src/util/rpiece.c

/* Copyright (c) 1992 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Generate sections of a picture.
 */
 
#include "standard.h"
#include <fcntl.h>
#include <signal.h>
#include "color.h"
#include "view.h"
#include "resolu.h"

                                /* set the following to 0 to forgo forking */
#ifndef MAXFORK
#define  MAXFORK                2       /* max. unreaped child processes */
#endif

                                /* rpict command */
char  *rpargv[128] = {"rpict", "-S", "1", "-x", "512", "-y", "512", "-pa", "1"};
int  rpargc = 9;
int  rpd[3];
FILE  *torp, *fromrp;
COLR  *pbuf;
                                /* our view parameters */
VIEW  ourview = STDVIEW;
double  pixaspect = 1.0;
int  hres = 512, vres = 512, hmult = 2, vmult = 2;
                                /* output file */
char  *outfile = NULL;
int  outfd;
long  scanorig;
int  syncfd = -1;               /* lock file descriptor */
int  nforked = 0;

char  *progname;
int  verbose = 0;

extern long  lseek(), ftell();

int  gotalrm = 0;
int  onalrm() { gotalrm++; }


main(argc, argv)
int  argc;
char  *argv[];
{
        register int  i, rval;
        
        progname = argv[0];
        for (i = 1; i < argc; i++) {
                if (argv[i][0] == '-')
                        switch (argv[i][1]) {
                        case 'v':
                                switch (argv[i][2]) {
                                case '\0':      /* verbose option */
                                        verbose = !verbose;
                                        continue;
                                case 'f':       /* view file */
                                        if (viewfile(argv[++i], &ourview, NULL) <= 0) {
                                                fprintf(stderr,
                                        "%s: not a view file\n", argv[i]);
                                                exit(1);
                                        }
                                        continue;
                                default:        /* view option? */
                                        rval = getviewopt(&ourview, argc-i, argv+i);
                                        if (rval >= 0) {
                                                i += rval;
                                                continue;
                                        }
                                        break;
                                }
                                break;
                        case 'p':               /* pixel aspect ratio? */
                                if (argv[i][2] == 'a' && !argv[i][3])
                                        pixaspect = atof(argv[i+1]);
                                break;
                        case 'x':               /* piece x resolution */
                                if (!argv[i][2])
                                        hres = atoi(argv[i+1]);
                                break;
                        case 'y':               /* piece y resolution */
                                if (!argv[i][2])
                                        vres = atoi(argv[i+1]);
                                break;
                        case 'X':               /* horizontal multiplier */
                                if (argv[i][2])
                                        break;
                                hmult = atoi(argv[++i]);
                                continue;
                        case 'Y':               /* vertical multiplier */
                                if (argv[i][2])
                                        break;
                                vmult = atoi(argv[++i]);
                                continue;
                        case 'F':               /* syncronization file */
                                if (argv[i][2])
                                        break;
                                if ((syncfd = open(argv[++i], O_RDWR)) < 0) {
                                        fprintf(stderr, "%s: cannot open\n",
                                                        argv[i]);
                                        exit(1);
                                }
                                continue;
                        case 'o':               /* output file */
                                if (argv[i][2])
                                        break;
                                outfile = argv[++i];
                                continue;
                        }
                rpargv[rpargc++] = argv[i];
        }
        rpargv[rpargc] = NULL;
        if (outfile == NULL) {
                fprintf(stderr, "%s: missing output file\n", argv[0]);
                exit(1);
        }
        init(argc, argv);
        rpiece();
        rval = cleanup();
        exit(rval);
}


