[unix-history] / usr / src / lib / libcompat / 4.3 / regex.c

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)regex.c	5.2 (Berkeley) %G%";
#endif LIBC_SCCS and not lint

#

/*
 * routines to do regular expression matching
 *
 * Entry points:
 *
 *	re_comp(s)
 *		char *s;
 *	 ... returns 0 if the string s was compiled successfully,
 *		     a pointer to an error message otherwise.
 *	     If passed 0 or a null string returns without changing
 *           the currently compiled re (see note 11 below).
 *
 *	re_exec(s)
 *		char *s;
 *	 ... returns 1 if the string s matches the last compiled regular
 *		       expression, 
 *		     0 if the string s failed to match the last compiled
 *		       regular expression, and
 *		    -1 if the compiled regular expression was invalid 
 *		       (indicating an internal error).
 *
 * The strings passed to both re_comp and re_exec may have trailing or
 * embedded newline characters; they are terminated by nulls.
 *
 * The identity of the author of these routines is lost in antiquity;
 * this is essentially the same as the re code in the original V6 ed.
 *
 * The regular expressions recognized are described below. This description
 * is essentially the same as that for ed.
 *
 *	A regular expression specifies a set of strings of characters.
 *	A member of this set of strings is said to be matched by
 *	the regular expression.  In the following specification for
 *	regular expressions the word `character' means any character but NUL.
 *
 *	1.  Any character except a special character matches itself.
 *	    Special characters are the regular expression delimiter plus
 *	    \ [ . and sometimes ^ * $.
 *	2.  A . matches any character.
 *	3.  A \ followed by any character except a digit or ( )
 *	    matches that character.
 *	4.  A nonempty string s bracketed [s] (or [^s]) matches any
 *	    character in (or not in) s. In s, \ has no special meaning,
 *	    and ] may only appear as the first letter. A substring 
 *	    a-b, with a and b in ascending ASCII order, stands for
 *	    the inclusive range of ASCII characters.
 *	5.  A regular expression of form 1-4 followed by * matches a
 *	    sequence of 0 or more matches of the regular expression.
 *	6.  A regular expression, x, of form 1-8, bracketed \(x\)
 *	    matches what x matches.
 *	7.  A \ followed by a digit n matches a copy of the string that the
 *	    bracketed regular expression beginning with the nth \( matched.
 *	8.  A regular expression of form 1-8, x, followed by a regular
 *	    expression of form 1-7, y matches a match for x followed by
 *	    a match for y, with the x match being as long as possible
 *	    while still permitting a y match.
 *	9.  A regular expression of form 1-8 preceded by ^ (or followed
 *	    by $), is constrained to matches that begin at the left
 *	    (or end at the right) end of a line.
 *	10. A regular expression of form 1-9 picks out the longest among
 *	    the leftmost matches in a line.
 *	11. An empty regular expression stands for a copy of the last
 *	    regular expression encountered.
 */

/*
 * constants for re's
 */
#define	CBRA	1
#define	CCHR	2
#define	CDOT	4
#define	CCL	6
#define	NCCL	8
#define	CDOL	10
#define	CEOF	11
#define	CKET	12
#define	CBACK	18

#define	CSTAR	01

#define	ESIZE	512
#define	NBRA	9

static	char	expbuf[ESIZE], *braslist[NBRA], *braelist[NBRA];
static	char	circf;

/*
 * compile the regular expression argument into a dfa
 */
char *
re_comp(sp)
	register char	*sp;
{
	register int	c;
	register char	*ep = expbuf;
	int	cclcnt, numbra = 0;
	char	*lastep = 0;
	char	bracket[NBRA];
	char	*bracketp = &bracket[0];
	static	char	*retoolong = "Regular expression too long";

