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Code Issues Releases Activity

avformat/dss: Avoid using intermediate buffer

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All one needs is one byte beyond the end of the normal data; and because
the packet is padded, one already has it.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2021-04-01 22:55:31 +02:00
parent ef8c8b4163
commit 48a594aba5
1 changed files with 11 additions and 14 deletions
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25
libavformat/dss.c
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@@ -50,7 +50,6 @@ typedef struct DSSDemuxContext {
int counter; int counter;
int swap; int swap;
int dss_sp_swap_byte; int dss_sp_swap_byte;
int8_t dss_sp_buf[DSS_FRAME_SIZE + 1];
int packet_size; int packet_size;
int dss_header_size; int dss_header_size;
@@ -182,26 +181,23 @@ static void dss_skip_audio_header(AVFormatContext *s, AVPacket *pkt)
ctx->counter += DSS_BLOCK_SIZE - DSS_AUDIO_BLOCK_HEADER_SIZE; ctx->counter += DSS_BLOCK_SIZE - DSS_AUDIO_BLOCK_HEADER_SIZE;
} }
static void dss_sp_byte_swap(DSSDemuxContext *ctx, static void dss_sp_byte_swap(DSSDemuxContext *ctx, uint8_t *data)
uint8_t *dst, const uint8_t *src)
{ {
int i; int i;
if (ctx->swap) { if (ctx->swap) {
for (i = 3; i < DSS_FRAME_SIZE; i += 2)
dst[i] = src[i];
for (i = 0; i < DSS_FRAME_SIZE - 2; i += 2) for (i = 0; i < DSS_FRAME_SIZE - 2; i += 2)
dst[i] = src[i + 4]; data[i] = data[i + 4];
dst[1] = ctx->dss_sp_swap_byte; /* Zero the padding. */
data[DSS_FRAME_SIZE] = 0;
data[1] = ctx->dss_sp_swap_byte;
} else { } else {
memcpy(dst, src, DSS_FRAME_SIZE); ctx->dss_sp_swap_byte = data[DSS_FRAME_SIZE - 2];
ctx->dss_sp_swap_byte = src[DSS_FRAME_SIZE - 2];
} }
/* make sure byte 40 is always 0 */ /* make sure byte 40 is always 0 */
dst[DSS_FRAME_SIZE - 2] = 0; data[DSS_FRAME_SIZE - 2] = 0;
ctx->swap ^= 1; ctx->swap ^= 1;
} }
@@ -229,7 +225,7 @@ static int dss_sp_read_packet(AVFormatContext *s, AVPacket *pkt)
pkt->stream_index = 0; pkt->stream_index = 0;
if (ctx->counter < read_size) { if (ctx->counter < read_size) {
ret = avio_read(s->pb, ctx->dss_sp_buf + buff_offset, ret = avio_read(s->pb, pkt->data + buff_offset,
ctx->counter); ctx->counter);
if (ret < ctx->counter) if (ret < ctx->counter)
goto error_eof; goto error_eof;
@@ -239,12 +235,13 @@ static int dss_sp_read_packet(AVFormatContext *s, AVPacket *pkt)
} }
ctx->counter -= read_size; ctx->counter -= read_size;
ret = avio_read(s->pb, ctx->dss_sp_buf + offset + buff_offset, /* This will write one byte into pkt's padding if buff_offset == 3 */
ret = avio_read(s->pb, pkt->data + offset + buff_offset,
read_size - offset); read_size - offset);
if (ret < read_size - offset) if (ret < read_size - offset)
goto error_eof; goto error_eof;
dss_sp_byte_swap(ctx, pkt->data, ctx->dss_sp_buf); dss_sp_byte_swap(ctx, pkt->data);
if (ctx->dss_sp_swap_byte < 0) { if (ctx->dss_sp_swap_byte < 0) {
return AVERROR(EAGAIN); return AVERROR(EAGAIN);