headphones/mutagen/_id3util.py

# Copyright (C) 2005  Michael Urman
#               2013  Christoph Reiter
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of version 2 of the GNU General Public License as
# published by the Free Software Foundation.


class error(Exception):
    pass


class ID3NoHeaderError(error, ValueError):
    pass


class ID3BadUnsynchData(error, ValueError):
    pass


class ID3BadCompressedData(error, ValueError):
    pass


class ID3TagError(error, ValueError):
    pass


class ID3UnsupportedVersionError(error, NotImplementedError):
    pass


class ID3EncryptionUnsupportedError(error, NotImplementedError):
    pass


class ID3JunkFrameError(error, ValueError):
    pass


class ID3Warning(error, UserWarning):
    pass


class unsynch(object):
    @staticmethod
    def decode(value):
        output = []
        safe = True
        append = output.append
        for val in value:
            if safe:
                append(val)
                safe = val != '\xFF'
            else:
                if val >= '\xE0':
                    raise ValueError('invalid sync-safe string')
                elif val != '\x00':
                    append(val)
                safe = True
        if not safe:
            raise ValueError('string ended unsafe')
        return ''.join(output)

    @staticmethod
    def encode(value):
        output = []
        safe = True
        append = output.append
        for val in value:
            if safe:
                append(val)
                if val == '\xFF':
                    safe = False
            elif val == '\x00' or val >= '\xE0':
                append('\x00')
                append(val)
                safe = val != '\xFF'
            else:
                append(val)
                safe = True
        if not safe:
            append('\x00')
        return ''.join(output)


class _BitPaddedMixin(object):

    def as_str(self, width=4, minwidth=4):
        return self.to_str(self, self.bits, self.bigendian, width, minwidth)

    @staticmethod
    def to_str(value, bits=7, bigendian=True, width=4, minwidth=4):
        mask = (1 << bits) - 1

        if width != -1:
            index = 0
            bytes_ = bytearray(width)
            try:
                while value:
                    bytes_[index] = value & mask
                    value >>= bits
                    index += 1
            except IndexError:
                raise ValueError('Value too wide (>%d bytes)' % width)
        else:
            # PCNT and POPM use growing integers
            # of at least 4 bytes (=minwidth) as counters.
            bytes_ = bytearray()
            append = bytes_.append
            while value:
                append(value & mask)
                value >>= bits
            bytes_ = bytes_.ljust(minwidth, "\x00")

        if bigendian:
            bytes_.reverse()
        return str(bytes_)

    @staticmethod
    def has_valid_padding(value, bits=7):
        """Whether the padding bits are all zero"""

        assert bits <= 8

        mask = (((1 << (8 - bits)) - 1) << bits)

        if isinstance(value, (int, long)):
            while value:
                if value & mask:
                    return False
                value >>= 8
        elif isinstance(value, str):
            for byte in value:
                if ord(byte) & mask:
                    return False
        else:
            raise TypeError

        return True


class BitPaddedInt(int, _BitPaddedMixin):

    def __new__(cls, value, bits=7, bigendian=True):

        mask = (1 << (bits)) - 1
        numeric_value = 0
        shift = 0

        if isinstance(value, (int, long)):
            while value:
                numeric_value += (value & mask) << shift
                value >>= 8
                shift += bits
        elif isinstance(value, str):
            if bigendian:
                value = reversed(value)
            for byte in value:
                numeric_value += (ord(byte) & mask) << shift
                shift += bits
        else:
            raise TypeError

        if isinstance(numeric_value, long):
            self = long.__new__(BitPaddedLong, numeric_value)
        else:
            self = int.__new__(BitPaddedInt, numeric_value)

        self.bits = bits
        self.bigendian = bigendian
        return self


class BitPaddedLong(long, _BitPaddedMixin):
    pass