add smf_length_is_explicit() to libsmf

libs/evoral/libsmf/smf.c

@@ -1023,6 +1023,45 @@ smf_get_length_pulses(const smf_t *smf)
 	return (pulses);
 }
 
+/**
+ * \return nonzero if the last event in the file has a non-zero delta time,
+ * and zero otherwise. A non-zero delta time is taken to indicate that the
+ * file creator explicitly set the length, although it is possible that
+ * this was done even with a zero delta time (if the last "real" event happened
+ * to be at the right time.
+ */
+int
+smf_length_is_explicit (const smf_t *smf)
+{
+	int i;
+	size_t pulses = 0;
+	smf_event_t* last_event = NULL;
+
+	for (i = 1; i <= smf->number_of_tracks; i++) {
+		smf_track_t *track;
+		smf_event_t *event;
+
+		track = smf_get_track_by_number(smf, i);
+		assert(track);
+
+		event = smf_track_get_last_event(track);
+		/* Empty track? */
+		if (event == NULL)
+			continue;
+
+		if (event->time_pulses > pulses) {
+			pulses = event->time_pulses;
+			last_event = event;
+		}
+	}
+
+	if (last_event) {
+		return last_event->delta_time_pulses != 0;
+	}
+
+	return 0;
+}
+
 /**
   * \return Nonzero, if there are no events in the SMF after this one.
   * Note that may be more than one "last event", if they occur at the same time.

libs/evoral/libsmf/smf.h

@@ -346,6 +346,7 @@ int  smf_seek_to_event(smf_t *smf, const smf_event_t *event) WARN_UNUSED_RESULT;
 
 size_t smf_get_length_pulses(const smf_t *smf) WARN_UNUSED_RESULT;
 int    smf_event_is_last(const smf_event_t *event) WARN_UNUSED_RESULT;
+int    smf_length_is_explicit(const smf_t *event) WARN_UNUSED_RESULT;
 
 void smf_add_track(smf_t *smf, smf_track_t *track);
 void smf_track_remove_from_smf(smf_track_t *track);