#define	comerr(msg) {expbuf[0] = 0; numbra = 0; return(msg); }

	if (sp == 0 || *sp == '\0') {
		if (*ep == 0)
			return("No previous regular expression");
		return(0);
	}
	if (*sp == '^') {
		circf = 1;
		sp++;
	}
	else
		circf = 0;
	for (;;) {
		if (ep >= &expbuf[ESIZE])
			comerr(retoolong);
		if ((c = *sp++) == '\0') {
			if (bracketp != bracket)
				comerr("unmatched \\(");
			*ep++ = CEOF;
			*ep++ = 0;
			return(0);
		}
		if (c != '*')
			lastep = ep;
		switch (c) {

		case '.':
			*ep++ = CDOT;
			continue;

		case '*':
			if (lastep == 0 || *lastep == CBRA || *lastep == CKET)
				goto defchar;
			*lastep |= CSTAR;
			continue;

		case '$':
			if (*sp != '\0')
				goto defchar;
			*ep++ = CDOL;
			continue;

		case '[':
			*ep++ = CCL;
			*ep++ = 0;
			cclcnt = 1;
			if ((c = *sp++) == '^') {
				c = *sp++;
				ep[-2] = NCCL;
			}
			do {
				if (c == '\0')
					comerr("missing ]");
				if (c == '-' && ep [-1] != 0) {
					if ((c = *sp++) == ']') {
						*ep++ = '-';
						cclcnt++;
						break;
					}
					while (ep[-1] < c) {
						*ep = ep[-1] + 1;
						ep++;
						cclcnt++;
						if (ep >= &expbuf[ESIZE])
							comerr(retoolong);
					}
				}
				*ep++ = c;
				cclcnt++;
				if (ep >= &expbuf[ESIZE])
					comerr(retoolong);
			} while ((c = *sp++) != ']');
			lastep[1] = cclcnt;
			continue;

		case '\\':
			if ((c = *sp++) == '(') {
				if (numbra >= NBRA)
					comerr("too many \\(\\) pairs");
				*bracketp++ = numbra;
				*ep++ = CBRA;
				*ep++ = numbra++;
				continue;
			}
			if (c == ')') {
				if (bracketp <= bracket)
					comerr("unmatched \\)");
				*ep++ = CKET;
				*ep++ = *--bracketp;
				continue;
			}
			if (c >= '1' && c < ('1' + NBRA)) {
				*ep++ = CBACK;
				*ep++ = c - '1';
				continue;
			}
			*ep++ = CCHR;
			*ep++ = c;
			continue;

		defchar:
		default:
			*ep++ = CCHR;
			*ep++ = c;
		}
	}
}

/* 
 * match the argument string against the compiled re
 */
int
re_exec(p1)
	register char	*p1;
{
	register char	*p2 = expbuf;
	register int	c;
	int	rv;

	for (c = 0; c < NBRA; c++) {
		braslist[c] = 0;
		braelist[c] = 0;
	}
	if (circf)
		return((advance(p1, p2)));
	/*
	 * fast check for first character
	 */
	if (*p2 == CCHR) {
		c = p2[1];
		do {
			if (*p1 != c)
				continue;
			if (rv = advance(p1, p2))
				return(rv);
		} while (*p1++);
		return(0);
	}
	/*
	 * regular algorithm
	 */
	do
		if (rv = advance(p1, p2))
			return(rv);
	while (*p1++);
	return(0);
}

/* 
 * try to match the next thing in the dfa
 */
static	int
advance(lp, ep)
	register char	*lp, *ep;
{
	register char	*curlp;
	int	ct, i;
	int	rv;

	for (;;)
		switch (*ep++) {

		case CCHR:
			if (*ep++ == *lp++)
				continue;
			return(0);

		case CDOT:
			if (*lp++)
				continue;
			return(0);

		case CDOL:
			if (*lp == '\0')
				continue;
			return(0);

		case CEOF:
			return(1);

		case CCL:
			if (cclass(ep, *lp++, 1)) {
				ep += *ep;
				continue;
			}
			return(0);

		case NCCL:
			if (cclass(ep, *lp++, 0)) {
				ep += *ep;
				continue;
			}
			return(0);

		case CBRA:
			braslist[*ep++] = lp;
			continue;

		case CKET:
			braelist[*ep++] = lp;
			continue;

		case CBACK:
			if (braelist[i = *ep++] == 0)
				return(-1);
			if (backref(i, lp)) {
				lp += braelist[i] - braslist[i];
				continue;
			}
			return(0);

