source: trunk/minix/commands/cawf/regexp.c@ 10

Last change on this file since 10 was 9, checked in by Mattia Monga, 14 years ago

Minix 3.1.2a
File size: 28.7 KB
Line 
1/*
2 * regcomp and regexec -- regsub and regerror are elsewhere
3 *
4 * Copyright (c) 1986 by University of Toronto.
5 * Written by Henry Spencer. Not derived from licensed software.
6 *
7 * Permission is granted to anyone to use this software for any
8 * purpose on any computer system, and to redistribute it freely,
9 * subject to the following restrictions:
10 *
11 * 1. The author is not responsible for the consequences of use of
12 * this software, no matter how awful, even if they arise
13 * from defects in it.
14 *
15 * 2. The origin of this software must not be misrepresented, either
16 * by explicit claim or by omission.
17 *
18 * 3. Altered versions must be plainly marked as such, and must not
19 * be misrepresented as being the original software.
20 *
21 * Beware that some of this code is subtly aware of the way operator
22 * precedence is structured in regular expressions. Serious changes in
23 * regular-expression syntax might require a total rethink.
24 */
25#include <stdio.h>
26#ifdef UNIX
27#ifdef USG
28#include <string.h>
29#else
30#include <strings.h>
31#endif
32#else
33#include <string.h>
34#endif
35#include "regexp.h"
36#include "regmagic.h"
37#include "proto.h"
38
39/*
40 * The "internal use only" fields in regexp.h are present to pass info from
41 * compile to execute that permits the execute phase to run lots faster on
42 * simple cases. They are:
43 *
44 * regstart char that must begin a match; '\0' if none obvious
45 * reganch is the match anchored (at beginning-of-line only)?
46 * regmust string (pointer into program) that match must include, or NULL
47 * regmlen length of regmust string
48 *
49 * Regstart and reganch permit very fast decisions on suitable starting points
50 * for a match, cutting down the work a lot. Regmust permits fast rejection
51 * of lines that cannot possibly match. The regmust tests are costly enough
52 * that regcomp() supplies a regmust only if the r.e. contains something
53 * potentially expensive (at present, the only such thing detected is * or +
54 * at the start of the r.e., which can involve a lot of backup). Regmlen is
55 * supplied because the test in regexec() needs it and regcomp() is computing
56 * it anyway.
57 */
58
59/*
60 * Structure for regexp "program". This is essentially a linear encoding
61 * of a nondeterministic finite-state machine (aka syntax charts or
62 * "railroad normal form" in parsing technology). Each node is an opcode
63 * plus a "next" pointer, possibly plus an operand. "Next" pointers of
64 * all nodes except BRANCH implement concatenation; a "next" pointer with
65 * a BRANCH on both ends of it is connecting two alternatives. (Here we
66 * have one of the subtle syntax dependencies: an individual BRANCH (as
67 * opposed to a collection of them) is never concatenated with anything
68 * because of operator precedence.) The operand of some types of node is
69 * a literal string; for others, it is a node leading into a sub-FSM. In
70 * particular, the operand of a BRANCH node is the first node of the branch.
71 * (NB this is *not* a tree structure: the tail of the branch connects
72 * to the thing following the set of BRANCHes.) The opcodes are:
73 */
74
75/* definition number opnd? meaning */
76#define END 0 /* no End of program. */
77#define BOL 1 /* no Match "" at beginning of line. */
78#define EOL 2 /* no Match "" at end of line. */
79#define ANY 3 /* no Match any one character. */
80#define ANYOF 4 /* str Match any character in this string. */
81#define ANYBUT 5 /* str Match any character not in this string. */
82#define BRANCH 6 /* node Match this alternative, or the next... */
83#define BACK 7 /* no Match "", "next" ptr points backward. */
84#define EXACTLY 8 /* str Match this string. */
85#define NOTHING 9 /* no Match empty string. */
86#define STAR 10 /* node Match this (simple) thing 0 or more times. */
87#define PLUS 11 /* node Match this (simple) thing 1 or more times. */
88#define OPEN 20 /* no Mark this point in input as start of #n. */
89 /* OPEN+1 is number 1, etc. */
90#define CLOSE 30 /* no Analogous to OPEN. */
91
92/*
93 * Opcode notes:
94 *
95 * BRANCH The set of branches constituting a single choice are hooked
96 * together with their "next" pointers, since precedence prevents
97 * anything being concatenated to any individual branch. The
98 * "next" pointer of the last BRANCH in a choice points to the
99 * thing following the whole choice. This is also where the
100 * final "next" pointer of each individual branch points; each
101 * branch starts with the operand node of a BRANCH node.
102 *
103 * BACK Normal "next" pointers all implicitly point forward; BACK
104 * exists to make loop structures possible.
