TgaRleDecode.c

/*
 * The Python Imaging Library.
 * $Id$
 *
 * decoder for Targa RLE data.
 *
 * history:
 * 97-01-04 fl	created
 * 98-09-11 fl	don't one byte per pixel; take orientation into account
 *
 * Copyright (c) Fredrik Lundh 1997.
 * Copyright (c) Secret Labs AB 1997-98.
 *
 * See the README file for information on usage and redistribution.
 */


#include "Imaging.h"


int
ImagingTgaRleDecode(Imaging im, ImagingCodecState state,
		    UINT8* buf, int bytes)
{
    int n, depth;
    UINT8* ptr;

    ptr = buf;

    if (state->state == 0) {

	/* check image orientation */
	if (state->ystep < 0) {
	    state->y = state->ysize-1;
	    state->ystep = -1;
	} else
	    state->ystep = 1;

	state->state = 1;

    }

    depth = state->count;

    for (;;) {

	if (bytes < 1)
	    return ptr - buf;

	if (ptr[0] & 0x80) {

	    /* Run (1 + pixelsize bytes) */

	    if (bytes < 1 + depth)
		break;

	    n = depth * ((ptr[0] & 0x7f) + 1);

	    if (state->x + n > state->bytes) {
		state->errcode = IMAGING_CODEC_OVERRUN;
		return -1;
	    }

            if (depth == 1)
                memset(state->buffer + state->x, ptr[1], n);
            else {
                int i;
                for (i = 0; i < n; i += depth)
                    memcpy(state->buffer + state->x + i, ptr+1, depth);
            }

            ptr += 1 + depth;
	    bytes -= 1 + depth;

	} else {

	    /* Literal (1+n+1 bytes block) */
	    n = depth * (ptr[0] + 1);

	    if (bytes < 1 + n)
		break;

	    if (state->x + n > state->bytes) {
		state->errcode = IMAGING_CODEC_OVERRUN;
		return -1;
	    }

	    memcpy(state->buffer + state->x, ptr + 1, n);

	    ptr += 1 + n;
	    bytes -= 1 + n;

	}

	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;

            state->y += state->ystep;

            if (state->y < 0 || state->y >= state->ysize) {
                /* End of file (errcode = 0) */
                return -1;
            }

	}

    }

    return ptr - buf;
}