source: trunk/src/sed/lib/memcmp.c@ 1077

Last change on this file since 1077 was 599, checked in by bird, 19 years ago

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1/* Copyright (C) 1991, 1993, 1995, 1997, 1998 Free Software Foundation, Inc.
2 Contributed by Torbjorn Granlund (tege@sics.se).
3
4 NOTE: The canonical source of this file is maintained with the GNU C Library.
5 Bugs can be reported to bug-glibc@gnu.org.
6
7 This program is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 2, or (at your option) any
10 later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
20 USA. */
21
22#ifdef HAVE_CONFIG_H
23# include "config.h"
24#endif
25
26#undef __ptr_t
27#if defined __cplusplus || (defined __STDC__ && __STDC__)
28# define __ptr_t void *
29#else /* Not C++ or ANSI C. */
30# undef const
31# define const
32# define __ptr_t char *
33#endif /* C++ or ANSI C. */
34
35#ifndef __P
36# if defined __GNUC__ || (defined __STDC__ && __STDC__)
37# define __P(args) args
38# else
39# define __P(args) ()
40# endif /* GCC. */
41#endif /* Not __P. */
42
43#if defined HAVE_STRING_H || defined _LIBC
44# include <string.h>
45#endif
46
47#undef memcmp
48
49#ifdef _LIBC
50
51# include <memcopy.h>
52# include <endian.h>
53
54# if __BYTE_ORDER == __BIG_ENDIAN
55# define WORDS_BIGENDIAN
56# endif
57
58#else /* Not in the GNU C library. */
59
60# include <sys/types.h>
61
62/* Type to use for aligned memory operations.
63 This should normally be the biggest type supported by a single load
64 and store. Must be an unsigned type. */
65# define op_t unsigned long int
66# define OPSIZ (sizeof(op_t))
67
68/* Threshold value for when to enter the unrolled loops. */
69# define OP_T_THRES 16
70
71/* Type to use for unaligned operations. */
72typedef unsigned char byte;
73
74# ifndef WORDS_BIGENDIAN
75# define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
76# else
77# define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
78# endif
79
80#endif /* In the GNU C library. */
81
82#ifdef WORDS_BIGENDIAN
83# define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1)
84#else
85# define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b))
86#endif
87
88/* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */
89
90/* The strategy of this memcmp is:
91
92 1. Compare bytes until one of the block pointers is aligned.
93
94 2. Compare using memcmp_common_alignment or
95 memcmp_not_common_alignment, regarding the alignment of the other
96 block after the initial byte operations. The maximum number of
97 full words (of type op_t) are compared in this way.
98
99 3. Compare the few remaining bytes. */
100
101#ifndef WORDS_BIGENDIAN
102/* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
103 A and B are known to be different.
104 This is needed only on little-endian machines. */
105
106static int memcmp_bytes __P((op_t, op_t));
107
108# ifdef __GNUC__
109__inline
110# endif
111static int
112memcmp_bytes (a, b)
113 op_t a, b;
114{
115 long int srcp1 = (long int) &a;
116 long int srcp2 = (long int) &b;
117 op_t a0, b0;
118
119 do
120 {
121 a0 = ((byte *) srcp1)[0];