105 *
106 * STAR,PLUS '?', and complex '*' and '+', are implemented as circular
107 * BRANCH structures using BACK. Simple cases (one character
108 * per match) are implemented with STAR and PLUS for speed
109 * and to minimize recursive plunges.
110 *
111 * OPEN,CLOSE ...are numbered at compile time.
112 */
113
114/*
115 * A node is one char of opcode followed by two chars of "next" pointer.
116 * "Next" pointers are stored as two 8-bit pieces, high order first. The
117 * value is a positive offset from the opcode of the node containing it.
118 * An operand, if any, simply follows the node. (Note that much of the
119 * code generation knows about this implicit relationship.)
120 *
121 * Using two bytes for the "next" pointer is vast overkill for most things,
122 * but allows patterns to get big without disasters.
123 */
124#define OP(p) (*(p))
125#define NEXT(p) (((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
126#define OPERAND(p) ((p) + 3)
127
128/*
129 * See regmagic.h for one further detail of program structure.
130 */
131
132
133/*
134 * Utility definitions.
135 */
136#ifndef CHARBITS
137#define UCHARAT(p) ((int)*(unsigned char *)(p))
138#else
139#define UCHARAT(p) ((int)*(p)&CHARBITS)
140#endif
141
142#define FAIL(m) { regerror(m); return(NULL); }
143#define ISMULT(c) ((c) == '*' || (c) == '+' || (c) == '?')
144#define META "^$.[()|?+*\\"
145
146/*
147 * Flags to be passed up and down.
148 */
149#define HASWIDTH 01 /* Known never to match null string. */
150#define SIMPLE 02 /* Simple enough to be STAR/PLUS operand. */
151#define SPSTART 04 /* Starts with * or +. */
152#define WORST 0 /* Worst case. */
153#define STATIC
154/*
155 * Global work variables for regcomp().
156 */
157
158STATIC char *regparse; /* Input-scan pointer. */
159STATIC int regnpar; /* () count. */
160STATIC unsigned char regdummy;
161STATIC unsigned char *regcode; /* Code-emit pointer; &regdummy = don't. */
162STATIC long regsize; /* Code size. */
163
164/*
165 * Forward declarations for regcomp()'s friends.
166 */
167_PROTOTYPE(STATIC unsigned char *reg, (int paren, int *flagp ));
168_PROTOTYPE(STATIC unsigned char *regbranch, (int *flagp ));
169_PROTOTYPE(STATIC unsigned char *regpiece, (int *flagp ));
170_PROTOTYPE(STATIC unsigned char *regatom, (int *flagp ));
171_PROTOTYPE(STATIC unsigned char *regnode, (int op ));
172_PROTOTYPE(STATIC void regc, (int b ));
173_PROTOTYPE(STATIC void reginsert, (int op, unsigned char *opnd ));
174_PROTOTYPE(STATIC void regtail, (unsigned char *p, unsigned char *val ));
175_PROTOTYPE(STATIC void regoptail, (unsigned char *p, unsigned char *val ));
176_PROTOTYPE(STATIC int regtry, (regexp *prog, unsigned char *string ));
177_PROTOTYPE(STATIC int regmatch, (unsigned char *prog ));
178_PROTOTYPE(STATIC int regrepeat, (unsigned char *p ));
179_PROTOTYPE(STATIC unsigned char *regnext, (unsigned char *p ));
180_PROTOTYPE(STATIC unsigned char *regprop, (unsigned char *op ));
181
182#ifdef STRCSPN
183_PROTOTYPE(STATIC int strcspn, (unsigned char *s1, unsigned char *s2 ));
184#endif
185
186/*
187 - regcomp - compile a regular expression into internal code
188 *
189 * We can't allocate space until we know how big the compiled form will be,
190 * but we can't compile it (and thus know how big it is) until we've got a
191 * place to put the code. So we cheat: we compile it twice, once with code
192 * generation turned off and size counting turned on, and once "for real".
193 * This also means that we don't allocate space until we are sure that the
194 * thing really will compile successfully, and we never have to move the
195 * code and thus invalidate pointers into it. (Note that it has to be in
196 * one piece because free() must be able to free it all.)
197 *
198 * Beware that the optimization-preparation code in here knows about some
199 * of the structure of the compiled regexp.
