add and use Source::empty() since it can be done more efficiently than length(pos) == 0

git-svn-id: svn://localhost/ardour2/branches/3.0@7300 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 12 insertions, 2 deletions

diff --git a/libs/ardour/midi_source.cc b/libs/ardour/midi_source.cc
index 54b287cbdf..94c1a9b811 100644
--- a/libs/ardour/midi_source.cc
+++ b/libs/ardour/midi_source.cc
@@ -112,9 +112,19 @@ MidiSource::set_state (const XMLNode& node, int /*version*/)
 	return 0;
 }
 
-sframes_t
-MidiSource::length (sframes_t pos) const
+bool
+MidiSource::empty () const
 {
+        return _length_beats == 0;
+}
+
+framecnt_t
+MidiSource::length (framepos_t pos) const
+{
+        if (_length_beats == 0) {
+                return 0;
+        }
+
 	BeatsFramesConverter converter(_session.tempo_map(), pos);
 	return converter.to(_length_beats);
 }