1/*
2 * DFA routines
3 * This file is #included by regexec.c.
4 *
5 * Copyright (c) 1998, 1999 Henry Spencer.  All rights reserved.
6 *
7 * Development of this software was funded, in part, by Cray Research Inc.,
8 * UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
9 * Corporation, none of whom are responsible for the results.  The author
10 * thanks all of them.
11 *
12 * Redistribution and use in source and binary forms -- with or without
13 * modification -- are permitted for any purpose, provided that
14 * redistributions in source form retain this entire copyright notice and
15 * indicate the origin and nature of any modifications.
16 *
17 * I'd appreciate being given credit for this package in the documentation
18 * of software which uses it, but that is not a requirement.
19 *
20 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
21 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
22 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
23 * HENRY SPENCER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
26 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
27 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
28 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
29 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 */
32
33/*
34 - longest - longest-preferred matching engine
35 ^ static chr *longest(struct vars *, struct dfa *, chr *, chr *, int *);
36 */
37static chr *			/* endpoint, or NULL */
38longest(
39    struct vars *v,		/* used only for debug and exec flags */
40    struct dfa *d,
41    chr *start,			/* where the match should start */
42    chr *stop,			/* match must end at or before here */
43    int *hitstopp)		/* record whether hit v->stop, if non-NULL */
44{
45    chr *cp;
46    chr *realstop = (stop == v->stop) ? stop : stop + 1;
47    color co;
48    struct sset *css;
49    struct sset *ss;
50    chr *post;
51    int i;
52    struct colormap *cm = d->cm;
53
54    /*
55     * Initialize.
56     */
57
58    css = initialize(v, d, start);
59    cp = start;
60    if (hitstopp != NULL) {
61	*hitstopp = 0;
62    }
63
64    /*
65     * Startup.
66     */
67
68    FDEBUG(("+++ startup +++\n"));
69    if (cp == v->start) {
70	co = d->cnfa->bos[(v->eflags&REG_NOTBOL) ? 0 : 1];
71	FDEBUG(("color %ld\n", (long)co));
72    } else {
73	co = GETCOLOR(cm, *(cp - 1));
74	FDEBUG(("char %c, color %ld\n", (char)*(cp-1), (long)co));
75    }
76    css = miss(v, d, css, co, cp, start);
77    if (css == NULL) {
78	return NULL;
79    }
80    css->lastseen = cp;
81
82    /*
83     * Main loop.
84     */
85
86    if (v->eflags&REG_FTRACE) {
87	while (cp < realstop) {
88	    FDEBUG(("+++ at c%d +++\n", css - d->ssets));
89	    co = GETCOLOR(cm, *cp);
90	    FDEBUG(("char %c, color %ld\n", (char)*cp, (long)co));
91	    ss = css->outs[co];
92	    if (ss == NULL) {
93		ss = miss(v, d, css, co, cp+1, start);
94		if (ss == NULL) {
95		    break;	/* NOTE BREAK OUT */
96		}
97	    }
98	    cp++;
99	    ss->lastseen = cp;
100	    css = ss;
101	}
102    } else {
103	while (cp < realstop) {
104	    co = GETCOLOR(cm, *cp);
105	    ss = css->outs[co];
106	    if (ss == NULL) {
107		ss = miss(v, d, css, co, cp+1, start);
108		if (ss == NULL) {
109		    break;	/* NOTE BREAK OUT */
110		}
111	    }
112	    cp++;
113	    ss->lastseen = cp;
114	    css = ss;
115	}
116    }
117
118    /*
119     * Shutdown.
120     */
121
122    FDEBUG(("+++ shutdown at c%d +++\n", css - d->ssets));
123    if (cp == v->stop && stop == v->stop) {
124	if (hitstopp != NULL) {
125	    *hitstopp = 1;
126	}
127	co = d->cnfa->eos[(v->eflags&REG_NOTEOL) ? 0 : 1];
128	FDEBUG(("color %ld\n", (long)co));
129	ss = miss(v, d, css, co, cp, start);
130
131	/*
132	 * Special case: match ended at eol?
133	 */
134
135	if (ss != NULL && (ss->flags&POSTSTATE)) {
136	    return cp;
137	} else if (ss != NULL) {
138	    ss->lastseen = cp;	/* to be tidy */
139	}
140    }
141
142    /*
143     * Find last match, if any.
