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root/radiance/ray/src/rt/ambient.c
Revision: 2.28
Committed: Sun Apr 30 13:24:36 1995 UTC (29 years ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.27: +14 -5 lines
Log Message:
adjustments to sort interval defaults and minor improvements

File Contents

# Content
1 /* Copyright (c) 1995 Regents of the University of California */
2
3 #ifndef lint
4 static char SCCSid[] = "$SunId$ LBL";
5 #endif
6
7 /*
8 * ambient.c - routines dealing with ambient (inter-reflected) component.
9 */
10
11 #include "ray.h"
12
13 #include "octree.h"
14
15 #include "otypes.h"
16
17 #include "ambient.h"
18
19 #include "random.h"
20
21 #define OCTSCALE 0.5 /* ceil((valid rad.)/(cube size)) */
22
23 typedef struct ambtree {
24 AMBVAL *alist; /* ambient value list */
25 struct ambtree *kid; /* 8 child nodes */
26 } AMBTREE; /* ambient octree */
27
28 extern CUBE thescene; /* contains space boundaries */
29
30 extern char *shm_boundary; /* memory sharing boundary */
31
32 #define MAXASET 511 /* maximum number of elements in ambient set */
33 OBJECT ambset[MAXASET+1]={0}; /* ambient include/exclude set */
34
35 double maxarad; /* maximum ambient radius */
36 double minarad; /* minimum ambient radius */
37
38 static AMBTREE atrunk; /* our ambient trunk node */
39
40 static FILE *ambfp = NULL; /* ambient file pointer */
41 static int nunflshed = 0; /* number of unflushed ambient values */
42
43 #ifndef SORT_THRESH
44 #ifdef BIGMEM
45 #define SORT_THRESH ((9L<<20)/sizeof(AMBVAL))
46 #else
47 #define SORT_THRESH ((3L<<20)/sizeof(AMBVAL))
48 #endif
49 #endif
50 #ifndef SORT_INTVL
51 #define SORT_INTVL (SORT_THRESH*32)
52 #endif
53 #ifndef MAX_SORT_INTVL
54 #define MAX_SORT_INTVL (SORT_INTVL<<8)
55 #endif
56
57 static unsigned long ambclock = 0; /* ambient access clock */
58 static unsigned int nambvals = 0; /* number of stored ambient values */
59 static unsigned long lastsort = 0; /* time of last value sort */
60 static long sortintvl = SORT_INTVL; /* time until next sort */
61
62 #define MAXACLOCK (1L<<30) /* clock turnover value */
63 /*
64 * Track access times unless we are sharing ambient values
65 * through memory on a multiprocessor, when we want to avoid
66 * claiming our own memory (copy on write).
67 */
68 #define tracktime (shm_boundary == NULL || ambfp == NULL)
69
70 #define AMBFLUSH (BUFSIZ/AMBVALSIZ)
71
72 #define newambval() (AMBVAL *)bmalloc(sizeof(AMBVAL))
73
74 extern long ftell(), lseek();
75 static int initambfile(), avsave(), avinsert(), sortambvals();
76 static AMBVAL *avstore();
77 #ifdef F_SETLKW
78 static aflock();
79 #endif
80
81
82 setambres(ar) /* set ambient resolution */
83 int ar;
84 {
85 ambres = ar < 0 ? 0 : ar; /* may be done already */
86 /* set min & max radii */
87 if (ar <= 0) {
88 minarad = 0;
89 maxarad = thescene.cusize / 2.0;
90 } else {
91 minarad = thescene.cusize / ar;
92 maxarad = 16 * minarad; /* heuristic */
93 if (maxarad > thescene.cusize / 2.0)
94 maxarad = thescene.cusize / 2.0;
95 }
96 if (minarad <= FTINY)
97 minarad = 10*FTINY;
98 if (maxarad <= minarad)
99 maxarad = 64 * minarad;
100 }
101
102
103 setambacc(newa) /* set ambient accuracy */
104 double newa;
105 {
106 static double oldambacc = -1.0;
107
108 ambacc = newa < 0.0 ? 0.0 : newa; /* may be done already */
109 if (oldambacc < -FTINY)
110 oldambacc = ambacc; /* do nothing first call */
