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source: downloads/boost_1_33_1/tools/build/jam_src/regexp.c @ 12

Last change on this file since 12 was 12, checked in by landauf, 17 years ago
added boost
File size: 31.1 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	*** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
21	*** hoptoad!gnu, on 27 Dec 1986, to add \n as an alternative to \|
22	*** to assist in implementing egrep.
23	*** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
24	*** hoptoad!gnu, on 27 Dec 1986, to add \< and \> for word-matching
25	*** as in BSD grep and ex.
26	*** THIS IS AN ALTERED VERSION. It was altered by John Gilmore,
27	*** hoptoad!gnu, on 28 Dec 1986, to optimize characters quoted with \.
28	*** THIS IS AN ALTERED VERSION. It was altered by James A. Woods,
29	*** ames!jaw, on 19 June 1987, to quash a regcomp() redundancy.
30	*** THIS IS AN ALTERED VERSION. It was altered by Christopher Seiwald
31	*** seiwald@vix.com, on 28 August 1993, for use in jam. Regmagic.h
32	*** was moved into regexp.h, and the include of regexp.h now uses "'s
33	*** to avoid conflicting with the system regexp.h. Const, bless its
34	*** soul, was removed so it can compile everywhere. The declaration
35	*** of strchr() was in conflict on AIX, so it was removed (as it is
36	*** happily defined in string.h).
37	*** THIS IS AN ALTERED VERSION. It was altered by Christopher Seiwald
38	*** seiwald@perforce.com, on 20 January 2000, to use function prototypes.
39	*
40	* Beware that some of this code is subtly aware of the way operator
41	* precedence is structured in regular expressions. Serious changes in
42	* regular-expression syntax might require a total rethink.
43	*/
44	#include "regexp.h"
45	#include <stdio.h>
46	#include <ctype.h>
47	#ifndef ultrix
48	#include <stdlib.h>
49	#endif
50	#include <string.h>
51
52	/*
53	* The "internal use only" fields in regexp.h are present to pass info from
54	* compile to execute that permits the execute phase to run lots faster on
55	* simple cases. They are:
56	*
57	* regstart char that must begin a match; '\0' if none obvious
58	* reganch is the match anchored (at beginning-of-line only)?
59	* regmust string (pointer into program) that match must include, or NULL
60	* regmlen length of regmust string
61	*
62	* Regstart and reganch permit very fast decisions on suitable starting points
63	* for a match, cutting down the work a lot. Regmust permits fast rejection
64	* of lines that cannot possibly match. The regmust tests are costly enough
65	* that regcomp() supplies a regmust only if the r.e. contains something
66	* potentially expensive (at present, the only such thing detected is * or +
67	* at the start of the r.e., which can involve a lot of backup). Regmlen is
68	* supplied because the test in regexec() needs it and regcomp() is computing
69	* it anyway.
70	*/
71
72	/*
73	* Structure for regexp "program". This is essentially a linear encoding
74	* of a nondeterministic finite-state machine (aka syntax charts or
75	* "railroad normal form" in parsing technology). Each node is an opcode
76	* plus a "next" pointer, possibly plus an operand. "Next" pointers of
77	* all nodes except BRANCH implement concatenation; a "next" pointer with
78	* a BRANCH on both ends of it is connecting two alternatives. (Here we
79	* have one of the subtle syntax dependencies: an individual BRANCH (as
80	* opposed to a collection of them) is never concatenated with anything
81	* because of operator precedence.) The operand of some types of node is
82	* a literal string; for others, it is a node leading into a sub-FSM. In
83	* particular, the operand of a BRANCH node is the first node of the branch.
84	* (NB this is not a tree structure: the tail of the branch connects
85	* to the thing following the set of BRANCHes.) The opcodes are:
86	*/
87
88	/* definition number opnd? meaning */
89	#define END 0 /* no End of program. */
90	#define BOL 1 /* no Match "" at beginning of line. */
91	#define EOL 2 /* no Match "" at end of line. */
92	#define ANY 3 /* no Match any one character. */
93	#define ANYOF 4 /* str Match any character in this string. */
94	#define ANYBUT 5 /* str Match any character not in this string. */
95	#define BRANCH 6 /* node Match this alternative, or the next... */
96	#define BACK 7 /* no Match "", "next" ptr points backward. */
97	#define EXACTLY 8 /* str Match this string. */
98	#define NOTHING 9 /* no Match empty string. */
99	#define STAR 10 /* node Match this (simple) thing 0 or more times. */
100	#define PLUS 11 /* node Match this (simple) thing 1 or more times. */
101	#define WORDA 12 /* no Match "" at wordchar, where prev is nonword */
102	#define WORDZ 13 /* no Match "" at nonwordchar, where prev is word */
103	#define OPEN 20 /* no Mark this point in input as start of #n. */
104	/* OPEN+1 is number 1, etc. */
105	#define CLOSE 30 /* no Analogous to OPEN. */
106
107	/*
108	* Opcode notes:
109	*
110	* BRANCH The set of branches constituting a single choice are hooked
111	* together with their "next" pointers, since precedence prevents
112	* anything being concatenated to any individual branch. The
113	* "next" pointer of the last BRANCH in a choice points to the
114	* thing following the whole choice. This is also where the
115	* final "next" pointer of each individual branch points; each
116	* branch starts with the operand node of a BRANCH node.
