def test_bits(self):
        data = b"\x12\x34\x56\x78\x89\xAB\xCD\xEF"
        ref = cdata.uint64_be(data)

        for i in xrange(64):
            fo = cBytesIO(data)
            r = BitReader(fo)
            v = r.bits(i) << (64 - i) | r.bits(64 - i)
            self.assertEqual(v, ref)

    def __init__(self, fileobj, length):
        """Raises DescriptorError"""

        r = BitReader(fileobj)

        try:
            self.objectTypeIndication = r.bits(8)
            self.streamType = r.bits(6)
            self.upStream = r.bits(1)
            self.reserved = r.bits(1)
            self.bufferSizeDB = r.bits(24)
            self.maxBitrate = r.bits(32)
            self.avgBitrate = r.bits(32)

            if (self.objectTypeIndication, self.streamType) != (0x40, 0x5):
                return

            # all from here is optional
            if length * 8 == r.get_position():
                return

            tag = r.bits(8)
        except BitReaderError as e:
            raise DescriptorError(e)

        if tag == DecoderSpecificInfo.TAG:
            assert r.is_aligned()
            self.decSpecificInfo = DecoderSpecificInfo.parse(fileobj)

    def find_stream(cls, fileobj, max_bytes):
        """Returns a possibly valid _ADTSStream or None.

        Args:
            max_bytes (int): maximum bytes to read
        """

        r = BitReader(fileobj)
        stream = cls(r)
        if stream.sync(max_bytes):
            stream.offset = (r.get_position() - 12) // 8
            return stream

    def _parse_dac3(self, atom, fileobj):
        # ETSI TS 102 366

        assert atom.name == b"dac3"

        ok, data = atom.read(fileobj)
        if not ok:
            raise ASEntryError("truncated %s atom" % atom.name)
        fileobj = cBytesIO(data)
        r = BitReader(fileobj)

        # sample_rate in AudioSampleEntry covers values in
        # fscod2 and not just fscod, so ignore fscod here.
        try:
            r.skip(2 + 5 + 3)  # fscod, bsid, bsmod
            acmod = r.bits(3)
            lfeon = r.bits(1)
            bit_rate_code = r.bits(5)
            r.skip(5)  # reserved
        except BitReaderError as e:
            raise ASEntryError(e)

        self.channels = [2, 1, 2, 3, 3, 4, 4, 5][acmod] + lfeon

        try:
            self.bitrate = [
                32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192,
                224, 256, 320, 384, 448, 512, 576, 640][bit_rate_code] * 1000
        except IndexError:
            pass

    def _parse_esds(self, esds, fileobj):
        assert esds.name == b"esds"

        ok, data = esds.read(fileobj)
        if not ok:
            raise ASEntryError("truncated %s atom" % esds.name)

        try:
            version, flags, data = parse_full_atom(data)
        except ValueError as e:
            raise ASEntryError(e)

        if version != 0:
            raise ASEntryError("Unsupported version %d" % version)

        fileobj = cBytesIO(data)
        r = BitReader(fileobj)

        try:
            tag = r.bits(8)
            if tag != ES_Descriptor.TAG:
                raise ASEntryError("unexpected descriptor: %d" % tag)
            assert r.is_aligned()
        except BitReaderError as e:
            raise ASEntryError(e)

        try:
            decSpecificInfo = ES_Descriptor.parse(fileobj)
        except DescriptorError as e:
            raise ASEntryError(e)
        dec_conf_desc = decSpecificInfo.decConfigDescr

        self.bitrate = dec_conf_desc.avgBitrate
        self.codec += dec_conf_desc.codec_param
        self.codec_description = dec_conf_desc.codec_desc

        decSpecificInfo = dec_conf_desc.decSpecificInfo
        if decSpecificInfo is not None:
            if decSpecificInfo.channels != 0:
                self.channels = decSpecificInfo.channels

            if decSpecificInfo.sample_rate != 0:
                self.sample_rate = decSpecificInfo.sample_rate

 def test_skip_too_much(self):
     r = BitReader(cBytesIO(b"\xAB\xCD"))
     # aligned skips don't fail, but the following read will
     r.skip(32 + 8)
     self.assertRaises(BitReaderError, r.bits, 1)
     self.assertRaises(BitReaderError, r.skip, 1)