111 if (fabs(newa - oldambacc) < 0.01)
112 return; /* insignificant -- don't bother */
113 if (ambacc <= FTINY)
114 return; /* cannot build new tree */
115 /* else need to rebuild tree */
116 sortambvals(1);
117 oldambacc = ambacc; /* remeber setting for next call */
118 }
119
120
121 setambient(afile) /* initialize calculation */
122 char *afile;
123 {
124 long headlen;
125 AMBVAL amb;
126 /* init ambient limits */
127 setambres(ambres);
128 setambacc(ambacc);
129 if (afile == NULL)
130 return;
131 if (ambacc <= FTINY) {
132 sprintf(errmsg, "zero ambient accuracy so \"%s\" not opened",
133 afile);
134 error(WARNING, errmsg);
135 return;
136 }
137 /* open ambient file */
138 if ((ambfp = fopen(afile, "r+")) != NULL) {
139 initambfile(0);
140 headlen = ftell(ambfp);
141 while (readambval(&amb, ambfp))
142 avinsert(avstore(&amb));
143 /* align */
144 fseek(ambfp, -((ftell(ambfp)-headlen)%AMBVALSIZ), 1);
145 } else if ((ambfp = fopen(afile, "w+")) != NULL)
146 initambfile(1);
147 else {
148 sprintf(errmsg, "cannot open ambient file \"%s\"", afile);
149 error(SYSTEM, errmsg);
150 }
151 nunflshed++; /* lie */
152 ambsync();
153 }
154
155
156 ambnotify(obj) /* record new modifier */
157 OBJECT obj;
158 {
159 static int hitlimit = 0;
160 register OBJREC *o = objptr(obj);
161 register char **amblp;
162
163 if (hitlimit || !ismodifier(o->otype))
164 return;
165 for (amblp = amblist; *amblp != NULL; amblp++)
166 if (!strcmp(o->oname, *amblp)) {
167 if (ambset[0] >= MAXASET) {
168 error(WARNING, "too many modifiers in ambient list");
169 hitlimit++;
170 return; /* should this be fatal? */
171 }
172 insertelem(ambset, obj);
173 return;
174 }
175 }
176
177
178 ambient(acol, r) /* compute ambient component for ray */
179 COLOR acol;
180 register RAY *r;
181 {
182 static int rdepth = 0; /* ambient recursion */
183 double d;
184
185 if (ambdiv <= 0) /* no ambient calculation */
186 goto dumbamb;
187 /* check number of bounces */
188 if (rdepth >= ambounce)
189 goto dumbamb;
190 /* check ambient list */
191 if (ambincl != -1 && r->ro != NULL &&
192 ambincl != inset(ambset, r->ro->omod))
193 goto dumbamb;
194
195 if (ambacc <= FTINY) { /* no ambient storage */
196 rdepth++;
197 d = doambient(acol, r, r->rweight, NULL, NULL);
198 rdepth--;
199 if (d == 0.0)
200 goto dumbamb;
201 return;
202 }
203 /* resort memory? */
204 sortambvals(0);
205 /* get ambient value */
206 setcolor(acol, 0.0, 0.0, 0.0);
207 d = sumambient(acol, r, rdepth,
208 &atrunk, thescene.cuorg, thescene.cusize);
209 if (d > FTINY)
210 scalecolor(acol, 1.0/d);
211 else {
212 d = makeambient(acol, r, rdepth++);
213 rdepth--;
214 }
215 if (d > FTINY)
216 return;
217 dumbamb: /* return global value */
218 copycolor(acol, ambval);
219 }
220
221
222 double
223 sumambient(acol, r, al, at, c0, s) /* get interpolated ambient value */
224 COLOR acol;
225 register RAY *r;
226 int al;
227 AMBTREE *at;
228 FVECT c0;
229 double s;
230 {
231 double d, e1, e2, wt, wsum;
232 COLOR ct;
233 FVECT ck0;
234 int i;
235 register int j;
236 register AMBVAL *av;
237 /* do this node */
238 wsum = 0.0;
239 for (av = at->alist; av != NULL; av = av->next) {
240 if (tracktime)
241 av->latick = ambclock++;
242 /*
243 * Ambient level test.
244 */
245 if (av->lvl > al) /* list sorted, so this works */
246 break;
247 if (av->weight < r->rweight-FTINY)
248 continue;
249 /*
250 * Ambient radius test.