117	*
118	* BACK Normal "next" pointers all implicitly point forward; BACK
119	* exists to make loop structures possible.
120	*
121	* STAR,PLUS '?', and complex '*' and '+', are implemented as circular
122	* BRANCH structures using BACK. Simple cases (one character
123	* per match) are implemented with STAR and PLUS for speed
124	* and to minimize recursive plunges.
125	*
126	* OPEN,CLOSE ...are numbered at compile time.
127	*/
128
129	/*
130	* A node is one char of opcode followed by two chars of "next" pointer.
131	* "Next" pointers are stored as two 8-bit pieces, high order first. The
132	* value is a positive offset from the opcode of the node containing it.
133	* An operand, if any, simply follows the node. (Note that much of the
134	* code generation knows about this implicit relationship.)
135	*
136	* Using two bytes for the "next" pointer is vast overkill for most things,
137	* but allows patterns to get big without disasters.
138	*/
139	#define OP(p) (*(p))
140	#define NEXT(p) (((((p)+1)&0377)<<8) + (((p)+2)&0377))
141	#define OPERAND(p) ((p) + 3)
142
143	/*
144	* See regmagic.h for one further detail of program structure.
145	*/
146
147
148	/*
149	* Utility definitions.
150	*/
151	#ifndef CHARBITS
152	#define UCHARAT(p) ((int)(unsigned char )(p))
153	#else
154	#define UCHARAT(p) ((int)*(p)&CHARBITS)
155	#endif
156
157	#define FAIL(m) { regerror(m); return(NULL); }
158	#define ISMULT(c) ((c) == '*' \|\| (c) == '+' \|\| (c) == '?')
159
160	/*
161	* Flags to be passed up and down.
162	*/
163	#define HASWIDTH 01 /* Known never to match null string. */
164	#define SIMPLE 02 /* Simple enough to be STAR/PLUS operand. */
165	#define SPSTART 04 /* Starts with * or +. */
166	#define WORST 0 /* Worst case. */
167
168	/*
169	* Global work variables for regcomp().
170	*/
171	static char regparse; / Input-scan pointer. */
172	static int regnpar; /* () count. */
173	static char regdummy;
174	static char regcode; / Code-emit pointer; &regdummy = don't. */
175	static long regsize; /* Code size. */
176
177	/*
178	* Forward declarations for regcomp()'s friends.
179	*/
180	#ifndef STATIC
181	#define STATIC static
182	#endif
183	STATIC char reg( int paren, int flagp );
184	STATIC char regbranch( int flagp );
185	STATIC char regpiece( int flagp );
186	STATIC char regatom( int flagp );
187	STATIC char *regnode( int op );
188	STATIC char regnext( register char p );
189	STATIC void regc( int b );
190	STATIC void reginsert( char op, char *opnd );
191	STATIC void regtail( char p, char val );
192	STATIC void regoptail( char p, char val );
193	#ifdef STRCSPN
194	STATIC int strcspn();
195	#endif
196
197	/*
198	- regcomp - compile a regular expression into internal code
199	*
200	* We can't allocate space until we know how big the compiled form will be,
201	* but we can't compile it (and thus know how big it is) until we've got a
202	* place to put the code. So we cheat: we compile it twice, once with code
203	* generation turned off and size counting turned on, and once "for real".
204	* This also means that we don't allocate space until we are sure that the
205	* thing really will compile successfully, and we never have to move the
206	* code and thus invalidate pointers into it. (Note that it has to be in
207	* one piece because free() must be able to free it all.)
208	*
209	* Beware that the optimization-preparation code in here knows about some
210	* of the structure of the compiled regexp.
211	*/
212	regexp *
213	regcomp( char *exp )
214	{
215	register regexp *r;
216	register char *scan;
217	register char *longest;
218	register unsigned len;
219	int flags;
220
221	if (exp == NULL)
222	FAIL("NULL argument");
223
224	/* First pass: determine size, legality. */
225	#ifdef notdef
226	if (exp[0] == '.' && exp[1] == '') exp += 2; / aid grep */
227	#endif
228	regparse = (char *)exp;
229	regnpar = 1;
230	regsize = 0L;
231	regcode = &regdummy;
232	regc(MAGIC);
233	if (reg(0, &flags) == NULL)
234	return(NULL);
235
236	/* Small enough for pointer-storage convention? */
237	if (regsize >= 32767L) /* Probably could be 65535L. */
238	FAIL("regexp too big");
239
240	/* Allocate space. */
241	r = (regexp *)malloc(sizeof(regexp) + (unsigned)regsize);
242	if (r == NULL)
243	FAIL("out of space");
244
245	/* Second pass: emit code. */
246	regparse = (char *)exp;
247	regnpar = 1;
248	regcode = r->program;
249	regc(MAGIC);
250	if (reg(0, &flags) == NULL)
251	return(NULL);
252
253	/* Dig out information for optimizations. */
254	r->regstart = '\0'; /* Worst-case defaults. */
255	r->reganch = 0;
256	r->regmust = NULL;
257	r->regmlen = 0;
258	scan = r->program+1; /* First BRANCH. */
259	if (OP(regnext(scan)) == END) { /* Only one top-level choice. */
260	scan = OPERAND(scan);
261
262	/* Starting-point info. */
263	if (OP(scan) == EXACTLY)
264	r->regstart = *OPERAND(scan);
265	else if (OP(scan) == BOL)
266	r->reganch++;
267
268	/*
269	* If there's something expensive in the r.e., find the
270	* longest literal string that must appear and make it the
271	* regmust. Resolve ties in favor of later strings, since
272	* the regstart check works with the beginning of the r.e.
