engine.c

关系型数据库 Postgresql 6.5.2

/*-
 * Copyright (c) 1992, 1993, 1994 Henry Spencer.
 * Copyright (c) 1992, 1993, 1994
 *		The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Henry Spencer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	  notice, this list of conditions and the following disclaimer in the
 *	  documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *	  must display the following acknowledgement:
 *		This product includes software developed by the University of
 *		California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *	  may be used to endorse or promote products derived from this software
 *	  without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.	IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *		@(#)engine.c	8.5 (Berkeley) 3/20/94
 */

/*
 * The matching engine and friends.  This file is #included by regexec.c
 * after suitable #defines of a variety of macros used herein, so that
 * different state representations can be used without duplicating masses
 * of code.
 */

#ifdef SNAMES
#define matcher smatcher
#define fast	sfast
#define slow	sslow
#define dissect sdissect
#define backref sbackref
#define step	sstep
#define print	sprint
#define at		sat
#define match	smat
#endif
#ifdef LNAMES
#define matcher lmatcher
#define fast	lfast
#define slow	lslow
#define dissect ldissect
#define backref lbackref
#define step	lstep
#define print	lprint
#define at		lat
#define match	lmat
#endif

/* another structure passed up and down to avoid zillions of parameters */
struct match
{
	struct re_guts *g;
	int			eflags;
	regmatch_t *pmatch;			/* [nsub+1] (0 element unused) */
	pg_wchar   *offp;			/* offsets work from here */
	pg_wchar   *beginp;			/* start of string -- virtual NUL precedes */
	pg_wchar   *endp;			/* end of string -- virtual NUL here */
	pg_wchar   *coldp;			/* can be no match starting before here */
	pg_wchar  **lastpos;		/* [nplus+1] */
				STATEVARS;
	states		st;				/* current states */
	states		fresh;			/* states for a fresh start */
	states		tmp;			/* temporary */
	states		empty;			/* empty set of states */
};

/* ========= begin header generated by ./mkh ========= */
#ifdef __cplusplus
extern		"C"
{
#endif

/* === engine.c === */
	static int
				matcher(struct re_guts * g, pg_wchar * string, size_t nmatch,
									regmatch_t *pmatch, int eflags);
	static pg_wchar *
				dissect(struct match * m, pg_wchar * start, pg_wchar * stop,
									sopno startst, sopno stopst);
	static pg_wchar *
				backref(struct match * m, pg_wchar * start, pg_wchar * stop,
								 sopno startst, sopno stopst, sopno lev);
	static pg_wchar *
				fast(struct match * m, pg_wchar * start, pg_wchar * stop,
								 sopno startst, sopno stopst);
	static pg_wchar *
				slow(struct match * m, pg_wchar * start, pg_wchar * stop, sopno startst, sopno stopst);
	static		states
				step(struct re_guts * g, sopno start,
							 sopno stop, states bef, int ch, states aft);
#define BOL		(OUT+1)
#define EOL		(BOL+1)
#define BOLEOL	(BOL+2)
#define NOTHING (BOL+3)
#define BOW		(BOL+4)
#define EOW		(BOL+5)
#define CODEMAX (BOL+5)			/* highest code used */

#ifdef MULTIBYTE
#define NONCHAR(c)	  ((c) > 16777216)	/* 16777216 == 2^24 == 3 bytes */
#define NNONCHAR  (CODEMAX-16777216)
#else
#define NONCHAR(c)		  ((c) > CHAR_MAX)
#define NNONCHAR	  (CODEMAX-CHAR_MAX)
#endif

#ifdef REDEBUG
	static void
				print(struct match * m, pg_wchar * caption, states st, int ch, FILE *d);
#endif
#ifdef REDEBUG
	static void
				at(struct match * m, pg_wchar * title, pg_wchar * start, pg_wchar * stop,
							   sopno startst, sopno stopst);
#endif
#ifdef REDEBUG
	static pg_wchar *
				p_char(int ch);
#endif

#ifdef __cplusplus
}

#endif
/* ========= end header generated by ./mkh ========= */

#ifdef REDEBUG
#define SP(t, s, c)		print(m, t, s, c, stdout)
#define AT(t, p1, p2, s1, s2)	at(m, t, p1, p2, s1, s2)
#define NOTE(str)		{ if (m->eflags&REG_TRACE) printf("=%s\n", (str)); }
#else
#define SP(t, s, c)				/* nothing */
#define AT(t, p1, p2, s1, s2)	/* nothing */
#define NOTE(s)					/* nothing */
#endif

