# Source code for canlib.ean

    import sys  # python 2 checking

    PRODUCT_EAN_LENGTH = 7

    def bcd_digits(bcd_bytes):
        """Split a byte sequence into four-bit BCD digits

        Used internally by `EAN` to decode BCD.

        For example 0x12345 is turned into 1, 2, 3, 4, 5.

        `bcd_bytes` must be an iterable of eight bit objects supporting `&` and
        `>>`.

        Note:
            The byteorder is currently assumed to be 'little'.

        """
        # byteorder is assumed to be 'little'
        for char in bcd_bytes:
            # Python 2 doesn't have bytes, only string
            if isinstance(char, str):
                char = ord(char)
            yield char & 0xF
            yield char >> 4

    def int_from_digits(digits, base=10):
        """Joins a sequence of decimal digits into a decimal number

        Used internally by `EAN`.

        For example (1, 2, 3, 4, 5) is turned into 54321.

        Iterating through `digits` is assumed to only yield integers between 0 and
        9, inclusive.

        """
        decimal = 0
        for pos, digit in enumerate(digits):
            decimal += digit * base**pos
        return decimal

    class IllegalEAN(ValueError):
        """Could not parse EAN"""
        pass

    class EAN(object):
        r"""Helper object for dealing with European Article Numbers

        Depending on the format the ean is in, `EAN` objects are created in
        different ways;

        For strings::

            EAN('73-30130-01234-5')

        For integers::

            EAN(7330130012345)

        For iterables of integers::

            EAN([7, 3, 3, 0, 1, 3, 0, 0, 1, 2, 3, 4, 5])

        For BCD-coded bytes or bytearrays (str in python 2)::

            EAN.from_bcd(b'\x45\x23\x01\x30\x01\x33\x07')

        For "hi-lo" format, i.e. two 32-bit integers containing half the ean each,
        both BCD-coded::

            EAN.from_hilo([eanHi, eanLo])

        The various representations can then be produced from the resulting object::

            >>> str(ean)
            '73-30130-01234-5'
            >>> int(ean)
            7330130012345
            >>> tuple(ean)  # or list(), or any other sequence type
            (7, 3, 3, 0, 1, 3, 0, 0, 1, 2, 3, 4, 5)
            >>> ean.bcd()
            b'E#\x010\x013\x07'
            >>> ean.hilo()
            (805380933, 471809)

        Sometimes it is easier to only use the last six digits of the ean, the
        product code and check digit. This is supported when working with string
        representations; the constructor supports six-digit (seven-character) input::

            EAN('01234-5')

        In that cases, the country and manufacturer code is assumed to be that of
        Kvaser AB (73-30130).

        A string containing only the product code and check digit can also be retrieved::

            ean.product()

        Instances can also be indexed which yields specific digits as integers::

            >>> ean[7]
            0
            >>> ean[7:]
            (0, 1, 2, 3, 4, 5)

        Note:
            The byteorder is currently always assumed to be 'little'.

        """
        fmt = "##-#####-#####-#"
        num_digits = len([s for s in fmt if s == '#'])

        @classmethod
        def from_bcd(cls, bcd_bytes):
            """Create an EAN object from a binary coded bytes-like object

            The EAN is automatically shortened to the correct length.

            """
            # The digits are in reverse order, and there is an extra zero
            digits = tuple(bcd_digits(bcd_bytes))[:cls.num_digits]
            digits = reversed(digits)
            return cls(digits)

        @classmethod
        def from_string(cls, ean_string):
            """Create an EAN object from a specially formatted string

            .. deprecated:: 1.6
               Use the constructor, ``EAN(ean_string)``, instead.