251 */
252 e1 = 0.0;
253 for (j = 0; j < 3; j++) {
254 d = av->pos[j] - r->rop[j];
255 e1 += d * d;
256 }
257 e1 /= av->rad * av->rad;
258 if (e1 > ambacc*ambacc*1.21)
259 continue;
260 /*
261 * Normal direction test.
262 */
263 e2 = (1.0 - DOT(av->dir, r->ron)) * r->rweight;
264 if (e2 < 0.0) e2 = 0.0;
265 if (e1 + e2 > ambacc*ambacc*1.21)
266 continue;
267 /*
268 * Ray behind test.
269 */
270 d = 0.0;
271 for (j = 0; j < 3; j++)
272 d += (r->rop[j] - av->pos[j]) *
273 (av->dir[j] + r->ron[j]);
274 if (d*0.5 < -minarad*ambacc-.001)
275 continue;
276 /*
277 * Jittering final test reduces image artifacts.
278 */
279 wt = sqrt(e1) + sqrt(e2);
280 wt *= .9 + .2*urand(9015+samplendx);
281 if (wt > ambacc)
282 continue;
283 if (wt <= 1e-3)
284 wt = 1e3;
285 else
286 wt = 1.0 / wt;
287 wsum += wt;
288 extambient(ct, av, r->rop, r->ron);
289 scalecolor(ct, wt);
290 addcolor(acol, ct);
291 }
292 if (at->kid == NULL)
293 return(wsum);
294 /* do children */
295 s *= 0.5;
296 for (i = 0; i < 8; i++) {
297 for (j = 0; j < 3; j++) {
298 ck0[j] = c0[j];
299 if (1<<j & i)
300 ck0[j] += s;
301 if (r->rop[j] < ck0[j] - OCTSCALE*s)
302 break;
303 if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
304 break;
305 }
306 if (j == 3)
307 wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
308 }
309 return(wsum);
310 }
311
312
313 double
314 makeambient(acol, r, al) /* make a new ambient value */
315 COLOR acol;
316 register RAY *r;
317 int al;
318 {
319 AMBVAL amb;
320 FVECT gp, gd;
321 /* compute weight */
322 amb.weight = pow(AVGREFL, (double)al);
323 if (r->rweight < 0.2*amb.weight) /* heuristic */
324 amb.weight = r->rweight;
325 /* compute ambient */
326 amb.rad = doambient(acol, r, amb.weight, gp, gd);
327 if (amb.rad == 0.0)
328 return(0.0);
329 /* store it */
330 VCOPY(amb.pos, r->rop);
331 VCOPY(amb.dir, r->ron);
332 amb.lvl = al;
333 copycolor(amb.val, acol);
334 VCOPY(amb.gpos, gp);
335 VCOPY(amb.gdir, gd);
336 /* insert into tree */
337 avsave(&amb); /* and save to file */
338 return(amb.rad);
339 }
340
341
342 extambient(cr, ap, pv, nv) /* extrapolate value at pv, nv */
343 COLOR cr;
344 register AMBVAL *ap;
345 FVECT pv, nv;
346 {
347 FVECT v1, v2;
348 register int i;
349 double d;
350
351 d = 1.0; /* zeroeth order */
352 /* gradient due to translation */
353 for (i = 0; i < 3; i++)
354 d += ap->gpos[i]*(pv[i]-ap->pos[i]);
355 /* gradient due to rotation */
356 VCOPY(v1, ap->dir);
357 fcross(v2, v1, nv);
358 d += DOT(ap->gdir, v2);
359 if (d <= 0.0) {
360 setcolor(cr, 0.0, 0.0, 0.0);
361 return;
362 }
363 copycolor(cr, ap->val);
364 scalecolor(cr, d);
365 }
366
367
368 static
369 initambfile(creat) /* initialize ambient file */
370 int creat;
371 {
372 extern char *progname, *octname, VersionID[];
373
374 #ifdef F_SETLKW
375 aflock(creat ? F_WRLCK : F_RDLCK);
376 #endif
377 #ifdef MSDOS
378 setmode(fileno(ambfp), O_BINARY);
379 #endif
380 setbuf(ambfp, bmalloc(BUFSIZ+8));
381 if (creat) { /* new file */
382 newheader("RADIANCE", ambfp);
383 fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
384 progname, colval(ambval,RED),
385 colval(ambval,GRN), colval(ambval,BLU),
386 ambounce, ambacc);
387 fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
388 ambdiv, ambssamp, ambres,
389 octname==NULL ? "" : octname);