		case CBACK|CSTAR:
			if (braelist[i = *ep++] == 0)
				return(-1);
			curlp = lp;
			ct = braelist[i] - braslist[i];
			while (backref(i, lp))
				lp += ct;
			while (lp >= curlp) {
				if (rv = advance(lp, ep))
					return(rv);
				lp -= ct;
			}
			continue;

		case CDOT|CSTAR:
			curlp = lp;
			while (*lp++)
				;
			goto star;

		case CCHR|CSTAR:
			curlp = lp;
			while (*lp++ == *ep)
				;
			ep++;
			goto star;

		case CCL|CSTAR:
		case NCCL|CSTAR:
			curlp = lp;
			while (cclass(ep, *lp++, ep[-1] == (CCL|CSTAR)))
				;
			ep += *ep;
			goto star;

		star:
			do {
				lp--;
				if (rv = advance(lp, ep))
					return(rv);
			} while (lp > curlp);
			return(0);

		default:
			return(-1);
		}
}

backref(i, lp)
	register int	i;
	register char	*lp;
{
	register char	*bp;

	bp = braslist[i];
	while (*bp++ == *lp++)
		if (bp >= braelist[i])
			return(1);
	return(0);
}

int
cclass(set, c, af)
	register char	*set, c;
	int	af;
{
	register int	n;

