[FFmpeg-devel] [PATCH] avformat/utils: add helper functions to retrieve index entries from an AVStream

[James Almer]

Signed-off-by: James Almer <jamrial at gmail.com>
---
Following "lavf: move AVStream.*index_entries* to AVStreamInternal", it was
revealed that some library users apparently found these fields useful and were
accessing them despite not being public.
This patch introduces a few functions to recover this functionality in a proper
and supported way.

We can't simply return a const pointer to the corresponding AVIndexEntry in the
array because it may change at any time by for example calling
av_add_index_entry(), so it's either a copy of the AVIndexEntry, or adding half
a dozen output parameters to the function signature for each field in
AVIndexEntry.

 libavformat/avformat.h | 39 +++++++++++++++++++++++++++++++++++++++
 libavformat/utils.c    | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 765bc3b6f5..ac8b57149e 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -2754,6 +2754,45 @@ int av_find_default_stream_index(AVFormatContext *s);
  */
 int av_index_search_timestamp(AVStream *st, int64_t timestamp, int flags);
 
+/**
+ * Get the index entry count for the given AVStream.
+ *
+ * @param st stream
+ * @return the number of index entries in the stream
+ */
+int av_index_get_entries_count(AVStream *st);
+
+/**
+ * Get the AVIndexEntry corresponding to the given index.
+ *
+ * @param st          stream containing the requested AVIndexEntry
+ * @param index_entry pointer to an AVIndexEntry where to store the entry. On failure,
+ *                    or if the index entry could not be found, this struct will remain
+ *                    untouched
+ * @param idx         the desired index
+ * @return >= 0 on success. AVERROR(ENOENT) if no entry for the requested index could
+           be found. other negative AVERROR codes on failure.
+ */
+int av_index_get_entry(AVStream *st, AVIndexEntry *index_entry, int idx);
+
+/**
+ * Get the AVIndexEntry corresponding to the given timestamp.
+ *
+ * @param st          stream containing the requested AVIndexEntry
+ * @param index_entry pointer to an AVIndexEntry where to store the entry. On failure,
+ *                    or if the index entry could not be found, this struct will remain
+ *                    untouched
+ * @param timestamp   timestamp to retrieve the index entry for
+ * @param flags       if AVSEEK_FLAG_BACKWARD then the returned entry will correspond
+ *                    to the timestamp which is <= the requested one, if backward
+ *                    is 0, then it will be >=
+ *                    if AVSEEK_FLAG_ANY seek to any frame, only keyframes otherwise
+ * @return >= 0 on success. AVERROR(ENOENT) if no entry for the requested timestamp could
+ *          be found. other negative AVERROR codes on failure.
+ */
+int av_index_get_entry_from_timestamp(AVStream *st, AVIndexEntry *index_entry,
+                                      int64_t wanted_timestamp, int flags);
+
 /**
  * Add an index entry into a sorted list. Update the entry if the list
  * already contains it.
diff --git a/libavformat/utils.c b/libavformat/utils.c
index f31826f2ea..4e7a8bf23e 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2129,6 +2129,38 @@ int av_index_search_timestamp(AVStream *st, int64_t wanted_timestamp, int flags)
                                      wanted_timestamp, flags);
 }
 
+int av_index_get_entries_count(AVStream *st)
+{
+    return st->internal->nb_index_entries;
+}
+
+int av_index_get_entry(AVStream *st, AVIndexEntry *index_entry, int idx)
+{
+    if (idx < 0)
+        return AVERROR(EINVAL);
+    if (idx >= st->internal->nb_index_entries)
+        return AVERROR(ENOENT);
+
+    memcpy(index_entry, &st->internal->index_entries[idx], sizeof(*index_entry));
+
+    return 0;
+}
+
+int av_index_get_entry_from_timestamp(AVStream *st, AVIndexEntry *index_entry,
+                                      int64_t wanted_timestamp, int flags)
+{
+    int idx = ff_index_search_timestamp(st->internal->index_entries,
+                                        st->internal->nb_index_entries,
+                                        wanted_timestamp, flags);
+
+    if (idx < 0)
+        return AVERROR(ENOENT);
+
+    memcpy(index_entry, &st->internal->index_entries[idx], sizeof(*index_entry));
+
+    return 0;
+}
+
 static int64_t ff_read_timestamp(AVFormatContext *s, int stream_index, int64_t *ppos, int64_t pos_limit,
                                  int64_t (*read_timestamp)(struct AVFormatContext *, int , int64_t *, int64_t ))
 {
-- 
2.31.0