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annotate cutils/crcmod/python3/crcmod.py @ 181:c4f737ec368c

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Add a unittest for the vendored crcmod2 (in cutils.crcmod)
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 13 Jan 2025 04:15:08 +0100
parents d038f0a9ba49
children 5c5c0c5a7402
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d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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1 #-----------------------------------------------------------------------------
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2 # Copyright (c) 2010 Raymond L. Buvel
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3 # Copyright (c) 2010 Craig McQueen
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4 #
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5 # Permission is hereby granted, free of charge, to any person obtaining a copy
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6 # of this software and associated documentation files (the "Software"), to deal
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7 # in the Software without restriction, including without limitation the rights
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8 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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9 # copies of the Software, and to permit persons to whom the Software is
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10 # furnished to do so, subject to the following conditions:
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11 #
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12 # The above copyright notice and this permission notice shall be included in
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13 # all copies or substantial portions of the Software.
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14 #
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15 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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17 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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18 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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19 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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20 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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21 # SOFTWARE.
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22 #-----------------------------------------------------------------------------
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23 '''crcmod is a Python module for gererating objects that compute the Cyclic
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24 Redundancy Check. Any 8, 16, 24, 32, or 64 bit polynomial can be used.
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25
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26 The following are the public components of this module.
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27
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28 Crc -- a class that creates instances providing the same interface as the
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29 algorithms in the hashlib module in the Python standard library. These
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30 instances also provide a method for generating a C/C++ function to compute
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31 the CRC.
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32
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33 mkCrcFun -- create a Python function to compute the CRC using the specified
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34 polynomial and initial value. This provides a much simpler interface if
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35 all you need is a function for CRC calculation.
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36 '''
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37
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38 __all__ = '''mkCrcFun Crc'''.split()
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39
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40 # Select the appropriate set of low-level CRC functions for this installation.
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41 # If the extension module was not built, drop back to the Python implementation
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42 # even though it is significantly slower.
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43 try:
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44 from . import _crcfunext as _crcfun
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45 _usingExtension = True
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46 except ImportError:
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47 from . import _crcfunpy as _crcfun
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48 _usingExtension = False
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49
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50 import sys, struct
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51
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52 #-----------------------------------------------------------------------------
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53 class Crc:
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54 '''Compute a Cyclic Redundancy Check (CRC) using the specified polynomial.
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55
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56 Instances of this class have the same interface as the algorithms in the
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57 hashlib module in the Python standard library. See the documentation of
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58 this module for examples of how to use a Crc instance.
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59
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60 The string representation of a Crc instance identifies the polynomial,
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61 initial value, XOR out value, and the current CRC value. The print
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62 statement can be used to output this information.
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63
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64 If you need to generate a C/C++ function for use in another application,
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65 use the generateCode method. If you need to generate code for another
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66 language, subclass Crc and override the generateCode method.
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67
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68 The following are the parameters supplied to the constructor.
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69
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70 poly -- The generator polynomial to use in calculating the CRC. The value
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71 is specified as a Python integer. The bits in this integer are the
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72 coefficients of the polynomial. The only polynomials allowed are those
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73 that generate 8, 16, 24, 32, or 64 bit CRCs.
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74
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75 initCrc -- Initial value used to start the CRC calculation. This initial
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76 value should be the initial shift register value XORed with the final XOR
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77 value. That is equivalent to the CRC result the algorithm should return for
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78 a zero-length string. Defaults to all bits set because that starting value
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79 will take leading zero bytes into account. Starting with zero will ignore
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80 all leading zero bytes.
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81
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82 rev -- A flag that selects a bit reversed algorithm when True. Defaults to
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83 True because the bit reversed algorithms are more efficient.
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84
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85 xorOut -- Final value to XOR with the calculated CRC value. Used by some
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86 CRC algorithms. Defaults to zero.
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87 '''
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88 def __init__(self, poly, initCrc=~0, rev=True, xorOut=0, initialize=True):
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89 if not initialize:
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90 # Don't want to perform the initialization when using new or copy
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91 # to create a new instance.
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92 return
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93
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94 (sizeBits, initCrc, xorOut) = _verifyParams(poly, initCrc, xorOut)
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95 self.digest_size = sizeBits//8
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96 self.initCrc = initCrc
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97 self.xorOut = xorOut
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98
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99 self.poly = poly
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100 self.reverse = rev
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101
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102 (crcfun, table) = _mkCrcFun(poly, sizeBits, initCrc, rev, xorOut)
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103 self._crc = crcfun
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104 self.table = table
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105
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diff changeset
106 self.crcValue = self.initCrc
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107
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108 def __str__(self):
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109 lst = []
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110 lst.append('poly = 0x%X' % self.poly)
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111 lst.append('reverse = %s' % self.reverse)
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112 fmt = '0x%%0%dX' % (self.digest_size*2)
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113 lst.append('initCrc = %s' % (fmt % self.initCrc))
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114 lst.append('xorOut = %s' % (fmt % self.xorOut))
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115 lst.append('crcValue = %s' % (fmt % self.crcValue))
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116 return '\n'.join(lst)
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117
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118 def new(self, arg=None):
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119 '''Create a new instance of the Crc class initialized to the same
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120 values as the original instance. The current CRC is set to the initial
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121 value. If a string is provided in the optional arg parameter, it is
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122 passed to the update method.
