
  40       ({ unsigned short int __x = (unsigned short int) (x);                   \
  41          __bswap_constant_16 (__x); }))
  42 # endif
  43 #else
  44 static __inline unsigned short int
  45 __bswap_16 (unsigned short int __bsx)
  46 {
  47   return __bswap_constant_16 (__bsx);
  48 }
  49 #endif