273	* and avoiding duplication strengthens checking. Not a
274	* strong reason, but sufficient in the absence of others.
275	*/
276	if (flags&SPSTART) {
277	longest = NULL;
278	len = 0;
279	for (; scan != NULL; scan = regnext(scan))
280	if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
281	longest = OPERAND(scan);
282	len = strlen(OPERAND(scan));
283	}
284	r->regmust = longest;
285	r->regmlen = len;
286	}
287	}
288
289	return(r);
290	}
291
292	/*
293	- reg - regular expression, i.e. main body or parenthesized thing
294	*
295	* Caller must absorb opening parenthesis.
296	*
297	* Combining parenthesis handling with the base level of regular expression
298	* is a trifle forced, but the need to tie the tails of the branches to what
299	* follows makes it hard to avoid.
300	*/
301	static char *
302	reg(
303	int paren, /* Parenthesized? */
304	int *flagp )
305	{
306	register char *ret;
307	register char *br;
308	register char *ender;
309	register int parno;
310	int flags;
311
312	flagp = HASWIDTH; / Tentatively. */
313
314	/* Make an OPEN node, if parenthesized. */
315	if (paren) {
316	if (regnpar >= NSUBEXP)
317	FAIL("too many ()");
318	parno = regnpar;
319	regnpar++;
320	ret = regnode(OPEN+parno);
321	} else
322	ret = NULL;
323
324	/* Pick up the branches, linking them together. */
325	br = regbranch(&flags);
326	if (br == NULL)
327	return(NULL);
328	if (ret != NULL)
329	regtail(ret, br); /* OPEN -> first. */
330	else
331	ret = br;
332	if (!(flags&HASWIDTH))
333	*flagp &= ~HASWIDTH;
334	*flagp \|= flags&SPSTART;
335	while (regparse == '\|' \|\| regparse == '\n') {
336	regparse++;
337	br = regbranch(&flags);
338	if (br == NULL)
339	return(NULL);
340	regtail(ret, br); /* BRANCH -> BRANCH. */
341	if (!(flags&HASWIDTH))
342	*flagp &= ~HASWIDTH;
343	*flagp \|= flags&SPSTART;
344	}
345
346	/* Make a closing node, and hook it on the end. */
347	ender = regnode((paren) ? CLOSE+parno : END);
348	regtail(ret, ender);
349
350	/* Hook the tails of the branches to the closing node. */
351	for (br = ret; br != NULL; br = regnext(br))
352	regoptail(br, ender);
353
354	/* Check for proper termination. */
355	if (paren && *regparse++ != ')') {
356	FAIL("unmatched ()");
357	} else if (!paren && *regparse != '\0') {
358	if (*regparse == ')') {
359	FAIL("unmatched ()");
360	} else
361	FAIL("junk on end"); /* "Can't happen". */
362	/* NOTREACHED */
363	}
364
365	return(ret);
366	}
367
368	/*
369	- regbranch - one alternative of an \| operator
370	*
371	* Implements the concatenation operator.
372	*/
373	static char *
374	regbranch( int *flagp )
375	{
376	register char *ret;
377	register char *chain;
378	register char *latest;
379	int flags;
380
381	flagp = WORST; / Tentatively. */
382
383	ret = regnode(BRANCH);
384	chain = NULL;
385	while (regparse != '\0' && regparse != ')' &&
386	regparse != '\n' && regparse != '\|') {
387	latest = regpiece(&flags);
388	if (latest == NULL)
389	return(NULL);
390	*flagp \|= flags&HASWIDTH;
391	if (chain == NULL) /* First piece. */
392	*flagp \|= flags&SPSTART;
393	else
394	regtail(chain, latest);
395	chain = latest;
396	}
397	if (chain == NULL) /* Loop ran zero times. */
398	(void) regnode(NOTHING);
399
400	return(ret);
401	}
402
403	/*
404	- regpiece - something followed by possible [*+?]
405	*
406	* Note that the branching code sequences used for ? and the general cases
407	* of * and + are somewhat optimized: they use the same NOTHING node as
408	* both the endmarker for their branch list and the body of the last branch.
