Logo Search packages:      
Sourcecode: tcl8.4 version File versions  Download package

rege_dfa.c

/*
 * 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.
 *
 */

/*
 - longest - longest-preferred matching engine
 ^ static chr *longest(struct vars *, struct dfa *, chr *, chr *, int *);
 */
static chr *                  /* endpoint, or NULL */
longest(v, d, start, stop, hitstopp)
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", 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", 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 *shortest(struct vars *, struct dfa *, chr *, chr *, chr *,
 ^    chr **, int *);
 */
static chr *                  /* endpoint, or NULL */
shortest(v, d, start, min, max, coldp, hitstopp)
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", 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 *lastcold(struct vars *, struct dfa *);
 */
static chr *                  /* endpoint, or NULL */
lastcold(v, d)
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 *, struct cnfa *,
 ^    struct colormap *, struct smalldfa *);
 */
static struct dfa *
newdfa(v, cnfa, cm, small)
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
 ^ static VOID freedfa(struct dfa *);
 */
static VOID
freedfa(d)
struct dfa *d;
{
      if (d->cptsmalloced) {
            if (d->ssets != NULL)
                  FREE(d->ssets);
            if (d->statesarea != NULL)
                  FREE(d->statesarea);
            if (d->outsarea != NULL)
                  FREE(d->outsarea);
            if (d->incarea != NULL)
                  FREE(d->incarea);
      }

      if (d->mallocarea != NULL)
            FREE(d->mallocarea);
}

/*
 - hash - construct a hash code for a bitvector
 * There are probably better ways, but they're more expensive.
 ^ static unsigned hash(unsigned *, int);
 */
static unsigned
hash(uv, n)
unsigned *uv;
int n;
{
      int i;
      unsigned h;

      h = 0;
      for (i = 0; i < n; i++)
            h ^= uv[i];
      return h;
}

/*
 - initialize - hand-craft a cache entry for startup, otherwise get ready
 ^ static struct sset *initialize(struct vars *, struct dfa *, chr *);
 */
static struct sset *
initialize(v, d, start)
struct vars *v;               /* used only for debug flags */
struct dfa *d;
chr *start;
{
      struct sset *ss;
      int i;

      /* is previous one still there? */
      if (d->nssused > 0 && (d->ssets[0].flags&STARTER))
            ss = &d->ssets[0];
      else {                        /* no, must (re)build it */
            ss = getvacant(v, d, start, start);
            for (i = 0; i < d->wordsper; i++)
                  ss->states[i] = 0;
            BSET(ss->states, d->cnfa->pre);
            ss->hash = HASH(ss->states, d->wordsper);
            assert(d->cnfa->pre != d->cnfa->post);
            ss->flags = STARTER|LOCKED|NOPROGRESS;
            /* lastseen dealt with below */
      }

      for (i = 0; i < d->nssused; i++)
            d->ssets[i].lastseen = NULL;
      ss->lastseen = start;         /* maybe untrue, but harmless */
      d->lastpost = NULL;
      d->lastnopr = NULL;
      return ss;
}

/*
 - miss - handle a cache miss
 ^ static struct sset *miss(struct vars *, struct dfa *, struct sset *,
 ^    pcolor, chr *, chr *);
 */
static struct sset *          /* NULL if goes to empty set */
miss(v, d, css, co, cp, start)
struct vars *v;               /* used only for debug flags */
struct dfa *d;
struct sset *css;
pcolor co;
chr *cp;                /* next chr */
chr *start;             /* where the attempt got started */
{
      struct cnfa *cnfa = d->cnfa;
      int i;
      unsigned h;
      struct carc *ca;
      struct sset *p;
      int ispost;
      int noprogress;
      int gotstate;
      int dolacons;
      int sawlacons;

      /* for convenience, we can be called even if it might not be a miss */
      if (css->outs[co] != NULL) {
            FDEBUG(("hit\n"));
            return css->outs[co];
      }
      FDEBUG(("miss\n"));

