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avformat/matroskadec: Accept more unknown-length elements II

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Up until now, one last kind of unknown-length element hasn't been
properly handled: Unknown-length elements that are supposed to be
skipped, i.e. the level 1 elements that might reside after the
clusters.

This commit changes this. To do this, ebml_parse got a mode that
essentially tries to skip everything except when parsing is needed
(namely for unknown-length elements for which parsing is necessary
as they can't be skipped). This mode is selected by using a NULL
as destination where the parsed data should be written to.
It is used to parse the level 1 elements in matroska_parse_cluster.

The syntax list used for parsing must of course include links to
the syntax of all the master elements that might need to be parsed.
In other words: Instead of matroska_clusters (which contained every
level 1 element except clusters as EBML_NONE elements designated to
be skipped) matroska_segment is needed and used; matroska_clusters has
been removed.

Furthermore, matroska_segment has been reordered so that clusters are at
the front as this is now the most common case for this list.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2019-05-17 00:30:18 +02:00 committed by James Almer
parent 9c6d14ab84
commit 71c908817e
1 changed files with 10 additions and 14 deletions
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24
libavformat/matroskadec.c
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@ -685,6 +685,7 @@ static const EbmlSyntax matroska_seekhead[] = {
};
static const EbmlSyntax matroska_segment[] = {
{ MATROSKA_ID_CLUSTER, EBML_STOP },
{ MATROSKA_ID_INFO, EBML_LEVEL1, 0, 0, { .n = matroska_info } },
{ MATROSKA_ID_TRACKS, EBML_LEVEL1, 0, 0, { .n = matroska_tracks } },
{ MATROSKA_ID_ATTACHMENTS, EBML_LEVEL1, 0, 0, { .n = matroska_attachments } },
@ -692,7 +693,6 @@ static const EbmlSyntax matroska_segment[] = {
{ MATROSKA_ID_CUES, EBML_LEVEL1, 0, 0, { .n = matroska_index } },
{ MATROSKA_ID_TAGS, EBML_LEVEL1, 0, 0, { .n = matroska_tags } },
{ MATROSKA_ID_SEEKHEAD, EBML_LEVEL1, 0, 0, { .n = matroska_seekhead } },
{ MATROSKA_ID_CLUSTER, EBML_STOP },
{ 0 } /* We don't want to go back to level 0, so don't add the parent. */
};
@ -740,18 +740,6 @@ static const EbmlSyntax matroska_cluster_enter[] = {
{ MATROSKA_ID_CLUSTER, EBML_NEST, 0, 0, { .n = &matroska_cluster_parsing[2] } },
{ 0 }
};
static const EbmlSyntax matroska_clusters[] = {
{ MATROSKA_ID_CLUSTER, EBML_STOP },
{ MATROSKA_ID_CUES, EBML_NONE },
{ MATROSKA_ID_TAGS, EBML_NONE },
{ MATROSKA_ID_INFO, EBML_NONE },
{ MATROSKA_ID_TRACKS, EBML_NONE },
{ MATROSKA_ID_ATTACHMENTS, EBML_NONE },
{ MATROSKA_ID_CHAPTERS, EBML_NONE },
{ MATROSKA_ID_SEEKHEAD, EBML_NONE },
{ 0 } /* We don't want to go back to level 0, so don't add the parent. */
};
#undef CHILD_OF
static const char *const matroska_doctypes[] = { "matroska", "webm" };
@ -1082,6 +1070,7 @@ static int ebml_parse_nest(MatroskaDemuxContext *matroska, EbmlSyntax *syntax,
{
int i, res;
if (data) {
for (i = 0; syntax[i].id; i++)
switch (syntax[i].type) {
case EBML_UINT:
@ -1109,6 +1098,7 @@ static int ebml_parse_nest(MatroskaDemuxContext *matroska, EbmlSyntax *syntax,
matroska->num_levels--;
return 0;
}
}
do {
res = ebml_parse(matroska, syntax, data);
@ -1238,6 +1228,7 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
update_pos = 0; /* Don't update resync_pos as an error might have happened. */
}
if (data) {
data = (char *) data + syntax->data_offset;
if (syntax->list_elem_size) {
EbmlList *list = data;
@ -1250,6 +1241,7 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
memset(data, 0, syntax->list_elem_size);
list->nb_elem++;
}
}
if (syntax->type != EBML_STOP) {
matroska->current_id = 0;
@ -1366,6 +1358,9 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
// of the element as the "last known good" position.
matroska->resync_pos = pos;
}
if (!data && length != EBML_UNKNOWN_LENGTH)
goto skip;
}
switch (syntax->type) {
@ -1404,6 +1399,7 @@ static int ebml_parse(MatroskaDemuxContext *matroska,
break;
case EBML_STOP:
return 1;
skip:
default:
if (length) {
int64_t res2;
@ -3671,7 +3667,7 @@ static int matroska_parse_cluster(MatroskaDemuxContext *matroska)
av_assert0(matroska->num_levels <= 2);
if (matroska->num_levels == 1) {
res = ebml_parse(matroska, matroska_clusters, NULL);
res = ebml_parse(matroska, matroska_segment, NULL);
if (res == 1) {
/* Found a cluster: subtract the size of the ID already read. */