ViewVC Help
View File | Revision Log | Show Annotations | Download File | Root Listing
root/radiance/ray/src/rt/ambient.c
Revision: 2.30
Committed: Wed May 3 09:46:27 1995 UTC (29 years ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.29: +1 -1 lines
Log Message:
changed maxarad heuristic limit and overrode super-sampling
for ambient values that have radii less than minarad after division sampling

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 1.0 /* 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*256)
52 #endif
53 #ifndef MAX_SORT_INTVL
54 #define MAX_SORT_INTVL (SORT_INTVL<<4)
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 = 64 * 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
238 wsum = 0.0;
239 /* do this node */
240 for (av = at->alist; av != NULL; av = av->next) {
241 if (tracktime)
242 av->latick = ambclock++;
243 /*
244 * Ambient level test.
245 */
246 if (av->lvl > al) /* list sorted, so this works */
247 break;
248 if (av->weight < r->rweight-FTINY)
249 continue;
250 /*
251 * Ambient radius test.
252 */
253 d = av->pos[0] - r->rop[0];
254 e1 = d * d;
255 d = av->pos[1] - r->rop[1];
256 e1 += d * d;
257 d = av->pos[2] - r->rop[2];
258 e1 += d * d;
259 e1 /= av->rad * av->rad;
260 if (e1 > ambacc*ambacc*1.21)
261 continue;
262 /*
263 * Normal direction test.
264 */
265 e2 = (1.0 - DOT(av->dir, r->ron)) * r->rweight;
266 if (e2 < 0.0) e2 = 0.0;
267 if (e1 + e2 > ambacc*ambacc*1.21)
268 continue;
269 /*
270 * Ray behind test.
271 */
272 d = 0.0;
273 for (j = 0; j < 3; j++)
274 d += (r->rop[j] - av->pos[j]) *
275 (av->dir[j] + r->ron[j]);
276 if (d*0.5 < -minarad*ambacc-.001)
277 continue;
278 /*
279 * Jittering final test reduces image artifacts.
280 */
281 wt = sqrt(e1) + sqrt(e2);
282 wt *= .9 + .2*urand(9015+samplendx);
283 if (wt > ambacc)
284 continue;
285 if (wt <= 1e-3)
286 wt = 1e3;
287 else
288 wt = 1.0 / wt;
289 wsum += wt;
290 extambient(ct, av, r->rop, r->ron);
291 scalecolor(ct, wt);
292 addcolor(acol, ct);
293 }
294 if (at->kid == NULL)
295 return(wsum);
296 /* do children */
297 s *= 0.5;
298 for (i = 0; i < 8; i++) {
299 for (j = 0; j < 3; j++) {
300 ck0[j] = c0[j];
301 if (1<<j & i)
302 ck0[j] += s;
303 if (r->rop[j] < ck0[j] - OCTSCALE*s)
304 break;
305 if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
306 break;
307 }
308 if (j == 3)
309 wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
310 }
311 return(wsum);
312 }
313
314
315 double
316 makeambient(acol, r, al) /* make a new ambient value */
317 COLOR acol;
318 register RAY *r;
319 int al;
320 {
321 AMBVAL amb;
322 FVECT gp, gd;
323 /* compute weight */
324 amb.weight = pow(AVGREFL, (double)al);
325 if (r->rweight < 0.2*amb.weight) /* heuristic */
326 amb.weight = r->rweight;
327 /* compute ambient */
328 amb.rad = doambient(acol, r, amb.weight, gp, gd);
329 if (amb.rad == 0.0)
330 return(0.0);
331 /* store it */
332 VCOPY(amb.pos, r->rop);
333 VCOPY(amb.dir, r->ron);
334 amb.lvl = al;
335 copycolor(amb.val, acol);
336 VCOPY(amb.gpos, gp);
337 VCOPY(amb.gdir, gd);
338 /* insert into tree */
339 avsave(&amb); /* and save to file */
340 return(amb.rad);
341 }
342
343
344 extambient(cr, ap, pv, nv) /* extrapolate value at pv, nv */
345 COLOR cr;
346 register AMBVAL *ap;
347 FVECT pv, nv;
348 {
349 FVECT v1, v2;
350 register int i;
351 double d;
352
353 d = 1.0; /* zeroeth order */
354 /* gradient due to translation */
355 for (i = 0; i < 3; i++)
356 d += ap->gpos[i]*(pv[i]-ap->pos[i]);
357 /* gradient due to rotation */
358 VCOPY(v1, ap->dir);
359 fcross(v2, v1, nv);
360 d += DOT(ap->gdir, v2);
361 if (d <= 0.0) {
362 setcolor(cr, 0.0, 0.0, 0.0);
