2002-08-11 Roland McGrath <roland@redhat.com>
[kopensolaris-gnu/glibc.git] / sysdeps / i386 / bits / byteswap.h
1 /* Macros to swap the order of bytes in integer values.
2    Copyright (C) 1997, 1998, 2000, 2002 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, write to the Free
17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18    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 #ifndef _BITS_BYTESWAP_H
25 #define _BITS_BYTESWAP_H 1
26
27 /* Swap bytes in 16 bit value.  */
28 #define __bswap_constant_16(x) \
29      ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
30
31 #if defined __GNUC__ && __GNUC__ >= 2
32 # define __bswap_16(x) \
33      (__extension__                                                           \
34       ({ register unsigned short int __v, __x = (x);                          \
35          if (__builtin_constant_p (__x))                                      \
36            __v = __bswap_constant_16 (__x);                                   \
37          else                                                                 \
38            __asm__ ("rorw $8, %w0"                                            \
39                     : "=r" (__v)                                              \
40                     : "0" (__x)                                               \
41                     : "cc");                                                  \
42          __v; }))
43 #else
44 /* This is better than nothing.  */
45 # define __bswap_16(x) \
46      (__extension__                                                           \
47       ({ register unsigned short int __x = (x); __bswap_constant_16 (__x); }))
48 #endif
49
50
51 /* Swap bytes in 32 bit value.  */
52 #define __bswap_constant_32(x) \
53      ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) |               \
54       (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))
55
56 #if defined __GNUC__ && __GNUC__ >= 2
57 /* To swap the bytes in a word the i486 processors and up provide the
58    `bswap' opcode.  On i386 we have to use three instructions.  */
59 # if !defined __i486__ && !defined __pentium__ && !defined __pentiumpro__
60 #  define __bswap_32(x)                                                       \
61      (__extension__                                                           \
62       ({ register unsigned int __v, __x = (x);                                \
63          if (__builtin_constant_p (__x))                                      \
64            __v = __bswap_constant_32 (__x);                                   \
65          else                                                                 \
66            __asm__ ("rorw $8, %w0;"                                           \
67                     "rorl $16, %0;"                                           \
68                     "rorw $8, %w0"                                            \
69                     : "=r" (__v)                                              \
70                     : "0" (__x)                                               \
71                     : "cc");                                                  \
72          __v; }))
73 # else
74 #  define __bswap_32(x) \
75      (__extension__                                                           \
76       ({ register unsigned int __v, __x = (x);                                \
77          if (__builtin_constant_p (__x))                                      \
78            __v = __bswap_constant_32 (__x);                                   \
79          else                                                                 \
80            __asm__ ("bswap %0" : "=r" (__v) : "0" (__x));                     \
81          __v; }))
82 # endif
83 #else
84 # define __bswap_16(x) \
85      (__extension__                                                           \
86       ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
87 #endif
88
89
90 #if defined __GNUC__ && __GNUC__ >= 2
91 /* Swap bytes in 64 bit value.  */
92 #define __bswap_constant_64(x) \
93      ((((x) & 0xff00000000000000ull) >> 56)                                   \
94       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
95       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
96       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
97       | (((x) & 0x00000000ff000000ull) << 8)                                  \
98       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
99       | (((x) & 0x000000000000ff00ull) << 40)                                 \
100       | (((x) & 0x00000000000000ffull) << 56))
101
102 # define __bswap_64(x) \
103      (__extension__                                                           \
104       ({ union { __extension__ unsigned long long int __ll;                   \
105                  unsigned long int __l[2]; } __w, __r;                        \
106          __w.__ll = (x);                                                      \
107          if (__builtin_constant_p (__w.__ll))                                 \
108            __r.__ll = __bswap_constant_64 (__w.__ll);                         \
109          else                                                                 \
110            {                                                                  \
111              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
112              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
113            }                                                                  \
114          __r.__ll; }))
115 #endif
116
117 #endif /* _BITS_BYTESWAP_H */