init(ac, av)                    /* set up output file and start rpict */
int  ac;
char  **av;
{
        extern char  VersionID[];
        char  *err;
        FILE  *fp;
        int  hr, vr;
                                        /* set up view */
        if ((err = setview(&ourview)) != NULL) {
                fprintf(stderr, "%s: %s\n", progname, err);
                exit(1);
        }
        if (syncfd != -1) {
                char  buf[32];
                buf[read(syncfd, buf, sizeof(buf)-1)] = '\0';
                sscanf(buf, "%d %d", &hmult, &vmult);
        }
        normaspect(viewaspect(&ourview)*hmult/vmult, &pixaspect, &hres, &vres);
                                        /* open output file */
        if ((outfd = open(outfile, O_WRONLY|O_CREAT|O_EXCL, 0666)) >= 0) {
                if ((fp = fdopen(dup(outfd), "w")) == NULL)
                        goto filerr;
                printargs(ac, av, fp);          /* write header */
                fprintf(fp, "SOFTWARE= %s\n", VersionID);
                fputs(VIEWSTR, fp);
                fprintview(&ourview, fp);
                putc('\n', fp);
                if (pixaspect < .99 || pixaspect > 1.01)
                        fputaspect(pixaspect, fp);
                fputformat(COLRFMT, fp);
                putc('\n', fp);
                fprtresolu(hres*hmult, vres*vmult, fp);
        } else if ((outfd = open(outfile, O_RDWR)) >= 0) {
                if ((fp = fdopen(dup(outfd), "r+")) == NULL)
                        goto filerr;
                getheader(fp, NULL);            /* skip header */
                if (fscnresolu(&hr, &vr, fp) < 0 ||     /* check resolution */
                                hr != hres*hmult || vr != vres*vmult) {
                        fprintf(stderr, "%s: resolution mismatch on file \"%s\"\n",
                                        progname, outfile);
                        exit(1);
                }
        } else {
                fprintf(stderr, "%s: cannot open file \"%s\"\n",
                                progname, outfile);
                exit(1);
        }
        scanorig = ftell(fp);           /* record position of first scanline */
        if (fclose(fp) == -1)           /* done with stream i/o */
                goto filerr;
        sync();                         /* flush NFS buffers */
                                        /* start rpict process */
        if (open_process(rpd, rpargv) <= 0) {
                fprintf(stderr, "%s: cannot start %s\n", progname, rpargv[0]);
                exit(1);
        }
        if ((fromrp = fdopen(rpd[0], "r")) == NULL ||
                        (torp = fdopen(rpd[1], "w")) == NULL) {
                fprintf(stderr, "%s: cannot open stream to %s\n",
                                progname, rpargv[0]);
                exit(1);
        }
        if ((pbuf = (COLR *)malloc(hres*vres*sizeof(COLR))) == NULL) {
                fprintf(stderr, "%s: out of memory\n", progname);
                exit(1);
        }
        signal(SIGALRM, onalrm);
        return;
filerr:
        fprintf(stderr, "%s: i/o error on file \"%s\"\n", progname, outfile);
        exit(1);
}


int
nextpiece(xp, yp)               /* get next piece assignment */
int  *xp, *yp;
{
        extern char  *fgets();
        struct flock  fls;
        char  buf[64];

        if (gotalrm)                    /* someone wants us to quit */
                return(0);
        if (syncfd != -1) {             /* use sync file */
                fls.l_type = F_WRLCK;           /* gain exclusive access */
                fls.l_whence = 0;
                fls.l_start = 0L;
                fls.l_len = 0L;
                fcntl(syncfd, F_SETLKW, &fls);
                lseek(syncfd, 0L, 0);
                buf[read(syncfd, buf, sizeof(buf)-1)] = '\0';
                if (sscanf(buf, "%*d %*d %d %d", xp, yp) < 2) {
                        *xp = hmult-1;
                        *yp = vmult;
                }
                if (--(*yp) < 0) {              /* decrement position */
                        *yp = vmult-1;
                        if (--(*xp) < 0) {      /* all done! */
                                close(syncfd);
                                return(0);
                        }
                }
                sprintf(buf, "%d %d\n%d %d\n", hmult, vmult, *xp, *yp);
                lseek(syncfd, 0L, 0);           /* write new position */
                write(syncfd, buf, strlen(buf));
                fls.l_type = F_UNLCK;           /* release sync file */
                fcntl(syncfd, F_SETLKW, &fls);
                return(1);
        }
        if (fgets(buf, sizeof(buf), stdin) == NULL)     /* use stdin */
                return(0);
        if (sscanf(buf, "%d %d", xp, yp) == 2)
                return(1);
        fprintf(stderr, "%s: input format error\n", progname);
        exit(1);
}