363 return;
364 }
365 copycolor(cr, ap->val);
366 scalecolor(cr, d);
367 }
368
369
370 static
371 initambfile(creat) /* initialize ambient file */
372 int creat;
373 {
374 extern char *progname, *octname, VersionID[];
375
376 #ifdef F_SETLKW
377 aflock(creat ? F_WRLCK : F_RDLCK);
378 #endif
379 #ifdef MSDOS
380 setmode(fileno(ambfp), O_BINARY);
381 #endif
382 setbuf(ambfp, bmalloc(BUFSIZ+8));
383 if (creat) { /* new file */
384 newheader("RADIANCE", ambfp);
385 fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
386 progname, colval(ambval,RED),
387 colval(ambval,GRN), colval(ambval,BLU),
388 ambounce, ambacc);
389 fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
390 ambdiv, ambssamp, ambres,
391 octname==NULL ? "" : octname);
392 fprintf(ambfp, "SOFTWARE= %s\n", VersionID);
393 fputformat(AMBFMT, ambfp);
394 putc('\n', ambfp);
395 putambmagic(ambfp);
396 } else if (checkheader(ambfp, AMBFMT, NULL) < 0 || !hasambmagic(ambfp))
397 error(USER, "bad ambient file");
398 }
399
400
401 static
402 avsave(av) /* insert and save an ambient value */
403 AMBVAL *av;
404 {
405 avinsert(avstore(av));
406 if (ambfp == NULL)
407 return;
408 if (writambval(av, ambfp) < 0)
409 goto writerr;
410 if (++nunflshed >= AMBFLUSH)
411 if (ambsync() == EOF)
412 goto writerr;
413 return;
414 writerr:
415 error(SYSTEM, "error writing ambient file");
416 }
417
418
419 static AMBVAL *
420 avstore(aval) /* allocate memory and store aval */
421 register AMBVAL *aval;
422 {
423 register AMBVAL *av;
424
425 if ((av = newambval()) == NULL)
426 error(SYSTEM, "out of memory in avstore");
427 copystruct(av, aval);
428 av->latick = ambclock;
429 av->next = NULL;
430 nambvals++;
431 return(av);
432 }
433
434
435 #define ATALLOCSZ 512 /* #/8 trees to allocate at once */
436
437 static AMBTREE *atfreelist = NULL; /* free ambient tree structures */
438
439
440 static
441 AMBTREE *
442 newambtree() /* allocate 8 ambient tree structs */
443 {
444 register AMBTREE *atp, *upperlim;
445
446 if (atfreelist == NULL) { /* get more nodes */
447 atfreelist = (AMBTREE *)bmalloc(ATALLOCSZ*8*sizeof(AMBTREE));
448 if (atfreelist == NULL)
449 return(NULL);
450 /* link new free list */
451 upperlim = atfreelist + 8*(ATALLOCSZ-1);
452 for (atp = atfreelist; atp < upperlim; atp += 8)
453 atp->kid = atp + 8;
454 atp->kid = NULL;
455 }
456 atp = atfreelist;
457 atfreelist = atp->kid;
458 bzero((char *)atp, 8*sizeof(AMBTREE));
459 return(atp);
460 }
461
462
463 static
464 freeambtree(atp) /* free 8 ambient tree structs */
465 AMBTREE *atp;
466 {
467 atp->kid = atfreelist;
468 atfreelist = atp;
469 }
470
471
472 static
473 avinsert(av) /* insert ambient value in our tree */
474 register AMBVAL *av;
475 {
476 register AMBTREE *at;
477 register AMBVAL *ap;
478 AMBVAL avh;
479 FVECT ck0;
480 double s;
481 int branch;
482 register int i;
483
484 if (av->rad <= FTINY)
485 error(CONSISTENCY, "zero ambient radius in avinsert");
486 at = &atrunk;
487 VCOPY(ck0, thescene.cuorg);
488 s = thescene.cusize;
489 while (s*(OCTSCALE/2) > av->rad*ambacc) {
490 if (at->kid == NULL)
491 if ((at->kid = newambtree()) == NULL)
492 error(SYSTEM, "out of memory in avinsert");
493 s *= 0.5;
494 branch = 0;
495 for (i = 0; i < 3; i++)
496 if (av->pos[i] > ck0[i] + s) {
497 ck0[i] += s;
498 branch |= 1 << i;
499 }
500 at = at->kid + branch;
501 }
502 avh.next = at->alist; /* order by increasing level */
503 for (ap = &avh; ap->next != NULL; ap = ap->next)
504 if (ap->next->lvl >= av->lvl)
505 break;
506 av->next = ap->next;
507 ap->next = av;
508 at->alist = avh.next;
509 }
510
511
512 static
513 unloadatree(at, f) /* unload an ambient value tree */
