Merge commit '29ccecd87709feda60d191f6aaba324ccad91f55' as 'tcl8.6'

1 files changed, 805 insertions, 0 deletions

diff --git a/tcl8.6/generic/rege_dfa.c b/tcl8.6/generic/rege_dfa.c
new file mode 100644
index 0000000..e5f22c4
--- /dev/null
+++ b/tcl8.6/generic/rege_dfa.c
@@ -0,0 +1,805 @@
+/*
+ * 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 *const v,	/* used only for debug and exec flags */
+    struct dfa *const d,
+    chr *const start,		/* where the match should start */
+    chr *const stop,		/* match must end at or before here */
+    int *const hitstopp)	/* record whether hit v->stop, if non-NULL */
+{
+    chr *cp;
+    chr *realstop = (stop == v->stop) ? stop : stop + 1;
+    color co;
+    struct sset *css, *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 *shortest(struct vars *, struct dfa *, chr *, chr *, chr *,
+ ^ 	chr **, int *);
+ */
+static chr *			/* endpoint, or NULL */
+shortest(
+    struct vars *const v,
+    struct dfa *const d,
+    chr *const start,		/* where the match should start */
+    chr *const min,		/* match must end at or after here */
+    chr *const max,		/* match must end at or before here */
+    chr **const coldp,		/* store coldstart pointer here, if nonNULL */
+    int *const 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, *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 *lastCold(struct vars *, struct dfa *);
+ */
+static chr *			/* endpoint, or NULL */
+lastCold(
+    struct vars *const v,
+    struct dfa *const d)
+{
+    struct sset *ss;
+    chr *nopr = d->lastnopr;
+    int i;
+
+    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 *const v,
+    struct cnfa *const cnfa,
+    struct colormap *const cm,
+    struct smalldfa *sml)	/* preallocated space, may be NULL */
+{
+    struct dfa *d;
+    size_t nss = cnfa->nstates * 2;
+    int wordsper = (cnfa->nstates + UBITS - 1) / UBITS;
+    struct smalldfa *smallwas = sml;
+
+    assert(cnfa != NULL && cnfa->nstates != 0);
+
+    if (nss <= FEWSTATES && cnfa->ncolors <= FEWCOLORS) {
+	assert(wordsper == 1);
+	if (sml == NULL) {
+	    sml = (struct smalldfa *) MALLOC(sizeof(struct smalldfa));
+	    if (sml == NULL) {
+		ERR(REG_ESPACE);
+		return NULL;
+	    }
+	}
+	d = &sml->dfa;
+	d->ssets = sml->ssets;
+	d->statesarea = sml->statesarea;
+	d->work = &d->statesarea[nss];
+	d->outsarea = sml->outsarea;
+	d->incarea = sml->incarea;
+	d->cptsmalloced = 0;
+	d->mallocarea = (smallwas == NULL) ? (char *)sml : 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 *const 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 *const uv,
+    const 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 *const v,	/* used only for debug flags */
+    struct dfa *const d,
+    chr *const 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 = getVacantSS(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 *const v,	/* used only for debug flags */
+    struct dfa *const d,
+    struct sset *const css,
+    const pcolor co,
+    chr *const cp,		/* next chr */
+    chr *const start)		/* where the attempt got started */
+{
+    struct cnfa *cnfa = d->cnfa;
+    unsigned h;
+    struct carc *ca;
+    struct sset *p;
+    int i, isPost, noProgress, gotState, doLAConstraints, sawLAConstraints;
+
+    /*
+     * 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]; ca->co != COLORLESS; ca++) {
+		if (ca->co == co) {
+		    BSET(d->work, ca->to);
+		    gotState = 1;
+		    if (ca->to == cnfa->post) {
+			isPost = 1;
+		    }
+		    if (!(cnfa->stflags[ca->to] & CNFA_NOPROGRESS)) {
+			noProgress = 0;
+		    }
+		    FDEBUG(("%d -> %d\n", i, ca->to));
+		}
+	    }
+	}
+    }
+    doLAConstraints = (gotState ? (cnfa->flags&HASLACONS) : 0);
+    sawLAConstraints = 0;
+    while (doLAConstraints) {		/* transitive closure */
+	doLAConstraints = 0;
+	for (i = 0; i < d->nstates; i++) {
+	    if (ISBSET(d->work, i)) {
+		for (ca = cnfa->states[i]; ca->co != COLORLESS; ca++) {
+		    if (ca->co < cnfa->ncolors) {
+			continue;	/* NOTE CONTINUE */
+		    }
+		    sawLAConstraints = 1;
+		    if (ISBSET(d->work, ca->to)) {
+			continue;	/* NOTE CONTINUE */
+		    }
+		    if (!checkLAConstraint(v, cnfa, cp, ca->co)) {
+			continue;	/* NOTE CONTINUE */
+		    }
+		    BSET(d->work, ca->to);
+		    doLAConstraints = 1;
+		    if (ca->to == cnfa->post) {
+			isPost = 1;
+		    }
+		    if (!(cnfa->stflags[ca->to] & CNFA_NOPROGRESS)) {
+			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", (int) (p - d->ssets)));
+	     break;			/* NOTE BREAK OUT */
+	 }
+    }
+    if (i == 0) {		/* nope, need a new cache entry */
+	p = getVacantSS(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 (!sawLAConstraints) {	/* lookahead conds. always cache miss */
+	FDEBUG(("c%d[%d]->c%d\n",
+		(int) (css - d->ssets), co, (int) (p - d->ssets)));
+	css->outs[co] = p;
+	css->inchain[co] = p->ins;
+	p->ins.ss = css;
+	p->ins.co = (color) co;
+    }
+    return p;
+}
+
+/*
+ - checkLAConstraint - lookahead-constraint checker for miss()
+ ^ static int checkLAConstraint(struct vars *, struct cnfa *, chr *, pcolor);
+ */
+static int			/* predicate:  constraint satisfied? */
+checkLAConstraint(
+    struct vars *const v,
+    struct cnfa *const pcnfa,	/* parent cnfa */
+    chr *const cp,
+    const 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, NULL);
+    freeDFA(d);
+    FDEBUG(("=== lacon %d match %d\n", n, (end != NULL)));
+    return (sub->subno) ? (end != NULL) : (end == NULL);
+}
+
+/*
+ - getVacantSS - 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 *getVacantSS(struct vars *, struct dfa *, chr *, chr *);
+ */
+static struct sset *
+getVacantSS(
+    struct vars *const v,	/* used only for debug flags */
+    struct dfa *const d,
+    chr *const cp,
+    chr *const start)
+{
+    int i;
+    struct sset *ss, *p;
+    struct arcp ap, lastap = {NULL, 0}; /* silence gcc 4 warning */
+    color co;
+
+    ss = pickNextSS(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", (int) (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, (int) (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;
+}
+
+/*
+ - pickNextSS - pick the next stateset to be used
+ ^ static struct sset *pickNextSS(struct vars *, struct dfa *, chr *, chr *);
+ */
+static struct sset *
+pickNextSS(
+    struct vars *const v,	/* used only for debug flags */
+    struct dfa *const d,
+    chr *const cp,
+    chr *const start)
+{
+    int i;
+    struct sset *ss, *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", (int) (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", (int) (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:
+ */