int
cleanup()                       /* close rpict process and clean up */
{
        register int  pid;
        int  status, rstat = 0;

        free((char *)pbuf);
        fclose(torp);
        fclose(fromrp);
        while ((pid = wait(&status)) != -1)
                if (rstat == 0)
                        rstat = status>>8 & 0xff;
        return(rstat);
}


rpiece()                        /* render picture piece by piece */
{
        VIEW  pview;
        int  xorg, yorg;
        
        while (nextpiece(&xorg, &yorg)) {
                copystruct(&pview, &ourview);   /* compute view for piece */
                switch (ourview.type) {
                case VT_PER:
                        pview.horiz = 2.*180./PI*atan(
                                        tan(PI/180./2.*ourview.horiz)/hmult );
                        pview.vert = 2.*180./PI*atan(
                                        tan(PI/180./2.*ourview.vert)/vmult );
                        break;
                case VT_PAR:
                case VT_ANG:
                        pview.horiz = ourview.horiz / hmult;
                        pview.vert = ourview.vert / vmult;
                        break;
                case VT_HEM:
                        pview.horiz = 2.*180./PI*asin(
                                        sin(PI/180./2.*ourview.horiz)/hmult );
                        pview.vert = 2.*180./PI*asin(
                                        sin(PI/180./2.*ourview.vert)/vmult );
                        break;
                default:
                        fprintf(stderr, "%s: unknown view type '-vt%c'\n",
                                        progname, ourview.type);
                        exit(1);
                }
                pview.hoff += xorg - 0.5*(hmult-1);
                pview.voff += yorg - 0.5*(vmult-1);
                fputs(VIEWSTR, torp);
                fprintview(&pview, torp);
                putc('\n', torp);
                fflush(torp);                   /* assign piece to rpict */
                putpiece(xorg, yorg);           /* place piece in output */
                if (verbose) {                  /* notify caller */
                        printf("%d %d done\n", xorg, yorg);
                        fflush(stdout);
                }
        }
}