      /* first, what set of states would we end up in? */
      for (i = 0; i < d->wordsper; i++)
            d->work[i] = 0;
      ispost = 0;
      noprogress = 1;
      gotstate = 0;
      for (i = 0; i < d->nstates; i++)
            if (ISBSET(css->states, i))
                  for (ca = cnfa->states[i]+1; ca->co != COLORLESS; ca++)
                        if (ca->co == co) {
                              BSET(d->work, ca->to);
                              gotstate = 1;
                              if (ca->to == cnfa->post)
                                    ispost = 1;
                              if (!cnfa->states[ca->to]->co)
                                    noprogress = 0;
                              FDEBUG(("%d -> %d\n", i, ca->to));
                        }
      dolacons = (gotstate) ? (cnfa->flags&HASLACONS) : 0;
      sawlacons = 0;
      while (dolacons) {            /* transitive closure */
            dolacons = 0;
            for (i = 0; i < d->nstates; i++)
                  if (ISBSET(d->work, i))
                        for (ca = cnfa->states[i]+1; ca->co != COLORLESS;
                                                      ca++) {
                              if (ca->co <= cnfa->ncolors)
                                    continue; /* NOTE CONTINUE */
                              sawlacons = 1;
                              if (ISBSET(d->work, ca->to))
                                    continue; /* NOTE CONTINUE */
                              if (!lacon(v, cnfa, cp, ca->co))
                                    continue; /* NOTE CONTINUE */
                              BSET(d->work, ca->to);
                              dolacons = 1;
                              if (ca->to == cnfa->post)
                                    ispost = 1;
                              if (!cnfa->states[ca->to]->co)
                                    noprogress = 0;
                              FDEBUG(("%d :> %d\n", i, ca->to));
                        }
      }
      if (!gotstate)
            return NULL;
      h = HASH(d->work, d->wordsper);

      /* next, is that in the cache? */
      for (p = d->ssets, i = d->nssused; i > 0; p++, i--)
            if (HIT(h, d->work, p, d->wordsper)) {
                  FDEBUG(("cached c%d\n", p - d->ssets));
                  break;                  /* NOTE BREAK OUT */
            }
      if (i == 0) {           /* nope, need a new cache entry */
            p = getvacant(v, d, cp, start);
            assert(p != css);
            for (i = 0; i < d->wordsper; i++)
                  p->states[i] = d->work[i];
            p->hash = h;
            p->flags = (ispost) ? POSTSTATE : 0;
            if (noprogress)
                  p->flags |= NOPROGRESS;
            /* lastseen to be dealt with by caller */
      }

      if (!sawlacons) {       /* lookahead conds. always cache miss */
            FDEBUG(("c%d[%d]->c%d\n", css - d->ssets, co, p - d->ssets));
            css->outs[co] = p;
            css->inchain[co] = p->ins;
            p->ins.ss = css;
            p->ins.co = (color)co;
      }
      return p;
}

/*
 - lacon - lookahead-constraint checker for miss()
 ^ static int lacon(struct vars *, struct cnfa *, chr *, pcolor);
 */
static int              /* predicate:  constraint satisfied? */
lacon(v, pcnfa, cp, co)
struct vars *v;
struct cnfa *pcnfa;           /* parent cnfa */
chr *cp;
pcolor co;              /* "color" of the lookahead constraint */
{
      int n;
      struct subre *sub;
      struct dfa *d;
      struct smalldfa sd;
      chr *end;

      n = co - pcnfa->ncolors;
      assert(n < v->g->nlacons && v->g->lacons != NULL);
      FDEBUG(("=== testing lacon %d\n", n));
      sub = &v->g->lacons[n];
      d = newdfa(v, &sub->cnfa, &v->g->cmap, &sd);
      if (d == NULL) {
            ERR(REG_ESPACE);
            return 0;
      }
      end = longest(v, d, cp, v->stop, (int *)NULL);
      freedfa(d);
      FDEBUG(("=== lacon %d match %d\n", n, (end != NULL)));
      return (sub->subno) ? (end != NULL) : (end == NULL);
}

/*
 - getvacant - get a vacant state set
 * This routine clears out the inarcs and outarcs, but does not otherwise
 * clear the innards of the state set -- that's up to the caller.
 ^ static struct sset *getvacant(struct vars *, struct dfa *, chr *, chr *);
 */
static struct sset *
getvacant(v, d, cp, start)
struct vars *v;               /* used only for debug flags */
struct dfa *d;
chr *cp;
chr *start;
{
      int i;
      struct sset *ss;
      struct sset *p;
      struct arcp ap;
      struct arcp lastap = {NULL, 0}; /* silence gcc 4 warning */
      color co;

      ss = pickss(v, d, cp, start);
      assert(!(ss->flags&LOCKED));