514 register AMBTREE *at;
515 int (*f)();
516 {
517 register AMBVAL *av;
518 register int i;
519 /* transfer values at this node */
520 for (av = at->alist; av != NULL; av = at->alist) {
521 at->alist = av->next;
522 (*f)(av);
523 }
524 if (at->kid == NULL)
525 return;
526 for (i = 0; i < 8; i++) /* transfer and free children */
527 unloadatree(at->kid+i, f);
528 freeambtree(at->kid);
529 at->kid = NULL;
530 }
531
532
533 static AMBVAL **avlist1, **avlist2; /* ambient value lists for sorting */
534 static int i_avlist; /* index for lists */
535
536
537 static
538 av2list(av)
539 AMBVAL *av;
540 {
541 #ifdef DEBUG
542 if (i_avlist >= nambvals)
543 error(CONSISTENCY, "too many ambient values in av2list1");
544 #endif
545 avlist1[i_avlist] = avlist2[i_avlist] = av;
546 i_avlist++;
547 }
548
549
550 static int
551 alatcmp(avp1, avp2) /* compare ambient values for MRA */
552 AMBVAL **avp1, **avp2;
553 {
554 return((**avp2).latick - (**avp1).latick);
555 }
556
557
558 static int
559 aposcmp(avp1, avp2) /* compare ambient value positions */
560 AMBVAL **avp1, **avp2;
561 {
562 return(*avp1 - *avp2);
563 }
564
565
566 #ifdef DEBUG
567 static int
568 avlmemi(avaddr) /* find list position from address */
569 AMBVAL *avaddr;
570 {
571 register AMBVAL **avlpp;
572
573 avlpp = (AMBVAL **)bsearch((char *)&avaddr, (char *)avlist2,
574 nambvals, sizeof(AMBVAL *), aposcmp);
575 if (avlpp == NULL)
576 error(CONSISTENCY, "address not found in avlmemi");
577 return(avlpp - avlist2);
578 }
579 #else
580 #define avlmemi(avaddr) ((AMBVAL **)bsearch((char *)&avaddr,(char *)avlist2, \
581 nambvals,sizeof(AMBVAL *),aposcmp) - avlist2)
582 #endif
583
584
585 static
586 sortambvals(always) /* resort ambient values */
587 int always;
588 {
589 AMBTREE oldatrunk;
590 AMBVAL tav, *tap, *pnext;
591 register int i, j;
592 /* see if it's time yet */
593 if (!always && (ambclock < lastsort+sortintvl ||
594 nambvals < SORT_THRESH))
595 return;
596 /*
597 * The idea here is to minimize memory thrashing
598 * in VM systems by improving reference locality.
599 * We do this by periodically sorting our stored ambient
600 * values in memory in order of most recently to least
601 * recently accessed. This ordering was chosen so that new
602 * ambient values (which tend to be less important) go into
603 * higher memory with the infrequently accessed values.
604 * Since we expect our values to need sorting less
605 * frequently as the process continues, we double our
606 * waiting interval after each call.
607 * This routine is also called by setambacc() with
608 * the "always" parameter set to 1 so that the ambient
609 * tree will be rebuilt with the new accuracy parameter.
610 */
611 if (tracktime) { /* allocate pointer arrays to sort */
612 avlist1 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
613 avlist2 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
614 } else
615 avlist1 = avlist2 = NULL;
616 if (avlist2 == NULL) { /* no time tracking -- rebuild tree? */
617 if (avlist1 != NULL)
618 free((char *)avlist1);
619 if (always) { /* rebuild without sorting */
620 copystruct(&oldatrunk, &atrunk);
621 atrunk.alist = NULL;
622 atrunk.kid = NULL;
623 unloadatree(&oldatrunk, avinsert);
624 }
625 } else { /* sort memory by last access time */
626 /*
627 * Sorting memory is tricky because it isn't contiguous.
628 * We have to sort an array of pointers by MRA and also
629 * by memory position. We then copy values in "loops"
630 * to minimize memory hits. Nevertheless, we will visit
631 * everyone at least twice, and this is an expensive process
632 * when we're thrashing, which is when we need to do it.
