/[pcre]/code/trunk/study.c
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Contents of /code/trunk/study.c

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Revision 75 - (show annotations) (download)
Sat Feb 24 21:40:37 2007 UTC (7 years, 8 months ago) by nigel
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File size: 14414 byte(s)
Load pcre-5.0 into code/trunk.

1 /*************************************************
2 * Perl-Compatible Regular Expressions *
3 *************************************************/
4
5 /*
6 This is a library of functions to support regular expressions whose syntax
7 and semantics are as close as possible to those of the Perl 5 language. See
8 the file Tech.Notes for some information on the internals.
9
10 Written by: Philip Hazel <ph10@cam.ac.uk>
11
12 Copyright (c) 1997-2004 University of Cambridge
13
14 -----------------------------------------------------------------------------
15 Redistribution and use in source and binary forms, with or without
16 modification, are permitted provided that the following conditions are met:
17
18 * Redistributions of source code must retain the above copyright notice,
19 this list of conditions and the following disclaimer.
20
21 * Redistributions in binary form must reproduce the above copyright
22 notice, this list of conditions and the following disclaimer in the
23 documentation and/or other materials provided with the distribution.
24
25 * Neither the name of the University of Cambridge nor the names of its
26 contributors may be used to endorse or promote products derived from
27 this software without specific prior written permission.
28
29 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
30 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
33 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
34 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
35 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
36 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
37 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
39 POSSIBILITY OF SUCH DAMAGE.
40 -----------------------------------------------------------------------------
41 */
42
43
44 /* Include the internals header, which itself includes Standard C headers plus
45 the external pcre header. */
46
47 #include "internal.h"
48
49
50
51 /*************************************************
52 * Set a bit and maybe its alternate case *
53 *************************************************/
54
55 /* Given a character, set its bit in the table, and also the bit for the other
56 version of a letter if we are caseless.
57
58 Arguments:
59 start_bits points to the bit map
60 c is the character
61 caseless the caseless flag
62 cd the block with char table pointers
63
64 Returns: nothing
65 */
66
67 static void
68 set_bit(uschar *start_bits, unsigned int c, BOOL caseless, compile_data *cd)
69 {
70 start_bits[c/8] |= (1 << (c&7));
71 if (caseless && (cd->ctypes[c] & ctype_letter) != 0)
72 start_bits[cd->fcc[c]/8] |= (1 << (cd->fcc[c]&7));
73 }
74
75
76
77 /*************************************************
78 * Create bitmap of starting chars *
79 *************************************************/
80
81 /* This function scans a compiled unanchored expression and attempts to build a
82 bitmap of the set of initial characters. If it can't, it returns FALSE. As time
83 goes by, we may be able to get more clever at doing this.
84
85 Arguments:
86 code points to an expression
87 start_bits points to a 32-byte table, initialized to 0
88 caseless the current state of the caseless flag
89 utf8 TRUE if in UTF-8 mode
90 cd the block with char table pointers
91
92 Returns: TRUE if table built, FALSE otherwise
93 */
94
95 static BOOL
