Support multiple fields with the same name

README.md

@@ -73,6 +73,10 @@ List of possible attributes you can get with TinyTag:
     tag.track_total   # total number of tracks as string
     tag.year          # year or date as string
 
+If multiple fields with the same name are provided, the values are separated with a null character:
+
+    tag.artist == 'artist 1\x00artist 2\x00artist 3'
+
 For non-common fields and fields specific to certain file formats, use `extra`:
 
     tag.extra         # a dict of additional data

tinytag/tests/test_all.py

@@ -130,7 +130,8 @@
     ('samples/id3v1_does_not_overwrite_id3v2.mp3',
         {'filesize': 1130, 'album': 'Somewhere Far Beyond', 'albumartist': 'Blind Guardian',
          'artist': 'Blind Guardian', 'extra': {'love rating': 'L'},
-         'genre': 'Power Metal', 'title': 'Time What Is Time', 'track': 1, 'year': '1992'}),
+         'genre': 'Power Metal\x00Other', 'title': 'Time What Is Time', 'track': 1,
+         'year': '1992'}),
     ('samples/nicotinetestdata.mp3',
         {'extra': {}, 'filesize': 80919, 'channels': 2,
          'duration': 5.067755102040817, 'samplerate': 44100, 'bitrate': 127.6701030927835}),
@@ -291,7 +292,8 @@
     ('samples/id3_header_with_a_zero_byte.wav',
         {'extra': {}, 'channels': 1, 'duration': 1.0, 'filesize': 44280, 'bitrate': 352.8,
          'samplerate': 22050, 'bitdepth': 16, 'artist': 'Purpley',
-         'title': 'Test000', 'track': 17, 'album': 'prototypes'}),
+         'title': 'Test000\x00Stacked\x00Test000\x00Stacked', 'track': 17,
+         'album': 'prototypes'}),
     ('samples/adpcm.wav',
         {'extra': {}, 'channels': 1, 'duration': 12.167256235827665, 'filesize': 268686,
          'bitrate': 176.4, 'samplerate': 44100, 'bitdepth': 4,
@@ -362,9 +364,9 @@
         {'extra': {}, 'filesize': 4692, 'bitrate': 10.186943678613627, 'channels': 2,
          'duration': 3.68, 'samplerate': 44100, 'bitdepth': 16}),
     ('samples/with_id3_header.flac',
-        {'extra': {'id': '8591671910'}, 'filesize': 64837, 'album': '   ',
-         'artist': '群星',
-         'title': 'A 梦 哆啦 机器猫 短信铃声', 'track': 1, 'bitrate': 1143.72468, 'channels': 1,
+        {'extra': {'id': '8591671910'}, 'filesize': 64837, 'album': '   \x00album',
+         'artist': '群星\x00artist',
+         'title': 'A 梦 哆啦 机器猫 短信铃声\x00title', 'track': 1, 'bitrate': 1143.72468, 'channels': 1,
          'duration': 0.45351473922902497, 'genre': 'genre', 'samplerate': 44100, 'bitdepth': 16,
          'year': '2018', 'comment': 'comment'}),
     ('samples/with_padded_id3_header.flac',
@@ -373,11 +375,11 @@
          'duration': 0.45351473922902497, 'genre': 'genre', 'samplerate': 44100, 'bitdepth': 16,
          'title': 'title', 'track': 1, 'year': '2018', 'comment': 'comment'}),
     ('samples/with_padded_id3_header2.flac',
-        {'extra': {}, 'filesize': 19522, 'album': 'Unbekannter Titel',
-         'artist': 'Unbekannter Künstler', 'bitrate': 344.36807999999996,
+        {'extra': {}, 'filesize': 19522, 'album': 'Unbekannter Titel\x00album',
+         'artist': 'Unbekannter Künstler\x00artist', 'bitrate': 344.36807999999996,
          'channels': 1, 'disc': 1, 'disc_total': 1,
          'duration': 0.45351473922902497, 'genre': 'genre', 'samplerate': 44100, 'bitdepth': 16,
-         'title': 'Track01', 'track': 1, 'track_total': 5, 'year': '2018',
+         'title': 'Track01\x00title', 'track': 1, 'track_total': 5, 'year': '2018',
          'comment': 'comment'}),
     ('samples/flac_with_image.flac',
         {'extra': {}, 'filesize': 80000, 'album': 'smilin´ in circles',
@@ -388,6 +390,11 @@
     ('samples/flac_invalid_track_number.flac',
         {'extra': {}, 'filesize': 235, 'bitrate': 18.8, 'channels': 1,
          'duration': 0.1, 'samplerate': 44100, 'bitdepth': 16}),
+    ('samples/flac_multiple_fields.flac',
+        {'extra': {}, 'filesize': 235, 'album': 'album 1\x00album 2',
+         'artist': 'artist 1\x00artist 2\x00artist 3',
+         'bitrate': 18.8, 'channels': 1, 'duration': 0.1, 'genre': 'genre 1\x00genre 2',
+         'samplerate': 44100, 'bitdepth': 16}),
 
