« back to all changes in this revision
Viewing changes to gnu/memcmp.c
- browse files at revision 656.1.28
- compare with another revision
- compare with revision 1254
- download diff
- download tarball
- view history from revision 656.1.28
- Committer: Monty Taylor
- Date: 2008-12-08 00:29:52 UTC
- mto: This revision was merged to the branch mainline in revision 670.
- Revision ID: monty@inaugust.com-20081208002952-d3h72a5cb9yvextu
Added gnulib compatibility functions to make solaris suck a little less.
- files added:
- gnu
- files modified:
- Makefile.am
added
removed
gnu/memcmp.c
1
/* Copyright (C) 1991, 1993, 1995, 1997, 1998, 2003, 2006 Free Software
2
Foundation, Inc.
3
4
Contributed by Torbjorn Granlund (tege@sics.se).
5
6
NOTE: The canonical source of this file is maintained with the GNU C Library.
7
Bugs can be reported to bug-glibc@prep.ai.mit.edu.
8
9
This program is free software: you can redistribute it and/or modify it
10
under the terms of the GNU Lesser General Public License as published by the
11
Free Software Foundation; either version 2.1 of the License, or any
12
later version.
13
14
This program is distributed in the hope that it will be useful,
15
but WITHOUT ANY WARRANTY; without even the implied warranty of
16
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17
GNU Lesser General Public License for more details.
18
19
You should have received a copy of the GNU Lesser General Public License
20
along with this program. If not, see <http://www.gnu.org/licenses/>. */
21
22
#ifndef _LIBC
23
# include <config.h>
24
#endif
25
26
#include <string.h>
27
28
#undef memcmp
29
30
#ifdef _LIBC
31
32
# include <memcopy.h>
33
# include <endian.h>
34
35
# if __BYTE_ORDER == __BIG_ENDIAN
36
# define WORDS_BIGENDIAN
37
# endif
38
39
#else /* Not in the GNU C library. */
40
41
# include <sys/types.h>
42
43
/* Type to use for aligned memory operations.
44
This should normally be the biggest type supported by a single load
45
and store. Must be an unsigned type. */
46
# define op_t unsigned long int
47
# define OPSIZ (sizeof(op_t))
48
49
/* Threshold value for when to enter the unrolled loops. */
50
# define OP_T_THRES 16
51
52
/* Type to use for unaligned operations. */
53
typedef unsigned char byte;
54
55
# ifndef WORDS_BIGENDIAN
56
# define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
57
# else
58
# define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
59
# endif
60
61
#endif /* In the GNU C library. */
62
63
#ifdef WORDS_BIGENDIAN
64
# define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1)
65
#else
66
# define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b))
67
#endif
68
69
/* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */
70
71
/* The strategy of this memcmp is:
72
73
1. Compare bytes until one of the block pointers is aligned.
74
75
2. Compare using memcmp_common_alignment or
76
memcmp_not_common_alignment, regarding the alignment of the other
77
block after the initial byte operations. The maximum number of
78
full words (of type op_t) are compared in this way.
79
80
3. Compare the few remaining bytes. */
81
82
#ifndef WORDS_BIGENDIAN
83
/* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
84
A and B are known to be different.