144     */
145
146    post = d->lastpost;
147    for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--) {
148	if ((ss->flags&POSTSTATE) && (post != ss->lastseen) &&
149		(post == NULL || post < ss->lastseen)) {
150	    post = ss->lastseen;
151	}
152    }
153    if (post != NULL) {		/* found one */
154	return post - 1;
155    }
156
157    return NULL;
158}
159
160/*
161 - shortest - shortest-preferred matching engine
162 ^ static chr *shortest(struct vars *, struct dfa *, chr *, chr *, chr *,
163 ^ 	chr **, int *);
164 */
165static chr *			/* endpoint, or NULL */
166shortest(
167    struct vars *v,
168    struct dfa *d,
169    chr *start,			/* where the match should start */
170    chr *min,			/* match must end at or after here */
171    chr *max,			/* match must end at or before here */
172    chr **coldp,		/* store coldstart pointer here, if nonNULL */
173    int *hitstopp)		/* record whether hit v->stop, if non-NULL */
174{
175    chr *cp;
176    chr *realmin = (min == v->stop) ? min : min + 1;
177    chr *realmax = (max == v->stop) ? max : max + 1;
178    color co;
179    struct sset *css;
180    struct sset *ss;
181    struct colormap *cm = d->cm;
182
183    /*
184     * Initialize.
185     */
186
187    css = initialize(v, d, start);
188    cp = start;
189    if (hitstopp != NULL) {
190	*hitstopp = 0;
191    }
192
193    /*
194     * Startup.
195     */
196
197    FDEBUG(("--- startup ---\n"));
198    if (cp == v->start) {
199	co = d->cnfa->bos[(v->eflags&REG_NOTBOL) ? 0 : 1];
200	FDEBUG(("color %ld\n", (long)co));
201    } else {
202	co = GETCOLOR(cm, *(cp - 1));
203	FDEBUG(("char %c, color %ld\n", (char)*(cp-1), (long)co));
204    }
205    css = miss(v, d, css, co, cp, start);
206    if (css == NULL) {
207	return NULL;
208    }
209    css->lastseen = cp;
210    ss = css;
211
212    /*
213     * Main loop.
214     */
215
216    if (v->eflags&REG_FTRACE) {
217	while (cp < realmax) {
218	    FDEBUG(("--- at c%d ---\n", css - d->ssets));
219	    co = GETCOLOR(cm, *cp);
220	    FDEBUG(("char %c, color %ld\n", (char)*cp, (long)co));
221	    ss = css->outs[co];
222	    if (ss == NULL) {
223		ss = miss(v, d, css, co, cp+1, start);
224		if (ss == NULL) {
225		    break;	/* NOTE BREAK OUT */
226		}
227	    }
228	    cp++;
229	    ss->lastseen = cp;
230	    css = ss;
231	    if ((ss->flags&POSTSTATE) && cp >= realmin) {
232		break;		/* NOTE BREAK OUT */
233	    }
234	}
235    } else {
236	while (cp < realmax) {
237	    co = GETCOLOR(cm, *cp);
238	    ss = css->outs[co];
239	    if (ss == NULL) {
240		ss = miss(v, d, css, co, cp+1, start);
241		if (ss == NULL) {
242		    break;	/* NOTE BREAK OUT */
243		}
244	    }
245	    cp++;
246	    ss->lastseen = cp;
247	    css = ss;
248	    if ((ss->flags&POSTSTATE) && cp >= realmin) {
249		break;		/* NOTE BREAK OUT */
250	    }
251	}
252    }
253
254    if (ss == NULL) {
255	return NULL;
256    }
257
258    if (coldp != NULL) {	/* report last no-progress state set, if any */
259	*coldp = lastcold(v, d);
260    }
261
262    if ((ss->flags&POSTSTATE) && cp > min) {
263	assert(cp >= realmin);
264	cp--;
265    } else if (cp == v->stop && max == v->stop) {
266	co = d->cnfa->eos[(v->eflags&REG_NOTEOL) ? 0 : 1];
267	FDEBUG(("color %ld\n", (long)co));
268	ss = miss(v, d, css, co, cp, start);
269
270	/*
271	 * Match might have ended at eol.