122 b0 = ((byte *) srcp2)[0];
123 srcp1 += 1;
124 srcp2 += 1;
125 }
126 while (a0 == b0);
127 return a0 - b0;
128}
129#endif
130
131static int memcmp_common_alignment __P((long, long, size_t));
132
133/* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t'
134 objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for
135 memory operations on `op_t's. */
136#ifdef __GNUC__
137__inline
138#endif
139static int
140memcmp_common_alignment (srcp1, srcp2, len)
141 long int srcp1;
142 long int srcp2;
143 size_t len;
144{
145 op_t a0, a1;
146 op_t b0, b1;
147
148 switch (len % 4)
149 {
150 default: /* Avoid warning about uninitialized local variables. */
151 case 2:
152 a0 = ((op_t *) srcp1)[0];
153 b0 = ((op_t *) srcp2)[0];
154 srcp1 -= 2 * OPSIZ;
155 srcp2 -= 2 * OPSIZ;
156 len += 2;
157 goto do1;
158 case 3:
159 a1 = ((op_t *) srcp1)[0];
160 b1 = ((op_t *) srcp2)[0];
161 srcp1 -= OPSIZ;
162 srcp2 -= OPSIZ;
163 len += 1;
164 goto do2;
165 case 0:
166 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
167 return 0;
168 a0 = ((op_t *) srcp1)[0];
169 b0 = ((op_t *) srcp2)[0];
170 goto do3;
171 case 1:
172 a1 = ((op_t *) srcp1)[0];
173 b1 = ((op_t *) srcp2)[0];
174 srcp1 += OPSIZ;
175 srcp2 += OPSIZ;
176 len -= 1;
177 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
178 goto do0;
179 /* Fall through. */
180 }
181
182 do
183 {
184 a0 = ((op_t *) srcp1)[0];
185 b0 = ((op_t *) srcp2)[0];
186 if (a1 != b1)
187 return CMP_LT_OR_GT (a1, b1);
188
189 do3:
190 a1 = ((op_t *) srcp1)[1];
191 b1 = ((op_t *) srcp2)[1];
192 if (a0 != b0)
193 return CMP_LT_OR_GT (a0, b0);
194
195 do2:
196 a0 = ((op_t *) srcp1)[2];
197 b0 = ((op_t *) srcp2)[2];
198 if (a1 != b1)
199 return CMP_LT_OR_GT (a1, b1);
200
201 do1:
202 a1 = ((op_t *) srcp1)[3];
203 b1 = ((op_t *) srcp2)[3];
204 if (a0 != b0)
205 return CMP_LT_OR_GT (a0, b0);
206
207 srcp1 += 4 * OPSIZ;
208 srcp2 += 4 * OPSIZ;
209 len -= 4;
210 }
211 while (len != 0);
212
213 /* This is the right position for do0. Please don't move
214 it into the loop. */
215 do0:
216 if (a1 != b1)
217 return CMP_LT_OR_GT (a1, b1);
218 return 0;
219}
220
221static int memcmp_not_common_alignment __P((long, long, size_t));
222
223/* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN
224 `op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory
225 operations on `op_t', but SRCP1 *should be unaligned*. */
226#ifdef __GNUC__
227__inline
228#endif
229static int
230memcmp_not_common_alignment (srcp1, srcp2, len)
231 long int srcp1;
232 long int srcp2;
233 size_t len;
234{
235 op_t a0, a1, a2, a3;
236 op_t b0, b1, b2, b3;
237 op_t x;
238 int shl, shr;
239
240 /* Calculate how to shift a word read at the memory operation
241 aligned srcp1 to make it aligned for comparison. */
242
243 shl = 8 * (srcp1 % OPSIZ);
244 shr = 8 * OPSIZ - shl;
245
246 /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t'
247 it points in the middle of. */
248 srcp1 &= -OPSIZ;
249
250 switch (len % 4)
251 {
252 default: /* Avoid warning about uninitialized local variables. */
253 case 2:
254 a1 = ((op_t *) srcp1)[0];
255 a2 = ((op_t *) srcp1)[1];
256 b2 = ((op_t *) srcp2)[0];
