+namespace {
+
+struct AttachmentCompare
+{
+ unsigned entry;
+
+ AttachmentCompare(unsigned e): entry(e) { }
+
+ bool operator()(const R2C2::TrackAttachment *a1, const R2C2::TrackAttachment *a2) const
+ { return a1->get_offset_from_endpoint(entry)<a2->get_offset_from_endpoint(entry); }
+};
+
+}
+