def __read_extended_header(self, file):
size = Syncsafe.decode(fileutil.xread(file, 4))
if size < 6:
warn("Unexpected size of ID3v2.4 extended header: {0}".format(size),
TagWarning)
data = fileutil.xread(file, size - 4)
numflags = data[0]
if numflags != 1:
warn("Unexpected number of ID3v2.4 extended flag bytes: {0}"
.format(numflags),
TagWarning)
flags = data[1]
data = data[1 + numflags:]
if flags & 0x40:
self.flags.add("ext:update")
(dummy, data) = self.__read_extended_header_flag_data(data)
if flags & 0x20:
self.flags.add("ext:crc_present")
(self.crc32, data) = self.__read_extended_header_flag_data(data)
self.crc32 = Syncsafe.decode(self.crc32)
if flags & 0x10:
self.flags.add("ext:restrictions")
(self.restrictions, data) = self.__read_extended_header_flag_data(
data)
def __read_extended_header(self, file):
(size, ext_flags, self.padding_size) = \
struct.unpack("!IHI", fileutil.xread(file, 10))
if size != 6 and size != 10:
warn("Unexpected size of ID3v2.3 extended header: {0}".format(size),
TagWarning)
if ext_flags & 128:
self.flags.add("ext:crc_present")
self.crc32 = struct.unpack("!I", fileutil.xread(file, 4))
def _read_frames(self, file):
if "unsynchronised" in self.flags:
ufile = UnsyncReader(file)
else:
ufile = file
while file.tell() < self.offset + self.size:
header = fileutil.xread(ufile, 6)
if not self._is_frame_id(header[0:3]):
break
frameid = header[0:3].decode("ASCII")
size = Int8.decode(header[3:6])
data = fileutil.xread(ufile, size)
yield (frameid, None, data)
def __read_extended_header(self, file):
(size, ext_flags, self.padding_size) = \
struct.unpack("!IHI", fileutil.xread(file, 10))
if size != 6 and size != 10:
warn("Unexpected size of ID3v2.3 extended header: {0}".format(size),
TagWarning)
if ext_flags & 32768:
if size < 10:
warn("Extended header is too short for a CRC field: {0} bytes instead of 10".format(size),
TagWarning)
else:
self.flags.add("ext:crc_present")
(self.crc32,) = struct.unpack("!I", fileutil.xread(file, 4))
size -= 6
if size > 6:
fileutil.xread(file, size - 6)
def _read_frames(self, file):
while file.tell() < self.offset + self.size:
header = fileutil.xread(file, 10)
if not self._is_frame_id(header[0:4]):
break
frameid = header[0:4].decode("ASCII")
if self.ITUNES_WORKAROUND:
# Work around iTunes frame size encoding bug.
# Older versions of iTunes stored frame sizes as
# straight 8bit integers, not syncsafe.
# (This is known to be fixed in iTunes 8.2.)
size = Int8.decode(header[4:8])
else:
size = Syncsafe.decode(header[4:8])
bflags = Int8.decode(header[8:10])
data = fileutil.xread(file, size)
yield (frameid, bflags, data)
def _read_frames(self, file, syncsafe_workaround=None):
# Older versions of iTunes stored frame sizes as straight 8bit integers,
# not syncsafe values as the spec requires.
# (The bug is known to be fixed in iTunes 8.2.)
#
# To work around such an erroneous encoding, we re-read the entire tag
# in non-syncsafe mode when we detect a frame with a bad size.
# This heuristic does not detect all badly encoded tags;
# it fails when the 8-bit frame size happens to be in syncsafe format.
#
# We could improve detection by parsing the tag both ways and see which
# interpretation produces more frames. However, the extra effort doesn't
# seem worthwhile to do by default.
#
# If you have many files with iTunes-encoded tags, you can force stagger
# to read them in non-syncsafe mode setting the ITUNES_WORKAROUND
# class attribute to True and let stagger reencode your tags. (Stagger
# will never produce a 2.4 tag with non-syncsafe frame lengths.)
if syncsafe_workaround is None:
syncsafe_workaround = self.ITUNES_WORKAROUND
origfpos = file.tell()
frames = []
while file.tell() < self.offset + self.size:
header = fileutil.xread(file, 10)
if not self._is_frame_id(header[0:4]):
break
frameid = header[0:4].decode("ASCII")
if syncsafe_workaround:
size = Int8.decode(header[4:8])
else:
try:
size = Syncsafe.decode(header[4:8])
except ValueError:
if syncsafe_workaround:
raise
warn(
"Invalid syncsafe frame size; switching to 8-bit mode")
file.seek(origfpos)
return self._read_frames(file, True)
bflags = Int8.decode(header[8:10])
data = fileutil.xread(file, size)
frames.append((frameid, bflags, data))
return frames
def _read_header(self, file):
self.offset = file.tell()
header = fileutil.xread(file, 10)
if header[0:5] != b"ID3\x02\00":
raise NoTagError("ID3v2.2 header not found")
if header[5] & 0x80:
self.flags.add("unsynchronised")
if header[5] & 0x40: # Compression bit is ill-defined in standard
raise TagError("ID3v2.2 tag compression is not supported")
if header[5] & 0x3F:
warn("Unknown ID3v2.2 flags", TagWarning)
self.size = Syncsafe.decode(header[6:10]) + 10
def _read_header(self, file):
self.offset = file.tell()
header = fileutil.xread(file, 10)
if header[0:5] != b"ID3\x03\x00":
raise NoTagError("ID3v2.3 header not found")
if header[5] & 0x80:
self.flags.add("unsynchronised")
if header[5] & 0x40:
self.flags.add("extended_header")
if header[5] & 0x20:
self.flags.add("experimental")
if header[5] & 0x1F:
warn("Unknown ID3v2.3 flags", TagWarning)
self.size = Syncsafe.decode(header[6:10]) + 10
if "extended_header" in self.flags:
self.__read_extended_header(file)
def _read_header(self, file):
self.offset = file.tell()
header = fileutil.xread(file, 10)
if header[0:5] != b"ID3\x04\x00":
raise NoTagError("ID3v2 header not found")
if header[5] & _TAG24_UNSYNCHRONISED:
self.flags.add("unsynchronised")
if header[5] & _TAG24_EXTENDED_HEADER:
self.flags.add("extended_header")
if header[5] & _TAG24_EXPERIMENTAL:
self.flags.add("experimental")
if header[5] & _TAG24_FOOTER:
self.flags.add("footer")
if header[5] & _TAG24_UNKNOWN_MASK:
warn("Unknown ID3v2.4 flags", TagWarning)
self.size = (Syncsafe.decode(header[6:10]) + 10
+ (10 if "footer" in self.flags else 0))
if "extended_header" in self.flags:
self.__read_extended_header(file)
