rege_dfa.c

从一个开源软件中摘取的正则表达式模块

/*
 * DFA routines
 * This file is #included by regexec.c.
 *
 * Copyright (c) 1998, 1999 Henry Spencer.	All rights reserved.
 *
 * Development of this software was funded, in part, by Cray Research Inc.,
 * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
 * Corporation, none of whom are responsible for the results.  The author
 * thanks all of them.
 *
 * Redistribution and use in source and binary forms -- with or without
 * modification -- are permitted for any purpose, provided that
 * redistributions in source form retain this entire copyright notice and
 * indicate the origin and nature of any modifications.
 *
 * I'd appreciate being given credit for this package in the documentation
 * of software which uses it, but that is not a requirement.
 *
 * THIS SOFTWARE IS PROVIDED ``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
 * HENRY SPENCER 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.
 *
 * $PostgreSQL: pgsql/src/backend/regex/rege_dfa.c,v 1.8 2007/10/06 16:05:54 tgl Exp $
 *
 */

/*
 * longest - longest-preferred matching engine
 */
static chr *					/* endpoint, or NULL */
longest(struct vars * v,		/* used only for debug and exec flags */
		struct dfa * d,
		chr *start,				/* where the match should start */
		chr *stop,				/* match must end at or before here */
		int *hitstopp)			/* record whether hit v->stop, if non-NULL */
{
	chr		   *cp;
	chr		   *realstop = (stop == v->stop) ? stop : stop + 1;
	color		co;
	struct sset *css;
	struct sset *ss;
	chr		   *post;
	int			i;
	struct colormap *cm = d->cm;

	/* initialize */
	css = initialize(v, d, start);
	cp = start;
	if (hitstopp != NULL)
		*hitstopp = 0;

	/* startup */
	FDEBUG(("+++ startup +++\n"));
	if (cp == v->start)
	{
		co = d->cnfa->bos[(v->eflags & REG_NOTBOL) ? 0 : 1];
		FDEBUG(("color %ld\n", (long) co));
	}
	else
	{
		co = GETCOLOR(cm, *(cp - 1));
		FDEBUG(("char %c, color %ld\n", (char) *(cp - 1), (long) co));
	}
	css = miss(v, d, css, co, cp, start);
	if (css == NULL)
		return NULL;
	css->lastseen = cp;

	/* main loop */
	if (v->eflags & REG_FTRACE)
		while (cp < realstop)
		{
			FDEBUG(("+++ at c%d +++\n", (int) (css - d->ssets)));
			co = GETCOLOR(cm, *cp);
			FDEBUG(("char %c, color %ld\n", (char) *cp, (long) co));
			ss = css->outs[co];
			if (ss == NULL)
			{
				ss = miss(v, d, css, co, cp + 1, start);
				if (ss == NULL)
					break;		/* NOTE BREAK OUT */
			}
			cp++;
			ss->lastseen = cp;
			css = ss;
		}
	else
		while (cp < realstop)
		{
			co = GETCOLOR(cm, *cp);
			ss = css->outs[co];
			if (ss == NULL)
			{
				ss = miss(v, d, css, co, cp + 1, start);
				if (ss == NULL)
					break;		/* NOTE BREAK OUT */
			}
			cp++;
			ss->lastseen = cp;
			css = ss;
		}

	/* shutdown */
	FDEBUG(("+++ shutdown at c%d +++\n", (int) (css - d->ssets)));
	if (cp == v->stop && stop == v->stop)
	{
		if (hitstopp != NULL)
			*hitstopp = 1;
		co = d->cnfa->eos[(v->eflags & REG_NOTEOL) ? 0 : 1];
		FDEBUG(("color %ld\n", (long) co));
		ss = miss(v, d, css, co, cp, start);
		/* special case:  match ended at eol? */
		if (ss != NULL && (ss->flags & POSTSTATE))
			return cp;
		else if (ss != NULL)
			ss->lastseen = cp;	/* to be tidy */
	}

	/* find last match, if any */
	post = d->lastpost;
	for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--)
		if ((ss->flags & POSTSTATE) && post != ss->lastseen &&
			(post == NULL || post < ss->lastseen))
			post = ss->lastseen;
	if (post != NULL)			/* found one */
		return post - 1;

	return NULL;
}

/*
 * shortest - shortest-preferred matching engine
 */
static chr *					/* endpoint, or NULL */
shortest(struct vars * v,
		 struct dfa * d,
		 chr *start,			/* where the match should start */
		 chr *min,				/* match must end at or after here */
		 chr *max,				/* match must end at or before here */
		 chr **coldp,			/* store coldstart pointer here, if nonNULL */
		 int *hitstopp)			/* record whether hit v->stop, if non-NULL */
{
	chr		   *cp;
	chr		   *realmin = (min == v->stop) ? min : min + 1;
	chr		   *realmax = (max == v->stop) ? max : max + 1;
	color		co;
	struct sset *css;
	struct sset *ss;
	struct colormap *cm = d->cm;

	/* initialize */
	css = initialize(v, d, start);
	cp = start;
	if (hitstopp != NULL)
		*hitstopp = 0;

	/* startup */
	FDEBUG(("--- startup ---\n"));
	if (cp == v->start)
	{
		co = d->cnfa->bos[(v->eflags & REG_NOTBOL) ? 0 : 1];
		FDEBUG(("color %ld\n", (long) co));
	}
	else
	{
		co = GETCOLOR(cm, *(cp - 1));
		FDEBUG(("char %c, color %ld\n", (char) *(cp - 1), (long) co));
	}
	css = miss(v, d, css, co, cp, start);
	if (css == NULL)
		return NULL;
	css->lastseen = cp;
	ss = css;

