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FFmpeg/libavcodec/c93.c
Andreas Rheinhardt fced3a17db avcodec/c93: Fix segfault when using negative linesizes 
c93.c used an int for the stride and an unsigned for the current
linenumber. This does not work when using negative linesizes.
So use ptrdiff_t for stride and int for linenumber.

This fixes the cyberia-c93 FATE test when using negative linesizes.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-10-05 14:38:52 +02:00

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/*
* Interplay C93 video decoder
* Copyright (c) 2007 Anssi Hannula <anssi.hannula@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "decode.h"
typedef struct C93DecoderContext {
AVFrame *pictures[2];
int currentpic;
} C93DecoderContext;
typedef enum {
C93_8X8_FROM_PREV = 0x02,
C93_4X4_FROM_PREV = 0x06,
C93_4X4_FROM_CURR = 0x07,
C93_8X8_2COLOR = 0x08,
C93_4X4_2COLOR = 0x0A,
C93_4X4_4COLOR_GRP = 0x0B,
C93_4X4_4COLOR = 0x0D,
C93_NOOP = 0x0E,
C93_8X8_INTRA = 0x0F,
} C93BlockType;
#define WIDTH 320
#define HEIGHT 192
#define C93_HAS_PALETTE 0x01
#define C93_FIRST_FRAME 0x02
static av_cold int decode_end(AVCodecContext *avctx)
{
C93DecoderContext * const c93 = avctx->priv_data;
av_frame_free(&c93->pictures[0]);
av_frame_free(&c93->pictures[1]);
return 0;
}
static av_cold int decode_init(AVCodecContext *avctx)
{
C93DecoderContext *s = avctx->priv_data;
avctx->pix_fmt = AV_PIX_FMT_PAL8;
s->pictures[0] = av_frame_alloc();
s->pictures[1] = av_frame_alloc();
if (!s->pictures[0] || !s->pictures[1])
return AVERROR(ENOMEM);
return 0;
}
static inline int copy_block(AVCodecContext *avctx, uint8_t *to,
uint8_t *from, int offset, int height, int stride)
{
int i;
int width = height;
int from_x = offset % WIDTH;
int from_y = offset / WIDTH;
int overflow = from_x + width - WIDTH;
if (!from) {
/* silently ignoring predictive blocks in first frame */
return 0;
}
if (from_y + height > HEIGHT) {
av_log(avctx, AV_LOG_ERROR, "invalid offset %d during C93 decoding\n",
offset);
return AVERROR_INVALIDDATA;
}
if (overflow > 0) {
width -= overflow;
for (i = 0; i < height; i++) {
memcpy(&to[i*stride+width], &from[(from_y+i)*stride], overflow);
}
}
for (i = 0; i < height; i++) {
memcpy(&to[i*stride], &from[(from_y+i)*stride+from_x], width);
}
return 0;
}
static inline void draw_n_color(uint8_t *out, int stride, int width,
int height, int bpp, uint8_t cols[4], uint8_t grps[4], uint32_t col)
{
int x, y;
for (y = 0; y < height; y++) {
if (grps)
cols[0] = grps[3 * (y >> 1)];
for (x = 0; x < width; x++) {
if (grps)
cols[1]= grps[(x >> 1) + 1];
out[x + y*stride] = cols[col & ((1 << bpp) - 1)];
col >>= bpp;
}
}
}
static int decode_frame(AVCodecContext *avctx, AVFrame *rframe,
int *got_frame, AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size = avpkt->size;
C93DecoderContext * const c93 = avctx->priv_data;
AVFrame * const newpic = c93->pictures[c93->currentpic];
AVFrame * const oldpic = c93->pictures[c93->currentpic^1];
GetByteContext gb;
uint8_t *out;
int ret, i, x, y, b, bt = 0;
ptrdiff_t stride;
if ((ret = ff_set_dimensions(avctx, WIDTH, HEIGHT)) < 0)
return ret;
c93->currentpic ^= 1;