85
This is needed only on little-endian machines. */
86
87
# ifdef __GNUC__
88
__inline
89
# endif
90
static int
91
memcmp_bytes (long unsigned int a, long unsigned int b)
92
{
93
long int srcp1 = (long int) &a;
94
long int srcp2 = (long int) &b;
95
op_t a0, b0;
96
97
do
98
{
99
a0 = ((byte *) srcp1)[0];
100
b0 = ((byte *) srcp2)[0];
101
srcp1 += 1;
102
srcp2 += 1;
103
}
104
while (a0 == b0);
105
return a0 - b0;
106
}
107
#endif
108
109
/* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t'
110
objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for
111
memory operations on `op_t's. */
112
#ifdef __GNUC__
113
__inline
114
#endif
115
static int
116
memcmp_common_alignment (long int srcp1, long int srcp2, size_t len)
117
{
118
op_t a0, a1;
119
op_t b0, b1;
120
121
switch (len % 4)
122
{
123
default: /* Avoid warning about uninitialized local variables. */
124
case 2:
125
a0 = ((op_t *) srcp1)[0];
126
b0 = ((op_t *) srcp2)[0];
127
srcp1 -= 2 * OPSIZ;
128
srcp2 -= 2 * OPSIZ;
129
len += 2;
130
goto do1;
131
case 3:
132
a1 = ((op_t *) srcp1)[0];
133
b1 = ((op_t *) srcp2)[0];
134
srcp1 -= OPSIZ;
135
srcp2 -= OPSIZ;
136
len += 1;
137
goto do2;
138
case 0:
139
if (OP_T_THRES <= 3 * OPSIZ && len == 0)
140
return 0;
141
a0 = ((op_t *) srcp1)[0];
142
b0 = ((op_t *) srcp2)[0];
143
goto do3;
144
case 1:
145
a1 = ((op_t *) srcp1)[0];
146
b1 = ((op_t *) srcp2)[0];
147
srcp1 += OPSIZ;
148
srcp2 += OPSIZ;
149
len -= 1;
150
if (OP_T_THRES <= 3 * OPSIZ && len == 0)
151
goto do0;
152
/* Fall through. */
153
}
154
155
do
156
{
157
a0 = ((op_t *) srcp1)[0];
158
b0 = ((op_t *) srcp2)[0];
159
if (a1 != b1)
160
return CMP_LT_OR_GT (a1, b1);
161
162
do3:
163
a1 = ((op_t *) srcp1)[1];
164
b1 = ((op_t *) srcp2)[1];
165
if (a0 != b0)
166
return CMP_LT_OR_GT (a0, b0);
167
168
do2:
169
a0 = ((op_t *) srcp1)[2];
170
b0 = ((op_t *) srcp2)[2];
171
if (a1 != b1)
172
return CMP_LT_OR_GT (a1, b1);
173
174
do1:
175
a1 = ((op_t *) srcp1)[3];
176
b1 = ((op_t *) srcp2)[3];
177
if (a0 != b0)
178
return CMP_LT_OR_GT (a0, b0);
179
180
srcp1 += 4 * OPSIZ;
181
srcp2 += 4 * OPSIZ;
182
len -= 4;
183
}
184
while (len != 0);
185
186
/* This is the right position for do0. Please don't move
187
it into the loop. */
188
do0:
189
if (a1 != b1)
190
return CMP_LT_OR_GT (a1, b1);
191
return 0;
192
}
193
194
/* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN
195
`op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory
196
operations on `op_t', but SRCP1 *should be unaligned*. */
197
#ifdef __GNUC__
198
__inline
199
#endif
200
static int
201
memcmp_not_common_alignment (long int srcp1, long int srcp2, size_t len)
202
{
203
op_t a0, a1, a2, a3;
204
op_t b0, b1, b2, b3;
205
op_t x;
206
int shl, shr;
207
208
/* Calculate how to shift a word read at the memory operation
209
aligned srcp1 to make it aligned for comparison. */
210
211
shl = 8 * (srcp1 % OPSIZ);
212
shr = 8 * OPSIZ - shl;
213
214
/* Make SRCP1 aligned by rounding it down to the beginning of the `op_t'
215
it points in the middle of. */
216
srcp1 &= -OPSIZ;
217
218
switch (len % 4)
219
{
220
default: /* Avoid warning about uninitialized local variables. */
221
case 2:
222
a1 = ((op_t *) srcp1)[0];
