Back to index

glibc  2.9
byteswap.h
Go to the documentation of this file.
00001 /* Macros to swap the order of bytes in integer values.  m68k version.
00002    Copyright (C) 1997, 2002, 2008 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H && !defined _ENDIAN_H
00021 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
00022 #endif
00023 
00024 #ifndef _BITS_BYTESWAP_H
00025 #define _BITS_BYTESWAP_H 1
00026 
00027 /* Swap bytes in 16 bit value.  We don't provide an assembler version
00028    because GCC is smart enough to generate optimal assembler output, and
00029    this allows for better cse.  */
00030 #define __bswap_constant_16(x) \
00031      ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
00032 
00033 #ifdef __GNUC__
00034 # define __bswap_16(x) \
00035     (__extension__                                                   \
00036      ({ unsigned short int __bsx = (x); __bswap_constant_16 (__bsx); }))
00037 #else
00038 static __inline unsigned short int
00039 __bswap_16 (unsigned short int __bsx)
00040 {
00041   return __bswap_constant_16 (__bsx);
00042 }
00043 #endif
00044 
00045 /* Swap bytes in 32 bit value.  */
00046 #define __bswap_constant_32(x) \
00047      ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) |           \
00048       (((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
00049 
00050 #if defined __GNUC__ && __GNUC__ >= 2 && !defined(__mcoldfire__)
00051 # define __bswap_32(x) \
00052   __extension__                                                \
00053   ({ unsigned int __bswap_32_v;                                \
00054      if (__builtin_constant_p (x))                      \
00055        __bswap_32_v = __bswap_constant_32 (x);                 \
00056      else                                               \
00057        __asm__ __volatile__ ("ror%.w %#8, %0;"                 \
00058                           "swap %0;"                           \
00059                           "ror%.w %#8, %0"                     \
00060                           : "=d" (__bswap_32_v)         \
00061                           : "0" ((unsigned int) (x)));  \
00062      __bswap_32_v; })
00063 #else
00064 static __inline unsigned int
00065 __bswap_32 (unsigned int __bsx)
00066 {
00067   return __bswap_constant_32 (__bsx);
00068 }
00069 #endif
00070 
00071 #if defined __GNUC__ && __GNUC__ >= 2
00072 /* Swap bytes in 64 bit value.  */
00073 # define __bswap_constant_64(x) \
00074      ((((x) & 0xff00000000000000ull) >> 56)                                 \
00075       | (((x) & 0x00ff000000000000ull) >> 40)                               \
00076       | (((x) & 0x0000ff0000000000ull) >> 24)                               \
00077       | (((x) & 0x000000ff00000000ull) >> 8)                                \
00078       | (((x) & 0x00000000ff000000ull) << 8)                                \
00079       | (((x) & 0x0000000000ff0000ull) << 24)                               \
00080       | (((x) & 0x000000000000ff00ull) << 40)                               \
00081       | (((x) & 0x00000000000000ffull) << 56))
00082 
00083 /* Swap bytes in 64 bit value.  */
00084 # define __bswap_64(x) \
00085   __extension__                                                       \
00086   ({ union { unsigned long long int __ll;                      \
00087             unsigned long int __l[2]; } __bswap_64_v, __bswap_64_r;   \
00088      if (__builtin_constant_p (x))                             \
00089        __bswap_64_r.__ll = __bswap_constant_64 (x);                   \
00090      else                                                      \
00091        {                                                       \
00092         __bswap_64_v.__ll = (x);                               \
00093         __bswap_64_r.__l[0] = __bswap_32 (__bswap_64_v.__l[1]);       \
00094         __bswap_64_r.__l[1] = __bswap_32 (__bswap_64_v.__l[0]);       \
00095        }                                                       \
00096      __bswap_64_r.__ll; })
00097 #endif
00098 
00099 #endif /* _BITS_BYTESWAP_H */