409	* It might seem that this node could be dispensed with entirely, but the
410	* endmarker role is not redundant.
411	*/
412	static char *
413	regpiece( int *flagp )
414	{
415	register char *ret;
416	register char op;
417	register char *next;
418	int flags;
419
420	ret = regatom(&flags);
421	if (ret == NULL)
422	return(NULL);
423
424	op = *regparse;
425	if (!ISMULT(op)) {
426	*flagp = flags;
427	return(ret);
428	}
429
430	if (!(flags&HASWIDTH) && op != '?')
431	FAIL("*+ operand could be empty");
432	*flagp = (op != '+') ? (WORST\|SPSTART) : (WORST\|HASWIDTH);
433
434	if (op == '*' && (flags&SIMPLE))
435	reginsert(STAR, ret);
436	else if (op == '*') {
437	/* Emit x* as (x&\|), where & means "self". */
438	reginsert(BRANCH, ret); /* Either x */
439	regoptail(ret, regnode(BACK)); /* and loop */
440	regoptail(ret, ret); /* back */
441	regtail(ret, regnode(BRANCH)); /* or */
442	regtail(ret, regnode(NOTHING)); /* null. */
443	} else if (op == '+' && (flags&SIMPLE))
444	reginsert(PLUS, ret);
445	else if (op == '+') {
446	/* Emit x+ as x(&\|), where & means "self". */
447	next = regnode(BRANCH); /* Either */
448	regtail(ret, next);
449	regtail(regnode(BACK), ret); /* loop back */
450	regtail(next, regnode(BRANCH)); /* or */
451	regtail(ret, regnode(NOTHING)); /* null. */
452	} else if (op == '?') {
453	/* Emit x? as (x\|) */
454	reginsert(BRANCH, ret); /* Either x */
455	regtail(ret, regnode(BRANCH)); /* or */
456	next = regnode(NOTHING); /* null. */
457	regtail(ret, next);
458	regoptail(ret, next);
459	}
460	regparse++;
461	if (ISMULT(*regparse))
462	FAIL("nested *?+");
463
464	return(ret);
465	}
466
467	/*
468	- regatom - the lowest level
469	*
470	* Optimization: gobbles an entire sequence of ordinary characters so that
471	* it can turn them into a single node, which is smaller to store and
472	* faster to run. Backslashed characters are exceptions, each becoming a
473	* separate node; the code is simpler that way and it's not worth fixing.
474	*/
475	static char *
476	regatom( int *flagp )
477	{
478	register char *ret;
479	int flags;
480
481	flagp = WORST; / Tentatively. */
482
483	switch (*regparse++) {
484	/* FIXME: these chars only have meaning at beg/end of pat? */
485	case '^':
486	ret = regnode(BOL);
487	break;
488	case '$':
489	ret = regnode(EOL);
490	break;
491	case '.':
492	ret = regnode(ANY);
493	*flagp \|= HASWIDTH\|SIMPLE;
494	break;
495	case '[': {
496	register int classr;
497	register int classend;
498
499	if (regparse == '^') { / Complement of range. */
500	ret = regnode(ANYBUT);
501	regparse++;
502	} else
503	ret = regnode(ANYOF);
504	if (regparse == ']' \|\| regparse == '-')
505	regc(*regparse++);
506	while (regparse != '\0' && regparse != ']') {
507	if (*regparse == '-') {
508	regparse++;
509	if (regparse == ']' \|\| regparse == '\0')
510	regc('-');
511	else {
512	classr = UCHARAT(regparse-2)+1;
513	classend = UCHARAT(regparse);
514	if (classr > classend+1)
515	FAIL("invalid [] range");
516	for (; classr <= classend; classr++)
517	regc(classr);
518	regparse++;
519	}
520	} else
521	regc(*regparse++);
522	}
523	regc('\0');
524	if (*regparse != ']')
525	FAIL("unmatched []");
526	regparse++;
527	*flagp \|= HASWIDTH\|SIMPLE;
528	}
529	break;
530	case '(':
531	ret = reg(1, &flags);
532	if (ret == NULL)
533	return(NULL);
534	*flagp \|= flags&(HASWIDTH\|SPSTART);
535	break;
536	case '\0':
537	case '\|':
538	case '\n':
539	case ')':
540	FAIL("internal urp"); /* Supposed to be caught earlier. */
541	break;
542	case '?':
543	case '+':
544	case '*':
545	FAIL("?+* follows nothing");
546	break;
547	case '\\':
548	switch (*regparse++) {
549	case '\0':
550	FAIL("trailing \\");
551	break;
552	case '<':
553	ret = regnode(WORDA);
554	break;
555	case '>':
556	ret = regnode(WORDZ);
557	break;
558	/* FIXME: Someday handle \1, \2, ... */
559	default:
560	/* Handle general quoted chars in exact-match routine */
561	goto de_fault;
562	}
563	break;
564	de_fault:
565	default:
566	/*
567	* Encode a string of characters to be matched exactly.
