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

/* @(#)regex.c	4.1 (Berkeley) %G% */
#

/*
 * 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
af509ab3 BJ	1	/* @(#)regex.c 4.1 (Berkeley) %G% */
	2	#
	3
	4	/*
	5	* routines to do regular expression matching
	6	*
	7	* Entry points:
	8	*
	9	* re_comp(s)
	10	* char *s;
	11	* ... returns 0 if the string s was compiled successfully,
	12	* a pointer to an error message otherwise.
	13	* If passed 0 or a null string returns without changing
	14	* the currently compiled re (see note 11 below).
	15	*
	16	* re_exec(s)
	17	* char *s;
	18	* ... returns 1 if the string s matches the last compiled regular
	19	* expression,
	20	* 0 if the string s failed to match the last compiled
	21	* regular expression, and
	22	* -1 if the compiled regular expression was invalid
	23	* (indicating an internal error).
	24	*
	25	* The strings passed to both re_comp and re_exec may have trailing or
	26	* embedded newline characters; they are terminated by nulls.
	27	*
	28	* The identity of the author of these routines is lost in antiquity;
	29	* this is essentially the same as the re code in the original V6 ed.
	30	*
	31	* The regular expressions recognized are described below. This description
	32	* is essentially the same as that for ed.
	33	*
	34	* A regular expression specifies a set of strings of characters.
	35	* A member of this set of strings is said to be matched by
	36	* the regular expression. In the following specification for
	37	* regular expressions the word `character' means any character but NUL.
	38	*
	39	* 1. Any character except a special character matches itself.
	40	* Special characters are the regular expression delimiter plus
	41	* \ [ . and sometimes ^ * $.
	42	* 2. A . matches any character.
	43	* 3. A \ followed by any character except a digit or ( )
	44	* matches that character.
	45	* 4. A nonempty string s bracketed [s] (or [^s]) matches any
	46	* character in (or not in) s. In s, \ has no special meaning,
	47	* and ] may only appear as the first letter. A substring
	48	* a-b, with a and b in ascending ASCII order, stands for
	49	* the inclusive range of ASCII characters.
	50	* 5. A regular expression of form 1-4 followed by * matches a
	51	* sequence of 0 or more matches of the regular expression.
	52	* 6. A regular expression, x, of form 1-8, bracketed \(x\)
	53	* matches what x matches.
	54	* 7. A \ followed by a digit n matches a copy of the string that the
	55	* bracketed regular expression beginning with the nth \( matched.
	56	* 8. A regular expression of form 1-8, x, followed by a regular
	57	* expression of form 1-7, y matches a match for x followed by
	58	* a match for y, with the x match being as long as possible
	59	* while still permitting a y match.
	60	* 9. A regular expression of form 1-8 preceded by ^ (or followed
	61	* by $), is constrained to matches that begin at the left
	62	* (or end at the right) end of a line.
	63	* 10. A regular expression of form 1-9 picks out the longest among
	64	* the leftmost matches in a line.
65	* 11. An empty regular expression stands for a copy of the last
66	* regular expression encountered.
67	*/
68
69	/*
70	* constants for re's
71	*/
72	#define CBRA 1
73	#define CCHR 2
74	#define CDOT 4
75	#define CCL 6
76	#define NCCL 8
77	#define CDOL 10
78	#define CEOF 11
79	#define CKET 12
80	#define CBACK 18
81
82	#define CSTAR 01
83
84	#define ESIZE 512
85	#define NBRA 9
86
87	static char expbuf[ESIZE], braslist[NBRA], braelist[NBRA];
88	static char circf;
89
90	/*
91	* compile the regular expression argument into a dfa
92	*/
93	char *
94	re_comp(sp)
95	register char *sp;
96	{
97	register int c;
98	register char *ep = expbuf;
99	int cclcnt, numbra = 0;
100	char *lastep = 0;
101	char bracket[NBRA];
102	char *bracketp = &bracket[0];
103	static char *retoolong = "Regular expression too long";
104
105	#define comerr(msg) {expbuf[0] = 0; numbra = 0; return(msg); }
106
107	if (sp == 0 \|\| *sp == '\0') {
108	if (*ep == 0)
109	return("No previous regular expression");
110	return(0);
111	}
112	if (*sp == '^') {
113	circf = 1;
114	sp++;
115	}
116	else
117	circf = 0;
118	for (;;) {
119	if (ep >= &expbuf[ESIZE])
120	comerr(retoolong);
121	if ((c = *sp++) == '\0') {
122	if (bracketp != bracket)
123	comerr("unmatched \\(");
124	*ep++ = CEOF;
125	*ep++ = 0;