int
putpiece(xpos, ypos)            /* get next piece from rpict */
int  xpos, ypos;
{
        struct flock  fls;
        int  pid, status;
        int  hr, vr;
        register int  y;
                                /* check bounds */
        if (xpos < 0 | ypos < 0 | xpos >= hmult | ypos >= vmult) {
                fprintf(stderr, "%s: requested piece (%d,%d) out of range\n",
                                progname, xpos, ypos);
                exit(1);
        }
                                /* check header from rpict */
        getheader(fromrp, NULL);
        if (fscnresolu(&hr, &vr, fromrp) < 0 || hr != hres || vr != vres) {
                fprintf(stderr, "%s: resolution mismatch from %s\n",
                                progname, rpargv[0]);
                exit(1);
        }
                                /* load new piece into buffer */
        for (y = 0; y < vr; y++)
                if (freadcolrs(pbuf+y*hr, hr, fromrp) < 0) {
                        fprintf(stderr, "%s: read error from %s\n",
                                        progname, rpargv[0]);
                        exit(1);
                }
#if MAXFORK
                                /* fork so we don't slow rpict down */
        if ((pid = fork()) > 0) {
                if (++nforked > MAXFORK) {
                        wait(&status);          /* reap a child */
                        if (status)
                                exit(status>>8 & 0xff);
                        nforked--;
                }
                return(pid);
        }
#else
        pid = -1;               /* no forking */
#endif
                                /* lock file section so NFS doesn't mess up */
        fls.l_whence = 0;
        fls.l_len = (long)vres*hmult*hres*sizeof(COLR);
        fls.l_start = scanorig + (vmult-1-ypos)*fls.l_len;
        fls.l_type = F_WRLCK;
        fcntl(outfd, F_SETLKW, &fls);
                                /* write new piece to file */
        if (lseek(outfd, fls.l_start+(long)xpos*hres*sizeof(COLR), 0) == -1)
                goto seekerr;
        if (hmult == 1) {
                if (writebuf(outfd, (char *)pbuf,
                                vr*hr*sizeof(COLR)) != vr*hr*sizeof(COLR))
                        goto writerr;
        } else
                for (y = 0; y < vr; y++) {
                        if (writebuf(outfd, (char *)(pbuf+y*hr),
                                        hr*sizeof(COLR)) != hr*sizeof(COLR))
                                goto writerr;
                        if (y < vr-1 && lseek(outfd,
                                        (long)(hmult-1)*hr*sizeof(COLR),
                                        1) == -1)
                                goto seekerr;
                }
        if (pid == -1) {        /* fork failed */
                fls.l_type = F_UNLCK;           /* release lock */
                fcntl(outfd, F_SETLKW, &fls);
                return(0);
        }
        _exit(0);               /* else exit child process (releasing lock) */
seekerr:
        fprintf(stderr, "%s: seek error on file \"%s\"\n", progname, outfile);
        _exit(1);
writerr:
        fprintf(stderr, "%s: write error on file \"%s\"\n", progname, outfile);
        _exit(1);
}
Revision:	2.9
Committed:	Sun Aug 9 13:31:30 1992 UTC (31 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.8:	+50 -19 lines
Log Message:	added process forking
#	User	Rev	Content
1	greg	2.1	/* Copyright (c) 1992 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Generate sections of a picture.
9			*/
10
11			#include "standard.h"
12			#include <fcntl.h>
13	greg	2.6	#include <signal.h>
14	greg	2.1	#include "color.h"
15			#include "view.h"
