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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(
    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(
    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(
    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(
    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(
    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(
    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(
    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(
    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(
    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(
    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(
    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;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */

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