1#----------------------------------------------------------------------------- 2# Copyright (c) 2010 Craig McQueen 3# 4# Permission is hereby granted, free of charge, to any person obtaining a copy 5# of this software and associated documentation files (the "Software"), to deal 6# in the Software without restriction, including without limitation the rights 7# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 8# copies of the Software, and to permit persons to whom the Software is 9# furnished to do so, subject to the following conditions: 10# 11# The above copyright notice and this permission notice shall be included in 12# all copies or substantial portions of the Software. 13# 14# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 15# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 16# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 17# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 18# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 19# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 20# SOFTWARE. 21#----------------------------------------------------------------------------- 22''' 23crcmod.predefined defines some well-known CRC algorithms. 24 25To use it, e.g.: 26 import crcmod.predefined 27 28 crc32func = crcmod.predefined.mkPredefinedCrcFun("crc-32") 29 crc32class = crcmod.predefined.PredefinedCrc("crc-32") 30 31crcmod.predefined.Crc is an alias for crcmod.predefined.PredefinedCrc 32But if doing 'from crc.predefined import *', only PredefinedCrc is imported. 33''' 34 35# local imports 36import crcmod 37 38__all__ = [ 39 'PredefinedCrc', 40 'mkPredefinedCrcFun', 41] 42 43REVERSE = True 44NON_REVERSE = False 45 46# The following table defines the parameters of well-known CRC algorithms. 47# The "Check" value is the CRC for the ASCII byte sequence "123456789". It 48# can be used for unit tests. 49_crc_definitions_table = [ 50# Name Identifier-name, Poly Reverse Init-value XOR-out Check 51 [ 'crc-8', 'Crc8', 0x107, NON_REVERSE, 0x00, 0x00, 0xF4, ], 52 [ 'crc-8-darc', 'Crc8Darc', 0x139, REVERSE, 0x00, 0x00, 0x15, ], 53 [ 'crc-8-i-code', 'Crc8ICode', 0x11D, NON_REVERSE, 0xFD, 0x00, 0x7E, ], 54 [ 'crc-8-itu', 'Crc8Itu', 0x107, NON_REVERSE, 0x55, 0x55, 0xA1, ], 55 [ 'crc-8-maxim', 'Crc8Maxim', 0x131, REVERSE, 0x00, 0x00, 0xA1, ], 56 [ 'crc-8-rohc', 'Crc8Rohc', 0x107, REVERSE, 0xFF, 0x00, 0xD0, ], 57 [ 'crc-8-wcdma', 'Crc8Wcdma', 0x19B, REVERSE, 0x00, 0x00, 0x25, ], 58 59 [ 'crc-16', 'Crc16', 0x18005, REVERSE, 0x0000, 0x0000, 0xBB3D, ], 60 [ 'crc-16-buypass', 'Crc16Buypass', 0x18005, NON_REVERSE, 0x0000, 0x0000, 0xFEE8, ], 61 [ 'crc-16-dds-110', 'Crc16Dds110', 0x18005, NON_REVERSE, 0x800D, 0x0000, 0x9ECF, ], 62 [ 'crc-16-dect', 'Crc16Dect', 0x10589, NON_REVERSE, 0x0001, 0x0001, 0x007E, ], 63 [ 'crc-16-dnp', 'Crc16Dnp', 0x13D65, REVERSE, 0xFFFF, 0xFFFF, 0xEA82, ], 64 [ 'crc-16-en-13757', 'Crc16En13757', 0x13D65, NON_REVERSE, 0xFFFF, 0xFFFF, 0xC2B7, ], 65 [ 'crc-16-genibus', 'Crc16Genibus', 0x11021, NON_REVERSE, 0x0000, 0xFFFF, 0xD64E, ], 66 [ 'crc-16-maxim', 'Crc16Maxim', 0x18005, REVERSE, 0xFFFF, 0xFFFF, 0x44C2, ], 67 [ 'crc-16-mcrf4xx', 'Crc16Mcrf4xx', 0x11021, REVERSE, 0xFFFF, 0x0000, 0x6F91, ], 68 [ 'crc-16-riello', 'Crc16Riello', 0x11021, REVERSE, 0x554D, 0x0000, 0x63D0, ], 69 [ 'crc-16-t10-dif', 'Crc16T10Dif', 0x18BB7, NON_REVERSE, 0x0000, 0x0000, 0xD0DB, ], 70 [ 'crc-16-teledisk', 'Crc16Teledisk', 0x1A097, NON_REVERSE, 0x0000, 0x0000, 0x0FB3, ], 71 [ 'crc-16-usb', 'Crc16Usb', 0x18005, REVERSE, 0x0000, 0xFFFF, 0xB4C8, ], 72 [ 'x-25', 'CrcX25', 0x11021, REVERSE, 0x0000, 0xFFFF, 0x906E, ], 73 [ 'xmodem', 'CrcXmodem', 0x11021, NON_REVERSE, 0x0000, 0x0000, 0x31C3, ], 74 [ 'modbus', 'CrcModbus', 0x18005, REVERSE, 0xFFFF, 0x0000, 0x4B37, ], 75 76 # Note definitions of CCITT are disputable. See: 77 # http://homepages.tesco.net/~rainstorm/crc-catalogue.htm 78 # http://web.archive.org/web/20071229021252/http://www.joegeluso.com/software/articles/ccitt.htm 