16			#include "resolu.h"
17
18	greg	2.9	/* set the following to 0 to forgo forking */
19			#ifndef MAXFORK
20			#define MAXFORK 2 /* max. unreaped child processes */
21			#endif
22
23	greg	2.1	/* rpict command */
24	greg	2.4	char *rpargv[128] = {"rpict", "-S", "1", "-x", "512", "-y", "512", "-pa", "1"};
25			int rpargc = 9;
26	greg	2.1	int rpd[3];
27			FILE torp, fromrp;
28	greg	2.8	COLR *pbuf;
29	greg	2.1	/* our view parameters */
30			VIEW ourview = STDVIEW;
31	greg	2.4	double pixaspect = 1.0;
32	greg	2.1	int hres = 512, vres = 512, hmult = 2, vmult = 2;
33			/* output file */
34			char *outfile = NULL;
35			int outfd;
36			long scanorig;
37	greg	2.5	int syncfd = -1; /* lock file descriptor */
38	greg	2.9	int nforked = 0;
39	greg	2.1
40			char *progname;
41			int verbose = 0;
42
43			extern long lseek(), ftell();
44
45	greg	2.6	int gotalrm = 0;
46			int onalrm() { gotalrm++; }
47	greg	2.1
48	greg	2.6
49	greg	2.1	main(argc, argv)
50			int argc;
51			char *argv[];
52			{
53			register int i, rval;
54
55			progname = argv[0];
56			for (i = 1; i < argc; i++) {
57			if (argv[i][0] == '-')
58			switch (argv[i][1]) {
59			case 'v':
60			switch (argv[i][2]) {
61			case '\0': /* verbose option */
62			verbose = !verbose;
63			continue;
64			case 'f': /* view file */
65			if (viewfile(argv[++i], &ourview, NULL) <= 0) {
66			fprintf(stderr,
67			"%s: not a view file\n", argv[i]);
68			exit(1);
69			}
70			continue;
71			default: /* view option? */
72			rval = getviewopt(&ourview, argc-i, argv+i);
73			if (rval >= 0) {
74			i += rval;
75			continue;
76			}
77			break;
78			}
79			break;
80			case 'p': /* pixel aspect ratio? */
81			if (argv[i][2] == 'a' && !argv[i][3])
82			pixaspect = atof(argv[i+1]);
83			break;
84			case 'x': /* piece x resolution */
85			if (!argv[i][2])
86			hres = atoi(argv[i+1]);
87			break;
88			case 'y': /* piece y resolution */
89			if (!argv[i][2])
90			vres = atoi(argv[i+1]);
91			break;
92			case 'X': /* horizontal multiplier */
93			if (argv[i][2])
94			break;
95			hmult = atoi(argv[++i]);
96			continue;
97			case 'Y': /* vertical multiplier */
98			if (argv[i][2])
99			break;
100			vmult = atoi(argv[++i]);
101			continue;
102	greg	2.5	case 'F': /* syncronization file */
103			if (argv[i][2])
104			break;
105			if ((syncfd = open(argv[++i], O_RDWR)) < 0) {
106			fprintf(stderr, "%s: cannot open\n",
107			argv[i]);
108			exit(1);
109			}
110			continue;
111	greg	2.1	case 'o': /* output file */
112			if (argv[i][2])
113			break;
114			outfile = argv[++i];
115			continue;
116			}
117			rpargv[rpargc++] = argv[i];
118			}
119			rpargv[rpargc] = NULL;
120			if (outfile == NULL) {
121			fprintf(stderr, "%s: missing output file\n", argv[0]);
122			exit(1);
123			}
124			init(argc, argv);
125			rpiece();
126			rval = cleanup();
127			exit(rval);
128			}
129
130
131			init(ac, av) /* set up output file and start rpict */
132			int ac;
133			char **av;
134			{
135	greg	2.2	extern char VersionID[];
136	greg	2.1	char *err;
137			FILE *fp;
138			int hr, vr;
139			/* set up view */
140			if ((err = setview(&ourview)) != NULL) {
141			fprintf(stderr, "%s: %s\n", progname, err);
142			exit(1);
143			}
144	greg	2.5	if (syncfd != -1) {
145			char buf[32];
146			buf[read(syncfd, buf, sizeof(buf)-1)] = '\0';
147			sscanf(buf, "%d %d", &hmult, &vmult);
148			}
149	greg	2.1	normaspect(viewaspect(&ourview)*hmult/vmult, &pixaspect, &hres, &vres);
150			/* open output file */
151			if ((outfd = open(outfile, O_WRONLY\|O_CREAT\|O_EXCL, 0666)) >= 0) {
152			if ((fp = fdopen(dup(outfd), "w")) == NULL)
153			goto filerr;
154			printargs(ac, av, fp); /* write header */
155	greg	2.2	fprintf(fp, "SOFTWARE= %s\n", VersionID);