 def test_skip_more(self):
     r = BitReader(cBytesIO(b"\xAB\xCD"))
     self.assertEqual(r.bits(4), 0xa)
     r.skip(8)
     self.assertEqual(r.bits(4), 0xd)
     self.assertRaises(BitReaderError, r.bits, 1)

 def test_skip(self):
     r = BitReader(cBytesIO(b"\xEF"))
     r.skip(4)
     self.assertEqual(r.bits(4), 0xf)

 def test_read_too_much(self):
     r = BitReader(cBytesIO(b""))
     self.assertEqual(r.bits(0), 0)
     self.assertRaises(BitReaderError, r.bits, 1)

    def test_is_aligned(self):
        r = BitReader(cBytesIO(b"\xAB\xCD\xEF"))
        self.assertTrue(r.is_aligned())

        r.skip(1)
        self.assertFalse(r.is_aligned())
        r.skip(7)
        self.assertTrue(r.is_aligned())

        r.bits(7)
        self.assertFalse(r.is_aligned())
        r.bits(1)
        self.assertTrue(r.is_aligned())

 def test_get_position(self):
     r = BitReader(cBytesIO(b"\xAB\xCD"))
     self.assertEqual(r.get_position(), 0)
     r.bits(3)
     self.assertEqual(r.get_position(), 3)
     r.skip(9)
     self.assertEqual(r.get_position(), 3 + 9)
     r.align()
     self.assertEqual(r.get_position(), 16)

    def _parse_alac(self, atom, fileobj):
        # https://alac.macosforge.org/trac/browser/trunk/
        #    ALACMagicCookieDescription.txt

        assert atom.name == b"alac"

        ok, data = atom.read(fileobj)
        if not ok:
            raise ASEntryError("truncated %s atom" % atom.name)

        try:
            version, flags, data = parse_full_atom(data)
        except ValueError as e:
            raise ASEntryError(e)

        if version != 0:
            raise ASEntryError("Unsupported version %d" % version)

        fileobj = cBytesIO(data)
        r = BitReader(fileobj)

        try:
            # for some files the AudioSampleEntry values default to 44100/2chan
            # and the real info is in the alac cookie, so prefer it
            r.skip(32)  # frameLength
            compatibleVersion = r.bits(8)
            if compatibleVersion != 0:
                return
            self.sample_size = r.bits(8)
            r.skip(8 + 8 + 8)
            self.channels = r.bits(8)
            r.skip(16 + 32)
            self.bitrate = r.bits(32)
            self.sample_rate = r.bits(32)
        except BitReaderError as e:
            raise ASEntryError(e)

    def _parse_adif(self, fileobj):
        r = BitReader(fileobj)
        try:
            copyright_id_present = r.bits(1)
            if copyright_id_present:
                r.skip(72)  # copyright_id
            r.skip(1 + 1)  # original_copy, home
            bitstream_type = r.bits(1)
            self.bitrate = r.bits(23)
            npce = r.bits(4)
            if bitstream_type == 0:
                r.skip(20)  # adif_buffer_fullness

            pce = ProgramConfigElement(r)
            try:
                self.sample_rate = _FREQS[pce.sampling_frequency_index]
            except IndexError:
                pass
            self.channels = pce.channels

            # other pces..
            for i in xrange(npce):
                ProgramConfigElement(r)
            r.align()
        except BitReaderError as e:
            raise AACError(e)

        # use bitrate + data size to guess length
        start = fileobj.tell()
        fileobj.seek(0, 2)
        length = fileobj.tell() - start
        if self.bitrate != 0:
            self.length = (8.0 * length) / self.bitrate

 def test_bytes(self):
     r = BitReader(cBytesIO(b"\xAB\xCD\xEF"))
     self.assertEqual(r.bytes(2), b"\xAB\xCD")
     self.assertEqual(r.bytes(0), b"")

 def test_bytes_unaligned(self):
     r = BitReader(cBytesIO(b"\xAB\xCD\xEF"))
     r.skip(4)
     self.assertEqual(r.bytes(2), b"\xBC\xDE")

 def test_align(self):
     r = BitReader(cBytesIO(b"\xAB\xCD\xEF"))
     r.skip(3)
     self.assertEqual(r.align(), 5)
     self.assertEqual(r.get_position(), 8)

    def __init__(self, fileobj):
        """Raises HeaderNotFoundError"""

        self.frame_offset = fileobj.tell()

        r = BitReader(fileobj)
        try:
            if r.bits(11) != 0x7ff:
                raise HeaderNotFoundError("invalid sync")
            version = r.bits(2)
            layer = r.bits(2)
            protection = r.bits(1)
            bitrate = r.bits(4)
            sample_rate = r.bits(2)
            padding = r.bits(1)
            r.skip(1)  # private
            self.mode = r.bits(2)
            r.skip(6)
        except BitReaderError:
            raise HeaderNotFoundError("truncated header")

        assert r.get_position() == 32 and r.is_aligned()