390 fprintf(ambfp, "SOFTWARE= %s\n", VersionID);
391 fputformat(AMBFMT, ambfp);
392 putc('\n', ambfp);
393 putambmagic(ambfp);
394 } else if (checkheader(ambfp, AMBFMT, NULL) < 0 || !hasambmagic(ambfp))
395 error(USER, "bad ambient file");
396 }
397
398
399 static
400 avsave(av) /* insert and save an ambient value */
401 AMBVAL *av;
402 {
403 avinsert(avstore(av));
404 if (ambfp == NULL)
405 return;
406 if (writambval(av, ambfp) < 0)
407 goto writerr;
408 if (++nunflshed >= AMBFLUSH)
409 if (ambsync() == EOF)
410 goto writerr;
411 return;
412 writerr:
413 error(SYSTEM, "error writing ambient file");
414 }
415
416
417 static AMBVAL *
418 avstore(aval) /* allocate memory and store aval */
419 register AMBVAL *aval;
420 {
421 register AMBVAL *av;
422
423 if ((av = newambval()) == NULL)
424 error(SYSTEM, "out of memory in avstore");
425 copystruct(av, aval);
426 av->latick = ambclock;
427 av->next = NULL;
428 nambvals++;
429 return(av);
430 }
431
432
433 #define ATALLOCSZ 512 /* #/8 trees to allocate at once */
434
435 static AMBTREE *atfreelist = NULL; /* free ambient tree structures */
436
437
438 static
439 AMBTREE *
440 newambtree() /* allocate 8 ambient tree structs */
441 {
442 register AMBTREE *atp, *upperlim;
443
444 if (atfreelist == NULL) { /* get more nodes */
445 atfreelist = (AMBTREE *)bmalloc(ATALLOCSZ*8*sizeof(AMBTREE));
446 if (atfreelist == NULL)
447 return(NULL);
448 /* link new free list */
449 upperlim = atfreelist + 8*(ATALLOCSZ-1);
450 for (atp = atfreelist; atp < upperlim; atp += 8)
451 atp->kid = atp + 8;
452 atp->kid = NULL;
453 }
454 atp = atfreelist;
455 atfreelist = atp->kid;
456 bzero((char *)atp, 8*sizeof(AMBTREE));
457 return(atp);
458 }
459
460
461 static
462 freeambtree(atp) /* free 8 ambient tree structs */
463 AMBTREE *atp;
464 {
465 atp->kid = atfreelist;
466 atfreelist = atp;
467 }
468
469
470 static
471 avinsert(av) /* insert ambient value in our tree */
472 register AMBVAL *av;
473 {
474 register AMBTREE *at;
475 register AMBVAL *ap;
476 AMBVAL avh;
477 FVECT ck0;
478 double s;
479 int branch;
480 register int i;
481
482 if (av->rad <= FTINY)
483 error(CONSISTENCY, "zero ambient radius in avinsert");
484 at = &atrunk;
485 VCOPY(ck0, thescene.cuorg);
486 s = thescene.cusize;
487 while (s*(OCTSCALE/2) > av->rad*ambacc) {
488 if (at->kid == NULL)
489 if ((at->kid = newambtree()) == NULL)
490 error(SYSTEM, "out of memory in avinsert");
491 s *= 0.5;
492 branch = 0;
493 for (i = 0; i < 3; i++)
494 if (av->pos[i] > ck0[i] + s) {
495 ck0[i] += s;
496 branch |= 1 << i;
497 }
498 at = at->kid + branch;
499 }
500 avh.next = at->alist; /* order by increasing level */
501 for (ap = &avh; ap->next != NULL; ap = ap->next)
502 if (ap->next->lvl >= av->lvl)
503 break;
504 av->next = ap->next;
505 ap->next = av;
506 at->alist = avh.next;
507 }
508
509
510 static
511 unloadatree(at, f) /* unload an ambient value tree */
512 register AMBTREE *at;
513 int (*f)();
514 {
515 register AMBVAL *av;
516 register int i;
517 /* transfer values at this node */
518 for (av = at->alist; av != NULL; av = at->alist) {
519 at->alist = av->next;
520 (*f)(av);
521 }
522 if (at->kid == NULL)
523 return;
524 for (i = 0; i < 8; i++) /* transfer and free children */
525 unloadatree(at->kid+i, f);