156	greg	2.1	fputs(VIEWSTR, fp);
157			fprintview(&ourview, fp);
158			putc('\n', fp);
159			if (pixaspect < .99 \|\| pixaspect > 1.01)
160			fputaspect(pixaspect, fp);
161			fputformat(COLRFMT, fp);
162			putc('\n', fp);
163			fprtresolu(hreshmult, vresvmult, fp);
164			} else if ((outfd = open(outfile, O_RDWR)) >= 0) {
165			if ((fp = fdopen(dup(outfd), "r+")) == NULL)
166			goto filerr;
167			getheader(fp, NULL); /* skip header */
168			if (fscnresolu(&hr, &vr, fp) < 0 \|\| /* check resolution */
169			hr != hreshmult \|\| vr != vresvmult) {
170	greg	2.8	fprintf(stderr, "%s: resolution mismatch on file \"%s\"\n",
171			progname, outfile);
172	greg	2.1	exit(1);
173			}
174			} else {
175	greg	2.8	fprintf(stderr, "%s: cannot open file \"%s\"\n",
176			progname, outfile);
177	greg	2.1	exit(1);
178			}
179			scanorig = ftell(fp); /* record position of first scanline */
180			if (fclose(fp) == -1) /* done with stream i/o */
181			goto filerr;
182	greg	2.8	sync(); /* flush NFS buffers */
183	greg	2.1	/* start rpict process */
184			if (open_process(rpd, rpargv) <= 0) {
185	greg	2.3	fprintf(stderr, "%s: cannot start %s\n", progname, rpargv[0]);
186	greg	2.1	exit(1);
187			}
188			if ((fromrp = fdopen(rpd[0], "r")) == NULL \|\|
189			(torp = fdopen(rpd[1], "w")) == NULL) {
190			fprintf(stderr, "%s: cannot open stream to %s\n",
191			progname, rpargv[0]);
192			exit(1);
193			}
194	greg	2.8	if ((pbuf = (COLR )malloc(hresvres*sizeof(COLR))) == NULL) {
195	greg	2.1	fprintf(stderr, "%s: out of memory\n", progname);
196			exit(1);
197			}
198	greg	2.6	signal(SIGALRM, onalrm);
199	greg	2.1	return;
200			filerr:
201	greg	2.8	fprintf(stderr, "%s: i/o error on file \"%s\"\n", progname, outfile);
202	greg	2.1	exit(1);
203			}
204
205
206			int
207	greg	2.5	nextpiece(xp, yp) /* get next piece assignment */
208			int xp, yp;
209			{
210			extern char *fgets();
211			struct flock fls;
212			char buf[64];
213
214	greg	2.6	if (gotalrm) /* someone wants us to quit */
215			return(0);
216			if (syncfd != -1) { /* use sync file */
217	greg	2.5	fls.l_type = F_WRLCK; /* gain exclusive access */
218			fls.l_whence = 0;
219			fls.l_start = 0L;
220			fls.l_len = 0L;
221			fcntl(syncfd, F_SETLKW, &fls);
222			lseek(syncfd, 0L, 0);
223			buf[read(syncfd, buf, sizeof(buf)-1)] = '\0';
224			if (sscanf(buf, "%d %d %d %d", xp, yp) < 2) {
225	greg	2.8	*xp = hmult-1;
226			*yp = vmult;
227			}
228			if (--(yp) < 0) { / decrement position */
229	greg	2.5	*yp = vmult-1;
230	greg	2.8	if (--(xp) < 0) { / all done! */
231	greg	2.5	close(syncfd);
232			return(0);
233			}
234			}
235			sprintf(buf, "%d %d\n%d %d\n", hmult, vmult, xp, yp);
236			lseek(syncfd, 0L, 0); /* write new position */
237			write(syncfd, buf, strlen(buf));
238			fls.l_type = F_UNLCK; /* release sync file */
239			fcntl(syncfd, F_SETLKW, &fls);
240			return(1);
241			}
242	greg	2.6	if (fgets(buf, sizeof(buf), stdin) == NULL) /* use stdin */
243	greg	2.5	return(0);
244			if (sscanf(buf, "%d %d", xp, yp) == 2)
245			return(1);
246			fprintf(stderr, "%s: input format error\n", progname);
247			exit(1);
248			}
249
250
251			int
252	greg	2.1	cleanup() /* close rpict process and clean up */
253			{
254	greg	2.9	register int pid;
255			int status, rstat = 0;
256	greg	2.1
257	greg	2.8	free((char *)pbuf);
258	greg	2.1	fclose(torp);
259			fclose(fromrp);
260	greg	2.9	while ((pid = wait(&status)) != -1)
261			if (rstat == 0)
262			rstat = status>>8 & 0xff;
263			return(rstat);
264	greg	2.1	}
265
266
267			rpiece() /* render picture piece by piece */
268			{
269			VIEW pview;
270			int xorg, yorg;
271
272	greg	2.5	while (nextpiece(&xorg, &yorg)) {
273	greg	2.1	copystruct(&pview, &ourview); /* compute view for piece */