200 */
201regexp *
202regcomp(exp)
203char *exp;
204{
205 register regexp *r;
206 register unsigned char *scan;
207 register unsigned char *longest;
208 register int len;
209 int flags;
210
211 if (exp == NULL)
212 FAIL("NULL argument");
213
214 /* First pass: determine size, legality. */
215 regparse = exp;
216 regnpar = 1;
217 regsize = 0L;
218 regcode = &regdummy;
219 regc(MAGIC);
220 if (reg(0, &flags) == NULL)
221 return(NULL);
222
223 /* Small enough for pointer-storage convention? */
224 if (regsize >= 32767L) /* Probably could be 65535L. */
225 FAIL("regexp too big");
226
227 /* Allocate space. */
228 r = (regexp *)malloc(sizeof(regexp) + (unsigned)regsize);
229 if (r == NULL)
230 FAIL("out of space");
231
232 /* Second pass: emit code. */
233 regparse = exp;
234 regnpar = 1;
235 regcode = r->program;
236 regc(MAGIC);
237 if (reg(0, &flags) == NULL)
238 return(NULL);
239
240 /* Dig out information for optimizations. */
241 r->regstart = '\0'; /* Worst-case defaults. */
242 r->reganch = 0;
243 r->regmust = NULL;
244 r->regmlen = 0;
245 scan = r->program+1; /* First BRANCH. */
246 if (OP(regnext(scan)) == END) { /* Only one top-level choice. */
247 scan = OPERAND(scan);
248
249 /* Starting-point info. */
250 if (OP(scan) == EXACTLY)
251 r->regstart = *OPERAND(scan);
252 else if (OP(scan) == BOL)
253 r->reganch++;
254
255 /*
256 * If there's something expensive in the r.e., find the
257 * longest literal string that must appear and make it the
258 * regmust. Resolve ties in favor of later strings, since
259 * the regstart check works with the beginning of the r.e.
260 * and avoiding duplication strengthens checking. Not a
261 * strong reason, but sufficient in the absence of others.
262 */
263 if (flags&SPSTART) {
264 longest = NULL;
265 len = 0;
266 for (; scan != NULL; scan = regnext(scan))
267 if (OP(scan) == EXACTLY
268 && strlen((char *)OPERAND(scan)) >= len) {
269 longest = OPERAND(scan);
270 len = strlen((char *)OPERAND(scan));
271 }
272 r->regmust = longest;
273 r->regmlen = len;
274 }
275 }
276
277 return(r);
278}
279
280/*
281 - reg - regular expression, i.e. main body or parenthesized thing
282 *
283 * Caller must absorb opening parenthesis.
284 *
285 * Combining parenthesis handling with the base level of regular expression
286 * is a trifle forced, but the need to tie the tails of the branches to what
287 * follows makes it hard to avoid.
288 */
289STATIC unsigned char *
290reg(paren, flagp)
291int paren; /* Parenthesized? */
292int *flagp;
293{
294 register unsigned char *ret;
295 register unsigned char *br;
296 register unsigned char *ender;
297 register int parno;
298 int flags;
299
300 *flagp = HASWIDTH; /* Tentatively. */
301
302 /* Make an OPEN node, if parenthesized. */
303 if (paren) {
304 if (regnpar >= NSUBEXP)
305 FAIL("too many ()");
306 parno = regnpar;
307 regnpar++;
308 ret = regnode(OPEN+parno);
309 } else
310 ret = NULL;
311
312 /* Pick up the branches, linking them together. */
313 br = regbranch(&flags);
314 if (br == NULL)
315 return(NULL);
316 if (ret != NULL)
317 regtail(ret, br); /* OPEN -> first. */
318 else
319 ret = br;
320 if (!(flags&HASWIDTH))
321 *flagp &= ~HASWIDTH;
322 *flagp |= flags&SPSTART;
323 while (*regparse == '|') {
324 regparse++;
325 br = regbranch(&flags);
326 if (br == NULL)
327 return(NULL);
328 regtail(ret, br); /* BRANCH -> BRANCH. */
329 if (!(flags&HASWIDTH))
330 *flagp &= ~HASWIDTH;
331 *flagp |= flags&SPSTART;
332 }
333
334 /* Make a closing node, and hook it on the end. */
335 ender = regnode((paren) ? CLOSE+parno : END);
336 regtail(ret, ender);
337
338 /* Hook the tails of the branches to the closing node. */
339 for (br = ret; br != NULL; br = regnext(br))
340 regoptail(br, ender);
341
342 /* Check for proper termination. */
343 if (paren && *regparse++ != ')') {
344 FAIL("unmatched ()");
345 } else if (!paren && *regparse != '\0') {
346 if (*regparse == ')') {
347 FAIL("unmatched ()");
348 } else
349 FAIL("junk on end"); /* "Can't happen". */
350 /* NOTREACHED */
351 }
352
353 return(ret);
354}
355
356/*
357 - regbranch - one alternative of an | operator
358 *
359 * Implements the concatenation operator.
