postgif.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	cmap = lcmap;
	gmap = lgmap;
	maplength = lmaplength;
    }

dbprt(stderr, "start reading raster data\n");
    fread(ibuf, sizeof(*ibuf), 1, fp_in);
    codesize = ibuf[0];
dbprt(stderr, "codesize: %d\n", codesize);
    pmap = (unsigned char *) allocate(imagewidth*imageheight);
    initstbl();
    while ((code = getcode()) != endcode) {
	if (code == clearcode) {
	    curstblsize = endcode + 1;
    	    code = getcode();
    	    putcode(code);
    	    oldcode = code;
	}
	else if (code < curstblsize) {
	    putcode(code);
	    prefix[curstblsize] = oldcode;
	    suffix[curstblsize] = firstof(code);
	    curstblsize++;
	    oldcode = code;
	}
	else {
	   if (code != curstblsize) error(FATAL, "code out of order");
	   prefix[curstblsize] = oldcode;
	   suffix[curstblsize] = firstof(oldcode);
	   curstblsize++;
	   putcode(curstblsize-1);
	   oldcode = code;
	}
    }
dbprt(stderr, "finish reading raster data\n");

    /* read the rest of the raster data */
    do {
    	fread(ibuf, sizeof(*ibuf), 1, fp_in);
    	bytecount = ibuf[0];
dbprt(stderr, "byte count: %d\n", bytecount);
	if (bytecount) fread(ibuf, sizeof(*ibuf), bytecount, fp_in);
	else zerobytecount = 1;
    } while (!zerobytecount);

    writeimage();

    if (lcolormap) {
	cmap = gcmap;
	gmap = ggmap;
	maplength = gmaplength;
	free(lcmap);
	free(lgmap);
    }
}

void
readextensionblock()
{
    int functioncode, bytecount, zerobytecount = 0;

    fread(ibuf, sizeof(*ibuf), 1, fp_in);
    functioncode = ibuf[0];
dbprt(stderr, "function code: %d\n", functioncode);
    do {
    	fread(ibuf, sizeof(*ibuf), 1, fp_in);
    	bytecount = ibuf[0];
dbprt(stderr, "byte count: %d\n", bytecount);
	if (bytecount) fread(ibuf, sizeof(*ibuf), bytecount, fp_in);
	else zerobytecount = 1;
    } while (!zerobytecount);
}

void
writebgscr()
{
    fprintf(fp_out, "%s %d %d\n", PAGE, page, printed+1);
    fputs("/saveobj save def\n", fp_out);
    fprintf(fp_out, "%s: %d %d %d %d\n",
	"%%PageBoundingBox", 0, 0, scrwidth, scrheight);
    if (scrwidth > bburx) bburx = scrwidth;
    if (scrheight > bbury) bbury = scrheight;
    fprintf(fp_out, "%d %d gifscreen\n", scrwidth, scrheight);
}

void
writeendscr()
{
    if ( fp_out == stdout ) printed++;
    fputs("showpage\n", fp_out);
    fputs("saveobj restore\n", fp_out);
    fprintf(fp_out, "%s %d %d\n", ENDPAGE, page, printed);
}

void
redirect(pg)
    int		pg;			/* next page we're printing */
{
    static FILE	*fp_null = NULL;	/* if output is turned off */

    if ( pg >= 0 && in_olist(pg) == ON )
	fp_out = stdout;
    else if ( (fp_out = fp_null) == NULL )
	fp_out = fp_null = fopen("/dev/null", "w");

}

void
readgif()
{
    int i, j, k;

    for (i = 0, j = 1, k = 0; i < 13; i++) {
	for (; k < j; k++) cstbl[k] = i;
	j *= 2;
    }

    fread(ibuf, sizeof(*ibuf), 6, fp_in);
dbprt(stderr, "%.6s\n", ibuf);
    if (strncmp((char *)ibuf, "GIF87a", 6) != 0) {
    	fread(ibuf, sizeof(*ibuf), 122, fp_in);
    	fread(ibuf, sizeof(*ibuf), 6, fp_in);
dbprt(stderr, "%.6s\n", ibuf);
    	if (strncmp((char *)ibuf, "GIF87a", 6) != 0)
		 error(FATAL, "wrong GIF signature");
    }
    fread(ibuf, sizeof(*ibuf), 7, fp_in);
    scrwidth = ibuf[0] + 256*ibuf[1];
    scrheight = ibuf[2] + 256*ibuf[3];
    gcolormap = ibuf[4] & 0200;
    bitperpixel = (ibuf[4] & 07) + 1;
    background = ibuf[5];
dbprt(stderr, "scrwidth: %d\n", scrwidth);
dbprt(stderr, "scrheight: %d\n", scrheight);
dbprt(stderr, "gcolormap: %d\n", gcolormap ? 1 : 0);
dbprt(stderr, "bitperpixel: %d\n", bitperpixel);
dbprt(stderr, "background: %d\n", background);
    if (ibuf[6] != 0) error(FATAL, "wrong screen descriptor");
    if (gcolormap) readgcolormap(bitperpixel);
    else setcolormap(bitperpixel);

    redirect(++page);
    writebgscr();

    cmap = gcmap;
    gmap = ggmap;
    maplength = gmaplength;

    do {
	fread(ibuf, sizeof(*ibuf), 1, fp_in);
	if (ibuf[0] == ',') readimage();
	else if (ibuf[0] == ';') terminate = 1;
	else if (ibuf[0] == '!') readextensionblock();
	else
	error(FATAL, "wrong image separator character or wrong GIF terminator");
    } while (!terminate);

    writeendscr();