96 set_start_bits(const uschar *code, uschar *start_bits, BOOL caseless,
97 BOOL utf8, compile_data *cd)
98 {
99 register int c;
100
101 /* This next statement and the later reference to dummy are here in order to
102 trick the optimizer of the IBM C compiler for OS/2 into generating correct
103 code. Apparently IBM isn't going to fix the problem, and we would rather not
104 disable optimization (in this module it actually makes a big difference, and
105 the pcre module can use all the optimization it can get). */
106
107 volatile int dummy;
108
109 do
110 {
111 const uschar *tcode = code + 1 + LINK_SIZE;
112 BOOL try_next = TRUE;
113
114 while (try_next)
115 {
116 /* If a branch starts with a bracket or a positive lookahead assertion,
117 recurse to set bits from within them. That's all for this branch. */
118
119 if ((int)*tcode >= OP_BRA || *tcode == OP_ASSERT)
120 {
121 if (!set_start_bits(tcode, start_bits, caseless, utf8, cd))
122 return FALSE;
123 try_next = FALSE;
124 }
125
126 else switch(*tcode)
127 {
128 default:
129 return FALSE;
130
131 /* Skip over callout */
132
133 case OP_CALLOUT:
134 tcode += 2 + 2*LINK_SIZE;
135 break;
136
137 /* Skip over extended extraction bracket number */
138
139 case OP_BRANUMBER:
140 tcode += 3;
141 break;
142
143 /* Skip over lookbehind and negative lookahead assertions */
144
145 case OP_ASSERT_NOT:
146 case OP_ASSERTBACK:
147 case OP_ASSERTBACK_NOT:
148 do tcode += GET(tcode, 1); while (*tcode == OP_ALT);
149 tcode += 1+LINK_SIZE;
150 break;
151
152 /* Skip over an option setting, changing the caseless flag */
153
154 case OP_OPT:
155 caseless = (tcode[1] & PCRE_CASELESS) != 0;
156 tcode += 2;
157 break;
158
159 /* BRAZERO does the bracket, but carries on. */
160
161 case OP_BRAZERO:
162 case OP_BRAMINZERO:
163 if (!set_start_bits(++tcode, start_bits, caseless, utf8, cd))
164 return FALSE;
165 dummy = 1;
166 do tcode += GET(tcode,1); while (*tcode == OP_ALT);
167 tcode += 1+LINK_SIZE;
168 break;
169
170 /* Single-char * or ? sets the bit and tries the next item */
171
172 case OP_STAR:
173 case OP_MINSTAR:
174 case OP_QUERY:
175 case OP_MINQUERY:
176 set_bit(start_bits, tcode[1], caseless, cd);
177 tcode += 2;
178 #ifdef SUPPORT_UTF8
179 if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;
180 #endif
181 break;
182
183 /* Single-char upto sets the bit and tries the next */
184
185 case OP_UPTO:
186 case OP_MINUPTO:
187 set_bit(start_bits, tcode[3], caseless, cd);
188 tcode += 4;
189 #ifdef SUPPORT_UTF8
190 if (utf8) while ((*tcode & 0xc0) == 0x80) tcode++;
191 #endif
192 break;
193
194 /* At least one single char sets the bit and stops */
195
196 case OP_EXACT: /* Fall through */
197 tcode += 2;
198
199 case OP_CHAR:
200 case OP_CHARNC:
201 case OP_PLUS:
202 case OP_MINPLUS:
203 set_bit(start_bits, tcode[1], caseless, cd);
204 try_next = FALSE;
205 break;
206
207 /* Single character type sets the bits and stops */
208
209 case OP_NOT_DIGIT:
210 for (c = 0; c < 32; c++)
211 start_bits[c] |= ~cd->cbits[c+cbit_digit];
212 try_next = FALSE;
213 break;
214
215 case OP_DIGIT:
216 for (c = 0; c < 32; c++)
217 start_bits[c] |= cd->cbits[c+cbit_digit];
218 try_next = FALSE;
219 break;
220
221 case OP_NOT_WHITESPACE:
222 for (c = 0; c < 32; c++)
223 start_bits[c] |= ~cd->cbits[c+cbit_space];
224 try_next = FALSE;
225 break;
226
227 case OP_WHITESPACE:
228 for (c = 0; c < 32; c++)
229 start_bits[c] |= cd->cbits[c+cbit_space];
230 try_next = FALSE;
231 break;
232
233 case OP_NOT_WORDCHAR:
234 for (c = 0; c < 32; c++)
235 start_bits[c] |= ~cd->cbits[c+cbit_word];
236 try_next = FALSE;
237 break;
238
239 case OP_WORDCHAR:
240 for (c = 0; c < 32; c++)
241 start_bits[c] |= cd->cbits[c+cbit_word];
242 try_next = FALSE;
243 break;
244
245 /* One or more character type fudges the pointer and restarts, knowing