360 */
361STATIC unsigned char *
362regbranch(flagp)
363int *flagp;
364{
365 register unsigned char *ret;
366 register unsigned char *chain;
367 register unsigned char *latest;
368 int flags;
369
370 *flagp = WORST; /* Tentatively. */
371
372 ret = regnode(BRANCH);
373 chain = NULL;
374 while (*regparse != '\0' && *regparse != '|' && *regparse != ')') {
375 latest = regpiece(&flags);
376 if (latest == NULL)
377 return(NULL);
378 *flagp |= flags&HASWIDTH;
379 if (chain == NULL) /* First piece. */
380 *flagp |= flags&SPSTART;
381 else
382 regtail(chain, latest);
383 chain = latest;
384 }
385 if (chain == NULL) /* Loop ran zero times. */
386 (void) regnode(NOTHING);
387
388 return(ret);
389}
390
391/*
392 - regpiece - something followed by possible [*+?]
393 *
394 * Note that the branching code sequences used for ? and the general cases
395 * of * and + are somewhat optimized: they use the same NOTHING node as
396 * both the endmarker for their branch list and the body of the last branch.
397 * It might seem that this node could be dispensed with entirely, but the
398 * endmarker role is not redundant.
399 */
400STATIC unsigned char *
401regpiece(flagp)
402int *flagp;
403{
404 register unsigned char *ret;
405 register unsigned char op;
406 register unsigned char *next;
407 int flags;
408
409 ret = regatom(&flags);
410 if (ret == NULL)
411 return(NULL);
412
413 op = *regparse;
414 if (!ISMULT(op)) {
415 *flagp = flags;
416 return(ret);
417 }
418
419 if (!(flags&HASWIDTH) && op != '?')
420 FAIL("*+ operand could be empty");
421 *flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
422
423 if (op == '*' && (flags&SIMPLE))
424 reginsert(STAR, ret);
425 else if (op == '*') {
426 /* Emit x* as (x&|), where & means "self". */
427 reginsert(BRANCH, ret); /* Either x */
428 regoptail(ret, regnode(BACK)); /* and loop */
429 regoptail(ret, ret); /* back */
430 regtail(ret, regnode(BRANCH)); /* or */
431 regtail(ret, regnode(NOTHING)); /* null. */
432 } else if (op == '+' && (flags&SIMPLE))
433 reginsert(PLUS, ret);
434 else if (op == '+') {
435 /* Emit x+ as x(&|), where & means "self". */
436 next = regnode(BRANCH); /* Either */
437 regtail(ret, next);
438 regtail(regnode(BACK), ret); /* loop back */
439 regtail(next, regnode(BRANCH)); /* or */
440 regtail(ret, regnode(NOTHING)); /* null. */
441 } else if (op == '?') {
442 /* Emit x? as (x|) */
443 reginsert(BRANCH, ret); /* Either x */
444 regtail(ret, regnode(BRANCH)); /* or */
445 next = regnode(NOTHING); /* null. */
446 regtail(ret, next);
447 regoptail(ret, next);
448 }
449 regparse++;
450 if (ISMULT(*regparse))
451 FAIL("nested *?+");
452
453 return(ret);
454}
455
456/*
457 - regatom - the lowest level
458 *
459 * Optimization: gobbles an entire sequence of ordinary characters so that
460 * it can turn them into a single node, which is smaller to store and
461 * faster to run. Backslashed characters are exceptions, each becoming a
462 * separate node; the code is simpler that way and it's not worth fixing.
463 */
464STATIC unsigned char *
465regatom(flagp)
466int *flagp;
467{
468 register unsigned char *ret;
469 int flags;
470
471 *flagp = WORST; /* Tentatively. */
472
473 switch (*regparse++) {
474 case '^':
475 ret = regnode(BOL);
476 break;
477 case '$':
478 ret = regnode(EOL);
479 break;
480 case '.':
481 ret = regnode(ANY);
482 *flagp |= HASWIDTH|SIMPLE;
483 break;
484 case '[': {
485 register int class;
486 register int classend;
487
488 if (*regparse == '^') { /* Complement of range. */
489 ret = regnode(ANYBUT);
490 regparse++;
491 } else
492 ret = regnode(ANYOF);
493 if (*regparse == ']' || *regparse == '-')
494 regc(*regparse++);
495 while (*regparse != '\0' && *regparse != ']') {
496 if (*regparse == '-') {
497 regparse++;
498 if (*regparse == ']' || *regparse == '\0')
499 regc('-');
500 else {
501 class = UCHARAT(regparse-2)+1;