126	return(0);
127	}
128	if (c != '*')
129	lastep = ep;
130	switch (c) {
131
132	case '.':
133	*ep++ = CDOT;
134	continue;
135
136	case '*':
137	if (lastep == 0 \|\| lastep == CBRA \|\| lastep == CKET)
138	goto defchar;
139	*lastep \|= CSTAR;
140	continue;
141
142	case '$':
143	if (*sp != '\0')
144	goto defchar;
145	*ep++ = CDOL;
146	continue;
147
148	case '[':
149	*ep++ = CCL;
150	*ep++ = 0;
151	cclcnt = 1;
152	if ((c = *sp++) == '^') {
153	c = *sp++;
154	ep[-2] = NCCL;
155	}
156	do {
157	if (c == '\0')
158	comerr("missing ]");
159	if (c == '-' && ep [-1] != 0) {
160	if ((c = *sp++) == ']') {
161	*ep++ = '-';
162	cclcnt++;
163	break;
164	}
165	while (ep[-1] < c) {
166	*ep = ep[-1] + 1;
167	ep++;
168	cclcnt++;
169	if (ep >= &expbuf[ESIZE])
170	comerr(retoolong);
171	}
172	}
173	*ep++ = c;
174	cclcnt++;
175	if (ep >= &expbuf[ESIZE])
176	comerr(retoolong);
177	} while ((c = *sp++) != ']');
178	lastep[1] = cclcnt;
179	continue;
180
181	case '\\':
182	if ((c = *sp++) == '(') {
183	if (numbra >= NBRA)
184	comerr("too many \\(\\) pairs");
185	*bracketp++ = numbra;
186	*ep++ = CBRA;
187	*ep++ = numbra++;
188	continue;
189	}
190	if (c == ')') {
191	if (bracketp <= bracket)
192	comerr("unmatched \\)");
193	*ep++ = CKET;
194	ep++ = --bracketp;
195	continue;
196	}
197	if (c >= '1' && c < ('1' + NBRA)) {
198	*ep++ = CBACK;
199	*ep++ = c - '1';
200	continue;
201	}
202	*ep++ = CCHR;
203	*ep++ = c;
204	continue;
205
206	defchar:
207	default:
208	*ep++ = CCHR;
209	*ep++ = c;
210	}
211	}
212	}
213
214	/*
215	* match the argument string against the compiled re
216	*/
217	int
218	re_exec(p1)
219	register char *p1;
220	{
221	register char *p2 = expbuf;
222	register int c;
223	int rv;
224
225	for (c = 0; c < NBRA; c++) {
226	braslist[c] = 0;
227	braelist[c] = 0;
228	}
229	if (circf)
230	return((advance(p1, p2)));
231	/*
232	* fast check for first character
233	*/
234	if (*p2 == CCHR) {
235	c = p2[1];
236	do {
237	if (*p1 != c)
238	continue;
239	if (rv = advance(p1, p2))
240	return(rv);
241	} while (*p1++);
242	return(0);
243	}
244	/*
245	* regular algorithm
246	*/
247	do
248	if (rv = advance(p1, p2))
249	return(rv);
250	while (*p1++);
251	return(0);
252	}
253
254	/*
255	* try to match the next thing in the dfa
256	*/
257	static int
258	advance(lp, ep)
259	register char lp, ep;
260	{
261	register char *curlp;
262	int ct, i;
263	int rv;
264
265	for (;;)
266	switch (*ep++) {
267
268	case CCHR:
269	if (ep++ == lp++)
270	continue;
271	return(0);
272
273	case CDOT:
274	if (*lp++)
275	continue;
276	return(0);
277
278	case CDOL:
279	if (*lp == '\0')
280	continue;
281	return(0);
282
283	case CEOF:
284	return(1);
285
286	case CCL:
287	if (cclass(ep, *lp++, 1)) {
288	ep += *ep;
289	continue;
290	}
291	return(0);
292
293	case NCCL:
294	if (cclass(ep, *lp++, 0)) {
295	ep += *ep;
296	continue;
297	}
298	return(0);
299
300	case CBRA:
301	braslist[*ep++] = lp;
302	continue;
303
304	case CKET:
305	braelist[*ep++] = lp;
306	continue;
307
308	case CBACK:
309	if (braelist[i = *ep++] == 0)
310	return(-1);
311	if (backref(i, lp)) {
312	lp += braelist[i] - braslist[i];
313	continue;
314	}
315	return(0);
316
317	case CBACK\|CSTAR:
318	if (braelist[i = *ep++] == 0)
319	return(-1);
320	curlp = lp;
321	ct = braelist[i] - braslist[i];
322	while (backref(i, lp))
323	lp += ct;
324	while (lp >= curlp) {
325	if (rv = advance(lp, ep))
326	return(rv);
327	lp -= ct;
328	}
329	continue;
330
331	case CDOT\|CSTAR:
332	curlp = lp;
333	while (*lp++)
334	;
335	goto star;
336
337	case CCHR\|CSTAR:
338	curlp = lp;
339	while (lp++ == ep)
340	;
341	ep++;
342	goto star;
343
344	case CCL\|CSTAR:
345	case NCCL\|CSTAR:
346	curlp = lp;
347	while (cclass(ep, *lp++, ep[-1] == (CCL\|CSTAR)))
348	;
349	ep += *ep;
350	goto star;
351
352	star:
353	do {
354	lp--;
355	if (rv = advance(lp, ep))
356	return(rv);
357	} while (lp > curlp);
358	return(0);
359
360	default:
361	return(-1);
362	}
363	}
364
365	backref(i, lp)
366	register int i;
367	register char *lp;
368	{
369	register char *bp;
370
371	bp = braslist[i];
372	while (bp++ == lp++)
373	if (bp >= braelist[i])
374	return(1);
375	return(0);
376	}
377
378	int
379	cclass(set, c, af)
380	register char *set, c;
381	int af;
382	{
383	register int n;
384
385	if (c == 0)
386	return(0);
387	n = *set++;
388	while (--n)
389	if (*set++ == c)
390	return(af);
391	return(! af);
392	}