246 it will hit a single character type and stop there. */
247
248 case OP_TYPEPLUS:
249 case OP_TYPEMINPLUS:
250 tcode++;
251 break;
252
253 case OP_TYPEEXACT:
254 tcode += 3;
255 break;
256
257 /* Zero or more repeats of character types set the bits and then
258 try again. */
259
260 case OP_TYPEUPTO:
261 case OP_TYPEMINUPTO:
262 tcode += 2; /* Fall through */
263
264 case OP_TYPESTAR:
265 case OP_TYPEMINSTAR:
266 case OP_TYPEQUERY:
267 case OP_TYPEMINQUERY:
268 switch(tcode[1])
269 {
270 case OP_ANY:
271 return FALSE;
272
273 case OP_NOT_DIGIT:
274 for (c = 0; c < 32; c++)
275 start_bits[c] |= ~cd->cbits[c+cbit_digit];
276 break;
277
278 case OP_DIGIT:
279 for (c = 0; c < 32; c++)
280 start_bits[c] |= cd->cbits[c+cbit_digit];
281 break;
282
283 case OP_NOT_WHITESPACE:
284 for (c = 0; c < 32; c++)
285 start_bits[c] |= ~cd->cbits[c+cbit_space];
286 break;
287
288 case OP_WHITESPACE:
289 for (c = 0; c < 32; c++)
290 start_bits[c] |= cd->cbits[c+cbit_space];
291 break;
292
293 case OP_NOT_WORDCHAR:
294 for (c = 0; c < 32; c++)
295 start_bits[c] |= ~cd->cbits[c+cbit_word];
296 break;
297
298 case OP_WORDCHAR:
299 for (c = 0; c < 32; c++)
300 start_bits[c] |= cd->cbits[c+cbit_word];
301 break;
302 }
303
304 tcode += 2;
305 break;
306
307 /* Character class where all the information is in a bit map: set the
308 bits and either carry on or not, according to the repeat count. If it was
309 a negative class, and we are operating with UTF-8 characters, any byte
310 with a value >= 0xc4 is a potentially valid starter because it starts a
311 character with a value > 255. */
312
313 case OP_NCLASS:
314 if (utf8)
315 {
316 start_bits[24] |= 0xf0; /* Bits for 0xc4 - 0xc8 */
317 memset(start_bits+25, 0xff, 7); /* Bits for 0xc9 - 0xff */
318 }
319 /* Fall through */
320
321 case OP_CLASS:
322 {
323 tcode++;
324
325 /* In UTF-8 mode, the bits in a bit map correspond to character
326 values, not to byte values. However, the bit map we are constructing is
327 for byte values. So we have to do a conversion for characters whose
328 value is > 127. In fact, there are only two possible starting bytes for
329 characters in the range 128 - 255. */
330
331 if (utf8)
332 {
333 for (c = 0; c < 16; c++) start_bits[c] |= tcode[c];
334 for (c = 128; c < 256; c++)
335 {
336 if ((tcode[c/8] && (1 << (c&7))) != 0)
337 {
338 int d = (c >> 6) | 0xc0; /* Set bit for this starter */
339 start_bits[d/8] |= (1 << (d&7)); /* and then skip on to the */
340 c = (c & 0xc0) + 0x40 - 1; /* next relevant character. */
341 }
342 }
343 }
344
345 /* In non-UTF-8 mode, the two bit maps are completely compatible. */
346
347 else
348 {
349 for (c = 0; c < 32; c++) start_bits[c] |= tcode[c];
350 }
351
352 /* Advance past the bit map, and act on what follows */
353
354 tcode += 32;
355 switch (*tcode)
356 {
357 case OP_CRSTAR:
358 case OP_CRMINSTAR:
359 case OP_CRQUERY:
360 case OP_CRMINQUERY:
361 tcode++;
362 break;
363
364 case OP_CRRANGE:
365 case OP_CRMINRANGE:
366 if (((tcode[1] << 8) + tcode[2]) == 0) tcode += 5;
367 else try_next = FALSE;
368 break;
369
370 default:
371 try_next = FALSE;
372 break;
373 }
374 }
375 break; /* End of bitmap class handling */
376
377 } /* End of switch */
378 } /* End of try_next loop */
379
380 code += GET(code, 1); /* Advance to next branch */
381 }
382 while (*code == OP_ALT);
383 return TRUE;
384 }
385
386
387
388 /*************************************************
389 * Study a compiled expression *
390 *************************************************/
391
392 /* This function is handed a compiled expression that it must study to produce
393 information that will speed up the matching. It returns a pcre_extra block
394 which then gets handed back to pcre_exec().