502 classend = UCHARAT(regparse);
503 if (class > classend+1)
504 FAIL("invalid [] range");
505 for (; class <= classend; class++)
506 regc(class);
507 regparse++;
508 }
509 } else
510 regc(*regparse++);
511 }
512 regc('\0');
513 if (*regparse != ']')
514 FAIL("unmatched []");
515 regparse++;
516 *flagp |= HASWIDTH|SIMPLE;
517 }
518 break;
519 case '(':
520 ret = reg(1, &flags);
521 if (ret == NULL)
522 return(NULL);
523 *flagp |= flags&(HASWIDTH|SPSTART);
524 break;
525 case '\0':
526 case '|':
527 case ')':
528 FAIL("internal urp"); /* Supposed to be caught earlier. */
529 break;
530 case '?':
531 case '+':
532 case '*':
533 FAIL("?+* follows nothing");
534 break;
535 case '\\':
536 if (*regparse == '\0')
537 FAIL("trailing \\");
538 ret = regnode(EXACTLY);
539 regc(*regparse++);
540 regc('\0');
541 *flagp |= HASWIDTH|SIMPLE;
542 break;
543 default: {
544 register int len;
545 register unsigned char ender;
546
547 regparse--;
548#ifdef STRCSPN
549 len = strcspn(regparse, (unsigned char *)META);
550#else
551 len = strcspn((char *)regparse, META);
552#endif
553 if (len <= 0)
554 FAIL("internal disaster");
555 ender = *(regparse+len);
556 if (len > 1 && ISMULT(ender))
557 len--; /* Back off clear of ?+* operand. */
558 *flagp |= HASWIDTH;
559 if (len == 1)
560 *flagp |= SIMPLE;
561 ret = regnode(EXACTLY);
562 while (len > 0) {
563 regc(*regparse++);
564 len--;
565 }
566 regc('\0');
567 }
568 break;
569 }
570
571 return(ret);
572}
573
574/*
575 - regnode - emit a node
576 */
577STATIC unsigned char * /* Location. */
578regnode(iop)
579int iop;
580{
581 register unsigned char *ret;
582 register unsigned char *ptr;
583 unsigned char op;
584
585 op = (unsigned char) iop;
586 ret = regcode;
587 if (ret == &regdummy) {
588 regsize += 3;
589 return(ret);
590 }
591
592 ptr = ret;
593 *ptr++ = op;
594 *ptr++ = '\0'; /* Null "next" pointer. */
595 *ptr++ = '\0';
596 regcode = ptr;
597
598 return(ret);
599}
600
601/*
602 - regc - emit (if appropriate) a byte of code
603 */
604STATIC void
605regc(ib)
606int ib;
607{
608 unsigned char b;
609
610 b = (unsigned char) ib;
611 if (regcode != &regdummy)
612 *regcode++ = b;
613 else
614 regsize++;
615}
616
617/*
618 - reginsert - insert an operator in front of already-emitted operand
619 *
620 * Means relocating the operand.
621 */
622STATIC void
623reginsert(iop, opnd)
624int iop;
625unsigned char *opnd;
626{
627 register unsigned char *src;
628 register unsigned char *dst;
629 register unsigned char *place;
630 unsigned char op;
631
632 op = (unsigned char) iop;
633 if (regcode == &regdummy) {
634 regsize += 3;
635 return;
636 }
637
638 src = regcode;
639 regcode += 3;
640 dst = regcode;
641 while (src > opnd)
642 *--dst = *--src;
643
644 place = opnd; /* Op node, where operand used to be. */
645 *place++ = op;
646 *place++ = '\0';
647 *place++ = '\0';
648}
649
650/*
651 - regtail - set the next-pointer at the end of a node chain
652 */
653STATIC void
654regtail(p, val)
655unsigned char *p;
656unsigned char *val;
657{
658 register unsigned char *scan;
659 register unsigned char *temp;
660 register int offset;
661
662 if (p == &regdummy)
663 return;
664
665 /* Find last node. */
666 scan = p;
667 for (;;) {
668 temp = regnext(scan);
669 if (temp == NULL)
670 break;
671 scan = temp;
672 }
673
674 if (OP(scan) == BACK)
675 offset = scan - val;
676 else
677 offset = val - scan;
678 *(scan+1) = (offset>>8)&0377;
679 *(scan+2) = offset&0377;
680}
681
682/*
683 - regoptail - regtail on operand of first argument; nop if operandless
684 */
685STATIC void
686regoptail(p, val)
687unsigned char *p;
688unsigned char *val;
689{
690 /* "Operandless" and "op != BRANCH" are synonymous in practice. */
691 if (p == NULL || p == &regdummy || OP(p) != BRANCH)
692 return;
693 regtail(OPERAND(p), val);
694}
695
696/*
697 * regexec and friends
698 */
699
700/*
701 * Global work variables for regexec().