568	*
569	* This is a bit tricky due to quoted chars and due to
570	* '*', '+', and '?' taking the SINGLE char previous
571	* as their operand.
572	*
573	* On entry, the char at regparse[-1] is going to go
574	* into the string, no matter what it is. (It could be
575	* following a \ if we are entered from the '\' case.)
576	*
577	* Basic idea is to pick up a good char in ch and
578	* examine the next char. If it's *+? then we twiddle.
579	* If it's \ then we frozzle. If it's other magic char
580	* we push ch and terminate the string. If none of the
581	* above, we push ch on the string and go around again.
582	*
583	* regprev is used to remember where "the current char"
584	* starts in the string, if due to a *+? we need to back
585	* up and put the current char in a separate, 1-char, string.
586	* When regprev is NULL, ch is the only char in the
587	* string; this is used in *+? handling, and in setting
588	* flags \|= SIMPLE at the end.
589	*/
590	{
591	char *regprev;
592	register char ch;
593
594	regparse--; /* Look at cur char */
595	ret = regnode(EXACTLY);
596	for ( regprev = 0 ; ; ) {
597	ch = regparse++; / Get current char */
598	switch (regparse) { / look at next one */
599
600	default:
601	regc(ch); /* Add cur to string */
602	break;
603
604	case '.': case '[': case '(':
605	case ')': case '\|': case '\n':
606	case '$': case '^':
607	case '\0':
608	/* FIXME, $ and ^ should not always be magic */
609	magic:
610	regc(ch); /* dump cur char */
611	goto done; /* and we are done */
612
613	case '?': case '+': case '*':
614	if (!regprev) /* If just ch in str, */
615	goto magic; /* use it */
616	/* End mult-char string one early */
617	regparse = regprev; /* Back up parse */
618	goto done;
619
620	case '\\':
621	regc(ch); /* Cur char OK */
622	switch (regparse[1]){ /* Look after \ */
623	case '\0':
624	case '<':
625	case '>':
626	/* FIXME: Someday handle \1, \2, ... */
627	goto done; /* Not quoted */
628	default:
629	/* Backup point is \, scan * point is after it. */
630	regprev = regparse;
631	regparse++;
632	continue; /* NOT break; */
633	}
634	}
635	regprev = regparse; /* Set backup point */
636	}
637	done:
638	regc('\0');
639	*flagp \|= HASWIDTH;
640	if (!regprev) /* One char? */
641	*flagp \|= SIMPLE;
642	}
643	break;
644	}
645
646	return(ret);
647	}
648
649	/*
650	- regnode - emit a node
651	*/
652	static char * /* Location. */
653	regnode( int op )
654	{
655	register char *ret;
656	register char *ptr;
657
658	ret = regcode;
659	if (ret == &regdummy) {
660	regsize += 3;
661	return(ret);
662	}
663
664	ptr = ret;
665	*ptr++ = op;
666	ptr++ = '\0'; / Null "next" pointer. */
667	*ptr++ = '\0';
668	regcode = ptr;
669
670	return(ret);
671	}
672
673	/*
674	- regc - emit (if appropriate) a byte of code
675	*/
676	static void
677	regc( int b )
678	{
679	if (regcode != &regdummy)
680	*regcode++ = b;
681	else
682	regsize++;
683	}
684
685	/*
686	- reginsert - insert an operator in front of already-emitted operand
687	*
688	* Means relocating the operand.
689	*/
690	static void
691	reginsert(
692	char op,
693	char *opnd )
694	{
695	register char *src;
696	register char *dst;
697	register char *place;
698
699	if (regcode == &regdummy) {
700	regsize += 3;
701	return;
702	}
703
704	src = regcode;
705	regcode += 3;
706	dst = regcode;
707	while (src > opnd)
708	--dst = --src;
709
710	place = opnd; /* Op node, where operand used to be. */
711	*place++ = op;
712	*place++ = '\0';
713	*place++ = '\0';
714	}
715
716	/*
717	- regtail - set the next-pointer at the end of a node chain
718	*/
719	static void
720	regtail(
721	char *p,
722	char *val )
723	{
724	register char *scan;
725	register char *temp;
726	register int offset;
727
728	if (p == &regdummy)
729	return;
730
731	/* Find last node. */
732	scan = p;
733	for (;;) {
734	temp = regnext(scan);
735	if (temp == NULL)
736	break;
737	scan = temp;
738	}
739
740	if (OP(scan) == BACK)
741	offset = scan - val;
742	else
743	offset = val - scan;
744	*(scan+1) = (offset>>8)&0377;
745	*(scan+2) = offset&0377;
746	}
747
748	/*
749	- regoptail - regtail on operand of first argument; nop if operandless
750	*/
751
752	static void
753	regoptail(
754	char *p,
755	char *val )
756	{
757	/* "Operandless" and "op != BRANCH" are synonymous in practice. */
758	if (p == NULL \|\| p == &regdummy \|\| OP(p) != BRANCH)
759	return;
760	regtail(OPERAND(p), val);
761	}
762
763	/*
764	* regexec and friends
765	*/
766
767	/*
768	* Global work variables for regexec().
