lib/xiph/OggFind: add parameter "synced"

src/lib/xiph/OggFind.cxx

@@ -57,13 +57,14 @@ OggSeekPageAtOffset(OggSyncState &oy, ogg_stream_state &os, InputStream &is,
 
 bool
 OggSeekFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet,
-	       InputStream &is)
+	       InputStream &is, bool synced)
 {
 	if (!is.KnownSize())
 		return false;
 
 	if (is.GetRest() < 65536)
-		return OggFindEOS(oy, os, packet);
+		return (synced || oy.ExpectPageSeekIn(os)) &&
+			OggFindEOS(oy, os, packet);
 
 	if (!is.CheapSeeking())
 		return false;

src/lib/xiph/OggFind.hxx

@@ -47,10 +47,13 @@ OggSeekPageAtOffset(OggSyncState &oy, ogg_stream_state &os, InputStream &is,
  * Try to find the end-of-stream (EOS) packet.  Seek to the end of the
  * file if necessary.
  *
+ * @param synced is the #OggSyncState currently synced?  If not, then
+ * we need to use ogg_sync_pageseek() instead of ogg_sync_pageout(),
+ * which is more expensive
  * @return true if the EOS packet was found
  */
 bool
 OggSeekFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet,
-	       InputStream &is);
+	       InputStream &is, bool synced=true);
 
 #endif