633 */
634 #ifdef DEBUG
635 sprintf(errmsg, "sorting %u ambient values at ambclock=%lu...",
636 nambvals, ambclock);
637 eputs(errmsg);
638 #endif
639 i_avlist = 0;
640 unloadatree(&atrunk, av2list); /* empty current tree */
641 #ifdef DEBUG
642 if (i_avlist < nambvals)
643 error(CONSISTENCY, "missing ambient values in sortambvals");
644 #endif
645 qsort((char *)avlist1, nambvals, sizeof(AMBVAL *), alatcmp);
646 qsort((char *)avlist2, nambvals, sizeof(AMBVAL *), aposcmp);
647 for (i = 0; i < nambvals; i++) {
648 if (avlist1[i] == NULL)
649 continue;
650 tap = avlist2[i];
651 copystruct(&tav, tap);
652 for (j = i; (pnext = avlist1[j]) != tap;
653 j = avlmemi(pnext)) {
654 copystruct(avlist2[j], pnext);
655 avinsert(avlist2[j]);
656 avlist1[j] = NULL;
657 }
658 copystruct(avlist2[j], &tav);
659 avinsert(avlist2[j]);
660 avlist1[j] = NULL;
661 }
662 free((char *)avlist1);
663 free((char *)avlist2);
664 /* compute new sort interval */
665 sortintvl = ambclock - lastsort;
666 if (sortintvl > MAX_SORT_INTVL)
667 sortintvl = MAX_SORT_INTVL;
668 else
669 sortintvl <<= 1; /* wait twice as long next */
670 #ifdef DEBUG
671 eputs("done\n");
672 #endif
673 }
674 if (ambclock >= MAXACLOCK)
675 ambclock = MAXACLOCK/2;
676 lastsort = ambclock;
677 }
678
679
680 #ifdef F_SETLKW
681
682 static
683 aflock(typ) /* lock/unlock ambient file */
684 int typ;
685 {
686 static struct flock fls; /* static so initialized to zeroes */
687
688 fls.l_type = typ;
689 if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
690 error(SYSTEM, "cannot (un)lock ambient file");
691 }
692
693
694 int
695 ambsync() /* synchronize ambient file */
696 {
697 static FILE *ambinp = NULL;
698 static long lastpos = -1;
699 long flen;
700 AMBVAL avs;
701 register int n;
702
703 if (nunflshed == 0)
704 return(0);
705 if (lastpos < 0) /* initializing (locked in initambfile) */
706 goto syncend;
707 /* gain exclusive access */
708 aflock(F_WRLCK);
709 /* see if file has grown */
710 if ((flen = lseek(fileno(ambfp), 0L, 2)) < 0)
711 goto seekerr;
712 if (n = flen - lastpos) { /* file has grown */
713 if (ambinp == NULL) { /* use duplicate filedes */
714 ambinp = fdopen(dup(fileno(ambfp)), "r");
715 if (ambinp == NULL)
716 error(SYSTEM, "fdopen failed in ambsync");
717 }
718 if (fseek(ambinp, lastpos, 0) < 0)
719 goto seekerr;
720 while (n >= AMBVALSIZ) { /* load contributed values */
721 readambval(&avs, ambinp);
722 avinsert(avstore(&avs));
723 n -= AMBVALSIZ;
724 }
725 /*** seek always as safety measure
726 if (n) ***/ /* alignment */
727 if (lseek(fileno(ambfp), flen-n, 0) < 0)
728 goto seekerr;
729 }
730 #ifdef DEBUG
731 if (ambfp->_ptr - ambfp->_base != nunflshed*AMBVALSIZ) {
732 sprintf(errmsg, "ambient file buffer at %d rather than %d",
733 ambfp->_ptr - ambfp->_base,
734 nunflshed*AMBVALSIZ);
735 error(CONSISTENCY, errmsg);
736 }
737 #endif
738 syncend:
739 n = fflush(ambfp); /* calls write() at last */
740 if ((lastpos = lseek(fileno(ambfp), 0L, 1)) < 0)
741 goto seekerr;
742 aflock(F_UNLCK); /* release file */
743 nunflshed = 0;
744 return(n);
745 seekerr:
746 error(SYSTEM, "seek failed in ambsync");
747 }
748
749 #else
750
751 int
752 ambsync() /* flush ambient file */
753 {
754 if (nunflshed == 0)
755 return(0);
756 nunflshed = 0;
757 return(fflush(ambfp));
758 }
759
760 #endif