702 */
703STATIC unsigned char *reginput; /* String-input pointer. */
704STATIC unsigned char *regbol; /* Beginning of input, for ^ check. */
705STATIC unsigned char **regstartp; /* Pointer to startp array. */
706STATIC unsigned char **regendp; /* Ditto for endp. */
707
708#ifdef DEBUG
709int regnarrate = 0;
710void regdump();
711STATIC unsigned char *regprop();
712#endif
713
714/*
715 - regexec - match a regexp against a string
716 */
717int
718regexec(prog, string)
719register regexp *prog;
720register unsigned char *string;
721{
722 register unsigned char *s;
723#ifndef STDLIB
724 extern char *strchr();
725#endif
726
727 /* Be paranoid... */
728 if (prog == NULL || string == NULL) {
729 regerror("NULL parameter");
730 return(0);
731 }
732
733 /* Check validity of program. */
734 if (UCHARAT(prog->program) != MAGIC) {
735 regerror("corrupted program");
736 return(0);
737 }
738
739 /* If there is a "must appear" string, look for it. */
740 if (prog->regmust != NULL) {
741 s = string;
742 while ((s = (unsigned char *)strchr((char *)s,prog->regmust[0]))
743 != NULL) {
744 if (strncmp((char *)s, (char *)prog->regmust,
745 prog->regmlen)
746 == 0)
747 break; /* Found it. */
748 s++;
749 }
750 if (s == NULL) /* Not present. */
751 return(0);
752 }
753
754 /* Mark beginning of line for ^ . */
755 regbol = string;
756
757 /* Simplest case: anchored match need be tried only once. */
758 if (prog->reganch)
759 return(regtry(prog, string));
760
761 /* Messy cases: unanchored match. */
762 s = string;
763 if (prog->regstart != '\0')
764 /* We know what char it must start with. */
765 while ((s = (unsigned char *)strchr((char *)s, prog->regstart))
766 != NULL) {
767 if (regtry(prog, s))
768 return(1);
769 s++;
770 }
771 else
772 /* We don't -- general case. */
773 do {
774 if (regtry(prog, s))
775 return(1);
776 } while (*s++ != '\0');
777
778 /* Failure. */
779 return(0);
780}
781
782/*
783 - regtry - try match at specific point
784 */
785STATIC int /* 0 failure, 1 success */
786regtry(prog, string)
787regexp *prog;
788unsigned char *string;
789{
790 register int i;
791 register unsigned char **sp;
792 register unsigned char **ep;
793
794 reginput = string;
795 regstartp = prog->startp;
796 regendp = prog->endp;
797
798 sp = prog->startp;
799 ep = prog->endp;
800 for (i = NSUBEXP; i > 0; i--) {
801 *sp++ = NULL;
802 *ep++ = NULL;
803 }
804 if (regmatch(prog->program + 1)) {
805 prog->startp[0] = string;
806 prog->endp[0] = reginput;
807 return(1);
808 } else
809 return(0);
810}
811
812/*
813 - regmatch - main matching routine
814 *
815 * Conceptually the strategy is simple: check to see whether the current
816 * node matches, call self recursively to see whether the rest matches,
817 * and then act accordingly. In practice we make some effort to avoid
818 * recursion, in particular by going through "ordinary" nodes (that don't
819 * need to know whether the rest of the match failed) by a loop instead of
820 * by recursion.
821 */
822STATIC int /* 0 failure, 1 success */
823regmatch(prog)
824unsigned char *prog;
825{
826 register unsigned char *scan; /* Current node. */
827 unsigned char *next; /* Next node. */
828#ifndef STDLIB
829 extern char *strchr();
830#endif
831
832 scan = prog;
833#ifdef DEBUG
834 if (scan != NULL && regnarrate)
835 fprintf(stderr, "%s(\n", regprop(scan));
836#endif
837 while (scan != NULL) {
838#ifdef DEBUG
839 if (regnarrate)
840 fprintf(stderr, "%s...\n", regprop(scan));
841#endif
842 next = regnext(scan);
843
844 switch (OP(scan)) {
845 case BOL:
846 if (reginput != regbol)
847 return(0);
848 break;
849 case EOL:
850 if (*reginput != '\0')
851 return(0);
852 break;
853 case ANY:
854 if (*reginput == '\0')
855 return(0);
856 reginput++;
857 break;
858 case EXACTLY: {
859 register int len;
860 register unsigned char *opnd;
861
862 opnd = OPERAND(scan);
863 /* Inline the first character, for speed. */
864 if (*opnd != *reginput)
865 return(0);
866 len = strlen((char *)opnd);
867 if (len > 1 && strncmp((char *)opnd,
868 (char *)reginput, len)
869 != 0)
870 return(0);
871 reginput += len;
872 }
873 break;
874 case ANYOF:
875 if (*reginput == '\0'
876 || strchr((char *)OPERAND(scan), *reginput) == NULL)
877 return(0);
878 reginput++;
879 break;
880 case ANYBUT:
881 if (*reginput == '\0'
882 || strchr((char *)OPERAND(scan), *reginput) != NULL)
883 return(0);
884 reginput++;
885 break;
886 case NOTHING:
887 break;
888 case BACK:
889 break;
890 case OPEN+1:
891 case OPEN+2:
892 case OPEN+3:
893 case OPEN+4:
894 case OPEN+5:
895 case OPEN+6:
896 case OPEN+7:
897 case OPEN+8:
898 case OPEN+9: {
899 register int no;
900 register unsigned char *save;
901
902 no = OP(scan) - OPEN;
903 save = reginput;
904
905 if (regmatch(next)) {
906 /*
907 * Don't set startp if some later
908 * invocation of the same parentheses
909 * already has.