769	*/
770	static char reginput; / String-input pointer. */
771	static char regbol; / Beginning of input, for ^ check. */
772	static char *regstartp; / Pointer to startp array. */
773	static char *regendp; / Ditto for endp. */
774
775	/*
776	* Forwards.
777	*/
778	STATIC int regtry( regexp prog, char string );
779	STATIC int regmatch( char *prog );
780	STATIC int regrepeat( char *p );
781
782	#ifdef DEBUG
783	int regnarrate = 0;
784	void regdump();
785	STATIC char *regprop();
786	#endif
787
788	/*
789	- regexec - match a regexp against a string
790	*/
791	int
792	regexec(
793	register regexp *prog,
794	register char *string )
795	{
796	register char *s;
797
798	/* Be paranoid... */
799	if (prog == NULL \|\| string == NULL) {
800	regerror("NULL parameter");
801	return(0);
802	}
803
804	/* Check validity of program. */
805	if (UCHARAT(prog->program) != MAGIC) {
806	regerror("corrupted program");
807	return(0);
808	}
809
810	/* If there is a "must appear" string, look for it. */
811	if (prog->regmust != NULL) {
812	s = (char *)string;
813	while ((s = strchr(s, prog->regmust[0])) != NULL) {
814	if (strncmp(s, prog->regmust, prog->regmlen) == 0)
815	break; /* Found it. */
816	s++;
817	}
818	if (s == NULL) /* Not present. */
819	return(0);
820	}
821
822	/* Mark beginning of line for ^ . */
823	regbol = (char *)string;
824
825	/* Simplest case: anchored match need be tried only once. */
826	if (prog->reganch)
827	return(regtry(prog, string));
828
829	/* Messy cases: unanchored match. */
830	s = (char *)string;
831	if (prog->regstart != '\0')
832	/* We know what char it must start with. */
833	while ((s = strchr(s, prog->regstart)) != NULL) {
834	if (regtry(prog, s))
835	return(1);
836	s++;
837	}
838	else
839	/* We don't -- general case. */
840	do {
841	if (regtry(prog, s))
842	return(1);
843	} while (*s++ != '\0');
844
845	/* Failure. */
846	return(0);
847	}
848
849	/*
850	- regtry - try match at specific point
851	*/
852	static int /* 0 failure, 1 success */
853	regtry(
854	regexp *prog,
855	char *string )
856	{
857	register int i;
858	register char **sp;
859	register char **ep;
860
861	reginput = string;
862	regstartp = prog->startp;
863	regendp = prog->endp;
864
865	sp = prog->startp;
866	ep = prog->endp;
867	for (i = NSUBEXP; i > 0; i--) {
868	*sp++ = NULL;
869	*ep++ = NULL;
870	}
871	if (regmatch(prog->program + 1)) {
872	prog->startp[0] = string;
873	prog->endp[0] = reginput;
874	return(1);
875	} else
876	return(0);
877	}
878
879	/*
880	- regmatch - main matching routine
881	*
882	* Conceptually the strategy is simple: check to see whether the current
883	* node matches, call self recursively to see whether the rest matches,
884	* and then act accordingly. In practice we make some effort to avoid
885	* recursion, in particular by going through "ordinary" nodes (that don't
886	* need to know whether the rest of the match failed) by a loop instead of
887	* by recursion.
888	*/
889	static int /* 0 failure, 1 success */
890	regmatch( char *prog )
891	{
892	register char scan; / Current node. */
893	char next; / Next node. */
894
895	scan = prog;
896	#ifdef DEBUG
897	if (scan != NULL && regnarrate)
898	fprintf(stderr, "%s(\n", regprop(scan));
899	#endif
900	while (scan != NULL) {
901	#ifdef DEBUG
902	if (regnarrate)
903	fprintf(stderr, "%s...\n", regprop(scan));
904	#endif
905	next = regnext(scan);
906
907	switch (OP(scan)) {
908	case BOL:
909	if (reginput != regbol)
910	return(0);
911	break;
912	case EOL:
913	if (*reginput != '\0')
914	return(0);
915	break;
916	case WORDA:
917	/* Must be looking at a letter, digit, or _ */
918	if ((!isalnum(reginput)) && reginput != '_')
919	return(0);
920	/* Prev must be BOL or nonword */
921	if (reginput > regbol &&
922	(isalnum(reginput[-1]) \|\| reginput[-1] == '_'))
923	return(0);
924	break;
925	case WORDZ:
926	/* Must be looking at non letter, digit, or _ */
927	if (isalnum(reginput) \|\| reginput == '_')
928	return(0);
929	/* We don't care what the previous char was */
930	break;
931	case ANY:
932	if (*reginput == '\0')
933	return(0);
934	reginput++;
935	break;
936	case EXACTLY: {
937	register int len;
938	register char *opnd;
939
940	opnd = OPERAND(scan);
941	/* Inline the first character, for speed. */
942	if (opnd != reginput)
943	return(0);
944	len = strlen(opnd);
945	if (len > 1 && strncmp(opnd, reginput, len) != 0)
946	return(0);
947	reginput += len;
948	}
949	break;
950	case ANYOF:
951	if (reginput == '\0' \|\| strchr(OPERAND(scan), reginput) == NULL)
952	return(0);
953	reginput++;
954	break;
955	case ANYBUT:
956	if (reginput == '\0' \|\| strchr(OPERAND(scan), reginput) != NULL)
957	return(0);
958	reginput++;
959	break;
960	case NOTHING:
961	break;
962	case BACK:
963	break;
964	case OPEN+1:
965	case OPEN+2:
966	case OPEN+3:
967	case OPEN+4:
968	case OPEN+5:
969	case OPEN+6:
970	case OPEN+7:
971	case OPEN+8:
972	case OPEN+9: {
973	register int no;
974	register char *save;
975
976	no = OP(scan) - OPEN;
977	save = reginput;
978
979	if (regmatch(next)) {
980	/*
981	* Don't set startp if some later
982	* invocation of the same parentheses
983	* already has.