    free(gcmap);
    free(ggmap);
}

void
init_signals()
{

    if ( signal(SIGINT, interrupt) == SIG_IGN )  {
        signal(SIGINT, SIG_IGN);
        signal(SIGQUIT, SIG_IGN);
        signal(SIGHUP, SIG_IGN);
    }
    else {
        signal(SIGHUP, interrupt);
        signal(SIGQUIT, interrupt);
    }

    signal(SIGTERM, interrupt);
}

void
header()
{
    int         ch;                     /* return value from getopt() */
    int         old_optind = optind;    /* for restoring optind - should be 1 */

    while ( (ch = getopt(argc, argv, optnames)) != EOF )
        if ( ch == 'L' )
            prologue = optarg;
        else if ( ch == '?' )
            error(FATAL, "");

    optind = old_optind;                /* get ready for option scanning */

    fprintf(stdout, "%s", CONFORMING);
    fprintf(stdout, "%s %s\n", VERSION, PROGRAMVERSION);
    fprintf(stdout, "%s %s\n", BOUNDINGBOX, ATEND);
    fprintf(stdout, "%s %s\n", PAGES, ATEND);
    fprintf(stdout, "%s", ENDCOMMENTS);

    if ( cat(prologue) == FALSE )
        error(FATAL, "can't read %s", prologue);

    fprintf(stdout, "%s", ENDPROLOG);
    fprintf(stdout, "%s", BEGINSETUP);
    fprintf(stdout, "mark\n");

}

void
options()
{
    int		ch;			/* return value from getopt() */

    while ( (ch = getopt(argc, argv, optnames)) != EOF )  {
	switch ( ch )  {

	    case 'a':			/* aspect ratio */
		    fprintf(stdout, "/aspectratio %s def\n", optarg);
		    break;

	    case 'c':			/* copies */
		    copies = atoi(optarg);
		    fprintf(stdout, "/#copies %s store\n", optarg);
		    break;

	    case 'f':
		    negative = TRUE;
		    break;

	    case 'g':
		    gray = TRUE;
		    break;

	    case 'l':
		    fprintf(stdout, "/alignment true def\n");
		    break;

	    case 'm':			/* magnification */
		    fprintf(stdout, "/magnification %s def\n", optarg);
		    break;

	    case 'n':			/* forms per page */
		    formsperpage = atoi(optarg);
		    fprintf(stdout, "%s %s\n", FORMSPERPAGE, optarg);
		    fprintf(stdout, "/formsperpage %s def\n", optarg);
		    break;

	    case 'o':			/* output page list */
		    out_list(optarg);
		    break;

	    case 'p':			/* landscape or portrait mode */
		    if ( *optarg == 'l' )
			fprintf(stdout, "/landscape true def\n");
		    else fprintf(stdout, "/landscape false def\n");
		    break;

	    case 'x':			/* shift things horizontally */
		    fprintf(stdout, "/xoffset %s def\n", optarg);
		    break;

	    case 'y':			/* and vertically on the page */
		    fprintf(stdout, "/yoffset %s def\n", optarg);
		    break;

	    case 'C':			/* copy file straight to output */
		    if ( cat(optarg) == FALSE )
			error(FATAL, "can't read %s", optarg);
		    break;

	    case 'E':			/* text font encoding - unnecessary */
		    fontencoding = optarg;
		    break;

	    case 'D':			/* debug flag */
		    debug = ON;
		    break;

	    case 'G':
		    gammaflag = ON;
		    gamma = atof(optarg);
		    break;

	    case 'I':			/* ignore FATAL errors */
		    ignore = ON;
		    break;

	    case 'L':			/* PostScript prologue file */
		    prologue = optarg;
		    break;

	    case 'P':			/* PostScript pass through */
		    fprintf(stdout, "%s\n", optarg);
		    break;

	    case '?':			/* don't understand the option */
		    error(FATAL, "");
		    break;

	    default:			/* don't know what to do for ch */
		    error(FATAL, "missing case for option %c\n", ch);
		    break;

	}
    }

    argc -= optind;			/* get ready for non-option args */
    argv += optind;
}

void
setup()
{
    /*setencoding(fontencoding);*/
    fprintf(stdout, "setup\n");

    if ( formsperpage > 1 )  {          /* followed by stuff for multiple pages
*/
        if ( cat(formfile) == FALSE )
            error(FATAL, "can't read %s", formfile);
        fprintf(stdout, "%d setupforms\n", formsperpage);
    }   /* End if */

    fprintf(stdout, "%s", ENDSETUP);

}

void
arguments()
{
    if ( argc < 1 ) {
	fp_in = stdin;
	readgif();
    }
    else  {				/* at least one argument is left */
	while ( argc > 0 )  {
	    if ( strcmp(*argv, "-") == 0 )
		fp_in = stdin;
	    else if ( (fp_in = fopen(*argv, "r")) == NULL )
		error(FATAL, "can't open %s", *argv);
	    readgif();
	    if ( fp_in != stdin )
		fclose(fp_in);
	    argc--;
	    argv++;
	}
    }
}

void
done()
{
    fprintf(stdout, "%s", TRAILER);
    fprintf(stdout, "done\n");
    fprintf(stdout, "%s 0 0 %d %d\n", BOUNDINGBOX, bburx, bbury);
    fprintf(stdout, "%s %d\n", PAGES, printed); 
}

main(agc, agv)
    int agc;
    char *agv[];
{
    argc = agc;
    argv = agv;
    prog_name = argv[0];

    init_signals();
    header();
    options();
    setup();
    arguments();
    done();

    exit(0);
}