	if (c == 0)
		return(0);
	n = *set++;
	while (--n)
		if (*set++ == c)
			return(af);
	return(! af);
}
Commit	Line	Data
bb0cfa24 DF	1	/*
	2	* Copyright (c) 1980 Regents of the University of California.
	3	* All rights reserved. The Berkeley software License Agreement
	4	* specifies the terms and conditions for redistribution.
	5	*/
	6
2ce81398 DS	7	#if defined(LIBC_SCCS) && !defined(lint)
	8	static char sccsid[] = "@(#)regex.c 5.2 (Berkeley) %G%";
	9	#endif LIBC_SCCS and not lint
bb0cfa24	10
af509ab3 BJ	11	#
	12
	13	/*
	14	* routines to do regular expression matching
	15	*
	16	* Entry points:
	17	*
	18	* re_comp(s)
	19	* char *s;
	20	* ... returns 0 if the string s was compiled successfully,
	21	* a pointer to an error message otherwise.
	22	* If passed 0 or a null string returns without changing
	23	* the currently compiled re (see note 11 below).
	24	*
	25	* re_exec(s)
	26	* char *s;
	27	* ... returns 1 if the string s matches the last compiled regular
	28	* expression,
	29	* 0 if the string s failed to match the last compiled
	30	* regular expression, and
	31	* -1 if the compiled regular expression was invalid
	32	* (indicating an internal error).
	33	*
	34	* The strings passed to both re_comp and re_exec may have trailing or
	35	* embedded newline characters; they are terminated by nulls.
	36	*
	37	* The identity of the author of these routines is lost in antiquity;
	38	* this is essentially the same as the re code in the original V6 ed.
	39	*
	40	* The regular expressions recognized are described below. This description
	41	* is essentially the same as that for ed.
	42	*
	43	* A regular expression specifies a set of strings of characters.
	44	* A member of this set of strings is said to be matched by
	45	* the regular expression. In the following specification for
	46	* regular expressions the word `character' means any character but NUL.
	47	*
	48	* 1. Any character except a special character matches itself.
	49	* Special characters are the regular expression delimiter plus
	50	* \ [ . and sometimes ^ * $.
	51	* 2. A . matches any character.
	52	* 3. A \ followed by any character except a digit or ( )
	53	* matches that character.
	54	* 4. A nonempty string s bracketed [s] (or [^s]) matches any
	55	* character in (or not in) s. In s, \ has no special meaning,
	56	* and ] may only appear as the first letter. A substring
	57	* a-b, with a and b in ascending ASCII order, stands for
	58	* the inclusive range of ASCII characters.
	59	* 5. A regular expression of form 1-4 followed by * matches a
	60	* sequence of 0 or more matches of the regular expression.
	61	* 6. A regular expression, x, of form 1-8, bracketed \(x\)
	62	* matches what x matches.
	63	* 7. A \ followed by a digit n matches a copy of the string that the
	64	* bracketed regular expression beginning with the nth \( matched.
	65	* 8. A regular expression of form 1-8, x, followed by a regular
	66	* expression of form 1-7, y matches a match for x followed by
	67	* a match for y, with the x match being as long as possible
	68	* while still permitting a y match.
	69	* 9. A regular expression of form 1-8 preceded by ^ (or followed
	70	* by $), is constrained to matches that begin at the left
	71	* (or end at the right) end of a line.
	72	* 10. A regular expression of form 1-9 picks out the longest among
	73	* the leftmost matches in a line.
	74	* 11. An empty regular expression stands for a copy of the last
75	* regular expression encountered.
76	*/
77
78	/*
79	* constants for re's
80	*/
81	#define CBRA 1
82	#define CCHR 2
83	#define CDOT 4
84	#define CCL 6
85	#define NCCL 8
86	#define CDOL 10
87	#define CEOF 11
88	#define CKET 12
89	#define CBACK 18
90
91	#define CSTAR 01
92
93	#define ESIZE 512
94	#define NBRA 9
95
96	static char expbuf[ESIZE], braslist[NBRA], braelist[NBRA];
97	static char circf;
98
99	/*
100	* compile the regular expression argument into a dfa
101	*/
102	char *
103	re_comp(sp)
104	register char *sp;
105	{
106	register int c;
107	register char *ep = expbuf;
108	int cclcnt, numbra = 0;
109	char *lastep = 0;
110	char bracket[NBRA];
111	char *bracketp = &bracket[0];
112	static char *retoolong = "Regular expression too long";
113
114	#define comerr(msg) {expbuf[0] = 0; numbra = 0; return(msg); }
115
116	if (sp == 0 \|\| *sp == '\0') {
117	if (*ep == 0)
118	return("No previous regular expression");
119	return(0);
120	}
121	if (*sp == '^') {
122	circf = 1;
123	sp++;
124	}
125	else
126	circf = 0;
127	for (;;) {
128	if (ep >= &expbuf[ESIZE])
