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README: omit -i option in examples
[neatmail.git] / regex.c
blob6e6d0f812e4110d26b1c6f22fe65115d80ca7aac
1 #include <ctype.h>
2 #include <stdio.h>
3 #include <stdlib.h>
4 #include <string.h>
5 #include "regex.h"
6
7 #define NGRPS 64 /* maximum number of groups */
8 #define NREPS 128 /* maximum repetitions */
9 #define NDEPT 256 /* re_rec() recursion depth limit */
10
11 #define MAX(a, b) ((a) < (b) ? (b) : (a))
12 #define LEN(a) (sizeof(a) / sizeof((a)[0]))
13
14 /* regular expressions atoms */
15 #define RA_CHR '\0' /* character literal */
16 #define RA_BEG '^' /* string start */
17 #define RA_END '$' /* string end */
18 #define RA_ANY '.' /* any character */
19 #define RA_BRK '[' /* bracket expression */
20 #define RA_WBEG '<' /* word start */
21 #define RA_WEND '>' /* word end */
22
23 /* regular expression node types */
24 #define RN_ATOM '\0' /* regular expression */
25 #define RN_CAT 'c' /* concatenation */
26 #define RN_ALT '|' /* alternate expressions */
27 #define RN_GRP '(' /* pattern group */
28
29 /* regular expression program instructions */
30 #define RI_ATOM '\0' /* regular expression */
31 #define RI_FORK 'f' /* fork the execution */
32 #define RI_JUMP 'j' /* jump to the given instruction */
33 #define RI_MARK 'm' /* mark the current position */
34 #define RI_MATCH 'q' /* the pattern is matched */
35
36 /* regular expression atom */
37 struct ratom {
38 int ra; /* atom type (RA_*) */
39 char *s; /* atom argument */
40 };
41
42 /* regular expression instruction */
43 struct rinst {
44 struct ratom ra; /* regular expression atom (RI_ATOM) */
45 int ri; /* instruction type (RI_*) */
46 int a1, a2; /* destination of RI_FORK and RI_JUMP */
47 int mark; /* mark (RI_MARK) */
48 };
49
50 /* regular expression program */
51 struct regex {
52 struct rinst *p; /* the program */
53 int n; /* number of instructions */
54 int flg; /* regcomp() flags */
55 };
56
57 /* regular expression matching state */
58 struct rstate {
59 char *s; /* the current position in the string */
60 char *o; /* the beginning of the string */
61 int mark[NGRPS * 2]; /* marks for RI_MARK */
62 int pc; /* program counter */
63 int flg; /* flags passed to regcomp() and regexec() */
64 int dep; /* re_rec() depth */
65 };
66
67 /* regular expression tree; used for parsing */
68 struct rnode {
69 struct ratom ra; /* regular expression atom (RN_ATOM) */
70 struct rnode *c1, *c2; /* children */
71 int mincnt, maxcnt; /* number of repetitions */
72 int grp; /* group number */
73 int rn; /* node type (RN_*) */
74 };
75
76 static struct rnode *rnode_make(int rn, struct rnode *c1, struct rnode *c2)
77 {
78 struct rnode *rnode = malloc(sizeof(*rnode));
79 memset(rnode, 0, sizeof(*rnode));
80 rnode->rn = rn;
81 rnode->c1 = c1;
82 rnode->c2 = c2;
83 rnode->mincnt = 1;
84 rnode->maxcnt = 1;
85 return rnode;
86 }
87
88 static void rnode_free(struct rnode *rnode)
89 {
90 if (rnode->c1)
91 rnode_free(rnode->c1);
92 if (rnode->c2)
93 rnode_free(rnode->c2);
94 free(rnode->ra.s);
95 free(rnode);
96 }
97
98 static int uc_len(char *s)
99 {