272	 */
273
274	if ((ss == NULL || !(ss->flags&POSTSTATE)) && hitstopp != NULL) {
275	    *hitstopp = 1;
276	}
277    }
278
279    if (ss == NULL || !(ss->flags&POSTSTATE)) {
280	return NULL;
281    }
282
283    return cp;
284}
285
286/*
287 - lastcold - determine last point at which no progress had been made
288 ^ static chr *lastcold(struct vars *, struct dfa *);
289 */
290static chr *			/* endpoint, or NULL */
291lastcold(
292    struct vars *v,
293    struct dfa *d)
294{
295    struct sset *ss;
296    chr *nopr;
297    int i;
298
299    nopr = d->lastnopr;
300    if (nopr == NULL) {
301	nopr = v->start;
302    }
303    for (ss = d->ssets, i = d->nssused; i > 0; ss++, i--) {
304	if ((ss->flags&NOPROGRESS) && nopr < ss->lastseen) {
305	    nopr = ss->lastseen;
306	}
307    }
308    return nopr;
309}
310
311/*
312 - newdfa - set up a fresh DFA
313 ^ static struct dfa *newdfa(struct vars *, struct cnfa *,
314 ^ 	struct colormap *, struct smalldfa *);
315 */
316static struct dfa *
317newdfa(
318    struct vars *v,
319    struct cnfa *cnfa,
320    struct colormap *cm,
321    struct smalldfa *sml)	/* preallocated space, may be NULL */
322{
323    struct dfa *d;
324    size_t nss = cnfa->nstates * 2;
325    int wordsper = (cnfa->nstates + UBITS - 1) / UBITS;
326    struct smalldfa *smallwas = sml;
327
328    assert(cnfa != NULL && cnfa->nstates != 0);
329
330    if (nss <= FEWSTATES && cnfa->ncolors <= FEWCOLORS) {
331	assert(wordsper == 1);
332	if (sml == NULL) {
333	    sml = (struct smalldfa *) MALLOC(sizeof(struct smalldfa));
334	    if (sml == NULL) {
335		ERR(REG_ESPACE);
336		return NULL;
337	    }
338	}
339	d = &sml->dfa;
340	d->ssets = sml->ssets;
341	d->statesarea = sml->statesarea;
342	d->work = &d->statesarea[nss];
343	d->outsarea = sml->outsarea;
344	d->incarea = sml->incarea;
345	d->cptsmalloced = 0;
346	d->mallocarea = (smallwas == NULL) ? (char *)sml : NULL;
347    } else {
348	d = (struct dfa *)MALLOC(sizeof(struct dfa));
349	if (d == NULL) {
350	    ERR(REG_ESPACE);
351	    return NULL;
352	}
353	d->ssets = (struct sset *)MALLOC(nss * sizeof(struct sset));
354	d->statesarea = (unsigned *)
355		MALLOC((nss+WORK) * wordsper * sizeof(unsigned));
356	d->work = &d->statesarea[nss * wordsper];
357	d->outsarea = (struct sset **)
358		MALLOC(nss * cnfa->ncolors * sizeof(struct sset *));
359	d->incarea = (struct arcp *)
360		MALLOC(nss * cnfa->ncolors * sizeof(struct arcp));
361	d->cptsmalloced = 1;
362	d->mallocarea = (char *)d;
363	if (d->ssets == NULL || d->statesarea == NULL ||
364		d->outsarea == NULL || d->incarea == NULL) {
365	    freedfa(d);
366	    ERR(REG_ESPACE);
367	    return NULL;
368	}
369    }
370
371    d->nssets = (v->eflags&REG_SMALL) ? 7 : nss;
372    d->nssused = 0;
373    d->nstates = cnfa->nstates;
374    d->ncolors = cnfa->ncolors;
375    d->wordsper = wordsper;
376    d->cnfa = cnfa;
377    d->cm = cm;
378    d->lastpost = NULL;
379    d->lastnopr = NULL;
380    d->search = d->ssets;
381
382    /*
383     * Initialization of sset fields is done as needed.
384     */
385
386    return d;
387}
388
389/*
390 - freedfa - free a DFA
391 ^ static void freedfa(struct dfa *);
392 */
393static void
394freedfa(
395    struct dfa *d)
396{
397    if (d->cptsmalloced) {
398	if (d->ssets != NULL) {
399	    FREE(d->ssets);
400	}
401	if (d->statesarea != NULL) {
402	    FREE(d->statesarea);
403	}
404	if (d->outsarea != NULL) {
405	    FREE(d->outsarea);
406	}
407	if (d->incarea != NULL) {
408	    FREE(d->incarea);
409	}
410    }
411
412    if (d->mallocarea != NULL) {
413	FREE(d->mallocarea);
414    }
415}
416
417/*
418 - hash - construct a hash code for a bitvector
419 * There are probably better ways, but they're more expensive.