     # WMA
     ('samples/test2.wma',

tinytag/tinytag.py

@@ -229,46 +229,50 @@ def load(self, tags, duration, image=False):
                 self._filehandler.seek(0)
             self._determine_duration(self._filehandler)
 
-    def _set_field(self, fieldname, value, overwrite=True):
+    def _set_field(self, fieldname, value):
         """convenience function to set fields of the tinytag by name"""
         write_dest = self  # write into the TinyTag by default
         get_func = getattr
         set_func = setattr
         is_extra = fieldname.startswith('extra.')  # but if it's marked as extra field
+        is_str = isinstance(value, str)
         if is_extra:
             fieldname = fieldname[6:]
             write_dest = self.extra  # write into the extra field instead
             get_func = operator.getitem
             set_func = operator.setitem
-        if isinstance(value, str) and not value:
+        if is_str and not value:
             # don't set empty value
             return
-        if get_func(write_dest, fieldname):  # do not overwrite existing data
+        old_value = get_func(write_dest, fieldname)
+        if old_value and fieldname == "comment":
+            # Don't combine comment fields for now
             return
+        if is_str and old_value and old_value != value:
+            # Combine same field with a null character
+            value = old_value + '\x00' + value
         if DEBUG:
             stderr(f'Setting field "{fieldname}" to "{value}"')
-        if overwrite or not get_func(write_dest, fieldname):
-            set_func(write_dest, fieldname, value)
+        set_func(write_dest, fieldname, value)
 
     def _determine_duration(self, fh):
         raise NotImplementedError()
 
     def _parse_tag(self, fh):
         raise NotImplementedError()
 
-    def update(self, other, all_fields=False):
+    def update(self, other):
         # update the values of this tag with the values from another tag
-        if all_fields:
-            self.__dict__.update(other.__dict__)
-            return
         for key in ['track', 'track_total', 'title', 'artist',
                     'album', 'albumartist', 'year', 'duration',
                     'genre', 'disc', 'disc_total', 'comment', 'composer',
-                    'extra', '_image_data']:
-            if not getattr(self, key) and getattr(other, key):
-                setattr(self, key, getattr(other, key))
-        if other.extra:
-            self.extra.update(other.extra)
+                    'bitdepth', 'bitrate', 'channels', 'samplerate',
+                    '_image_data']:
+            new_value = getattr(other, key)
+            if new_value:
+                self._set_field(key, new_value)
+        for key, value in other.extra.items():
+            self._set_field("extra." + key, value)
 
     @staticmethod
     def _unpad(s):
@@ -779,18 +783,18 @@ def _parse_id3v1(self, fh):
             def asciidecode(x):
                 return self._unpad(x.decode(self._default_encoding or 'latin1'))
             fields = fh.read(30 + 30 + 30 + 4 + 30 + 1)
-            self._set_field('title', asciidecode(fields[:30]), overwrite=False)
-            self._set_field('artist', asciidecode(fields[30:60]), overwrite=False)
-            self._set_field('album', asciidecode(fields[60:90]), overwrite=False)
-            self._set_field('year', asciidecode(fields[90:94]), overwrite=False)
+            self._set_field('title', asciidecode(fields[:30]))
+            self._set_field('artist', asciidecode(fields[30:60]))
+            self._set_field('album', asciidecode(fields[60:90]))
+            self._set_field('year', asciidecode(fields[90:94]))
             comment = fields[94:124]
             if b'\x00\x00' < comment[-2:] < b'\x01\x00':
-                self._set_field('track', ord(comment[-1:]), overwrite=False)
+                self._set_field('track', ord(comment[-1:]))
                 comment = comment[:-2]
-            self._set_field('comment', asciidecode(comment), overwrite=False)
+            self._set_field('comment', asciidecode(comment))
             genre_id = ord(fields[124:125])
             if genre_id < len(self.ID3V1_GENRES):
-                self._set_field('genre', self.ID3V1_GENRES[genre_id], overwrite=False)
+                self._set_field('genre', self.ID3V1_GENRES[genre_id])
 
     @staticmethod
     def index_utf16(s, search):
@@ -975,7 +979,7 @@ def _parse_tag(self, fh):
                 flactag = _Flac(io.BufferedReader(walker), self.filesize)
                 flactag.load(tags=self._parse_tags, duration=self._parse_duration,
                              image=self._load_image)
-                self.update(flactag, all_fields=True)
+                self.update(flactag)
                 check_flac_second_packet = True
             elif check_flac_second_packet:
                 # second packet contains FLAC metadata block