100 int c = (unsigned char) s[0];
101 if (~c & 0xc0) /* ASCII or invalid */
102 return c > 0;
103 if (~c & 0x20)
104 return 2;
105 if (~c & 0x10)
106 return 3;
107 if (~c & 0x08)
108 return 4;
109 return 1;
110 }
111
112 static int uc_dec(char *s)
113 {
114 int c = (unsigned char) s[0];
115 if (~c & 0xc0) /* ASCII or invalid */
116 return c;
117 if (~c & 0x20)
118 return ((c & 0x1f) << 6) | (s[1] & 0x3f);
119 if (~c & 0x10)
120 return ((c & 0x0f) << 12) | ((s[1] & 0x3f) << 6) | (s[2] & 0x3f);
121 if (~c & 0x08)
122 return ((c & 0x07) << 18) | ((s[1] & 0x3f) << 12) | ((s[2] & 0x3f) << 6) | (s[3] & 0x3f);
123 return c;
124 }
125
126 static void ratom_copy(struct ratom *dst, struct ratom *src)
127 {
128 dst->ra = src->ra;
129 dst->s = NULL;
130 if (src->s) {
131 int len = strlen(src->s);
132 dst->s = malloc(len + 1);
133 memcpy(dst->s, src->s, len + 1);
134 }
135 }
136
137 static int brk_len(char *s)
138 {
139 int n = 1;
140 if (s[n] == '^') /* exclusion mark */
141 n++;
142 if (s[n] == ']') /* handling []a] */
143 n++;
144 while (s[n] && s[n] != ']') {
145 if (s[n] == '[' && (s[n + 1] == ':' || s[n + 1] == '='))
146 while (s[n] && s[n] != ']')
147 n++;
148 if (s[n])
149 n++;
150 }
151 return s[n] == ']' ? n + 1 : n;
152 }
153
154 static void ratom_readbrk(struct ratom *ra, char **pat)
155 {
156 int len = brk_len(*pat);
157 ra->ra = RA_BRK;
158 ra->s = malloc(len + 1);
159 memcpy(ra->s, *pat, len);
160 ra->s[len] = '\0';
161 *pat += len;
162 }
163
164 static void ratom_read(struct ratom *ra, char **pat)
165 {
166 int len;
167 switch ((unsigned char) **pat) {
168 case '.':
169 ra->ra = RA_ANY;
170 (*pat)++;
171 break;
172 case '^':
173 ra->ra = RA_BEG;
174 (*pat)++;
175 break;
176 case '$':
177 ra->ra = RA_END;
178 (*pat)++;
179 break;
180 case '[':
181 ratom_readbrk(ra, pat);
182 break;
183 case '\\':
184 if ((*pat)[1] == '<' || (*pat)[1] == '>') {
185 ra->ra = (*pat)[1] == '<' ? RA_WBEG : RA_WEND;
186 *pat += 2;
187 break;
188 }
189 (*pat)++;
190 default:
191 ra->ra = RA_CHR;
192 len = uc_len(*pat);
193 ra->s = malloc(8);
194 memcpy(ra->s, *pat, len);
195 ra->s[len] = '\0';
196 *pat += len;
197 }
198 }
199
200 static char *uc_beg(char *beg, char *s)
201 {
202 while (s > beg && (((unsigned char) *s) & 0xc0) == 0x80)
203 s--;
204 return s;
205 }
206
207 static int isword(char *s)
208 {
209 int c = (unsigned char) s[0];
210 return isalnum(c) || c == '_' || c > 127;
211 }
212
213 static char *brk_classes[][2] = {
214 {":alnum:", "a-zA-Z0-9"},
215 {":alpha:", "a-zA-Z"},
216 {":blank:", " \t"},
217 {":digit:", "0-9"},
218 {":lower:", "a-z"},
219 {":print:", "\x20-\x7e"},
220 {":punct:", "][!\"#$%&'()*+,./:;<=>?@\\^_`{|}~-"},
221 {":space:", " \t\r\n\v\f"},
222 {":upper:", "A-Z"},
223 {":word:", "a-zA-Z0-9_"},
224 {":xdigit:", "a-fA-F0-9"},
225 };
226
227 static int brk_match(char *brk, int c, int flg)
228 {
229 int beg, end;
230 int i;
231 int not = brk[0] == '^';
232 char *p = not ? brk + 1 : brk;
233 char *p0 = p;
234 if (flg & REG_ICASE && c < 128 && isupper(c))
235 c = tolower(c);
236 while (*p && (p == p0 || *p != ']')) {
237 if (p[0] == '[' && p[1] == ':') {