420 ^ static unsigned hash(unsigned *, int);
421 */
422static unsigned
423hash(
424    unsigned *uv,
425    int n)
426{
427    int i;
428    unsigned h;
429
430    h = 0;
431    for (i = 0; i < n; i++) {
432	h ^= uv[i];
433    }
434    return h;
435}
436
437/*
438 - initialize - hand-craft a cache entry for startup, otherwise get ready
439 ^ static struct sset *initialize(struct vars *, struct dfa *, chr *);
440 */
441static struct sset *
442initialize(
443    struct vars *v,		/* used only for debug flags */
444    struct dfa *d,
445    chr *start)
446{
447    struct sset *ss;
448    int i;
449
450    /*
451     * Is previous one still there?
452     */
453
454    if (d->nssused > 0 && (d->ssets[0].flags&STARTER)) {
455	ss = &d->ssets[0];
456    } else {			/* no, must (re)build it */
457	ss = getvacant(v, d, start, start);
458	for (i = 0; i < d->wordsper; i++) {
459	    ss->states[i] = 0;
460	}
461	BSET(ss->states, d->cnfa->pre);
462	ss->hash = HASH(ss->states, d->wordsper);
463	assert(d->cnfa->pre != d->cnfa->post);
464	ss->flags = STARTER|LOCKED|NOPROGRESS;
465
466	/*
467	 * lastseen dealt with below
468	 */
469    }
470
471    for (i = 0; i < d->nssused; i++) {
472	d->ssets[i].lastseen = NULL;
473    }
474    ss->lastseen = start;	/* maybe untrue, but harmless */
475    d->lastpost = NULL;
476    d->lastnopr = NULL;
477    return ss;
478}
479
480/*
481 - miss - handle a cache miss
482 ^ static struct sset *miss(struct vars *, struct dfa *, struct sset *,
483 ^ 	pcolor, chr *, chr *);
484 */
485static struct sset *		/* NULL if goes to empty set */
486miss(
487    struct vars *v,		/* used only for debug flags */
488    struct dfa *d,
489    struct sset *css,
490    pcolor co,
491    chr *cp,			/* next chr */
492    chr *start)			/* where the attempt got started */
493{
494    struct cnfa *cnfa = d->cnfa;
495    int i;
496    unsigned h;
497    struct carc *ca;
498    struct sset *p;
499    int ispost;
500    int noprogress;
501    int gotstate;
502    int dolacons;
503    int sawlacons;
504
505    /*
506     * For convenience, we can be called even if it might not be a miss.
507     */
508
509    if (css->outs[co] != NULL) {
510	FDEBUG(("hit\n"));
511	return css->outs[co];
512    }
513    FDEBUG(("miss\n"));
514
515    /*
516     * First, what set of states would we end up in?
517     */
518
519    for (i = 0; i < d->wordsper; i++) {
520	d->work[i] = 0;
521    }
522    ispost = 0;
523    noprogress = 1;
524    gotstate = 0;
525    for (i = 0; i < d->nstates; i++) {
526	if (ISBSET(css->states, i)) {
527	    for (ca = cnfa->states[i]+1; ca->co != COLORLESS; ca++) {
528		if (ca->co == co) {
529		    BSET(d->work, ca->to);
530		    gotstate = 1;
531		    if (ca->to == cnfa->post) {
532			ispost = 1;
533		    }
534		    if (!cnfa->states[ca->to]->co) {
535			noprogress = 0;
536		    }
537		    FDEBUG(("%d -> %d\n", i, ca->to));
538		}
539	    }
540	}
541    }
542    dolacons = (gotstate) ? (cnfa->flags&HASLACONS) : 0;
543    sawlacons = 0;
544    while (dolacons) {		/* transitive closure */
545	dolacons = 0;
546	for (i = 0; i < d->nstates; i++) {
547	    if (ISBSET(d->work, i)) {
548		for (ca = cnfa->states[i]+1; ca->co != COLORLESS; ca++) {
549		    if (ca->co <= cnfa->ncolors) {
550			continue; /* NOTE CONTINUE */
551		    }
552		    sawlacons = 1;
553		    if (ISBSET(d->work, ca->to)) {
554			continue; /* NOTE CONTINUE */
555		    }
556		    if (!lacon(v, cnfa, cp, ca->co)) {
557			continue; /* NOTE CONTINUE */
558		    }
559		    BSET(d->work, ca->to);
560		    dolacons = 1;
561		    if (ca->to == cnfa->post) {
562			ispost = 1;
563		    }
564		    if (!cnfa->states[ca->to]->co) {
565			noprogress = 0;
566		    }
567		    FDEBUG(("%d :> %d\n", i, ca->to));
568		}
569	    }
570	}
571    }
572    if (!gotstate) {
573	return NULL;
574    }
575    h = HASH(d->work, d->wordsper);
576
577    /*
578     * Next, is that in the cache?
