156 lines
6 KiB
Python
156 lines
6 KiB
Python
# isan.py - functions for handling International Standard Audiovisual Numbers
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# (ISANs)
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#
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# Copyright (C) 2010, 2011, 2012, 2013 Arthur de Jong
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301 USA
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"""ISAN (International Standard Audiovisual Number).
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The ISAN (International Standard Audiovisual Number) is used to identify
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audiovisual works.
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The number is hexadecimal and can consists of at least a root identifier,
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and an episode or part. After that an optional check digit, optional
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version and optionally another check digit can be provided. The check
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digits are validated using the ISO 7064 Mod 37, 36 algorithm.
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>>> validate('000000018947000000000000')
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'000000018947000000000000'
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>>> compact('0000-0000-D07A-0090-Q-0000-0000-X')
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'00000000D07A009000000000'
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>>> validate('0000-0001-8CFA-0000-I-0000-0000-K')
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'000000018CFA0000I00000000K'
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>>> validate('0000-0001-8CFA-0000-A-0000-0000-K')
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Traceback (most recent call last):
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...
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InvalidChecksum: ...
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>>> format('000000018947000000000000')
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'0000-0001-8947-0000-8-0000-0000-D'
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>>> to_urn('00000000D07A009000000000')
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'URN:ISAN:0000-0000-D07A-0090-Q-0000-0000-X'
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>>> to_xml('1881-66C7-3420-6541-Y-9F3A-0245-O')
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'<ISAN root="1881-66C7-3420" episode="6541" version="9F3A-0245" />'
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"""
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from stdnum.exceptions import *
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from stdnum.iso7064 import mod_37_36
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from stdnum.util import clean
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def split(number):
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"""Splits the number into a root, an episode or part, a check digit a
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version and another check digit. If any of the parts are missing an
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empty string is returned."""
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number = clean(number, ' -').strip().upper()
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if len(number) == 17 or len(number) == 26:
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return number[0:12], number[12:16], number[16], number[17:25], number[25:]
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elif len(number) > 16:
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return number[0:12], number[12:16], '', number[16:24], number[24:]
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else:
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return number[0:12], number[12:16], number[16:], '', ''
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def compact(number, strip_check_digits=True):
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"""Convert the ISAN to the minimal representation. This strips the number
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of any valid separators and removes surrounding whitespace. The check
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digits are removed by default."""
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number = list(split(number))
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if strip_check_digits:
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number[2] = number[4] = ''
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return ''.join(number)
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def validate(number, strip_check_digits=False, add_check_digits=False):
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"""Checks to see if the number provided is a valid ISAN. If check digits
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are present in the number they are validated. If strip_check_digits is
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True any existing check digits will be removed (after checking). If
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add_check_digits is True the check digit will be added if they are not
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present yet."""
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(root, episode, check1, version, check2) = split(number)
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# check digits used
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for x in root + episode + version:
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if x not in '0123456789ABCDEF':
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raise InvalidFormat()
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# check length of all components
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if len(root) != 12 or len(episode) != 4 or len(check1) not in (0, 1) or \
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len(version) not in (0, 8) or len(check1) not in (0, 1):
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raise InvalidLength()
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# allow removing check digits
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if strip_check_digits:
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check1 = check2 = ''
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# check check digits
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if check1:
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mod_37_36.validate(root + episode + check1)
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if check2:
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mod_37_36.validate(root + episode + version + check2)
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# add check digits
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if add_check_digits and not check1:
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check1 = mod_37_36.calc_check_digit(root + episode)
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if add_check_digits and not check2 and version:
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check2 = mod_37_36.calc_check_digit(root + episode + version)
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return root + episode + check1 + version + check2
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def is_valid(number):
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"""Checks to see if the number provided is a valid ISAN. If check digits
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are present in the number they are validated."""
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try:
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return bool(validate(number))
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except ValidationError:
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return False
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def format(number, separator='-', strip_check_digits=False, add_check_digits=True):
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"""Reformat the passed number to the standard format. If
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add_check_digits is True the check digit will be added if they are not
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present yet. If both strip_check_digits and add_check_digits are True the
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check digits will be recalculated."""
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(root, episode, check1, version, check2) = split(number)
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if strip_check_digits:
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check1 = check2 = ''
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if add_check_digits and not check1:
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check1 = mod_37_36.calc_check_digit(root + episode)
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if add_check_digits and not check2 and version:
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check2 = mod_37_36.calc_check_digit(root + episode + version)
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number = [root[i:i + 4] for i in range(0, 12, 4)] + [episode]
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if check1:
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number.append(check1)
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if version:
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number.extend((version[0:4], version[4:]))
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if check2:
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number.append(check2)
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return separator.join(number)
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def to_binary(number):
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"""Convert the number to its binary representation (without the check
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digits)."""
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from binascii import a2b_hex
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return a2b_hex(compact(number, strip_check_digits=True))
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def to_xml(number):
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"""Returns the XML form of the ISAN as a string."""
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number = format(number, strip_check_digits=True, add_check_digits=False)
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return '<ISAN root="%s" episode="%s" version="%s" />' % (
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number[0:14], number[15:19], number[20:])
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def to_urn(number):
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"""Returns the URN representation of the ISAN."""
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return 'URN:ISAN:' + format(number, add_check_digits=True)
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