decode.c

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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <memory.h>

char inbuf[1000 * 1000];
char outbuf[1000 * 1000];

int insize;
int outsize;

int vflag;

long
RLEC (char *src, char *dest, unsigned int src_size)
{
    short src_i, dest_i, limit;
    short togo;
    
    dest_i = 0;
    src_i = 0;
    while ((togo = src_size - src_i) > 0) {
        int thistime;

        limit = togo - 1;
        if (limit >= 128)
            limit = 128;

        thistime = 0;
        while (thistime < limit && src[src_i] != src[src_i+1]) {
            thistime++;
            src_i++;
        }
        if (thistime) {
            dest[dest_i++] = (thistime-1);
            memcpy (&dest[dest_i], &src[src_i-thistime], thistime);
            dest_i += thistime;
        } else {
            thistime = 2;   /* at least 2 chars to be repeated */
            src_i++; /* advance pointer beyond the first match*/
            while (thistime < limit && src[src_i] == src[src_i+1]){
                thistime++;
                src_i++;
            }
            dest[dest_i++] = (-thistime+1);
            dest[dest_i++] = src[src_i++];
        }
    }
    return (dest_i);
}


int
RLED (void *src_raw, void *dest_raw, unsigned int src_size)
{
    signed char *src = src_raw;
    signed char *dest = dest_raw;
    unsigned short used;
    short count, val;
    short i;

    used = 0;
    while (used < src_size) {
        count = src[used++];
        
        if (count < 0) {
            count = -(count - 1);
            val = src[used++];
            
            if (vflag)
                printf ("%6d: repeat %02x\n", count, val&0xff);

            for (i = 0; i < count; i++)
                *dest++ = val;
        } else {
            count++;

            if (vflag)
                printf ("%6d:", count);

            for (i = 0; i < count; i++) {
                if (vflag)
                    printf (" %02x", src[used] & 0xff);
                *dest++ = src[used++];
            }

            if (vflag)
                printf ("\n");
        }
    }

    return ((void *)dest - (void *)dest_raw);
}

int
RLED2 (char *src, char *dest, unsigned int src_size)
{
    short ax, bx, cx;
    char const *si;
    char *di;

    di = dest;
    si = src;
    cx = 0;
    bx = src_size;

loa:
    ax = *si++ & 0xff;
    bx--;
    if (ax & 0x80)
        goto repeat;

    ax = (ax + 1) & 0xff;
    cx = ax;

    do
        *di++ = *si++;
    while (--cx);

    bx -= ax;

    if (bx > 0)
        goto loa;
    goto bot;

repeat:
    ax = -ax;
    ax++;
    cx = ax & 0xff;

    ax = *si++ & 0xff;

lob:
    *di++ = ax;
    if (--cx)
        goto lob;
    bx--;
    if (bx > 0)
        goto loa;

bot: 
    return (di - dest);
}

void
usage (void)
{
    fprintf (stderr, "usage: decode file\n");
    exit (1);
}

int width, height;

int
main (int argc, char **argv)
{
    int c;
    char *filename;
    FILE *f;
    FILE *outf;

    while ((c = getopt (argc, argv, "vw:h:")) != EOF) {
        switch (c) {
        case 'w':
            width = atoi (optarg);
            break;
        case 'h':
            height = atoi (optarg);
            break;
        case 'v':
            vflag = 1;
            break;
        default:
            usage ();
        }
    }

    if (optind >= argc)
        usage ();

    filename = argv[optind++];

    if (optind != argc)
        usage ();

    if ((f = fopen (filename, "rb")) == NULL) {
        fprintf (stderr, "can't open %s\n", filename);
        exit (1);
    }

    fread (inbuf, 1, 80, f);
    insize = fread (inbuf, 1, sizeof inbuf, f);

    printf ("input size %d\n", insize);

    outsize = RLED (inbuf, outbuf, insize);

    printf ("output size %d\n", outsize);

    if (width && height) {
        if ((outf = fopen ("d.pgm", "wb")) == NULL) {
            fprintf (stderr, "can't create d.pgm\n");
            exit (1);
        }
        fprintf (outf, "P5\n%d %d\n255\n", width, height);
        fwrite (outbuf, 1, width * height, outf);
        fclose (outf);
    }

    return (0);
}

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