/*
 - matcher - the actual matching engine
 == static int matcher(struct re_guts *g, pg_wchar *string, \
 ==		size_t nmatch, regmatch_t *pmatch, int eflags);
 */
static int						/* 0 success, REG_NOMATCH failure */
matcher(g, string, nmatch, pmatch, eflags)
struct re_guts *g;
pg_wchar   *string;
size_t		nmatch;
regmatch_t *pmatch;
int			eflags;
{
	pg_wchar   *endp;
	int			i;
	struct match mv;
	struct match *m = &mv;
	pg_wchar   *dp;
	const sopno gf = g->firststate + 1; /* +1 for OEND */
	const sopno gl = g->laststate;
	pg_wchar   *start;
	pg_wchar   *stop;

	/* simplify the situation where possible */
	if (g->cflags & REG_NOSUB)
		nmatch = 0;
	if (eflags & REG_STARTEND)
	{
		start = string + pmatch[0].rm_so;
		stop = string + pmatch[0].rm_eo;
	}
	else
	{
		start = string;
#ifdef MULTIBYTE
		stop = start + pg_wchar_strlen(start);
#else
		stop = start + strlen(start);
#endif
	}
	if (stop < start)
		return REG_INVARG;

	/* prescreening; this does wonders for this rather slow code */
	if (g->must != NULL)
	{
		for (dp = start; dp < stop; dp++)
			if (*dp == g->must[0] && stop - dp >= g->mlen &&
#ifdef MULTIBYTE
				memcmp(dp, g->must, (size_t) (g->mlen * sizeof(pg_wchar))) == 0)
#else
				memcmp(dp, g->must, (size_t) g->mlen) == 0)
#endif
				break;
		if (dp == stop)			/* we didn't find g->must */
			return REG_NOMATCH;
	}

	/* match struct setup */
	m->g = g;
	m->eflags = eflags;
	m->pmatch = NULL;
	m->lastpos = NULL;
	m->offp = string;
	m->beginp = start;
	m->endp = stop;
	STATESETUP(m, 4);
	SETUP(m->st);
	SETUP(m->fresh);
	SETUP(m->tmp);
	SETUP(m->empty);
	CLEAR(m->empty);

	/* this loop does only one repetition except for backrefs */
	for (;;)
	{
		endp = fast(m, start, stop, gf, gl);
		if (endp == NULL)
		{						/* a miss */
			STATETEARDOWN(m);
			return REG_NOMATCH;
		}
		if (nmatch == 0 && !g->backrefs)
			break;				/* no further info needed */

		/* where? */
		assert(m->coldp != NULL);
		for (;;)
		{
			NOTE("finding start");
			endp = slow(m, m->coldp, stop, gf, gl);
			if (endp != NULL)
				break;
			assert(m->coldp < m->endp);
			m->coldp++;
		}
		if (nmatch == 1 && !g->backrefs)
			break;				/* no further info needed */

		/* oh my, he wants the subexpressions... */
		if (m->pmatch == NULL)
			m->pmatch = (regmatch_t *) malloc((m->g->nsub + 1) *
											  sizeof(regmatch_t));
		if (m->pmatch == NULL)
		{
			STATETEARDOWN(m);
			return REG_ESPACE;
		}
		for (i = 1; i <= m->g->nsub; i++)
			m->pmatch[i].rm_so = m->pmatch[i].rm_eo = -1;
		if (!g->backrefs && !(m->eflags & REG_BACKR))
		{
			NOTE("dissecting");
			dp = dissect(m, m->coldp, endp, gf, gl);
		}
		else
		{
			if (g->nplus > 0 && m->lastpos == NULL)
				m->lastpos = (pg_wchar **) malloc((g->nplus + 1) *
												  sizeof(pg_wchar *));
			if (g->nplus > 0 && m->lastpos == NULL)
			{
				free(m->pmatch);
				STATETEARDOWN(m);
				return REG_ESPACE;
			}
			NOTE("backref dissect");
			dp = backref(m, m->coldp, endp, gf, gl, (sopno) 0);
		}
		if (dp != NULL)
			break;

