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byteswap1.h
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1 /* Macros to swap the order of bytes in integer values.
2  Copyright (C) 1997, 1998, 2000, 2002, 2003 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., 51 Franklin Street, Fifth Floor,
18  Boston, MA 02110-1301, USA.
19 */
20 
21 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H
22 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
23 #endif
24 
25 #ifndef _BITS_BYTESWAP_H
26 #define _BITS_BYTESWAP_H 1
27 
28 /* Swap bytes in 16 bit value. */
29 #define __bswap_constant_16(x) \
30  ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
31 
32 #ifdef __GNUC__
33 # if __GNUC__ >= 2
34 # define __bswap_16(x) \
35  (__extension__ \
36  ({ register unsigned short int __v, __x = (x); \
37  if (__builtin_constant_p (__x)) \
38  __v = __bswap_constant_16 (__x); \
39  else \
40  __asm__ ("rorw $8, %w0" \
41  : "=r" (__v) \
42  : "0" (__x) \
43  : "cc"); \
44  __v; }))
45 # else
46 /* This is better than nothing. */
47 # define __bswap_16(x) \
48  (__extension__ \
49  ({ register unsigned short int __x = (x); __bswap_constant_16 (__x); }))
50 # endif
51 #else
52 static __inline unsigned short int
53 __bswap_16 (unsigned short int __bsx)
54 {
55  return __bswap_constant_16 (__bsx);
56 }
57 #endif
58 
59 /* Swap bytes in 32 bit value. */
60 #define __bswap_constant_32(x) \
61  ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >> 8) | \
62  (((x) & 0x0000ff00) << 8) | (((x) & 0x000000ff) << 24))
63 
64 #ifdef __GNUC__
65 # if __GNUC__ >= 2
66 /* To swap the bytes in a word the i486 processors and up provide the
67  `bswap' opcode. On i386 we have to use three instructions. */
68 # if !defined __i486__ && !defined __pentium__ && !defined __pentiumpro__ \
69  && !defined __pentium4__
70 # define __bswap_32(x) \
71  (__extension__ \
72  ({ register unsigned int __v, __x = (x); \
73  if (__builtin_constant_p (__x)) \
74  __v = __bswap_constant_32 (__x); \
75  else \
76  __asm__ ("rorw $8, %w0;" \
77  "rorl $16, %0;" \
78  "rorw $8, %w0" \
79  : "=r" (__v) \
80  : "0" (__x) \
81  : "cc"); \
82  __v; }))
83 # else
84 # define __bswap_32(x) \
85  (__extension__ \
86  ({ register unsigned int __v, __x = (x); \
87  if (__builtin_constant_p (__x)) \
88  __v = __bswap_constant_32 (__x); \
89  else \
90  __asm__ ("bswap %0" : "=r" (__v) : "0" (__x)); \
91  __v; }))
92 # endif
93 # else
94 # define __bswap_32(x) \
95  (__extension__ \
96  ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
97 # endif
98 #else
99 static __inline unsigned int
100 __bswap_32 (unsigned int __bsx)
101 {
102  return __bswap_constant_32 (__bsx);
103 }
104 #endif
105 
106 
107 #if defined __GNUC__ && __GNUC__ >= 2
108 /* Swap bytes in 64 bit value. */
109 #define __bswap_constant_64(x) \
110  ((((x) & 0xff00000000000000ull) >> 56) \
111  | (((x) & 0x00ff000000000000ull) >> 40) \
112  | (((x) & 0x0000ff0000000000ull) >> 24) \
113  | (((x) & 0x000000ff00000000ull) >> 8) \
114  | (((x) & 0x00000000ff000000ull) << 8) \
115  | (((x) & 0x0000000000ff0000ull) << 24) \
116  | (((x) & 0x000000000000ff00ull) << 40) \
117  | (((x) & 0x00000000000000ffull) << 56))
118 
119 # define __bswap_64(x) \
120  (__extension__ \
121  ({ union { __extension__ unsigned long long int __ll; \
122  unsigned long int __l[2]; } __w, __r; \
123  if (__builtin_constant_p (x)) \
124  __r.__ll = __bswap_constant_64 (x); \
125  else \
126  { \
127  __w.__ll = (x); \
128  __r.__l[0] = __bswap_32 (__w.__l[1]); \
129  __r.__l[1] = __bswap_32 (__w.__l[0]); \
130  } \
131  __r.__ll; }))
132 #endif
133 
134 #endif /* _BITS_BYTESWAP_H */
static __inline unsigned int __bswap_32(unsigned int __bsx)
Definition: byteswap1.h:100
static __inline unsigned short int __bswap_16(unsigned short int __bsx)
Definition: byteswap1.h:53
#define __bswap_constant_16(x)
Definition: byteswap1.h:29
#define __bswap_constant_32(x)
Definition: byteswap1.h:60