flvdemux: Do not build an index if upstream is not seekable

An index is not useful if upstream cannot handle seeks and building it
for infinite files, for instance FLV streams, results in a memory leak.

gst/flv/gstflvdemux.c

@@ -103,6 +103,10 @@ gst_flv_demux_parse_and_add_index_entry (GstFlvDemux * demux, GstClockTime ts,
       "adding key=%d association %" GST_TIME_FORMAT "-> %" G_GUINT64_FORMAT,
       keyframe, GST_TIME_ARGS (ts), pos);
 
+  /* if upstream is not seekable there is no point in building an index */
+  if (!demux->upstream_seekable)
+    return;
+
   /* entry may already have been added before, avoid adding indefinitely */
   entry = gst_index_get_assoc_entry (demux->index, demux->index_id,
       GST_INDEX_LOOKUP_EXACT, GST_ASSOCIATION_FLAG_NONE, GST_FORMAT_BYTES, pos);
@@ -186,6 +190,41 @@ gst_flv_demux_query_types (GstPad * pad)
   return query_types;
 }
 
+static void
+gst_flv_demux_check_seekability (GstFlvDemux * demux)
+{
+  GstQuery *query;
+  gint64 start = -1, stop = -1;
+
+  demux->upstream_seekable = FALSE;
+
+  query = gst_query_new_seeking (GST_FORMAT_BYTES);
+  if (!gst_pad_peer_query (demux->sinkpad, query)) {
+    GST_DEBUG_OBJECT (demux, "seeking query failed");
+    return;
+  }
+
+  gst_query_parse_seeking (query, NULL, &demux->upstream_seekable,
+      &start, &stop);
+
+  /* try harder to query upstream size if we didn't get it the first time */
+  if (demux->upstream_seekable && stop == -1) {
+    GstFormat fmt = GST_FORMAT_BYTES;
+
+    GST_DEBUG_OBJECT (demux, "doing duration query to fix up unset stop");
+    gst_pad_query_peer_duration (demux->sinkpad, &fmt, &stop);
+  }
+
+  /* if upstream doesn't know the size, it's likely that it's not seekable in
+   * practice even if it technically may be seekable */
+  if (demux->upstream_seekable && (start != 0 || stop <= start)) {
+    GST_DEBUG_OBJECT (demux, "seekable but unknown start/stop -> disable");
+    demux->upstream_seekable = FALSE;
+  }
+
+  GST_DEBUG_OBJECT (demux, "upstream seekable: %d", demux->upstream_seekable);
+}
+
 static void
 parse_flv_demux_parse_date_string (GDate * date, const gchar * s)
 {
@@ -1491,6 +1530,9 @@ gst_flv_demux_parse_header (GstFlvDemux * demux, GstBuffer * buffer)
     }
   }
 
+  /* do a one-time seekability check */
+  gst_flv_demux_check_seekability (demux);
+
   /* We don't care about the rest */
   demux->need_header = FALSE;
 
@@ -1544,6 +1586,7 @@ gst_flv_demux_cleanup (GstFlvDemux * demux)
   demux->got_par = FALSE;
 
   demux->indexed = FALSE;
+  demux->upstream_seekable = FALSE;
   demux->file_size = 0;
 
   demux->index_max_pos = 0;

gst/flv/gstflvdemux.h

@@ -123,6 +123,7 @@ struct _GstFlvDemux
   gboolean seeking;
   gboolean building_index;
   gboolean indexed; /* TRUE if index is completely built */
+  gboolean upstream_seekable; /* TRUE if upstream is seekable */
   gint64 file_size;
   GstEvent *seek_event;
   gint64 seek_time;