129	comerr(retoolong);
130	if ((c = *sp++) == '\0') {
131	if (bracketp != bracket)
132	comerr("unmatched \\(");
133	*ep++ = CEOF;
134	*ep++ = 0;
135	return(0);
136	}
137	if (c != '*')
138	lastep = ep;
139	switch (c) {
140
141	case '.':
142	*ep++ = CDOT;
143	continue;
144
145	case '*':
146	if (lastep == 0 \|\| lastep == CBRA \|\| lastep == CKET)
147	goto defchar;
148	*lastep \|= CSTAR;
149	continue;
150
151	case '$':
152	if (*sp != '\0')
153	goto defchar;
154	*ep++ = CDOL;
155	continue;
156
157	case '[':
158	*ep++ = CCL;
159	*ep++ = 0;
160	cclcnt = 1;
161	if ((c = *sp++) == '^') {
162	c = *sp++;
163	ep[-2] = NCCL;
164	}
165	do {
166	if (c == '\0')
167	comerr("missing ]");
168	if (c == '-' && ep [-1] != 0) {
169	if ((c = *sp++) == ']') {
170	*ep++ = '-';
171	cclcnt++;
172	break;
173	}
174	while (ep[-1] < c) {
175	*ep = ep[-1] + 1;
176	ep++;
177	cclcnt++;
178	if (ep >= &expbuf[ESIZE])
179	comerr(retoolong);
180	}
181	}
182	*ep++ = c;
183	cclcnt++;
184	if (ep >= &expbuf[ESIZE])
185	comerr(retoolong);
186	} while ((c = *sp++) != ']');
187	lastep[1] = cclcnt;
188	continue;
189
190	case '\\':
191	if ((c = *sp++) == '(') {
192	if (numbra >= NBRA)
193	comerr("too many \\(\\) pairs");
194	*bracketp++ = numbra;
195	*ep++ = CBRA;
196	*ep++ = numbra++;
197	continue;
198	}
199	if (c == ')') {
200	if (bracketp <= bracket)
201	comerr("unmatched \\)");
202	*ep++ = CKET;
203	ep++ = --bracketp;
204	continue;
205	}
206	if (c >= '1' && c < ('1' + NBRA)) {
207	*ep++ = CBACK;
208	*ep++ = c - '1';
209	continue;
210	}
211	*ep++ = CCHR;
212	*ep++ = c;
213	continue;
214
215	defchar:
216	default:
217	*ep++ = CCHR;
218	*ep++ = c;
219	}
220	}
221	}
222
223	/*
224	* match the argument string against the compiled re
225	*/
226	int
227	re_exec(p1)
228	register char *p1;
229	{
230	register char *p2 = expbuf;
231	register int c;
232	int rv;
233
234	for (c = 0; c < NBRA; c++) {
235	braslist[c] = 0;
236	braelist[c] = 0;
237	}
238	if (circf)
239	return((advance(p1, p2)));
240	/*
241	* fast check for first character
242	*/
243	if (*p2 == CCHR) {
244	c = p2[1];
245	do {
246	if (*p1 != c)
247	continue;
248	if (rv = advance(p1, p2))
249	return(rv);
250	} while (*p1++);
251	return(0);
252	}
253	/*
254	* regular algorithm
255	*/
256	do
257	if (rv = advance(p1, p2))
258	return(rv);
259	while (*p1++);
260	return(0);
261	}
262
263	/*
264	* try to match the next thing in the dfa
265	*/
266	static int
267	advance(lp, ep)
268	register char lp, ep;
269	{
270	register char *curlp;
271	int ct, i;
272	int rv;
273
274	for (;;)
275	switch (*ep++) {
276
277	case CCHR:
278	if (ep++ == lp++)
279	continue;
280	return(0);
281
282	case CDOT:
283	if (*lp++)
284	continue;
285	return(0);
286
287	case CDOL:
288	if (*lp == '\0')
289	continue;
290	return(0);
291
292	case CEOF:
293	return(1);
294
295	case CCL:
296	if (cclass(ep, *lp++, 1)) {
297	ep += *ep;
298	continue;
299	}
300	return(0);
301
302	case NCCL:
303	if (cclass(ep, *lp++, 0)) {
304	ep += *ep;
305	continue;
306	}
307	return(0);
308
309	case CBRA:
310	braslist[*ep++] = lp;
311	continue;
312
313	case CKET:
314	braelist[*ep++] = lp;
315	continue;
316
317	case CBACK:
318	if (braelist[i = *ep++] == 0)
319	return(-1);
320	if (backref(i, lp)) {
321	lp += braelist[i] - braslist[i];
322	continue;
323	}
324	return(0);
325
326	case CBACK\|CSTAR:
327	if (braelist[i = *ep++] == 0)
328	return(-1);
329	curlp = lp;
330	ct = braelist[i] - braslist[i];
331	while (backref(i, lp))
332	lp += ct;
333	while (lp >= curlp) {
334	if (rv = advance(lp, ep))
335	return(rv);
336	lp -= ct;
337	}
338	continue;
339
340	case CDOT\|CSTAR:
341	curlp = lp;
342	while (*lp++)
343	;
344	goto star;
345
346	case CCHR\|CSTAR:
347	curlp = lp;
348	while (lp++ == ep)
349	;
350	ep++;
351	goto star;
352
353	case CCL\|CSTAR:
354	case NCCL\|CSTAR:
355	curlp = lp;
356	while (cclass(ep, *lp++, ep[-1] == (CCL\|CSTAR)))
357	;
358	ep += *ep;
359	goto star;
360
361	star:
362	do {
363	lp--;
364	if (rv = advance(lp, ep))
365	return(rv);
366	} while (lp > curlp);
367	return(0);
368
369	default:
370	return(-1);
371	}
372	}
373
374	backref(i, lp)
375	register int i;
376	register char *lp;
377	{
378	register char *bp;
379
380	bp = braslist[i];
381	while (bp++ == lp++)
382	if (bp >= braelist[i])
383	return(1);
384	return(0);
385	}
386
387	int
388	cclass(set, c, af)
389	register char *set, c;
390	int af;
391	{
392	register int n;
393
394	if (c == 0)
395	return(0);
396	n = *set++;
397	while (--n)
398	if (*set++ == c)
399	return(af);
400	return(! af);
401	}