238 for (i = 0; i < LEN(brk_classes); i++) {
239 char *cc = brk_classes[i][0];
240 char *cp = brk_classes[i][1];
241 if (!strncmp(cc, p + 1, strlen(cc)))
242 if (!brk_match(cp, c, flg))
243 return not;
244 }
245 p += brk_len(p);
246 continue;
247 }
248 beg = uc_dec(p);
249 p += uc_len(p);
250 end = beg;
251 if (p[0] == '-' && p[1] && p[1] != ']') {
252 p++;
253 end = uc_dec(p);
254 p += uc_len(p);
255 }
256 if (flg & REG_ICASE && beg < 128 && isupper(beg))
257 beg = tolower(beg);
258 if (flg & REG_ICASE && end < 128 && isupper(end))
259 end = tolower(end);
260 if (c >= beg && c <= end)
261 return not;
262 }
263 return !not;
264 }
265
266 static int ratom_match(struct ratom *ra, struct rstate *rs)
267 {
268 if (ra->ra == RA_CHR) {
269 int c1 = uc_dec(ra->s);
270 int c2 = uc_dec(rs->s);
271 if (rs->flg & REG_ICASE && c1 < 128 && isupper(c1))
272 c1 = tolower(c1);
273 if (rs->flg & REG_ICASE && c2 < 128 && isupper(c2))
274 c2 = tolower(c2);
275 if (c1 != c2)
276 return 1;
277 rs->s += uc_len(ra->s);
278 return 0;
279 }
280 if (ra->ra == RA_ANY) {
281 if (!rs->s[0] || (rs->s[0] == '\n' && !(rs->flg & REG_NOTEOL)))
282 return 1;
283 rs->s += uc_len(rs->s);
284 return 0;
285 }
286 if (ra->ra == RA_BRK) {
287 int c = uc_dec(rs->s);
288 if (!c || (c == '\n' && !(rs->flg & REG_NOTEOL)))
289 return 1;
290 rs->s += uc_len(rs->s);
291 return brk_match(ra->s + 1, c, rs->flg);
292 }
293 if (ra->ra == RA_BEG && !(rs->flg & REG_NOTBOL))
294 return !(rs->s == rs->o || rs->s[-1] == '\n');
295 if (ra->ra == RA_END && !(rs->flg & REG_NOTEOL))
296 return rs->s[0] != '\0' && rs->s[0] != '\n';
297 if (ra->ra == RA_WBEG)
298 return !((rs->s == rs->o || !isword(uc_beg(rs->o, rs->s - 1))) &&
299 isword(rs->s));
300 if (ra->ra == RA_WEND)
301 return !(rs->s != rs->o && isword(uc_beg(rs->o, rs->s - 1)) &&
302 (!rs->s[0] || !isword(rs->s)));
303 return 1;
304 }
305
306 static struct rnode *rnode_parse(char **pat);
307
308 static struct rnode *rnode_grp(char **pat)
309 {
310 struct rnode *rnode = NULL;
311 if ((*pat)[0] != '(')
312 return NULL;
313 *pat += 1;
314 if ((*pat)[0] != ')') {
315 rnode = rnode_parse(pat);
316 if (!rnode)
317 return NULL;
318 }
319 if ((*pat)[0] != ')') {
320 rnode_free(rnode);
321 return NULL;
322 }
323 *pat += 1;
324 return rnode_make(RN_GRP, rnode, NULL);
325 }
326
327 static struct rnode *rnode_atom(char **pat)
328 {
329 struct rnode *rnode;
330 if (!**pat)
331 return NULL;
332 if ((*pat)[0] == '|' || (*pat)[0] == ')')
333 return NULL;
334 if ((*pat)[0] == '(') {
335 rnode = rnode_grp(pat);
336 } else {
337 rnode = rnode_make(RN_ATOM, NULL, NULL);
338 ratom_read(&rnode->ra, pat);
339 }
340 if (!rnode)
341 return NULL;
342 if ((*pat)[0] == '*' || (*pat)[0] == '?') {
343 rnode->mincnt = 0;
344 rnode->maxcnt = (*pat)[0] == '*' ? -1 : 1;
345 *pat += 1;
346 }
347 if ((*pat)[0] == '+') {
348 rnode->mincnt = 1;
349 rnode->maxcnt = -1;
350 *pat += 1;
351 }
352 if ((*pat)[0] == '{') {
353 rnode->mincnt = 0;
354 rnode->maxcnt = 0;
355 *pat += 1;
356 while (isdigit((unsigned char) **pat))
357 rnode->mincnt = rnode->mincnt * 10 + *(*pat)++ - '0';
358 if (**pat == ',') {
359 (*pat)++;