910 */
911 if (regstartp[no] == NULL)
912 regstartp[no] = save;
913 return(1);
914 } else
915 return(0);
916 }
917 break;
918 case CLOSE+1:
919 case CLOSE+2:
920 case CLOSE+3:
921 case CLOSE+4:
922 case CLOSE+5:
923 case CLOSE+6:
924 case CLOSE+7:
925 case CLOSE+8:
926 case CLOSE+9: {
927 register int no;
928 register unsigned char *save;
929
930 no = OP(scan) - CLOSE;
931 save = reginput;
932
933 if (regmatch(next)) {
934 /*
935 * Don't set endp if some later
936 * invocation of the same parentheses
937 * already has.
938 */
939 if (regendp[no] == NULL)
940 regendp[no] = save;
941 return(1);
942 } else
943 return(0);
944 }
945 break;
946 case BRANCH: {
947 register unsigned char *save;
948
949 if (OP(next) != BRANCH) /* No choice. */
950 next = OPERAND(scan); /* Avoid recursion. */
951 else {
952 do {
953 save = reginput;
954 if (regmatch(OPERAND(scan)))
955 return(1);
956 reginput = save;
957 scan = regnext(scan);
958 } while (scan != NULL && OP(scan) == BRANCH);
959 return(0);
960 /* NOTREACHED */
961 }
962 }
963 break;
964 case STAR:
965 case PLUS: {
966 register unsigned char nextch;
967 register int no;
968 register unsigned char *save;
969 register int min;
970
971 /*
972 * Lookahead to avoid useless match attempts
973 * when we know what character comes next.
974 */
975 nextch = '\0';
976 if (OP(next) == EXACTLY)
977 nextch = *OPERAND(next);
978 min = (OP(scan) == STAR) ? 0 : 1;
979 save = reginput;
980 no = regrepeat(OPERAND(scan));
981 while (no >= min) {
982 /* If it could work, try it. */
983 if (nextch == '\0' || *reginput == nextch)
984 if (regmatch(next))
985 return(1);
986 /* Couldn't or didn't -- back up. */
987 no--;
988 reginput = save + no;
989 }
990 return(0);
991 }
992 break;
993 case END:
994 return(1); /* Success! */
995 break;
996 default:
997 regerror("memory corruption");
998 return(0);
999 break;
1000 }
1001
1002 scan = next;
1003 }
1004
1005 /*
1006 * We get here only if there's trouble -- normally "case END" is
1007 * the terminating point.
1008 */
1009 regerror("corrupted pointers");
1010 return(0);
1011}
1012
1013/*
1014 - regrepeat - repeatedly match something simple, report how many
1015 */
1016STATIC int
1017regrepeat(p)
1018unsigned char *p;
1019{
1020 register int count = 0;
1021 register unsigned char *scan;
1022 register unsigned char *opnd;
1023
1024 scan = reginput;
1025 opnd = OPERAND(p);
1026 switch (OP(p)) {
1027 case ANY:
1028 count = strlen((char *)scan);
1029 scan += count;
1030 break;
1031 case EXACTLY:
1032 while (*opnd == *scan) {
1033 count++;
1034 scan++;
1035 }
1036 break;
1037 case ANYOF:
1038 while (*scan != '\0' && strchr((char *)opnd, *scan) != NULL) {
1039 count++;
1040 scan++;
1041 }
1042 break;
1043 case ANYBUT:
1044 while (*scan != '\0' && strchr((char *)opnd, *scan) == NULL) {
1045 count++;
1046 scan++;
1047 }
1048 break;
1049 default: /* Oh dear. Called inappropriately. */
1050 regerror("internal foulup");
1051 count = 0; /* Best compromise. */
1052 break;
1053 }
1054 reginput = scan;
1055
1056 return(count);
1057}
1058
1059/*
1060 - regnext - dig the "next" pointer out of a node
1061 */
1062STATIC unsigned char *
1063regnext(p)
1064register unsigned char *p;
1065{
1066 register int offset;
1067
1068 if (p == &regdummy)
1069 return(NULL);
1070
1071 offset = NEXT(p);
1072 if (offset == 0)
1073 return(NULL);
1074
1075 if (OP(p) == BACK)
1076 return(p-offset);
1077 else
1078 return(p+offset);
1079}
1080
1081#ifdef DEBUG
1082
1083STATIC unsigned char *regprop();
1084
1085/*
