(__bswap_64): Handle constant argument case separately.
[kopensolaris-gnu/glibc.git] / bits / byteswap.h
1 /* Macros to swap the order of bytes in integer values.
2    Copyright (C) 1997, 1998, 2000 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 Library General Public License as
7    published by the Free Software Foundation; either version 2 of the
8    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    Library General Public License for more details.
14
15    You should have received a copy of the GNU Library General Public
16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18    Boston, MA 02111-1307, USA.  */
19
20 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H
21 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
22 #endif
23
24 /* Swap bytes in 16 bit value.  */
25 #ifdef __GNUC__
26 # define __bswap_16(x) \
27     (__extension__                                                            \
28      ({ unsigned short int __bsx = (x);                                       \
29         ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8)); }))
30 #else
31 static __inline unsigned short int
32 __bswap_16 (unsigned short int __bsx)
33 {
34   return ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8));
35 }
36 #endif
37
38 /* Swap bytes in 32 bit value.  */
39 #ifdef __GNUC__
40 # define __bswap_32(x) \
41     (__extension__                                                            \
42      ({ unsigned int __bsx = (x);                                             \
43         ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |    \
44          (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24)); }))
45 #else
46 static __inline unsigned int
47 __bswap_32 (unsigned int __bsx)
48 {
49   return ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |
50           (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24));
51 }
52 #endif
53
54 #if defined __GNUC__ && __GNUC__ >= 2
55 /* Swap bytes in 64 bit value.  */
56 #define __bswap_constant_64(x) \
57      ((((x) & 0xff00000000000000ull) >> 56)                                   \
58       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
59       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
60       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
61       | (((x) & 0x00000000ff000000ull) << 8)                                  \
62       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
63       | (((x) & 0x000000000000ff00ull) << 40)                                 \
64       | (((x) & 0x00000000000000ffull) << 56))
65
66 # define __bswap_64(x) \
67      (__extension__                                                           \
68       ({ union { __extension__ unsigned long long int __ll;                   \
69                  unsigned long int __l[2]; } __w, __r;                        \
70          if (__builtin_constant_p (x))                                        \
71            __r.__ll = __bswap_constant_64 (x);                                \
72          else                                                                 \
73            {                                                                  \
74              __w.__ll = (x);                                                  \
75              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
76              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
77            }                                                                  \
78          __r.__ll; }))
79 #endif