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avformat/subtitles: extend ff_subtitles_queue_insert() to support not yet available events 

If ff_subtitles_queue_insert() were given a NULL buffer
with 0 length, it would still attempt to grow the packet
or memcpy depending on if merge option is enabled.

In this commit, allow passing a NULL buffer with 0 length
without attempting to do such operations. This way, if a
subtitle demuxer happens to pass an empty cue or wants to
use av_get_packet() to read bytes, there are no unnecessary
operations on the packet after it is allocated.

Signed-off-by: Marth64 <marth64@proxyid.net>
This commit is contained in:
Marth64 2024-04-02 00:24:53 -05:00 committed by Stefano Sabatini
parent ed9363052f
commit 1c35333671
2 changed files with 16 additions and 9 deletions
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23
libavformat/subtitles.c
View File

@ -21,6 +21,7 @@
#include "avformat.h"
#include "subtitles.h"
#include "avio_internal.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/mem.h"
@ -112,15 +113,19 @@ AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
{
AVPacket **subs, *sub;
av_assert1(event || len == 0);
if (merge && q->nb_subs > 0) {
/* merge with previous event */
int old_len;
sub = q->subs[q->nb_subs - 1];
old_len = sub->size;
if (av_grow_packet(sub, len) < 0)
return NULL;
memcpy(sub->data + old_len, event, len);
if (event) {
if (av_grow_packet(sub, len) < 0)
return NULL;
memcpy(sub->data + old_len, event, len);
}
} else {
/* new event */
@ -134,14 +139,16 @@ AVPacket *ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q,
sub = av_packet_alloc();
if (!sub)
return NULL;
if (av_new_packet(sub, len) < 0) {
av_packet_free(&sub);
return NULL;
if (event) {
if (av_new_packet(sub, len) < 0) {
av_packet_free(&sub);
return NULL;
}
memcpy(sub->data, event, len);
}
subs[q->nb_subs++] = sub;
sub->flags |= AV_PKT_FLAG_KEY;
sub->pts = sub->dts = 0;
memcpy(sub->data, event, len);
subs[q->nb_subs++] = sub;
}
return sub;
}

2
libavformat/subtitles.h
View File

@ -112,7 +112,7 @@ typedef struct {
/**
* Insert a new subtitle event.
*
* @param event the subtitle line, may not be zero terminated
* @param event the subtitle line (not zero terminated) or NULL on not yet available event
* @param len the length of the event (in strlen() sense, so without '\0')
* @param merge set to 1 if the current event should be concatenated with the
* previous one instead of adding a new entry, 0 otherwise