byteswap1.h

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/* Macros to swap the order of bytes in integer values.
   Copyright (C) 1997, 1998, 2000, 2002, 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/

#if !defined _BYTESWAP_H && !defined _NETINET_IN_H
# error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
#endif

#ifndef _BITS_BYTESWAP_H
#define _BITS_BYTESWAP_H 1

/* Swap bytes in 16 bit value.  */
#define __bswap_constant_16(x) \
     ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))

#ifdef __GNUC__
# if __GNUC__ >= 2
#  define __bswap_16(x) \
     (__extension__                               \
      ({ register unsigned short int __v, __x = (x);                  \
     if (__builtin_constant_p (__x))                      \
       __v = __bswap_constant_16 (__x);                   \
     else                                     \
       __asm__ ("rorw $8, %w0"                        \
            : "=r" (__v)                          \
            : "0" (__x)                           \
            : "cc");                              \
     __v; }))
# else
/* This is better than nothing.  */
#  define __bswap_16(x) \
     (__extension__                               \
      ({ register unsigned short int __x = (x); __bswap_constant_16 (__x); }))
# endif
#else
static __inline unsigned short int
__bswap_16 (unsigned short int __bsx)
{
  return __bswap_constant_16 (__bsx);
}
#endif

/* Swap bytes in 32 bit value.  */
#define __bswap_constant_32(x) \
     ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) |           \
      (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))

#ifdef __GNUC__
# if __GNUC__ >= 2
/* To swap the bytes in a word the i486 processors and up provide the
   `bswap' opcode.  On i386 we have to use three instructions.  */
#  if !defined __i486__ && !defined __pentium__ && !defined __pentiumpro__ \
      && !defined __pentium4__
#   define __bswap_32(x)                              \
     (__extension__                               \
      ({ register unsigned int __v, __x = (x);                    \
     if (__builtin_constant_p (__x))                      \
       __v = __bswap_constant_32 (__x);                   \
     else                                     \
       __asm__ ("rorw $8, %w0;"                       \
            "rorl $16, %0;"                       \
            "rorw $8, %w0"                        \
            : "=r" (__v)                          \
            : "0" (__x)                           \
            : "cc");                              \
     __v; }))
#  else
#   define __bswap_32(x) \
     (__extension__                               \
      ({ register unsigned int __v, __x = (x);                    \
     if (__builtin_constant_p (__x))                      \
       __v = __bswap_constant_32 (__x);                   \
     else                                     \
       __asm__ ("bswap %0" : "=r" (__v) : "0" (__x));             \
     __v; }))
#  endif
# else
#  define __bswap_32(x) \
     (__extension__                               \
      ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
# endif
#else
static __inline unsigned int
__bswap_32 (unsigned int __bsx)
{
  return __bswap_constant_32 (__bsx);
}
#endif


#if defined __GNUC__ && __GNUC__ >= 2
/* Swap bytes in 64 bit value.  */
#define __bswap_constant_64(x) \
     ((((x) & 0xff00000000000000ull) >> 56)                   \
      | (((x) & 0x00ff000000000000ull) >> 40)                     \
      | (((x) & 0x0000ff0000000000ull) >> 24)                     \
      | (((x) & 0x000000ff00000000ull) >> 8)                      \
      | (((x) & 0x00000000ff000000ull) << 8)                      \
      | (((x) & 0x0000000000ff0000ull) << 24)                     \
      | (((x) & 0x000000000000ff00ull) << 40)                     \
      | (((x) & 0x00000000000000ffull) << 56))

# define __bswap_64(x) \
     (__extension__                               \
      ({ union { __extension__ unsigned long long int __ll;           \
         unsigned long int __l[2]; } __w, __r;                \
         if (__builtin_constant_p (x))                        \
       __r.__ll = __bswap_constant_64 (x);                    \
     else                                     \
       {                                      \
         __w.__ll = (x);                              \
         __r.__l[0] = __bswap_32 (__w.__l[1]);                \
         __r.__l[1] = __bswap_32 (__w.__l[0]);                \
       }                                      \
     __r.__ll; }))
#endif

#endif /* _BITS_BYTESWAP_H */