		/* uh-oh... we couldn't find a subexpression-level match */
		assert(g->backrefs);	/* must be back references doing it */
		assert(g->nplus == 0 || m->lastpos != NULL);
		for (;;)
		{
			if (dp != NULL || endp <= m->coldp)
				break;			/* defeat */
			NOTE("backoff");
			endp = slow(m, m->coldp, endp - 1, gf, gl);
			if (endp == NULL)
				break;			/* defeat */
			/* try it on a shorter possibility */
#ifndef NDEBUG
			for (i = 1; i <= m->g->nsub; i++)
			{
				assert(m->pmatch[i].rm_so == -1);
				assert(m->pmatch[i].rm_eo == -1);
			}
#endif
			NOTE("backoff dissect");
			dp = backref(m, m->coldp, endp, gf, gl, (sopno) 0);
		}
		assert(dp == NULL || dp == endp);
		if (dp != NULL)			/* found a shorter one */
			break;

		/* despite initial appearances, there is no match here */
		NOTE("false alarm");
		start = m->coldp + 1;	/* recycle starting later */
		assert(start <= stop);
	}

	/* fill in the details if requested */
	if (nmatch > 0)
	{
		pmatch[0].rm_so = m->coldp - m->offp;
		pmatch[0].rm_eo = endp - m->offp;
	}
	if (nmatch > 1)
	{
		assert(m->pmatch != NULL);
		for (i = 1; i < nmatch; i++)
			if (i <= m->g->nsub)
				pmatch[i] = m->pmatch[i];
			else
			{
				pmatch[i].rm_so = -1;
				pmatch[i].rm_eo = -1;
			}
	}

	if (m->pmatch != NULL)
		free((pg_wchar *) m->pmatch);
	if (m->lastpos != NULL)
		free((pg_wchar *) m->lastpos);
	STATETEARDOWN(m);
	return 0;
}

/*
 - dissect - figure out what matched what, no back references
 == static char *dissect(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst);
 */
static pg_wchar *				/* == stop (success) always */
dissect(m, start, stop, startst, stopst)
struct match *m;
pg_wchar   *start;
pg_wchar   *stop;
sopno		startst;
sopno		stopst;
{
	int			i;
	sopno		ss;				/* start sop of current subRE */
	sopno		es;				/* end sop of current subRE */
	pg_wchar   *sp;				/* start of string matched by it */
	pg_wchar   *stp;			/* string matched by it cannot pass here */
	pg_wchar   *rest;			/* start of rest of string */
	pg_wchar   *tail;			/* string unmatched by rest of RE */
	sopno		ssub;			/* start sop of subsubRE */
	sopno		esub;			/* end sop of subsubRE */
	pg_wchar   *ssp;			/* start of string matched by subsubRE */
	pg_wchar   *sep;			/* end of string matched by subsubRE */
	pg_wchar   *oldssp;			/* previous ssp */
	pg_wchar   *dp;

	AT("diss", start, stop, startst, stopst);
	sp = start;
	for (ss = startst; ss < stopst; ss = es)
	{
		/* identify end of subRE */
		es = ss;
		switch (OP(m->g->strip[es]))
		{
			case OPLUS_:
			case OQUEST_:
				es += OPND(m->g->strip[es]);
				break;
			case OCH_:
				while (OP(m->g->strip[es]) != O_CH)
					es += OPND(m->g->strip[es]);
				break;
		}
		es++;