257 srcp1 -= 1 * OPSIZ;
258 srcp2 -= 2 * OPSIZ;
259 len += 2;
260 goto do1;
261 case 3:
262 a0 = ((op_t *) srcp1)[0];
263 a1 = ((op_t *) srcp1)[1];
264 b1 = ((op_t *) srcp2)[0];
265 srcp2 -= 1 * OPSIZ;
266 len += 1;
267 goto do2;
268 case 0:
269 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
270 return 0;
271 a3 = ((op_t *) srcp1)[0];
272 a0 = ((op_t *) srcp1)[1];
273 b0 = ((op_t *) srcp2)[0];
274 srcp1 += 1 * OPSIZ;
275 goto do3;
276 case 1:
277 a2 = ((op_t *) srcp1)[0];
278 a3 = ((op_t *) srcp1)[1];
279 b3 = ((op_t *) srcp2)[0];
280 srcp1 += 2 * OPSIZ;
281 srcp2 += 1 * OPSIZ;
282 len -= 1;
283 if (OP_T_THRES <= 3 * OPSIZ && len == 0)
284 goto do0;
285 /* Fall through. */
286 }
287
288 do
289 {
290 a0 = ((op_t *) srcp1)[0];
291 b0 = ((op_t *) srcp2)[0];
292 x = MERGE(a2, shl, a3, shr);
293 if (x != b3)
294 return CMP_LT_OR_GT (x, b3);
295
296 do3:
297 a1 = ((op_t *) srcp1)[1];
298 b1 = ((op_t *) srcp2)[1];
299 x = MERGE(a3, shl, a0, shr);
300 if (x != b0)
301 return CMP_LT_OR_GT (x, b0);
302
303 do2:
304 a2 = ((op_t *) srcp1)[2];
305 b2 = ((op_t *) srcp2)[2];
306 x = MERGE(a0, shl, a1, shr);
307 if (x != b1)
308 return CMP_LT_OR_GT (x, b1);
309
310 do1:
311 a3 = ((op_t *) srcp1)[3];
312 b3 = ((op_t *) srcp2)[3];
313 x = MERGE(a1, shl, a2, shr);
314 if (x != b2)
315 return CMP_LT_OR_GT (x, b2);
316
317 srcp1 += 4 * OPSIZ;
318 srcp2 += 4 * OPSIZ;
319 len -= 4;
320 }
321 while (len != 0);
322
323 /* This is the right position for do0. Please don't move
324 it into the loop. */
325 do0:
326 x = MERGE(a2, shl, a3, shr);
327 if (x != b3)
328 return CMP_LT_OR_GT (x, b3);
329 return 0;
330}
331
332int
333memcmp (s1, s2, len)
334 const __ptr_t s1;
335 const __ptr_t s2;
336 size_t len;
337{
338 op_t a0;
339 op_t b0;
340 long int srcp1 = (long int) s1;
341 long int srcp2 = (long int) s2;
342 op_t res;
343
344 if (len >= OP_T_THRES)
345 {
346 /* There are at least some bytes to compare. No need to test
347 for LEN == 0 in this alignment loop. */
348 while (srcp2 % OPSIZ != 0)
349 {
350 a0 = ((byte *) srcp1)[0];
351 b0 = ((byte *) srcp2)[0];
352 srcp1 += 1;
353 srcp2 += 1;
354 res = a0 - b0;
355 if (res != 0)
356 return res;
357 len -= 1;
358 }
359
360 /* SRCP2 is now aligned for memory operations on `op_t'.
361 SRCP1 alignment determines if we can do a simple,
362 aligned compare or need to shuffle bits. */
363
364 if (srcp1 % OPSIZ == 0)
365 res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ);
366 else
367 res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ);
368 if (res != 0)
369 return res;
370
371 /* Number of bytes remaining in the interval [0..OPSIZ-1]. */
372 srcp1 += len & -OPSIZ;
373 srcp2 += len & -OPSIZ;
374 len %= OPSIZ;
375 }
376
377 /* There are just a few bytes to compare. Use byte memory operations. */
378 while (len != 0)
379 {
380 a0 = ((byte *) srcp1)[0];
381 b0 = ((byte *) srcp2)[0];
382 srcp1 += 1;
383 srcp2 += 1;
384 res = a0 - b0;
385 if (res != 0)
386 return res;
387 len -= 1;
388 }
389
390 return 0;
391}
392
393#ifdef weak_alias
394# undef bcmp
395weak_alias (memcmp, bcmp)
396#endif
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