	/* main loop */
	if (v->eflags & REG_FTRACE)
		while (cp < realmax)
		{
			FDEBUG(("--- at c%d ---\n", (int) (css - d->ssets)));
			co = GETCOLOR(cm, *cp);
			FDEBUG(("char %c, color %ld\n", (char) *cp, (long) co));
			ss = css->outs[co];
			if (ss == NULL)
			{
				ss = miss(v, d, css, co, cp + 1, start);
				if (ss == NULL)
					break;		/* NOTE BREAK OUT */
			}
			cp++;
			ss->lastseen = cp;
			css = ss;
			if ((ss->flags & POSTSTATE) && cp >= realmin)
				break;			/* NOTE BREAK OUT */
		}
	else
		while (cp < realmax)
		{
			co = GETCOLOR(cm, *cp);
			ss = css->outs[co];
			if (ss == NULL)
			{
				ss = miss(v, d, css, co, cp + 1, start);
				if (ss == NULL)
					break;		/* NOTE BREAK OUT */
			}
			cp++;
			ss->lastseen = cp;
			css = ss;
			if ((ss->flags & POSTSTATE) && cp >= realmin)
				break;			/* NOTE BREAK OUT */
		}

	if (ss == NULL)
		return NULL;

	if (coldp != NULL)			/* report last no-progress state set, if any */
		*coldp = lastcold(v, d);

	if ((ss->flags & POSTSTATE) && cp > min)
	{
		assert(cp >= realmin);
		cp--;
	}
	else if (cp == v->stop && max == v->stop)
	{
		co = d->cnfa->eos[(v->eflags & REG_NOTEOL) ? 0 : 1];
		FDEBUG(("color %ld\n", (long) co));
		ss = miss(v, d, css, co, cp, start);
		/* match might have ended at eol */
		if ((ss == NULL || !(ss->flags & POSTSTATE)) && hitstopp != NULL)
			*hitstopp = 1;
	}

	if (ss == NULL || !(ss->flags & POSTSTATE))
		return NULL;

	return cp;
}

/*
 * lastcold - determine last point at which no progress had been made
 */
static chr *					/* endpoint, or NULL */
lastcold(struct vars * v,
		 struct dfa * d)
{
	struct sset *ss;
	chr		   *nopr;
	int			i;

	nopr = d->lastnopr;
	if (nopr == NULL)
		nopr = v->start;
	for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--)
		if ((ss->flags & NOPROGRESS) && nopr < ss->lastseen)
			nopr = ss->lastseen;
	return nopr;
}

/*
 * newdfa - set up a fresh DFA
 */
static struct dfa *
newdfa(struct vars * v,
	   struct cnfa * cnfa,
	   struct colormap * cm,
	   struct smalldfa * small) /* preallocated space, may be NULL */
{
	struct dfa *d;
	size_t		nss = cnfa->nstates * 2;
	int			wordsper = (cnfa->nstates + UBITS - 1) / UBITS;
	struct smalldfa *smallwas = small;

	assert(cnfa != NULL && cnfa->nstates != 0);

	if (nss <= FEWSTATES && cnfa->ncolors <= FEWCOLORS)
	{
		assert(wordsper == 1);
		if (small == NULL)
		{
			small = (struct smalldfa *) MALLOC(
											   sizeof(struct smalldfa));
			if (small == NULL)
			{
				ERR(REG_ESPACE);
				return NULL;
			}
		}
		d = &small->dfa;
		d->ssets = small->ssets;
		d->statesarea = small->statesarea;
		d->work = &d->statesarea[nss];
		d->outsarea = small->outsarea;
		d->incarea = small->incarea;
		d->cptsmalloced = 0;
		d->mallocarea = (smallwas == NULL) ? (char *) small : NULL;
	}
	else
	{
		d = (struct dfa *) MALLOC(sizeof(struct dfa));
		if (d == NULL)
		{
			ERR(REG_ESPACE);
			return NULL;
		}
		d->ssets = (struct sset *) MALLOC(nss * sizeof(struct sset));
		d->statesarea = (unsigned *) MALLOC((nss + WORK) * wordsper *
											sizeof(unsigned));
		d->work = &d->statesarea[nss * wordsper];
		d->outsarea = (struct sset **) MALLOC(nss * cnfa->ncolors *
											  sizeof(struct sset *));
		d->incarea = (struct arcp *) MALLOC(nss * cnfa->ncolors *
											sizeof(struct arcp));
		d->cptsmalloced = 1;
		d->mallocarea = (char *) d;
		if (d->ssets == NULL || d->statesarea == NULL ||
			d->outsarea == NULL || d->incarea == NULL)
		{
			freedfa(d);
			ERR(REG_ESPACE);
			return NULL;
		}
	}

	d->nssets = (v->eflags & REG_SMALL) ? 7 : nss;
	d->nssused = 0;
	d->nstates = cnfa->nstates;
	d->ncolors = cnfa->ncolors;
	d->wordsper = wordsper;
	d->cnfa = cnfa;
	d->cm = cm;
	d->lastpost = NULL;
	d->lastnopr = NULL;
	d->search = d->ssets;

	/* initialization of sset fields is done as needed */

	return d;
}

/*
 * freedfa - free a DFA