223
a2 = ((op_t *) srcp1)[1];
224
b2 = ((op_t *) srcp2)[0];
225
srcp1 -= 1 * OPSIZ;
226
srcp2 -= 2 * OPSIZ;
227
len += 2;
228
goto do1;
229
case 3:
230
a0 = ((op_t *) srcp1)[0];
231
a1 = ((op_t *) srcp1)[1];
232
b1 = ((op_t *) srcp2)[0];
233
srcp2 -= 1 * OPSIZ;
234
len += 1;
235
goto do2;
236
case 0:
237
if (OP_T_THRES <= 3 * OPSIZ && len == 0)
238
return 0;
239
a3 = ((op_t *) srcp1)[0];
240
a0 = ((op_t *) srcp1)[1];
241
b0 = ((op_t *) srcp2)[0];
242
srcp1 += 1 * OPSIZ;
243
goto do3;
244
case 1:
245
a2 = ((op_t *) srcp1)[0];
246
a3 = ((op_t *) srcp1)[1];
247
b3 = ((op_t *) srcp2)[0];
248
srcp1 += 2 * OPSIZ;
249
srcp2 += 1 * OPSIZ;
250
len -= 1;
251
if (OP_T_THRES <= 3 * OPSIZ && len == 0)
252
goto do0;
253
/* Fall through. */
254
}
255
256
do
257
{
258
a0 = ((op_t *) srcp1)[0];
259
b0 = ((op_t *) srcp2)[0];
260
x = MERGE(a2, shl, a3, shr);
261
if (x != b3)
262
return CMP_LT_OR_GT (x, b3);
263
264
do3:
265
a1 = ((op_t *) srcp1)[1];
266
b1 = ((op_t *) srcp2)[1];
267
x = MERGE(a3, shl, a0, shr);
268
if (x != b0)
269
return CMP_LT_OR_GT (x, b0);
270
271
do2:
272
a2 = ((op_t *) srcp1)[2];
273
b2 = ((op_t *) srcp2)[2];
274
x = MERGE(a0, shl, a1, shr);
275
if (x != b1)
276
return CMP_LT_OR_GT (x, b1);
277
278
do1:
279
a3 = ((op_t *) srcp1)[3];
280
b3 = ((op_t *) srcp2)[3];
281
x = MERGE(a1, shl, a2, shr);
282
if (x != b2)
283
return CMP_LT_OR_GT (x, b2);
284
285
srcp1 += 4 * OPSIZ;
286
srcp2 += 4 * OPSIZ;
287
len -= 4;
288
}
289
while (len != 0);
290
291
/* This is the right position for do0. Please don't move
292
it into the loop. */
293
do0:
294
x = MERGE(a2, shl, a3, shr);
295
if (x != b3)
296
return CMP_LT_OR_GT (x, b3);
297
return 0;
298
}
299
300
int
301
rpl_memcmp (const void *s1, const void *s2, size_t len)
302
{
303
op_t a0;
304
op_t b0;
305
long int srcp1 = (long int) s1;
306
long int srcp2 = (long int) s2;
307
op_t res;
308
309
if (len >= OP_T_THRES)
310
{
311
/* There are at least some bytes to compare. No need to test
312
for LEN == 0 in this alignment loop. */
313
while (srcp2 % OPSIZ != 0)
314
{
315
a0 = ((byte *) srcp1)[0];
316
b0 = ((byte *) srcp2)[0];
317
srcp1 += 1;
318
srcp2 += 1;
319
res = a0 - b0;
320
if (res != 0)
321
return res;
322
len -= 1;
323
}
324
325
/* SRCP2 is now aligned for memory operations on `op_t'.
326
SRCP1 alignment determines if we can do a simple,
327
aligned compare or need to shuffle bits. */
328
329
if (srcp1 % OPSIZ == 0)
330
res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ);
331
else
332
res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ);
333
if (res != 0)
334
return res;
335
336
/* Number of bytes remaining in the interval [0..OPSIZ-1]. */
337
srcp1 += len & -OPSIZ;
338
srcp2 += len & -OPSIZ;
339
len %= OPSIZ;
340
}
341
342
/* There are just a few bytes to compare. Use byte memory operations. */
343
while (len != 0)
344
{
345
a0 = ((byte *) srcp1)[0];
346
b0 = ((byte *) srcp2)[0];
347
srcp1 += 1;
348
srcp2 += 1;
349
res = a0 - b0;
350
if (res != 0)
351
return res;
352
len -= 1;
353
}
354
355
return 0;
356
}
357
358
#ifdef weak_alias
359
# undef bcmp
360
weak_alias (memcmp, bcmp)
361
#endif
Loggerhead is a web-based interface for Breezy
Version: 2.0.1