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FFmpeg/libavcodec/bmvvideo.c
Andreas Rheinhardt 20f9727018 avcodec/codec_internal: Add FFCodec, hide internal part of AVCodec 
Up until now, codec.h contains both public and private parts
of AVCodec. This exposes the internals of AVCodec to users
and leads them into the temptation of actually using them
and forces us to forward-declare structures and types that
users can't use at all.

This commit changes this by adding a new structure FFCodec to
codec_internal.h that extends AVCodec, i.e. contains the public
AVCodec as first member; the private fields of AVCodec are moved
to this structure, leaving codec.h clean.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-03-21 01:33:09 +01:00

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/*
* Discworld II BMV video decoder
* Copyright (c) 2011 Konstantin Shishkov
*
* 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 "libavutil/avassert.h"
#include "libavutil/common.h"
#include "avcodec.h"
#include "bytestream.h"
#include "codec_internal.h"
#include "internal.h"
enum BMVFlags{
BMV_NOP = 0,
BMV_END,
BMV_DELTA,
BMV_INTRA,
BMV_SCROLL = 0x04,
BMV_PALETTE = 0x08,
BMV_COMMAND = 0x10,
BMV_AUDIO = 0x20,
BMV_EXT = 0x40,
BMV_PRINT = 0x80
};
#define SCREEN_WIDE 640
#define SCREEN_HIGH 429
typedef struct BMVDecContext {
AVCodecContext *avctx;
uint8_t *frame, frame_base[SCREEN_WIDE * (SCREEN_HIGH + 1)];
uint32_t pal[256];
const uint8_t *stream;
} BMVDecContext;
#define NEXT_BYTE(v) (v) = forward ? (v) + 1 : (v) - 1;
static int decode_bmv_frame(const uint8_t *source, int src_len, uint8_t *frame, int frame_off)
{
unsigned val, saved_val = 0;
int tmplen = src_len;
const uint8_t *src, *source_end = source + src_len;
uint8_t *frame_end = frame + SCREEN_WIDE * SCREEN_HIGH;
uint8_t *dst, *dst_end;
int len, mask;
int forward = (frame_off <= -SCREEN_WIDE) || (frame_off >= 0);
int read_two_nibbles, flag;
int advance_mode;
int mode = 0;
int i;
if (src_len <= 0)
return AVERROR_INVALIDDATA;
if (forward) {
src = source;
dst = frame;
dst_end = frame_end;
} else {
src = source + src_len - 1;
dst = frame_end - 1;
dst_end = frame - 1;
}
for (;;) {
int shift = 0;
flag = 0;
/* The mode/len decoding is a bit strange:
* values are coded as variable-length codes with nibble units,
* code end is signalled by two top bits in the nibble being nonzero.
* And since data is bytepacked and we read two nibbles at a time,
* we may get a nibble belonging to the next code.
* Hence this convoluted loop.
*/
if (!mode || (tmplen == 4)) {
if (src < source || src >= source_end)
return AVERROR_INVALIDDATA;
val = *src;
read_two_nibbles = 1;
} else {
val = saved_val;
read_two_nibbles = 0;
}
if (!(val & 0xC)) {
for (;;) {
if(shift>22)
return -1;
if (!read_two_nibbles) {
if (src < source || src >= source_end)
return AVERROR_INVALIDDATA;
shift += 2;
val |= (unsigned)*src << shift;
if (*src & 0xC)
break;
}
// two upper bits of the nibble is zero,
// so shift top nibble value down into their place
read_two_nibbles = 0;
shift += 2;
mask = (1 << shift) - 1;
val = ((val >> 2) & ~mask) | (val & mask);
NEXT_BYTE(src);
if ((val & (0xC << shift))) {
flag = 1;
break;
}
}
} else if (mode) {
flag = tmplen != 4;
}
if (flag) {
tmplen = 4;
} else {
saved_val = val >> (4 + shift);
tmplen = 0;
val &= (1 << (shift + 4)) - 1;
NEXT_BYTE(src);
}
advance_mode = val & 1;
len = (val >> 1) - 1;
av_assert0(len>0);
mode += 1 + advance_mode;
if (mode >= 4)
mode -= 3;
if (len <= 0 || FFABS(dst_end - dst) < len)
return AVERROR_INVALIDDATA;
switch (mode) {
case 1:
if (forward) {
if (dst - frame + SCREEN_WIDE < frame_off ||