360 if ((*pat)[0] == '}')
361 rnode->maxcnt = -1;
362 while (isdigit((unsigned char) **pat))
363 rnode->maxcnt = rnode->maxcnt * 10 + *(*pat)++ - '0';
364 } else {
365 rnode->maxcnt = rnode->mincnt;
366 }
367 *pat += 1;
368 if (rnode->mincnt > NREPS || rnode->maxcnt > NREPS) {
369 rnode_free(rnode);
370 return NULL;
371 }
372 }
373 return rnode;
374 }
375
376 static struct rnode *rnode_seq(char **pat)
377 {
378 struct rnode *c1 = rnode_atom(pat);
379 struct rnode *c2;
380 if (!c1)
381 return NULL;
382 c2 = rnode_seq(pat);
383 return c2 ? rnode_make(RN_CAT, c1, c2) : c1;
384 }
385
386 static struct rnode *rnode_parse(char **pat)
387 {
388 struct rnode *c1 = rnode_seq(pat);
389 struct rnode *c2;
390 if ((*pat)[0] != '|')
391 return c1;
392 *pat += 1;
393 c2 = rnode_parse(pat);
394 return c2 ? rnode_make(RN_ALT, c1, c2) : c1;
395 }
396
397 static int rnode_count(struct rnode *rnode)
398 {
399 int n = 1;
400 if (!rnode)
401 return 0;
402 if (rnode->rn == RN_CAT)
403 n = rnode_count(rnode->c1) + rnode_count(rnode->c2);
404 if (rnode->rn == RN_ALT)
405 n = rnode_count(rnode->c1) + rnode_count(rnode->c2) + 2;
406 if (rnode->rn == RN_GRP)
407 n = rnode_count(rnode->c1) + 2;
408 if (rnode->mincnt == 0 && rnode->maxcnt == 0)
409 return 0;
410 if (rnode->mincnt == 1 && rnode->maxcnt == 1)
411 return n;
412 if (rnode->maxcnt < 0) {
413 n = (rnode->mincnt + 1) * n + 1;
414 } else {
415 n = (rnode->mincnt + rnode->maxcnt) * n +
416 rnode->maxcnt - rnode->mincnt;
417 }
418 if (!rnode->mincnt)
419 n++;
420 return n;
421 }
422
423 static int rnode_grpnum(struct rnode *rnode, int num)
424 {
425 int cur = 0;
426 if (!rnode)
427 return 0;
428 if (rnode->rn == RN_GRP)
429 rnode->grp = num + cur++;
430 cur += rnode_grpnum(rnode->c1, num + cur);
431 cur += rnode_grpnum(rnode->c2, num + cur);
432 return cur;
433 }
434
435 static int re_insert(struct regex *p, int ri)
436 {
437 p->p[p->n++].ri = ri;
438 return p->n - 1;
439 }
440
441 static void rnode_emit(struct rnode *n, struct regex *p);
442
443 static void rnode_emitnorep(struct rnode *n, struct regex *p)
444 {
445 int fork, done, mark;
446 if (n->rn == RN_ALT) {
447 fork = re_insert(p, RI_FORK);
448 p->p[fork].a1 = p->n;
449 rnode_emit(n->c1, p);
450 done = re_insert(p, RI_JUMP);
451 p->p[fork].a2 = p->n;
452 rnode_emit(n->c2, p);
453 p->p[done].a1 = p->n;
454 }
455 if (n->rn == RN_CAT) {
456 rnode_emit(n->c1, p);
457 rnode_emit(n->c2, p);
458 }
459 if (n->rn == RN_GRP) {
460 mark = re_insert(p, RI_MARK);
461 p->p[mark].mark = 2 * n->grp;
462 rnode_emit(n->c1, p);
463 mark = re_insert(p, RI_MARK);
464 p->p[mark].mark = 2 * n->grp + 1;
465 }
466 if (n->rn == RN_ATOM) {
467 int atom = re_insert(p, RI_ATOM);
468 ratom_copy(&p->p[atom].ra, &n->ra);
469 }
470 }
471
472 static void rnode_emit(struct rnode *n, struct regex *p)
473 {
474 int last;
475 int jmpend[NREPS];
476 int jmpend_cnt = 0;
477 int i;
478 if (!n)
479 return;
480 if (n->mincnt == 0 && n->maxcnt == 0)
481 return;
482 if (n->mincnt == 1 && n->maxcnt == 1) {
483 rnode_emitnorep(n, p);
484 return;
485 }
486 if (n->mincnt == 0) {
487 int fork = re_insert(p, RI_FORK);
488 p->p[fork].a1 = p->n;