579     */
580
581    for (p = d->ssets, i = d->nssused; i > 0; p++, i--) {
582	 if (HIT(h, d->work, p, d->wordsper)) {
583	     FDEBUG(("cached c%d\n", p - d->ssets));
584	     break;			/* NOTE BREAK OUT */
585	 }
586    }
587    if (i == 0) {		/* nope, need a new cache entry */
588	p = getvacant(v, d, cp, start);
589	assert(p != css);
590	for (i = 0; i < d->wordsper; i++) {
591	    p->states[i] = d->work[i];
592	}
593	p->hash = h;
594	p->flags = (ispost) ? POSTSTATE : 0;
595	if (noprogress) {
596	    p->flags |= NOPROGRESS;
597	}
598
599	/*
600	 * lastseen to be dealt with by caller
601	 */
602    }
603
604    if (!sawlacons) {		/* lookahead conds. always cache miss */
605	FDEBUG(("c%d[%d]->c%d\n", css - d->ssets, co, p - d->ssets));
606	css->outs[co] = p;
607	css->inchain[co] = p->ins;
608	p->ins.ss = css;
609	p->ins.co = (color)co;
610    }
611    return p;
612}
613
614/*
615 - lacon - lookahead-constraint checker for miss()
616 ^ static int lacon(struct vars *, struct cnfa *, chr *, pcolor);
617 */
618static int			/* predicate:  constraint satisfied? */
619lacon(
620    struct vars *v,
621    struct cnfa *pcnfa,		/* parent cnfa */
622    chr *cp,
623    pcolor co)			/* "color" of the lookahead constraint */
624{
625    int n;
626    struct subre *sub;
627    struct dfa *d;
628    struct smalldfa sd;
629    chr *end;
630
631    n = co - pcnfa->ncolors;
632    assert(n < v->g->nlacons && v->g->lacons != NULL);
633    FDEBUG(("=== testing lacon %d\n", n));
634    sub = &v->g->lacons[n];
635    d = newdfa(v, &sub->cnfa, &v->g->cmap, &sd);
636    if (d == NULL) {
637	ERR(REG_ESPACE);
638	return 0;
639    }
640    end = longest(v, d, cp, v->stop, (int *)NULL);
641    freedfa(d);
642    FDEBUG(("=== lacon %d match %d\n", n, (end != NULL)));
643    return (sub->subno) ? (end != NULL) : (end == NULL);
644}
645
646/*
647 - getvacant - get a vacant state set
648 * This routine clears out the inarcs and outarcs, but does not otherwise
649 * clear the innards of the state set -- that's up to the caller.
650 ^ static struct sset *getvacant(struct vars *, struct dfa *, chr *, chr *);
651 */
652static struct sset *
653getvacant(
654    struct vars *v,		/* used only for debug flags */
655    struct dfa *d,
656    chr *cp,
657    chr *start)
658{
659    int i;
660    struct sset *ss;
661    struct sset *p;
662    struct arcp ap;
663    struct arcp lastap = {NULL, 0}; /* silence gcc 4 warning */
664    color co;
665
666    ss = pickss(v, d, cp, start);
667    assert(!(ss->flags&LOCKED));
668
669    /*
670     * Clear out its inarcs, including self-referential ones.
671     */
672
673    ap = ss->ins;
674    while ((p = ap.ss) != NULL) {
675	co = ap.co;
676	FDEBUG(("zapping c%d's %ld outarc\n", p - d->ssets, (long)co));
677	p->outs[co] = NULL;
678	ap = p->inchain[co];
679	p->inchain[co].ss = NULL; /* paranoia */
680    }
681    ss->ins.ss = NULL;
682
683    /*
684     * Take it off the inarc chains of the ssets reached by its outarcs.