dst - frame + SCREEN_WIDE + frame_off < 0 ||
frame_end - dst < frame_off + len ||
frame_end - dst < len)
return AVERROR_INVALIDDATA;
for (i = 0; i < len; i++)
dst[i] = dst[frame_off + i];
dst += len;
} else {
dst -= len;
if (dst - frame + SCREEN_WIDE < frame_off ||
dst - frame + SCREEN_WIDE + frame_off < 0 ||
frame_end - dst < frame_off + len ||
frame_end - dst < len)
return AVERROR_INVALIDDATA;
for (i = len - 1; i >= 0; i--)
dst[i] = dst[frame_off + i];
}
break;
case 2:
if (forward) {
if (source + src_len - src < len)
return AVERROR_INVALIDDATA;
memcpy(dst, src, len);
dst += len;
src += len;
} else {
if (src - source < len)
return AVERROR_INVALIDDATA;
dst -= len;
src -= len;
memcpy(dst, src, len);
}
break;
case 3:
val = forward ? dst[-1] : dst[1];
if (forward) {
memset(dst, val, len);
dst += len;
} else {
dst -= len;
memset(dst, val, len);
}
break;
}
if (dst == dst_end)
return 0;
}
}
static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
AVPacket *pkt)
{
BMVDecContext * const c = avctx->priv_data;
AVFrame *frame = data;
int type, scr_off;
int i, ret;
uint8_t *srcptr, *outptr;
c->stream = pkt->data;
type = bytestream_get_byte(&c->stream);
if (type & BMV_AUDIO) {
int blobs = bytestream_get_byte(&c->stream);
if (pkt->size < blobs * 65 + 2) {
av_log(avctx, AV_LOG_ERROR, "Audio data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
c->stream += blobs * 65;
}
if (type & BMV_COMMAND) {
int command_size = (type & BMV_PRINT) ? 8 : 10;
if (c->stream - pkt->data + command_size > pkt->size) {
av_log(avctx, AV_LOG_ERROR, "Command data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
c->stream += command_size;
}
if (type & BMV_PALETTE) {
if (c->stream - pkt->data > pkt->size - 768) {
av_log(avctx, AV_LOG_ERROR, "Palette data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
for (i = 0; i < 256; i++)
c->pal[i] = 0xFFU << 24 | bytestream_get_be24(&c->stream);
}
if (type & BMV_SCROLL) {
if (c->stream - pkt->data > pkt->size - 2) {
av_log(avctx, AV_LOG_ERROR, "Screen offset data doesn't fit in frame\n");
return AVERROR_INVALIDDATA;
}
scr_off = (int16_t)bytestream_get_le16(&c->stream);
} else if ((type & BMV_INTRA) == BMV_INTRA) {
scr_off = -640;
} else {
scr_off = 0;
}
if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
return ret;
if (decode_bmv_frame(c->stream, pkt->size - (c->stream - pkt->data), c->frame, scr_off)) {
av_log(avctx, AV_LOG_ERROR, "Error decoding frame data\n");
return AVERROR_INVALIDDATA;
}
memcpy(frame->data[1], c->pal, AVPALETTE_SIZE);
frame->palette_has_changed = type & BMV_PALETTE;
outptr = frame->data[0];
srcptr = c->frame;
for (i = 0; i < avctx->height; i++) {
memcpy(outptr, srcptr, avctx->width);
srcptr += avctx->width;
outptr += frame->linesize[0];
}
*got_frame = 1;
/* always report that the buffer was completely consumed */
return pkt->size;
}
static av_cold int decode_init(AVCodecContext *avctx)
{
BMVDecContext * const c = avctx->priv_data;
c->avctx = avctx;
avctx->pix_fmt = AV_PIX_FMT_PAL8;
if (avctx->width != SCREEN_WIDE || avctx->height != SCREEN_HIGH) {
av_log(avctx, AV_LOG_ERROR, "Invalid dimension %dx%d\n", avctx->width, avctx->height);
return AVERROR_INVALIDDATA;
}
c->frame = c->frame_base + 640;
return 0;
}
const FFCodec ff_bmv_video_decoder = {
.p.name = "bmv_video",
.p.long_name = NULL_IF_CONFIG_SMALL("Discworld II BMV video"),
.p.type = AVMEDIA_TYPE_VIDEO,
.p.id = AV_CODEC_ID_BMV_VIDEO,
.priv_data_size = sizeof(BMVDecContext),
.init = decode_init,
.decode = decode_frame,
.p.capabilities = AV_CODEC_CAP_DR1,
.caps_internal = FF_CODEC_CAP_INIT_THREADSAFE,
};
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