489 jmpend[jmpend_cnt++] = fork;
490 }
491 for (i = 0; i < MAX(1, n->mincnt); i++) {
492 last = p->n;
493 rnode_emitnorep(n, p);
494 }
495 if (n->maxcnt < 0) {
496 int fork;
497 fork = re_insert(p, RI_FORK);
498 p->p[fork].a1 = last;
499 p->p[fork].a2 = p->n;
500 }
501 for (i = MAX(1, n->mincnt); i < n->maxcnt; i++) {
502 int fork = re_insert(p, RI_FORK);
503 p->p[fork].a1 = p->n;
504 jmpend[jmpend_cnt++] = fork;
505 rnode_emitnorep(n, p);
506 }
507 for (i = 0; i < jmpend_cnt; i++)
508 p->p[jmpend[i]].a2 = p->n;
509 }
510
511 int regcomp(regex_t *preg, char *pat, int flg)
512 {
513 struct rnode *rnode = rnode_parse(&pat);
514 struct regex *re;
515 int n = rnode_count(rnode) + 3;
516 int mark;
517 if (!rnode)
518 return 1;
519 rnode_grpnum(rnode, 1);
520 re = malloc(sizeof(*re));
521 memset(re, 0, sizeof(*re));
522 re->p = malloc(n * sizeof(re->p[0]));
523 memset(re->p, 0, n * sizeof(re->p[0]));
524 mark = re_insert(re, RI_MARK);
525 re->p[mark].mark = 0;
526 rnode_emit(rnode, re);
527 mark = re_insert(re, RI_MARK);
528 re->p[mark].mark = 1;
529 mark = re_insert(re, RI_MATCH);
530 rnode_free(rnode);
531 re->flg = flg;
532 *preg = re;
533 return 0;
534 }
535
536 void regfree(regex_t *preg)
537 {
538 struct regex *re = *preg;
539 int i;
540 for (i = 0; i < re->n; i++)
541 if (re->p[i].ri == RI_ATOM)
542 free(re->p[i].ra.s);
543 free(re->p);
544 free(re);
545 }
546
547 static int re_rec(struct regex *re, struct rstate *rs)
548 {
549 struct rinst *ri = NULL;
550 if (rs->dep >= NDEPT)
551 return 1;
552 rs->dep++;
553 while (1) {
554 ri = &re->p[rs->pc];
555 if (ri->ri == RI_ATOM) {
556 if (ratom_match(&ri->ra, rs))
557 return 1;
558 rs->pc++;
559 continue;
560 }
561 if (ri->ri == RI_MARK) {
562 if (ri->mark < NGRPS)
563 rs->mark[ri->mark] = rs->s - rs->o;
564 rs->pc++;
565 continue;
566 }
567 if (ri->ri == RI_JUMP) {
568 rs->pc = ri->a1;
569 continue;
570 }
571 if (ri->ri == RI_FORK) {
572 struct rstate base = *rs;
573 rs->pc = ri->a1;
574 if (!re_rec(re, rs))
575 return 0;
576 *rs = base;
577 rs->pc = ri->a2;
578 continue;
579 }
580 break;
581 }
582 rs->dep--;
583 return ri->ri != RI_MATCH;
584 }
585
586 static int re_recmatch(struct regex *re, struct rstate *rs, int nsub, regmatch_t *psub)
587 {
588 int i;
589 rs->pc = 0;
590 for (i = 0; i < LEN(rs->mark); i++)
591 rs->mark[i] = -1;
592 rs->dep = 0;
593 if (!re_rec(re, rs)) {
594 for (i = 0; i < nsub; i++) {
595 psub[i].rm_so = i * 2 < LEN(rs->mark) ? rs->mark[i * 2] : -1;
596 psub[i].rm_eo = i * 2 < LEN(rs->mark) ? rs->mark[i * 2 + 1] : -1;
597 }
598 return 0;
599 }
600 return 1;
601 }
602
603 int regexec(regex_t *preg, char *s, int nsub, regmatch_t psub[], int flg)
604 {
605 struct regex *re = *preg;
606 struct rstate rs;
607 memset(&rs, 0, sizeof(rs));
608 rs.flg = re->flg | flg;
609 rs.o = s;
610 while (*s) {
611 rs.s = s;
612 s += uc_len(s);
613 if (!re_recmatch(re, &rs, flg & REG_NOSUB ? 0 : nsub, psub))
614 return 0;
615 }
616 return 1;
617 }
618
619 int regerror(int errcode, regex_t *preg, char *errbuf, int errbuf_size)
620 {
621 return 0;
622 }
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