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avformat: Change avpriv_new_chapter() from O(n) to (1) in the common case

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Fixes: timeout (slow -> 300ms)
Fixes: 28876/clusterfuzz-testcase-minimized-ffmpeg_dem_MOV_fuzzer-5664824587583488

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2021-01-06 23:24:49 +01:00
parent fc45d924d7
commit a899d6ca10
2 changed files with 13 additions and 3 deletions
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5
libavformat/internal.h
View File

@ -142,6 +142,11 @@ struct AVFormatInternal {
* Prefer the codec framerate for avg_frame_rate computation. * Prefer the codec framerate for avg_frame_rate computation.
*/ */
int prefer_codec_framerate; int prefer_codec_framerate;
/**
* Set if chapter ids are strictly monotonic.
*/
int chapter_ids_monotonic;
}; };
struct AVStreamInternal { struct AVStreamInternal {

11
libavformat/utils.c
View File

@ -4614,9 +4614,14 @@ AVChapter *avpriv_new_chapter(AVFormatContext *s, int id, AVRational time_base,
return NULL; return NULL;
} }
for (i = 0; i < s->nb_chapters; i++) if (!s->nb_chapters) {
if (s->chapters[i]->id == id) s->internal->chapter_ids_monotonic = 1;
chapter = s->chapters[i]; } else if (!s->internal->chapter_ids_monotonic || s->chapters[s->nb_chapters-1]->id >= id) {
s->internal->chapter_ids_monotonic = 0;
for (i = 0; i < s->nb_chapters; i++)
if (s->chapters[i]->id == id)
chapter = s->chapters[i];
}
if (!chapter) { if (!chapter) {
chapter = av_mallocz(sizeof(AVChapter)); chapter = av_mallocz(sizeof(AVChapter));