1086 - regdump - dump a regexp onto stdout in vaguely comprehensible form
1087 */
1088void
1089regdump(r)
1090regexp *r;
1091{
1092 register unsigned char *s;
1093 register unsigned char op = EXACTLY; /* Arbitrary non-END op. */
1094 register unsigned char *next;
1095 extern char *strchr();
1096
1097
1098 s = r->program + 1;
1099 while (op != END) { /* While that wasn't END last time... */
1100 op = OP(s);
1101 printf("%2d%s", s-r->program, regprop(s)); /* Where, what. */
1102 next = regnext(s);
1103 if (next == NULL) /* Next ptr. */
1104 printf("(0)");
1105 else
1106 printf("(%d)", (s-r->program)+(next-s));
1107 s += 3;
1108 if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
1109 /* Literal string, where present. */
1110 while (*s != '\0') {
1111 putchar(*s);
1112 s++;
1113 }
1114 s++;
1115 }
1116 putchar('\n');
1117 }
1118
1119 /* Header fields of interest. */
1120 if (r->regstart != '\0')
1121 printf("start `%c' ", r->regstart);
1122 if (r->reganch)
1123 printf("anchored ");
1124 if (r->regmust != NULL)
1125 printf("must have \"%s\"", r->regmust);
1126 printf("\n");
1127}
1128
1129/*
1130 - regprop - printable representation of opcode
1131 */
1132STATIC unsigned char *
1133regprop(op)
1134unsigned char *op;
1135{
1136 register unsigned char *p;
1137 STATIC unsigned char buf[50];
1138
1139 (void) strcpy(buf, ":");
1140
1141 switch (OP(op)) {
1142 case BOL:
1143 p = "BOL";
1144 break;
1145 case EOL:
1146 p = "EOL";
1147 break;
1148 case ANY:
1149 p = "ANY";
1150 break;
1151 case ANYOF:
1152 p = "ANYOF";
1153 break;
1154 case ANYBUT:
1155 p = "ANYBUT";
1156 break;
1157 case BRANCH:
1158 p = "BRANCH";
1159 break;
1160 case EXACTLY:
1161 p = "EXACTLY";
1162 break;
1163 case NOTHING:
1164 p = "NOTHING";
1165 break;
1166 case BACK:
1167 p = "BACK";
1168 break;
1169 case END:
1170 p = "END";
1171 break;
1172 case OPEN+1:
1173 case OPEN+2:
1174 case OPEN+3:
1175 case OPEN+4:
1176 case OPEN+5:
1177 case OPEN+6:
1178 case OPEN+7:
1179 case OPEN+8:
1180 case OPEN+9:
1181 sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
1182 p = NULL;
1183 break;
1184 case CLOSE+1:
1185 case CLOSE+2:
1186 case CLOSE+3:
1187 case CLOSE+4:
1188 case CLOSE+5:
1189 case CLOSE+6:
1190 case CLOSE+7:
1191 case CLOSE+8:
1192 case CLOSE+9:
1193 sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
1194 p = NULL;
1195 break;
1196 case STAR:
1197 p = "STAR";
1198 break;
1199 case PLUS:
1200 p = "PLUS";
1201 break;
1202 default:
1203 regerror("corrupted opcode");
1204 break;
1205 }
1206 if (p != NULL)
1207 (void) strcat(buf, p);
1208 return(buf);
1209}
1210#endif
1211
1212/*
1213 * The following is provided for those people who do not have strcspn() in
1214 * their C libraries. They should get off their butts and do something
1215 * about it; at least one public-domain implementation of those (highly
1216 * useful) string routines has been published on Usenet.
1217 */
1218#ifdef STRCSPN
1219/*
1220 * strcspn - find length of initial segment of s1 consisting entirely
1221 * of characters not from s2
1222 */
1223
1224STATIC int
1225strcspn(s1, s2)
1226unsigned char *s1;
1227unsigned char *s2;
1228{
1229 register unsigned char *scan1;
1230 register unsigned char *scan2;
1231 register int count;
1232
1233 count = 0;
1234 for (scan1 = s1; *scan1 != '\0'; scan1++) {
1235 for (scan2 = s2; *scan2 != '\0';) /* ++ moved down. */
1236 if (*scan1 == *scan2++)
1237 return(count);
1238 count++;
1239 }
1240 return(count);
1241}
1242#endif
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