Add support for track numbering in ID3 TRCK style (NN/MM).

src/components/flac_tag.rs

@@ -125,12 +125,9 @@ impl AudioTagEdit for FlacTag {
     }
 
     fn track_number(&self) -> Option<u16> {
-        if let Some(Ok(n)) = self.get_first("TRACKNUMBER").map(|x| x.parse::<u16>()) {
-            Some(n)
-        } else {
-            None
-        }
+	self.track_number_pair().0
     }
+
     fn set_track_number(&mut self, v: u16) {
         self.set_first("TRACKNUMBER", &v.to_string())
     }
@@ -140,7 +137,8 @@ impl AudioTagEdit for FlacTag {
         if let Some(Ok(n)) = self.get_first("TOTALTRACKS").map(|x| x.parse::<u16>()) {
             Some(n)
         } else {
-            None
+	    // Support "NN/MM" in the style of ID3-style TRCK.
+            self.track_number_pair().1
         }
     }
     fn set_total_tracks(&mut self, v: u16) {
@@ -214,3 +212,18 @@ impl AudioTagWrite for FlacTag {
         Ok(())
     }
 }
+
+impl FlacTag {
+    fn track_number_pair(&self) -> (Option<u16>, Option<u16>) {
+	if let Some(s) = self.get_first("TRACKNUMBER") {
+	    let mut parts = s.split("/").fuse().map(|t| t.parse().ok());
+	    // Manually unpack the first two items instead of using
+	    // collect() so that we can avoid allocating a Vec.
+	    let track = parts.next().flatten();
+	    let total = parts.next().flatten();
+	    (track, total)
+	} else {
+	    (None, None)
+	}
+    }
+}

tests/io.rs

@@ -52,3 +52,14 @@ macro_rules! test_file {
 test_file!(test_mp3, "assets/a.mp3");
 test_file!(test_m4a, "assets/a.m4a");
 test_file!(test_flac, "assets/a.flac");
+
+#[test]
+fn test_id3_style_track_number() {
+    // Verify that we can consume TRACKNUMER tags in the style of the
+    // ID3 TRCK tag.  This is non-standard (for Vorbis comments) but
+    // other tools (such as easytags) will read it (but, AFAIK, not
+    // write it).
+    let tags = Tag::default().read_from_path("assets/meep.flac").unwrap();
+    assert_eq!(tags.track_number(), Some(1));
+    assert_eq!(tags.total_tracks(), Some(6));
+}