395
396 Arguments:
397 re points to the compiled expression
398 options contains option bits
399 errorptr points to where to place error messages;
400 set NULL unless error
401
402 Returns: pointer to a pcre_extra block, with study_data filled in and the
403 appropriate flag set;
404 NULL on error or if no optimization possible
405 */
406
407 EXPORT pcre_extra *
408 pcre_study(const pcre *external_re, int options, const char **errorptr)
409 {
410 uschar start_bits[32];
411 pcre_extra *extra;
412 pcre_study_data *study;
413 const uschar *tables;
414 const real_pcre *re = (const real_pcre *)external_re;
415 uschar *code = (uschar *)re + re->name_table_offset +
416 (re->name_count * re->name_entry_size);
417 compile_data compile_block;
418
419 *errorptr = NULL;
420
421 if (re == NULL || re->magic_number != MAGIC_NUMBER)
422 {
423 *errorptr = "argument is not a compiled regular expression";
424 return NULL;
425 }
426
427 if ((options & ~PUBLIC_STUDY_OPTIONS) != 0)
428 {
429 *errorptr = "unknown or incorrect option bit(s) set";
430 return NULL;
431 }
432
433 /* For an anchored pattern, or an unanchored pattern that has a first char, or
434 a multiline pattern that matches only at "line starts", no further processing
435 at present. */
436
437 if ((re->options & (PCRE_ANCHORED|PCRE_FIRSTSET|PCRE_STARTLINE)) != 0)
438 return NULL;
439
440 /* Set the character tables in the block that is passed around */
441
442 tables = re->tables;
443 if (tables == NULL)
444 (void)pcre_fullinfo(external_re, NULL, PCRE_INFO_DEFAULT_TABLES, &tables);
445
446 compile_block.lcc = tables + lcc_offset;
447 compile_block.fcc = tables + fcc_offset;
448 compile_block.cbits = tables + cbits_offset;
449 compile_block.ctypes = tables + ctypes_offset;
450
451 /* See if we can find a fixed set of initial characters for the pattern. */
452
453 memset(start_bits, 0, 32 * sizeof(uschar));
454 if (!set_start_bits(code, start_bits, (re->options & PCRE_CASELESS) != 0,
455 (re->options & PCRE_UTF8) != 0, &compile_block)) return NULL;
456
457 /* Get a pcre_extra block and a pcre_study_data block. The study data is put in
458 the latter, which is pointed to by the former, which may also get additional
459 data set later by the calling program. At the moment, the size of
460 pcre_study_data is fixed. We nevertheless save it in a field for returning via
461 the pcre_fullinfo() function so that if it becomes variable in the future, we
462 don't have to change that code. */
463
464 extra = (pcre_extra *)(pcre_malloc)
465 (sizeof(pcre_extra) + sizeof(pcre_study_data));
466
467 if (extra == NULL)
468 {
469 *errorptr = "failed to get memory";
470 return NULL;
471 }
472
473 study = (pcre_study_data *)((char *)extra + sizeof(pcre_extra));
474 extra->flags = PCRE_EXTRA_STUDY_DATA;
475 extra->study_data = study;
476
477 study->size = sizeof(pcre_study_data);
478 study->options = PCRE_STUDY_MAPPED;
479 memcpy(study->start_bits, start_bits, sizeof(start_bits));
480
481 return extra;
482 }
483
484 /* End of study.c */

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