274			switch (ourview.type) {
275			case VT_PER:
276			pview.horiz = 2.180./PIatan(
277			tan(PI/180./2.*ourview.horiz)/hmult );
278			pview.vert = 2.180./PIatan(
279			tan(PI/180./2.*ourview.vert)/vmult );
280			break;
281			case VT_PAR:
282			case VT_ANG:
283			pview.horiz = ourview.horiz / hmult;
284			pview.vert = ourview.vert / vmult;
285			break;
286			case VT_HEM:
287	greg	2.3	pview.horiz = 2.180./PIasin(
288			sin(PI/180./2.*ourview.horiz)/hmult );
289			pview.vert = 2.180./PIasin(
290			sin(PI/180./2.*ourview.vert)/vmult );
291			break;
292	greg	2.1	default:
293			fprintf(stderr, "%s: unknown view type '-vt%c'\n",
294			progname, ourview.type);
295			exit(1);
296			}
297			pview.hoff += xorg - 0.5*(hmult-1);
298			pview.voff += yorg - 0.5*(vmult-1);
299			fputs(VIEWSTR, torp);
300			fprintview(&pview, torp);
301			putc('\n', torp);
302			fflush(torp); /* assign piece to rpict */
303			putpiece(xorg, yorg); /* place piece in output */
304			if (verbose) { /* notify caller */
305	greg	2.5	printf("%d %d done\n", xorg, yorg);
306			fflush(stdout);
307	greg	2.1	}
308			}
309			}
310
311
312	greg	2.9	int
313	greg	2.1	putpiece(xpos, ypos) /* get next piece from rpict */
314			int xpos, ypos;
315			{
316	greg	2.7	struct flock fls;
317	greg	2.9	int pid, status;
318	greg	2.1	int hr, vr;
319	greg	2.8	register int y;
320			/* check bounds */
321	greg	2.5	if (xpos < 0 \| ypos < 0 \| xpos >= hmult \| ypos >= vmult) {
322			fprintf(stderr, "%s: requested piece (%d,%d) out of range\n",
323			progname, xpos, ypos);
324			exit(1);
325			}
326	greg	2.8	/* check header from rpict */
327			getheader(fromrp, NULL);
328			if (fscnresolu(&hr, &vr, fromrp) < 0 \|\| hr != hres \|\| vr != vres) {
329	greg	2.3	fprintf(stderr, "%s: resolution mismatch from %s\n",
330			progname, rpargv[0]);
331	greg	2.1	exit(1);
332			}
333	greg	2.8	/* load new piece into buffer */
334			for (y = 0; y < vr; y++)
335			if (freadcolrs(pbuf+y*hr, hr, fromrp) < 0) {
336	greg	2.3	fprintf(stderr, "%s: read error from %s\n",
337			progname, rpargv[0]);
338	greg	2.1	exit(1);
339			}
340	greg	2.9	#if MAXFORK
341			/* fork so we don't slow rpict down */
342			if ((pid = fork()) > 0) {
343			if (++nforked > MAXFORK) {
344			wait(&status); /* reap a child */
345			if (status)
346			exit(status>>8 & 0xff);
347			nforked--;
348			}
349			return(pid);
350			}
351			#else
352			pid = -1; /* no forking */
353			#endif
354	greg	2.8	/* lock file section so NFS doesn't mess up */
355			fls.l_whence = 0;
356			fls.l_len = (long)vreshmulthres*sizeof(COLR);
357			fls.l_start = scanorig + (vmult-1-ypos)*fls.l_len;
358			fls.l_type = F_WRLCK;
359			fcntl(outfd, F_SETLKW, &fls);
360			/* write new piece to file */
361			if (lseek(outfd, fls.l_start+(long)xposhressizeof(COLR), 0) == -1)
362			goto seekerr;
363	greg	2.9	if (hmult == 1) {
364			if (writebuf(outfd, (char *)pbuf,
365			vrhrsizeof(COLR)) != vrhrsizeof(COLR))
366			goto writerr;
367			} else
368			for (y = 0; y < vr; y++) {
369			if (writebuf(outfd, (char )(pbuf+yhr),
370			hrsizeof(COLR)) != hrsizeof(COLR))
371			goto writerr;
372			if (y < vr-1 && lseek(outfd,
373			(long)(hmult-1)hrsizeof(COLR),
374			1) == -1)
375			goto seekerr;
376	greg	2.1	}
377	greg	2.9	if (pid == -1) { /* fork failed */
378			fls.l_type = F_UNLCK; /* release lock */
379			fcntl(outfd, F_SETLKW, &fls);
380			return(0);
381	greg	2.1	}
382	greg	2.9	_exit(0); /* else exit child process (releasing lock) */
383	greg	2.8	seekerr:
384			fprintf(stderr, "%s: seek error on file \"%s\"\n", progname, outfile);
385	greg	2.9	_exit(1);
386			writerr:
387			fprintf(stderr, "%s: write error on file \"%s\"\n", progname, outfile);
388			_exit(1);
389	greg	2.1	}