526 freeambtree(at->kid);
527 at->kid = NULL;
528 }
529
530
531 static AMBVAL **avlist1, **avlist2; /* ambient value lists for sorting */
532 static int i_avlist; /* index for lists */
533
534
535 static
536 av2list(av)
537 AMBVAL *av;
538 {
539 #ifdef DEBUG
540 if (i_avlist >= nambvals)
541 error(CONSISTENCY, "too many ambient values in av2list1");
542 #endif
543 avlist1[i_avlist] = avlist2[i_avlist] = av;
544 i_avlist++;
545 }
546
547
548 static int
549 alatcmp(avp1, avp2) /* compare ambient values for MRA */
550 AMBVAL **avp1, **avp2;
551 {
552 return((**avp2).latick - (**avp1).latick);
553 }
554
555
556 static int
557 aposcmp(avp1, avp2) /* compare ambient value positions */
558 AMBVAL **avp1, **avp2;
559 {
560 return(*avp1 - *avp2);
561 }
562
563
564 #ifdef DEBUG
565 static int
566 avlmemi(avaddr) /* find list position from address */
567 AMBVAL *avaddr;
568 {
569 register AMBVAL **avlpp;
570
571 avlpp = (AMBVAL **)bsearch((char *)&avaddr, (char *)avlist2,
572 nambvals, sizeof(AMBVAL *), aposcmp);
573 if (avlpp == NULL)
574 error(CONSISTENCY, "address not found in avlmemi");
575 return(avlpp - avlist2);
576 }
577 #else
578 #define avlmemi(avaddr) ((AMBVAL **)bsearch((char *)&avaddr,(char *)avlist2, \
579 nambvals,sizeof(AMBVAL *),aposcmp) - avlist2)
580 #endif
581
582
583 static
584 sortambvals(always) /* resort ambient values */
585 int always;
586 {
587 AMBTREE oldatrunk;
588 AMBVAL tav, *tap, *pnext;
589 register int i, j;
590 /* see if it's time yet */
591 if (!always && (ambclock < lastsort+sortintvl ||
592 nambvals < SORT_THRESH))
593 return;
594 /*
595 * The idea here is to minimize memory thrashing
596 * in VM systems by improving reference locality.
597 * We do this by periodically sorting our stored ambient
598 * values in memory in order of most recently to least
599 * recently accessed. This ordering was chosen so that new
600 * ambient values (which tend to be less important) go into
601 * higher memory with the infrequently accessed values.
602 * Since we expect our values to need sorting less
603 * frequently as the process continues, we double our
604 * waiting interval after each call.
605 * This routine is also called by setambacc() with
606 * the "always" parameter set to 1 so that the ambient
607 * tree will be rebuilt with the new accuracy parameter.
608 */
609 if (tracktime) { /* allocate pointer arrays to sort */
610 avlist1 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
611 avlist2 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
612 } else
613 avlist1 = avlist2 = NULL;
614 if (avlist2 == NULL) { /* no time tracking -- rebuild tree? */
615 if (avlist1 != NULL)
616 free((char *)avlist1);
617 if (always) { /* rebuild without sorting */
618 copystruct(&oldatrunk, &atrunk);
619 atrunk.alist = NULL;
620 atrunk.kid = NULL;
621 unloadatree(&oldatrunk, avinsert);
622 }
623 } else { /* sort memory by last access time */
624 /*
625 * Sorting memory is tricky because it isn't contiguous.
626 * We have to sort an array of pointers by MRA and also
627 * by memory position. We then copy values in "loops"
628 * to minimize memory hits. Nevertheless, we will visit
629 * everyone at least twice, and this is an expensive process
630 * when we're thrashing, which is when we need to do it.
