symuid.Track._get_mp4_freeform_int()

symuid/__init__.py

@@ -27,6 +27,12 @@ class Track:
     def has_mp4_tags(self):
         return self.has_tags and isinstance(self._mutagen.tags, mutagen.mp4.MP4Tags)
 
+    def _get_mp4_freeform_int(self, tag_label):
+        tag, = self._mutagen.tags['----:' + tag_label]
+        # "a signed big-endian integer with length one of { 1,2,3,4,8 } bytes"
+        assert tag.dataformat == mutagen.mp4.AtomDataType.INTEGER, tag.dataformat
+        return int.from_bytes(tag, byteorder='big', signed=True)
+
     def _set_mp4_freeform_int(self, tag_label, data):
         assert isinstance(data, int)
         tag = mutagen.mp4.MP4FreeForm(
@@ -63,17 +69,10 @@ class Track:
                 if tag_set_cb:
                     tag_set_cb(self, tag)
         elif self.has_mp4_tags:
-            tag_label_mp4 = '----:' + tag_label
-            if tag_label_mp4 in self._mutagen.tags:
-                reg_data = self._mutagen.tags[tag_label_mp4]
-                assert len(reg_data) == 1, reg_data
-                reg_count = int.from_bytes(
-                    bytes=reg_data[0],
-                    byteorder='big',
-                    signed=True,
-                )
+            try:
+                reg_count = self._get_mp4_freeform_int(tag_label)
                 assert reg_count == play_count, (reg_count, play_count)
-            else:
+            except KeyError:
                 tag = self._set_mp4_freeform_int(
                     tag_label=tag_label,
                     data=play_count,