Pillow/libImaging/SunRleDecode.c

/*
 * THIS IS WORK IN PROGRESS
 *
 * The Python Imaging Library.
 * $Id$
 *
 * decoder for SUN RLE data.
 *
 * history:
 *      97-01-04 fl     Created
 *
 * Copyright (c) Fredrik Lundh 1997.
 * Copyright (c) Secret Labs AB 1997.
 *
 * See the README file for information on usage and redistribution.
 */


#include "Imaging.h"


int
ImagingSunRleDecode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
{
    int n;
    UINT8* ptr;
    UINT8 extra_data = 0;
    UINT8 extra_bytes = 0;
    int ct_bytes = 0;

    ptr = buf;

    for (;;) {

        if (bytes < 1)
            return ptr - buf;

        if (ptr[0] == 0x80) {

            if (bytes < 2)
                break;

            n = ptr[1];


            if (n == 0) {

                /* Literal 0x80 (2 bytes) */
                n = 1;
                ct_bytes += n;        

                state->buffer[state->x] = 0x80;

                ptr += 2;
                bytes -= 2;

            } else {

                /* Run (3 bytes) */
                if (bytes < 3)
                    break;

                ct_bytes += n;        

                if (state->x + n > state->bytes) {
                    extra_bytes = n;  /* full value */
                    n = state->bytes - state->x;
                    extra_bytes -= n;
                    extra_data = ptr[2];
                }

                memset(state->buffer + state->x, ptr[2], n);

                ptr += 3;
                bytes -= 3;

            }

        } else {

            /* Literal byte */ 
            n = 1; 
            ct_bytes += n;        

            state->buffer[state->x] = ptr[0];

            ptr += 1;
            bytes -= 1;

        }

        for (;;) {
            state->x += n;
        
            if (state->x >= state->bytes) {

                /* Got a full line, unpack it */
                state->shuffle((UINT8*) im->image[state->y + state->yoff] +
                               state->xoff * im->pixelsize, state->buffer,
                               state->xsize);

                state->x = 0;

                if (++state->y >= state->ysize) {
                    /* End of file (errcode = 0) */
                    printf("%d", ct_bytes);
                    return -1;
                }
            }
            
            if (extra_bytes == 0) {
                break;
            }

            if (state->x > 0) {
                break; // assert
            }

            if (extra_bytes >= state->bytes) {
                n = state->bytes;
            } else {
                n = extra_bytes;
            }
            memset(state->buffer + state->x, extra_data, n);
            extra_bytes -= n;
        }
    }

    return ptr - buf;
}