if ((ret = ff_reget_buffer(avctx, newpic, 0)) < 0)
return ret;
stride = newpic->linesize[0];
bytestream2_init(&gb, buf, buf_size);
b = bytestream2_get_byte(&gb);
if (b & C93_FIRST_FRAME) {
newpic->pict_type = AV_PICTURE_TYPE_I;
newpic->key_frame = 1;
} else {
newpic->pict_type = AV_PICTURE_TYPE_P;
newpic->key_frame = 0;
}
for (y = 0; y < HEIGHT; y += 8) {
out = newpic->data[0] + y * stride;
for (x = 0; x < WIDTH; x += 8) {
uint8_t *copy_from = oldpic->data[0];
uint8_t cols[4], grps[4];
C93BlockType block_type;
if (!bt)
bt = bytestream2_get_byte(&gb);
block_type= bt & 0x0F;
switch (block_type) {
case C93_8X8_FROM_PREV: {
int offset = bytestream2_get_le16(&gb);
if ((ret = copy_block(avctx, out, copy_from, offset, 8, stride)) < 0)
return ret;
break;
}
case C93_4X4_FROM_CURR:
copy_from = newpic->data[0];
case C93_4X4_FROM_PREV:
for (int j = 0; j < 8; j += 4) {
for (i = 0; i < 8; i += 4) {
int offset = bytestream2_get_le16(&gb);
int from_x = offset % WIDTH;
int from_y = offset / WIDTH;
if (block_type == C93_4X4_FROM_CURR && from_y == y+j &&
(FFABS(from_x - x-i) < 4 || FFABS(from_x - x-i) > WIDTH-4)) {
avpriv_request_sample(avctx, "block overlap %d %d %d %d", from_x, x+i, from_y, y+j);
return AVERROR_INVALIDDATA;
}
if ((ret = copy_block(avctx, &out[j*stride+i],
copy_from, offset, 4, stride)) < 0)
return ret;
}
}
break;
case C93_8X8_2COLOR:
bytestream2_get_buffer(&gb, cols, 2);
for (i = 0; i < 8; i++) {
draw_n_color(out + i*stride, stride, 8, 1, 1, cols,
NULL, bytestream2_get_byte(&gb));
}
break;
case C93_4X4_2COLOR:
case C93_4X4_4COLOR:
case C93_4X4_4COLOR_GRP:
for (int j = 0; j < 8; j += 4) {
for (i = 0; i < 8; i += 4) {
if (block_type == C93_4X4_2COLOR) {
bytestream2_get_buffer(&gb, cols, 2);
draw_n_color(out + i + j*stride, stride, 4, 4,
1, cols, NULL, bytestream2_get_le16(&gb));
} else if (block_type == C93_4X4_4COLOR) {
bytestream2_get_buffer(&gb, cols, 4);
draw_n_color(out + i + j*stride, stride, 4, 4,
2, cols, NULL, bytestream2_get_le32(&gb));
} else {
bytestream2_get_buffer(&gb, grps, 4);
draw_n_color(out + i + j*stride, stride, 4, 4,
1, cols, grps, bytestream2_get_le16(&gb));
}
}
}
break;
case C93_NOOP:
break;
case C93_8X8_INTRA:
for (int j = 0; j < 8; j++)
bytestream2_get_buffer(&gb, out + j*stride, 8);
break;
default:
av_log(avctx, AV_LOG_ERROR, "unexpected type %x at %dx%d\n",
block_type, x, y);
return AVERROR_INVALIDDATA;
}
bt >>= 4;
out += 8;
}
}
if (b & C93_HAS_PALETTE) {
uint32_t *palette = (uint32_t *) newpic->data[1];
for (i = 0; i < 256; i++) {
palette[i] = 0xFFU << 24 | bytestream2_get_be24(&gb);
}
newpic->palette_has_changed = 1;
} else {
if (oldpic->data[1])
memcpy(newpic->data[1], oldpic->data[1], 256 * 4);
}
if ((ret = av_frame_ref(rframe, newpic)) < 0)
return ret;
*got_frame = 1;
return buf_size;
}
const FFCodec ff_c93_decoder = {
.p.name = "c93",
CODEC_LONG_NAME("Interplay C93"),
.p.type = AVMEDIA_TYPE_VIDEO,
.p.id = AV_CODEC_ID_C93,
.priv_data_size = sizeof(C93DecoderContext),
.init = decode_init,
.close = decode_end,
FF_CODEC_DECODE_CB(decode_frame),
.p.capabilities = AV_CODEC_CAP_DR1,
.caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
};
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