79 [ 'kermit', 'CrcKermit', 0x11021, REVERSE, 0x0000, 0x0000, 0x2189, ], 80 [ 'crc-ccitt-false', 'CrcCcittFalse', 0x11021, NON_REVERSE, 0xFFFF, 0x0000, 0x29B1, ], 81 [ 'crc-aug-ccitt', 'CrcAugCcitt', 0x11021, NON_REVERSE, 0x1D0F, 0x0000, 0xE5CC, ], 82 83 [ 'crc-24', 'Crc24', 0x1864CFB, NON_REVERSE, 0xB704CE, 0x000000, 0x21CF02, ], 84 [ 'crc-24-flexray-a', 'Crc24FlexrayA', 0x15D6DCB, NON_REVERSE, 0xFEDCBA, 0x000000, 0x7979BD, ], 85 [ 'crc-24-flexray-b', 'Crc24FlexrayB', 0x15D6DCB, NON_REVERSE, 0xABCDEF, 0x000000, 0x1F23B8, ], 86 87 [ 'crc-32', 'Crc32', 0x104C11DB7, REVERSE, 0x00000000, 0xFFFFFFFF, 0xCBF43926, ], 88 [ 'crc-32-bzip2', 'Crc32Bzip2', 0x104C11DB7, NON_REVERSE, 0x00000000, 0xFFFFFFFF, 0xFC891918, ], 89 [ 'crc-32c', 'Crc32C', 0x11EDC6F41, REVERSE, 0x00000000, 0xFFFFFFFF, 0xE3069283, ], 90 [ 'crc-32d', 'Crc32D', 0x1A833982B, REVERSE, 0x00000000, 0xFFFFFFFF, 0x87315576, ], 91 [ 'crc-32-mpeg', 'Crc32Mpeg', 0x104C11DB7, NON_REVERSE, 0xFFFFFFFF, 0x00000000, 0x0376E6E7, ], 92 [ 'posix', 'CrcPosix', 0x104C11DB7, NON_REVERSE, 0xFFFFFFFF, 0xFFFFFFFF, 0x765E7680, ], 93 [ 'crc-32q', 'Crc32Q', 0x1814141AB, NON_REVERSE, 0x00000000, 0x00000000, 0x3010BF7F, ], 94 [ 'jamcrc', 'CrcJamCrc', 0x104C11DB7, REVERSE, 0xFFFFFFFF, 0x00000000, 0x340BC6D9, ], 95 [ 'xfer', 'CrcXfer', 0x1000000AF, NON_REVERSE, 0x00000000, 0x00000000, 0xBD0BE338, ], 96 97# 64-bit 98# Name Identifier-name, Poly Reverse Init-value XOR-out Check 99 [ 'crc-64', 'Crc64', 0x1000000000000001B, REVERSE, 0x0000000000000000, 0x0000000000000000, 0x46A5A9388A5BEFFE, ], 100 [ 'crc-64-we', 'Crc64We', 0x142F0E1EBA9EA3693, NON_REVERSE, 0x0000000000000000, 0xFFFFFFFFFFFFFFFF, 0x62EC59E3F1A4F00A, ], 101 [ 'crc-64-jones', 'Crc64Jones', 0x1AD93D23594C935A9, REVERSE, 0xFFFFFFFFFFFFFFFF, 0x0000000000000000, 0xCAA717168609F281, ], 102] 103 104 105def _simplify_name(name): 106 """ 107 Reduce CRC definition name to a simplified form: 108 * lowercase 109 * dashes removed 110 * spaces removed 111 * any initial "CRC" string removed 112 """ 113 name = name.lower() 114 name = name.replace('-', '') 115 name = name.replace(' ', '') 116 if name.startswith('crc'): 117 name = name[len('crc'):] 118 return name 119 120 121_crc_definitions_by_name = {} 122_crc_definitions_by_identifier = {} 123_crc_definitions = [] 124 125_crc_table_headings = [ 'name', 'identifier', 'poly', 'reverse', 'init', 'xor_out', 'check' ] 126 127for table_entry in _crc_definitions_table: 128 crc_definition = dict(zip(_crc_table_headings, table_entry)) 129 _crc_definitions.append(crc_definition) 130 name = _simplify_name(table_entry[0]) 131 if name in _crc_definitions_by_name: 132 raise Exception("Duplicate entry for '%s' in CRC table" % name) 133 _crc_definitions_by_name[name] = crc_definition 134 _crc_definitions_by_identifier[table_entry[1]] = crc_definition 135 136 137def _get_definition_by_name(crc_name): 138 definition = _crc_definitions_by_name.get(_simplify_name(crc_name), None) 139 if not definition: 140 definition = _crc_definitions_by_identifier.get(crc_name, None) 141 if not definition: 142 raise KeyError("Unkown CRC name '%s'" % crc_name) 143 return definition 144 145 146class PredefinedCrc(crcmod.Crc): 147 def __init__(self, crc_name): 148 definition = _get_definition_by_name(crc_name) 149 crcmod.Crc.__init__(self, poly=definition['poly'], initCrc=definition['init'], rev=definition['reverse'], xorOut=definition['xor_out']) 150 151 152# crcmod.predefined.Crc is an alias for crcmod.predefined.PredefinedCrc 153Crc = PredefinedCrc 154 155 156def mkPredefinedCrcFun(crc_name): 157 definition = _get_definition_by_name(crc_name) 158 return crcmod.mkCrcFun(poly=definition['poly'], initCrc=definition['init'], rev=definition['reverse'], xorOut=definition['xor_out']) 159 160 161# crcmod.predefined.mkCrcFun is an alias for crcmod.predefined.mkPredefinedCrcFun 162mkCrcFun = mkPredefinedCrcFun 163