      /* clear out its inarcs, including self-referential ones */
      ap = ss->ins;
      while ((p = ap.ss) != NULL) {
            co = ap.co;
            FDEBUG(("zapping c%d's %ld outarc\n", p - d->ssets, (long)co));
            p->outs[co] = NULL;
            ap = p->inchain[co];
            p->inchain[co].ss = NULL;     /* paranoia */
      }
      ss->ins.ss = NULL;

      /* take it off the inarc chains of the ssets reached by its outarcs */
      for (i = 0; i < d->ncolors; i++) {
            p = ss->outs[i];
            assert(p != ss);        /* not self-referential */
            if (p == NULL)
                  continue;         /* NOTE CONTINUE */
            FDEBUG(("del outarc %d from c%d's in chn\n", i, p - d->ssets));
            if (p->ins.ss == ss && p->ins.co == i)
                  p->ins = ss->inchain[i];
            else {
                  assert(p->ins.ss != NULL);
                  for (ap = p->ins; ap.ss != NULL &&
                                    !(ap.ss == ss && ap.co == i);
                                    ap = ap.ss->inchain[ap.co])
                        lastap = ap;
                  assert(ap.ss != NULL);
                  lastap.ss->inchain[lastap.co] = ss->inchain[i];
            }
            ss->outs[i] = NULL;
            ss->inchain[i].ss = NULL;
      }

      /* if ss was a success state, may need to remember location */
      if ((ss->flags&POSTSTATE) && ss->lastseen != d->lastpost &&
                  (d->lastpost == NULL || d->lastpost < ss->lastseen))
            d->lastpost = ss->lastseen;

      /* likewise for a no-progress state */
      if ((ss->flags&NOPROGRESS) && ss->lastseen != d->lastnopr &&
                  (d->lastnopr == NULL || d->lastnopr < ss->lastseen))
            d->lastnopr = ss->lastseen;

      return ss;
}

/*
 - pickss - pick the next stateset to be used
 ^ static struct sset *pickss(struct vars *, struct dfa *, chr *, chr *);
 */
static struct sset *
pickss(v, d, cp, start)
struct vars *v;               /* used only for debug flags */
struct dfa *d;
chr *cp;
chr *start;
{
      int i;
      struct sset *ss;
      struct sset *end;
      chr *ancient;

      /* shortcut for cases where cache isn't full */
      if (d->nssused < d->nssets) {
            i = d->nssused;
            d->nssused++;
            ss = &d->ssets[i];
            FDEBUG(("new c%d\n", i));
            /* set up innards */
            ss->states = &d->statesarea[i * d->wordsper];
            ss->flags = 0;
            ss->ins.ss = NULL;
            ss->ins.co = WHITE;           /* give it some value */
            ss->outs = &d->outsarea[i * d->ncolors];
            ss->inchain = &d->incarea[i * d->ncolors];
            for (i = 0; i < d->ncolors; i++) {
                  ss->outs[i] = NULL;
                  ss->inchain[i].ss = NULL;
            }
            return ss;
      }

      /* look for oldest, or old enough anyway */
      if (cp - start > d->nssets*2/3)           /* oldest 33% are expendable */
            ancient = cp - d->nssets*2/3;
      else
            ancient = start;
      for (ss = d->search, end = &d->ssets[d->nssets]; ss < end; ss++)
            if ((ss->lastseen == NULL || ss->lastseen < ancient) &&
                                          !(ss->flags&LOCKED)) {
                  d->search = ss + 1;
                  FDEBUG(("replacing c%d\n", ss - d->ssets));
                  return ss;
            }
      for (ss = d->ssets, end = d->search; ss < end; ss++)
            if ((ss->lastseen == NULL || ss->lastseen < ancient) &&
                                          !(ss->flags&LOCKED)) {
                  d->search = ss + 1;
                  FDEBUG(("replacing c%d\n", ss - d->ssets));
                  return ss;
            }

      /* nobody's old enough?!? -- something's really wrong */
      FDEBUG(("can't find victim to replace!\n"));
      assert(NOTREACHED);
      ERR(REG_ASSERT);
      return d->ssets;
}

Generated by  Doxygen 1.6.0   Back to index