54 lines
1.6 KiB
Python
54 lines
1.6 KiB
Python
# -*- coding: utf-8 -*-
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'''
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librfid - RFID EPC Class 1 Gen2 / ISO/IEC 18000-6C compliant library
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Copyright (C) 2013 Entr'ouvert
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as
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published by the Free Software Foundation, either version 3 of the
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License, or (at your option) any later version.
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This program 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
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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Helper functions
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'''
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import crc16
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from binascii import unhexlify
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from librfid.exceptions import OverheadException
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def get_length_on_2_bytes(string):
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length = len(string)
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fmt = '%%0%dx' % (16 // 4)
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return unhexlify(fmt % length)
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def get_integer_on_two_bytes(integer):
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if integer > 65535:
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raise OverheadException('Integer to big to be converted in a string '
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'of two bytes')
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fmt = '%%0%dx' % (16 // 4)
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return unhexlify(fmt % integer)
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def get_crc_16_CCITT(string):
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# Polynome x16 + x12 + x5 + 1, 0x1021
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crc = crc16.crc16xmodem(string, 0xffff)
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fmt = '%%0%dx' % (16 // 4)
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return unhexlify(fmt % crc)
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def switch_big_to_little_indian(string):
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return string[::-1]
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def hex_to_int(hex_value):
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return int(hex_value.encode('hex'), 16)
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