984	*/
985	if (regstartp[no] == NULL)
986	regstartp[no] = save;
987	return(1);
988	} else
989	return(0);
990	}
991	break;
992	case CLOSE+1:
993	case CLOSE+2:
994	case CLOSE+3:
995	case CLOSE+4:
996	case CLOSE+5:
997	case CLOSE+6:
998	case CLOSE+7:
999	case CLOSE+8:
1000	case CLOSE+9: {
1001	register int no;
1002	register char *save;
1003
1004	no = OP(scan) - CLOSE;
1005	save = reginput;
1006
1007	if (regmatch(next)) {
1008	/*
1009	* Don't set endp if some later
1010	* invocation of the same parentheses
1011	* already has.
1012	*/
1013	if (regendp[no] == NULL)
1014	regendp[no] = save;
1015	return(1);
1016	} else
1017	return(0);
1018	}
1019	break;
1020	case BRANCH: {
1021	register char *save;
1022
1023	if (OP(next) != BRANCH) /* No choice. */
1024	next = OPERAND(scan); /* Avoid recursion. */
1025	else {
1026	do {
1027	save = reginput;
1028	if (regmatch(OPERAND(scan)))
1029	return(1);
1030	reginput = save;
1031	scan = regnext(scan);
1032	} while (scan != NULL && OP(scan) == BRANCH);
1033	return(0);
1034	/* NOTREACHED */
1035	}
1036	}
1037	break;
1038	case STAR:
1039	case PLUS: {
1040	register char nextch;
1041	register int no;
1042	register char *save;
1043	register int min;
1044
1045	/*
1046	* Lookahead to avoid useless match attempts
1047	* when we know what character comes next.
1048	*/
1049	nextch = '\0';
1050	if (OP(next) == EXACTLY)
1051	nextch = *OPERAND(next);
1052	min = (OP(scan) == STAR) ? 0 : 1;
1053	save = reginput;
1054	no = regrepeat(OPERAND(scan));
1055	while (no >= min) {
1056	/* If it could work, try it. */
1057	if (nextch == '\0' \|\| *reginput == nextch)
1058	if (regmatch(next))
1059	return(1);
1060	/* Couldn't or didn't -- back up. */
1061	no--;
1062	reginput = save + no;
1063	}
1064	return(0);
1065	}
1066	break;
1067	case END:
1068	return(1); /* Success! */
1069	break;
1070	default:
1071	regerror("memory corruption");
1072	return(0);
1073	break;
1074	}
1075
1076	scan = next;
1077	}
1078
1079	/*
1080	* We get here only if there's trouble -- normally "case END" is
1081	* the terminating point.