            """
            return cls(ean_string)

        @classmethod
        def from_hilo(cls, hilo):
            """Create an EAN object from a pair of 32-bit integers, (eanHi, eanLo)"""
            # Python 2 does not have int.to_bytes. And also has longs.
            if sys.version_info < (3, 0):
                hi, lo = hilo
                conc = (hi << 32) + lo
                digits = []
                for i in xrange(16):
                    v = conc & 0xf
                    digits.append(int(v))
                    conc = conc >> 4
                return cls(reversed(digits[:-3]))

            high, low = hilo
            # we get three extra digits in 'high'
            high = tuple(bcd_digits(high.to_bytes(4, byteorder='little')))[:-3]
            low = tuple(bcd_digits(low.to_bytes(4, byteorder='little')))
            return cls(high[::-1] + low[::-1])  # and the digits are reversed

        @classmethod
        def _parse_int(cls, ean_int):
            digits_string = str(ean_int).rjust(cls.num_digits, '0')
            internal = tuple(int(d) for d in digits_string)
            if len(internal) != cls.num_digits:
                raise IllegalEAN("Too large EAN integer: " + str(ean_int))
            else:
                return internal

        @classmethod
        def _parse_str(cls, ean_string):
            if len(ean_string) == PRODUCT_EAN_LENGTH:
                ean_string = "73-30130-" + ean_string

            if len(ean_string) != len(cls.fmt):
                raise IllegalEAN("Wrong length for EAN string: " + repr(ean_string))
            if not all(
                    s.isdigit() if (f == '#') else (f == s)
                    for f, s in zip(cls.fmt, ean_string)):
                raise IllegalEAN("Unreconized format for EAN string: " + repr(ean_string))

            internal = tuple(int(s) for f, s in zip(cls.fmt, ean_string) if f == '#')
            return internal

        def __init__(self, source):
            if isinstance(source, str):
                self._internal = self._parse_str(source)
            elif isinstance(source, int):
                self._internal = self._parse_int(source)
            elif sys.version_info < (3, 0) and isinstance(source, long):
                self._internal = self._parse_int(source)
            else:
                # Assumed to be a iterable
                internal = tuple(source)
                if len(internal) != self.num_digits:
                    raise IllegalEAN("Wrong length of EAN sequence (%d)" % len(internal))
                elif not all(isinstance(d, int) for d in internal):
                    raise IllegalEAN("EAN sequence must contain only ints")
                else:
                    self._internal = internal

        # required in python 2
        def __ne__(self, other):
            return not self == other

        def __eq__(self, other):
            if isinstance(other, EAN):
                return self._internal == other._internal
            elif isinstance(other, str):
                return str(self) == other
            else:
                return NotImplemented

        def __getitem__(self, index):
            return self._internal[index]

        def __int__(self):
            return int_from_digits(reversed(self._internal))

        def __iter__(self):
            return iter(self._internal)

        def __str__(self):
            num_only = map(str, self._internal)
            if sys.version_info < (3, 0):
                # In python 2, map returns a list
                num_only = iter(num_only)
            out = ''.join(
                next(num_only) if s == '#' else s
                for s in self.fmt)
            if __debug__:
                # check that all digits where printed
                rest = tuple(num_only)
                assert len(rest) == 0, rest
            return out

        def __repr__(self):
            return "<{cls}: {s}>".format(
                cls=self.__class__.__name__, s=str(self))

        def __hash__(self):
            return hash(str(self))

        def bcd(self):
            """Return a binary-coded bytes object with this EAN"""
            if sys.version_info < (3, 0):
                # python 2
                bcd = ''
                digits = iter((0, ) + self._internal)
                for d1 in digits:
                    d0 = next(digits)
                    bcd += chr(d1 * 16 + d0)
                bcd = bcd[::-1]
                return bcd

            digits_string = ''.join(str(d) for d in self._internal)
            # fromhex requires an even number of digits
            bcd = bytes.fromhex('0' + digits_string)
            bcd = bytes(reversed(bcd))
            return bcd

        def hilo(self):
            """Return a pair of 32-bit integers, (eanHi, eanLo), with this EAN"""
            high = self._internal[:-8]
            low = self._internal[-8:]
            high = int_from_digits(reversed(high), base=16)
            low = int_from_digits(reversed(low), base=16)
            return (high, low)

        def product(self):
            """Return only the product code and check digit of the string representation"""
            return str(self)[-PRODUCT_EAN_LENGTH:]