        # try to be strict here to redice the chance of a false positive
        if version == 1 or layer == 0 or sample_rate == 0x3 or \
                bitrate == 0xf or bitrate == 0:
            raise HeaderNotFoundError("invalid header")

        self.channels = 1 if self.mode == MONO else 2

        self.version = [2.5, None, 2, 1][version]
        self.layer = 4 - layer
        self.protected = not protection
        self.padding = bool(padding)

        self.bitrate = self.__BITRATE[(self.version, self.layer)][bitrate]
        self.bitrate *= 1000
        self.sample_rate = self.__RATES[self.version][sample_rate]

        if self.layer == 1:
            frame_size = 384
            slot = 4
        elif self.version >= 2 and self.layer == 3:
            frame_size = 576
            slot = 1
        else:
            frame_size = 1152
            slot = 1

        frame_length = (
            ((frame_size // 8 * self.bitrate) // self.sample_rate) +
            padding) * slot

        self.sketchy = True

        # Try to find/parse the Xing header, which trumps the above length
        # and bitrate calculation.
        if self.layer == 3:
            self._parse_vbr_header(fileobj, self.frame_offset, frame_size,
                                   frame_length)

        fileobj.seek(self.frame_offset + frame_length, 0)

    def __init__(self, xing, fileobj):
        """Raises LAMEError if parsing fails"""

        payload = fileobj.read(27)
        if len(payload) != 27:
            raise LAMEError("Not enough data")

        # extended lame header
        r = BitReader(cBytesIO(payload))
        revision = r.bits(4)
        if revision != 0:
            raise LAMEError("unsupported header revision %d" % revision)

        self.vbr_method = r.bits(4)
        self.lowpass_filter = r.bits(8) * 100

        # these have a different meaning for lame; expose them again here
        self.quality = (100 - xing.vbr_scale) % 10
        self.vbr_quality = (100 - xing.vbr_scale) // 10

        track_peak_data = r.bytes(4)
        if track_peak_data == b"\x00\x00\x00\x00":
            self.track_peak = None
        else:
            # see PutLameVBR() in LAME's VbrTag.c
            self.track_peak = (
                cdata.uint32_be(track_peak_data) - 0.5) / 2 ** 23
        track_gain_type = r.bits(3)
        self.track_gain_origin = r.bits(3)
        sign = r.bits(1)
        gain_adj = r.bits(9) / 10.0
        if sign:
            gain_adj *= -1
        if track_gain_type == 1:
            self.track_gain_adjustment = gain_adj
        else:
            self.track_gain_adjustment = None
        assert r.is_aligned()

        album_gain_type = r.bits(3)
        self.album_gain_origin = r.bits(3)
        sign = r.bits(1)
        album_gain_adj = r.bits(9) / 10.0
        if album_gain_type == 2:
            self.album_gain_adjustment = album_gain_adj
        else:
            self.album_gain_adjustment = None

        self.encoding_flags = r.bits(4)
        self.ath_type = r.bits(4)

        self.bitrate = r.bits(8)

        self.encoder_delay_start = r.bits(12)
        self.encoder_padding_end = r.bits(12)

        self.source_sample_frequency_enum = r.bits(2)
        self.unwise_setting_used = r.bits(1)
        self.stereo_mode = r.bits(3)
        self.noise_shaping = r.bits(2)

        sign = r.bits(1)
        mp3_gain = r.bits(7)
        if sign:
            mp3_gain *= -1
        self.mp3_gain = mp3_gain

        r.skip(2)
        self.surround_info = r.bits(3)
        self.preset_used = r.bits(11)
        self.music_length = r.bits(32)
        self.music_crc = r.bits(16)

        self.header_crc = r.bits(16)
        assert r.is_aligned()

 def test_bits_null(self):
     r = BitReader(cBytesIO(b""))
     self.assertEqual(r.bits(0), 0)