631 */
632 #ifdef DEBUG
633 sprintf(errmsg, "sorting %u ambient values...", nambvals);
634 eputs(errmsg);
635 #endif
636 i_avlist = 0;
637 unloadatree(&atrunk, av2list); /* empty current tree */
638 #ifdef DEBUG
639 if (i_avlist < nambvals)
640 error(CONSISTENCY, "missing ambient values in sortambvals");
641 #endif
642 qsort((char *)avlist1, nambvals, sizeof(AMBVAL *), alatcmp);
643 qsort((char *)avlist2, nambvals, sizeof(AMBVAL *), aposcmp);
644 for (i = 0; i < nambvals; i++) {
645 if (avlist1[i] == NULL)
646 continue;
647 tap = avlist2[i];
648 copystruct(&tav, tap);
649 for (j = i; (pnext = avlist1[j]) != tap;
650 j = avlmemi(pnext)) {
651 copystruct(avlist2[j], pnext);
652 avinsert(avlist2[j]);
653 avlist1[j] = NULL;
654 }
655 copystruct(avlist2[j], &tav);
656 avinsert(avlist2[j]);
657 avlist1[j] = NULL;
658 }
659 free((char *)avlist1);
660 free((char *)avlist2);
661 /* compute new sort interval */
662 sortintvl = ambclock - lastsort;
663 if (sortintvl > MAX_SORT_INTVL)
664 sortintvl = MAX_SORT_INTVL;
665 else
666 sortintvl <<= 1; /* wait twice as long next */
667 #ifdef DEBUG
668 eputs("done\n");
669 #endif
670 }
671 if (ambclock >= MAXACLOCK)
672 ambclock = MAXACLOCK/2;
673 lastsort = ambclock;
674 }
675
676
677 #ifdef F_SETLKW
678
679 static
680 aflock(typ) /* lock/unlock ambient file */
681 int typ;
682 {
683 static struct flock fls; /* static so initialized to zeroes */
684
685 fls.l_type = typ;
686 if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
687 error(SYSTEM, "cannot (un)lock ambient file");
688 }
689
690
691 int
692 ambsync() /* synchronize ambient file */
693 {
694 static FILE *ambinp = NULL;
695 static long lastpos = -1;
696 long flen;
697 AMBVAL avs;
698 register int n;
699
700 if (nunflshed == 0)
701 return(0);
702 if (lastpos < 0) /* initializing (locked in initambfile) */
703 goto syncend;
704 /* gain exclusive access */
705 aflock(F_WRLCK);
706 /* see if file has grown */
707 if ((flen = lseek(fileno(ambfp), 0L, 2)) < 0)
708 goto seekerr;
709 if (n = flen - lastpos) { /* file has grown */
710 if (ambinp == NULL) { /* use duplicate filedes */
711 ambinp = fdopen(dup(fileno(ambfp)), "r");
712 if (ambinp == NULL)
713 error(SYSTEM, "fdopen failed in ambsync");
714 }
715 if (fseek(ambinp, lastpos, 0) < 0)
716 goto seekerr;
717 while (n >= AMBVALSIZ) { /* load contributed values */
718 readambval(&avs, ambinp);
719 avinsert(avstore(&avs));
720 n -= AMBVALSIZ;
721 }
722 /*** seek always as safety measure
723 if (n) ***/ /* alignment */
724 if (lseek(fileno(ambfp), flen-n, 0) < 0)
725 goto seekerr;
726 }
727 #ifdef DEBUG
728 if (ambfp->_ptr - ambfp->_base != nunflshed*AMBVALSIZ) {
729 sprintf(errmsg, "ambient file buffer at %d rather than %d",
730 ambfp->_ptr - ambfp->_base,
731 nunflshed*AMBVALSIZ);
732 error(CONSISTENCY, errmsg);
733 }
734 #endif
735 syncend:
736 n = fflush(ambfp); /* calls write() at last */
737 if ((lastpos = lseek(fileno(ambfp), 0L, 1)) < 0)
738 goto seekerr;
739 aflock(F_UNLCK); /* release file */
740 nunflshed = 0;
741 return(n);
742 seekerr:
743 error(SYSTEM, "seek failed in ambsync");
744 }
745
746 #else
747
748 int
749 ambsync() /* flush ambient file */
750 {
751 if (nunflshed == 0)
752 return(0);
753 nunflshed = 0;
754 return(fflush(ambfp));
755 }
756
757 #endif