685     */
686
687    for (i = 0; i < d->ncolors; i++) {
688	p = ss->outs[i];
689	assert(p != ss);	/* not self-referential */
690	if (p == NULL) {
691	    continue;		/* NOTE CONTINUE */
692	}
693	FDEBUG(("del outarc %d from c%d's in chn\n", i, p - d->ssets));
694	if (p->ins.ss == ss && p->ins.co == i) {
695	    p->ins = ss->inchain[i];
696	} else {
697	    assert(p->ins.ss != NULL);
698	    for (ap = p->ins; ap.ss != NULL &&
699		    !(ap.ss == ss && ap.co == i);
700		    ap = ap.ss->inchain[ap.co]) {
701		lastap = ap;
702	    }
703	    assert(ap.ss != NULL);
704	    lastap.ss->inchain[lastap.co] = ss->inchain[i];
705	}
706	ss->outs[i] = NULL;
707	ss->inchain[i].ss = NULL;
708    }
709
710    /*
711     * If ss was a success state, may need to remember location.
712     */
713
714    if ((ss->flags&POSTSTATE) && ss->lastseen != d->lastpost &&
715	    (d->lastpost == NULL || d->lastpost < ss->lastseen)) {
716	d->lastpost = ss->lastseen;
717    }
718
719    /*
720     * Likewise for a no-progress state.
721     */
722
723    if ((ss->flags&NOPROGRESS) && ss->lastseen != d->lastnopr &&
724	    (d->lastnopr == NULL || d->lastnopr < ss->lastseen)) {
725	d->lastnopr = ss->lastseen;
726    }
727
728    return ss;
729}
730
731/*
732 - pickss - pick the next stateset to be used
733 ^ static struct sset *pickss(struct vars *, struct dfa *, chr *, chr *);
734 */
735static struct sset *
736pickss(
737    struct vars *v,		/* used only for debug flags */
738    struct dfa *d,
739    chr *cp,
740    chr *start)
741{
742    int i;
743    struct sset *ss;
744    struct sset *end;
745    chr *ancient;
746
747    /*
748     * Shortcut for cases where cache isn't full.
749     */
750
751    if (d->nssused < d->nssets) {
752	i = d->nssused;
753	d->nssused++;
754	ss = &d->ssets[i];
755	FDEBUG(("new c%d\n", i));
756
757	/*
758	 * Set up innards.
759	 */
760
761	ss->states = &d->statesarea[i * d->wordsper];
762	ss->flags = 0;
763	ss->ins.ss = NULL;
764	ss->ins.co = WHITE;	/* give it some value */
765	ss->outs = &d->outsarea[i * d->ncolors];
766	ss->inchain = &d->incarea[i * d->ncolors];
767	for (i = 0; i < d->ncolors; i++) {
768	    ss->outs[i] = NULL;
769	    ss->inchain[i].ss = NULL;
770	}
771	return ss;
772    }
773
774    /*
775     * Look for oldest, or old enough anyway.
776     */
777
778    if (cp - start > d->nssets*2/3) {	/* oldest 33% are expendable */
779	ancient = cp - d->nssets*2/3;
780    } else {
781	ancient = start;
782    }
783    for (ss = d->search, end = &d->ssets[d->nssets]; ss < end; ss++) {
784	if ((ss->lastseen == NULL || ss->lastseen < ancient)
785		&& !(ss->flags&LOCKED)) {
786	    d->search = ss + 1;
787	    FDEBUG(("replacing c%d\n", ss - d->ssets));
788	    return ss;
789	}
790    }
791    for (ss = d->ssets, end = d->search; ss < end; ss++) {
792	if ((ss->lastseen == NULL || ss->lastseen < ancient)
793		&& !(ss->flags&LOCKED)) {
794	    d->search = ss + 1;
795	    FDEBUG(("replacing c%d\n", ss - d->ssets));
796	    return ss;
797	}
798    }
799
800    /*
801     * Nobody's old enough?!? -- something's really wrong.
802     */
803
804    FDEBUG(("can't find victim to replace!\n"));
805    assert(NOTREACHED);
806    ERR(REG_ASSERT);
807    return d->ssets;
808}
809
810/*
811 * Local Variables:
812 * mode: c
813 * c-basic-offset: 4
814 * fill-column: 78
815 * End:
816 */
817