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Code Issues Releases Activity

avformat/matroskadec: Reuse positions

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Up until now, avio_tell was used multiple times in ebml_parse and its
subroutines, although the result of these calls can usually be simply
derived from the result of earlier calls to avio_tell. This has been
changed. Unnecessary calls to avio_tell in ebml_parse are avoided now.

Furthermore, there has been a slight change in the output of some error
messages relating to elements exceeding their containing master element:
The reported position of the element now points to the first byte of the
element ID and no longer to the first byte of the element's payload.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2019-05-17 00:30:12 +02:00 committed by James Almer
parent 3ed2755baa
commit 7087fc95b2
1 changed files with 19 additions and 14 deletions
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33
libavformat/matroskadec.c
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@ -976,7 +976,8 @@ static int ebml_read_ascii(AVIOContext *pb, int size, char **str)
* Read the next element as binary data.
* 0 is success, < 0 or NEEDS_CHECKING is failure.
*/
static int ebml_read_binary(AVIOContext *pb, int length, EbmlBin *bin)
static int ebml_read_binary(AVIOContext *pb, int length,
int64_t pos, EbmlBin *bin)
{
int ret;
@ -987,7 +988,7 @@ static int ebml_read_binary(AVIOContext *pb, int length, EbmlBin *bin)
bin->data = bin->buf->data;
bin->size = length;
bin->pos = avio_tell(pb);
bin->pos = pos;
if ((ret = avio_read(pb, bin->data, length)) != length) {
av_buffer_unref(&bin->buf);
bin->data = NULL;
@ -1003,9 +1004,9 @@ static int ebml_read_binary(AVIOContext *pb, int length, EbmlBin *bin)
* are supposed to be sub-elements which can be read separately.
* 0 is success, < 0 is failure.
*/
static int ebml_read_master(MatroskaDemuxContext *matroska, uint64_t length)
static int ebml_read_master(MatroskaDemuxContext *matroska,
uint64_t length, int64_t pos)
{
AVIOContext *pb = matroska->ctx->pb;
MatroskaLevel *level;
if (matroska->num_levels >= EBML_MAX_DEPTH) {
@ -1015,7 +1016,7 @@ static int ebml_read_master(MatroskaDemuxContext *matroska, uint64_t length)
}
level = &matroska->levels[matroska->num_levels++];
level->start = avio_tell(pb);
level->start = pos;
level->length = length;
return 0;
@ -1173,7 +1174,7 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
AVIOContext *pb = matroska->ctx->pb;
uint32_t id;
uint64_t length;
int64_t pos = avio_tell(pb);
int64_t pos = avio_tell(pb), pos_alt;
int res, update_pos = 1, level_check;
void *newelem;
MatroskaLevel1Element *level1_elem;
@ -1201,8 +1202,11 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
return res;
}
matroska->current_id = id | 1 << 7 * res;
} else
pos -= (av_log2(matroska->current_id) + 7) / 8;
pos_alt = pos + res;
} else {
pos_alt = pos;
pos -= (av_log2(matroska->current_id) + 7) / 8;
}
id = matroska->current_id;
@ -1247,14 +1251,15 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
length, max_lengths[syntax->type], syntax->type);
return AVERROR_INVALIDDATA;
}
pos_alt += res;
if (matroska->num_levels > 0) {
MatroskaLevel *level = &matroska->levels[matroska->num_levels - 1];
AVIOContext *pb = matroska->ctx->pb;
int64_t pos = avio_tell(pb);
if (length != EBML_UNKNOWN_LENGTH &&
level->length != EBML_UNKNOWN_LENGTH) {
uint64_t elem_end = pos + length,
uint64_t elem_end = pos_alt + length,
level_end = level->start + level->length;
if (elem_end < level_end) {
@ -1309,14 +1314,14 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
res = ebml_read_ascii(pb, length, data);
break;
case EBML_BIN:
res = ebml_read_binary(pb, length, data);
res = ebml_read_binary(pb, length, pos_alt, data);
break;
case EBML_LEVEL1:
case EBML_NEST:
if ((res = ebml_read_master(matroska, length)) < 0)
if ((res = ebml_read_master(matroska, length, pos_alt)) < 0)
return res;
if (id == MATROSKA_ID_SEGMENT)
matroska->segment_start = avio_tell(matroska->ctx->pb);
matroska->segment_start = pos_alt;
if (id == MATROSKA_ID_CUES)
matroska->cues_parsing_deferred = 0;
if (syntax->type == EBML_LEVEL1 &&