		/* figure out what it matched */
		switch (OP(m->g->strip[ss]))
		{
			case OEND:
				assert(nope);
				break;
			case OCHAR:
				sp++;
				break;
			case OBOL:
			case OEOL:
			case OBOW:
			case OEOW:
				break;
			case OANY:
			case OANYOF:
				sp++;
				break;
			case OBACK_:
			case O_BACK:
				assert(nope);
				break;
				/* cases where length of match is hard to find */
			case OQUEST_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = es - 1;
				/* did innards match? */
				if (slow(m, sp, rest, ssub, esub) != NULL)
				{
					dp = dissect(m, sp, rest, ssub, esub);
					assert(dp == rest);
				}
				else
/* no */
					assert(sp == rest);
				sp = rest;
				break;
			case OPLUS_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = es - 1;
				ssp = sp;
				oldssp = ssp;
				for (;;)
				{				/* find last match of innards */
					sep = slow(m, ssp, rest, ssub, esub);
					if (sep == NULL || sep == ssp)
						break;	/* failed or matched null */
					oldssp = ssp;		/* on to next try */
					ssp = sep;
				}
				if (sep == NULL)
				{
					/* last successful match */
					sep = ssp;
					ssp = oldssp;
				}
				assert(sep == rest);	/* must exhaust substring */
				assert(slow(m, ssp, sep, ssub, esub) == rest);
				dp = dissect(m, ssp, sep, ssub, esub);
				assert(dp == sep);
				sp = rest;
				break;
			case OCH_:
				stp = stop;
				for (;;)
				{
					/* how long could this one be? */
					rest = slow(m, sp, stp, ss, es);
					assert(rest != NULL);		/* it did match */
					/* could the rest match the rest? */
					tail = slow(m, rest, stop, es, stopst);
					if (tail == stop)
						break;	/* yes! */
					/* no -- try a shorter match for this one */
					stp = rest - 1;
					assert(stp >= sp);	/* it did work */
				}
				ssub = ss + 1;
				esub = ss + OPND(m->g->strip[ss]) - 1;
				assert(OP(m->g->strip[esub]) == OOR1);
				for (;;)
				{				/* find first matching branch */
					if (slow(m, sp, rest, ssub, esub) == rest)
						break;	/* it matched all of it */
					/* that one missed, try next one */
					assert(OP(m->g->strip[esub]) == OOR1);
					esub++;
					assert(OP(m->g->strip[esub]) == OOR2);
					ssub = esub + 1;
					esub += OPND(m->g->strip[esub]);
					if (OP(m->g->strip[esub]) == OOR2)
						esub--;
					else
						assert(OP(m->g->strip[esub]) == O_CH);
				}
				dp = dissect(m, sp, rest, ssub, esub);
				assert(dp == rest);
				sp = rest;
				break;
			case O_PLUS:
			case O_QUEST:
			case OOR1:
			case OOR2:
			case O_CH:
				assert(nope);
				break;
			case OLPAREN:
				i = OPND(m->g->strip[ss]);
				assert(0 < i && i <= m->g->nsub);
				m->pmatch[i].rm_so = sp - m->offp;
				break;
			case ORPAREN:
				i = OPND(m->g->strip[ss]);
				assert(0 < i && i <= m->g->nsub);
				m->pmatch[i].rm_eo = sp - m->offp;
				break;
			default:			/* uh oh */
				assert(nope);
				break;
		}
	}

	assert(sp == stop);
	return sp;
}

/*
 - backref - figure out what matched what, figuring in back references
 == static char *backref(struct match *m, char *start, \
 ==		char *stop, sopno startst, sopno stopst, sopno lev);
 */
static pg_wchar *				/* == stop (success) or NULL (failure) */
backref(m, start, stop, startst, stopst, lev)
struct match *m;
pg_wchar   *start;
pg_wchar   *stop;
sopno		startst;
sopno		stopst;
sopno		lev;				/* PLUS nesting level */
{
	int			i;
	sopno		ss;				/* start sop of current subRE */
	pg_wchar   *sp;				/* start of string matched by it */
	sopno		ssub;			/* start sop of subsubRE */
	sopno		esub;			/* end sop of subsubRE */
	pg_wchar   *ssp;			/* start of string matched by subsubRE */
	pg_wchar   *dp;
	size_t		len;
	int			hard;
	sop			s;
	regoff_t	offsave;
	cset	   *cs;

	AT("back", start, stop, startst, stopst);
	sp = start;

	/* get as far as we can with easy stuff */
	hard = 0;
	for (ss = startst; !hard && ss < stopst; ss++)
		switch (OP(s = m->g->strip[ss]))
		{
			case OCHAR:
				if (sp == stop || *sp++ != (pg_wchar) OPND(s))
					return NULL;
				break;
			case OANY:
				if (sp == stop)
					return NULL;
				sp++;
				break;
			case OANYOF:
				cs = &m->g->sets[OPND(s)];
				if (sp == stop || !CHIN(cs, *sp++))