1082	*/
1083	regerror("corrupted pointers");
1084	return(0);
1085	}
1086
1087	/*
1088	- regrepeat - repeatedly match something simple, report how many
1089	*/
1090	static int
1091	regrepeat( char *p )
1092	{
1093	register int count = 0;
1094	register char *scan;
1095	register char *opnd;
1096
1097	scan = reginput;
1098	opnd = OPERAND(p);
1099	switch (OP(p)) {
1100	case ANY:
1101	count = strlen(scan);
1102	scan += count;
1103	break;
1104	case EXACTLY:
1105	while (opnd == scan) {
1106	count++;
1107	scan++;
1108	}
1109	break;
1110	case ANYOF:
1111	while (scan != '\0' && strchr(opnd, scan) != NULL) {
1112	count++;
1113	scan++;
1114	}
1115	break;
1116	case ANYBUT:
1117	while (scan != '\0' && strchr(opnd, scan) == NULL) {
1118	count++;
1119	scan++;
1120	}
1121	break;
1122	default: /* Oh dear. Called inappropriately. */
1123	regerror("internal foulup");
1124	count = 0; /* Best compromise. */
1125	break;
1126	}
1127	reginput = scan;
1128
1129	return(count);
1130	}
1131
1132	/*
1133	- regnext - dig the "next" pointer out of a node
1134	*/
1135	static char *
1136	regnext( register char *p )
1137	{
1138	register int offset;
1139
1140	if (p == &regdummy)
1141	return(NULL);
1142
1143	offset = NEXT(p);
1144	if (offset == 0)
1145	return(NULL);
1146
1147	if (OP(p) == BACK)
1148	return(p-offset);
1149	else
1150	return(p+offset);
1151	}
1152
1153	#ifdef DEBUG
1154
1155	STATIC char *regprop();
1156
1157	/*
1158	- regdump - dump a regexp onto stdout in vaguely comprehensible form
1159	*/
1160	void
1161	regdump( regexp *r )
1162	{
1163	register char *s;
1164	register char op = EXACTLY; /* Arbitrary non-END op. */
1165	register char *next;
1166
1167
1168	s = r->program + 1;
1169	while (op != END) { /* While that wasn't END last time... */
1170	op = OP(s);
1171	printf("%2d%s", s-r->program, regprop(s)); /* Where, what. */
1172	next = regnext(s);
1173	if (next == NULL) /* Next ptr. */
1174	printf("(0)");
1175	else
1176	printf("(%d)", (s-r->program)+(next-s));
1177	s += 3;
1178	if (op == ANYOF \|\| op == ANYBUT \|\| op == EXACTLY) {
1179	/* Literal string, where present. */
1180	while (*s != '\0') {
1181	putchar(*s);
1182	s++;
1183	}
1184	s++;
1185	}
1186	putchar('\n');
1187	}
1188
1189	/* Header fields of interest. */
1190	if (r->regstart != '\0')
1191	printf("start `%c' ", r->regstart);
1192	if (r->reganch)
1193	printf("anchored ");
1194	if (r->regmust != NULL)
1195	printf("must have \"%s\"", r->regmust);
1196	printf("\n");
1197	}
1198
1199	/*
1200	- regprop - printable representation of opcode
1201	*/
1202	static char *
1203	regprop( char *op )
1204	{
1205	register char *p;
1206	static char buf[50];
1207
1208	(void) strcpy(buf, ":");
1209
1210	switch (OP(op)) {
1211	case BOL:
1212	p = "BOL";
1213	break;
1214	case EOL:
1215	p = "EOL";
1216	break;
1217	case ANY:
1218	p = "ANY";
1219	break;
1220	case ANYOF:
1221	p = "ANYOF";
1222	break;
1223	case ANYBUT:
1224	p = "ANYBUT";
1225	break;
1226	case BRANCH:
1227	p = "BRANCH";
1228	break;
1229	case EXACTLY:
1230	p = "EXACTLY";
1231	break;
1232	case NOTHING:
1233	p = "NOTHING";
1234	break;
1235	case BACK:
1236	p = "BACK";
1237	break;
1238	case END:
1239	p = "END";
1240	break;
1241	case OPEN+1:
1242	case OPEN+2:
1243	case OPEN+3:
1244	case OPEN+4:
1245	case OPEN+5:
1246	case OPEN+6:
1247	case OPEN+7:
1248	case OPEN+8:
1249	case OPEN+9:
1250	sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
1251	p = NULL;
1252	break;
1253	case CLOSE+1:
1254	case CLOSE+2:
1255	case CLOSE+3:
1256	case CLOSE+4:
1257	case CLOSE+5:
1258	case CLOSE+6:
1259	case CLOSE+7:
1260	case CLOSE+8:
1261	case CLOSE+9:
1262	sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
1263	p = NULL;
1264	break;
1265	case STAR:
1266	p = "STAR";
1267	break;
1268	case PLUS:
1269	p = "PLUS";
1270	break;
1271	case WORDA:
1272	p = "WORDA";
1273	break;
1274	case WORDZ:
1275	p = "WORDZ";
1276	break;
1277	default:
1278	regerror("corrupted opcode");
1279	break;
1280	}
1281	if (p != NULL)
1282	(void) strcat(buf, p);
1283	return(buf);
1284	}
1285	#endif
1286
1287	/*
1288	* The following is provided for those people who do not have strcspn() in
1289	* their C libraries. They should get off their butts and do something
1290	* about it; at least one public-domain implementation of those (highly
1291	* useful) string routines has been published on Usenet.
1292	*/
1293	#ifdef STRCSPN
1294	/*
1295	* strcspn - find length of initial segment of s1 consisting entirely
1296	* of characters not from s2
1297	*/
1298
1299	static int
1300	strcspn(
1301	char *s1,
1302	char *s2 )
1303	{
1304	register char *scan1;
1305	register char *scan2;
1306	register int count;
1307
1308	count = 0;
1309	for (scan1 = s1; *scan1 != '\0'; scan1++) {
1310	for (scan2 = s2; scan2 != '\0';) / ++ moved down. */
1311	if (scan1 == scan2++)
1312	return(count);
1313	count++;
1314	}
1315	return(count);
1316	}
1317	#endif

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