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123 '''
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124 n = Crc(poly=None, initialize=False)
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125 n._crc = self._crc
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126 n.digest_size = self.digest_size
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127 n.initCrc = self.initCrc
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128 n.xorOut = self.xorOut
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129 n.table = self.table
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130 n.crcValue = self.initCrc
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131 n.reverse = self.reverse
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132 n.poly = self.poly
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133 if arg is not None:
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134 n.update(arg)
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135 return n
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136
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137 def copy(self):
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138 '''Create a new instance of the Crc class initialized to the same
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139 values as the original instance. The current CRC is set to the current
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140 value. This allows multiple CRC calculations using a common initial
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141 string.
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142 '''
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143 c = self.new()
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144 c.crcValue = self.crcValue
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145 return c
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146
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147 def update(self, data):
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148 '''Update the current CRC value using the string specified as the data
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149 parameter.
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150 '''
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151 self.crcValue = self._crc(data, self.crcValue)
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152
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153 def digest(self):
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154 '''Return the current CRC value as a string of bytes. The length of
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diff changeset
155 this string is specified in the digest_size attribute.
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156 '''
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157 n = self.digest_size
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158 crc = self.crcValue
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159 lst = []
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160 while n > 0:
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161 lst.append(crc & 0xFF)
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162 crc = crc >> 8
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163 n -= 1
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164 lst.reverse()
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165 return bytes(lst)
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166
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167 def hexdigest(self):
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168 '''Return the current CRC value as a string of hex digits. The length
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169 of this string is twice the digest_size attribute.
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170 '''
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171 n = self.digest_size
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172 crc = self.crcValue
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173 lst = []
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174 while n > 0:
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175 lst.append('%02X' % (crc & 0xFF))
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176 crc = crc >> 8
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177 n -= 1
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178 lst.reverse()
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179 return ''.join(lst)
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180
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181 def generateCode(self, functionName, out, dataType=None, crcType=None):
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182 '''Generate a C/C++ function.
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183
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diff changeset
184 functionName -- String specifying the name of the function.
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185
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186 out -- An open file-like object with a write method. This specifies
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187 where the generated code is written.
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188
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189 dataType -- An optional parameter specifying the data type of the input
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190 data to the function. Defaults to UINT8.
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191
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192 crcType -- An optional parameter specifying the data type of the CRC
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193 value. Defaults to one of UINT8, UINT16, UINT32, or UINT64 depending
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194 on the size of the CRC value.
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195 '''
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196 if dataType is None:
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197 dataType = 'UINT8'
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198
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199 if crcType is None:
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200 size = 8*self.digest_size
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201 if size == 24:
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202 size = 32
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203 crcType = 'UINT%d' % size
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204
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205 if self.digest_size == 1:
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206 # Both 8-bit CRC algorithms are the same
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207 crcAlgor = 'table[*data ^ (%s)crc]'
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208 elif self.reverse:
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209 # The bit reverse algorithms are all the same except for the data
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210 # type of the crc variable which is specified elsewhere.
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211 crcAlgor = 'table[*data ^ (%s)crc] ^ (crc >> 8)'
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212 else:
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213 # The forward CRC algorithms larger than 8 bits have an extra shift
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214 # operation to get the high byte.
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215 shift = 8*(self.digest_size - 1)
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216 crcAlgor = 'table[*data ^ (%%s)(crc >> %d)] ^ (crc << 8)' % shift
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217
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218 fmt = '0x%%0%dX' % (2*self.digest_size)
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219 if self.digest_size <= 4:
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220 fmt = fmt + 'U,'
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221 else:
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222 # Need the long long type identifier to keep gcc from complaining.
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223 fmt = fmt + 'ULL,'
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224
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225 # Select the number of entries per row in the output code.
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226 n = {1:8, 2:8, 3:4, 4:4, 8:2}[self.digest_size]
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227
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228 lst = []
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229 for i, val in enumerate(self.table):
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230 if (i % n) == 0:
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231 lst.append('\n ')
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232 lst.append(fmt % val)
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233
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234 poly = 'polynomial: 0x%X' % self.poly
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235 if self.reverse:
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236 poly = poly + ', bit reverse algorithm'
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237
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238 if self.xorOut:
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239 # Need to remove the comma from the format.
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240 preCondition = '\n crc = crc ^ %s;' % (fmt[:-1] % self.xorOut)
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241 postCondition = preCondition
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242 else:
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243 preCondition = ''
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244 postCondition = ''
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245
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246 if self.digest_size == 3:
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247 # The 24-bit CRC needs to be conditioned so that only 24-bits are
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248 # used from the 32-bit variable.
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249 if self.reverse:
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250 preCondition += '\n crc = crc & 0xFFFFFFU;'
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251 else:
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252 postCondition += '\n crc = crc & 0xFFFFFFU;'
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253
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254
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255 parms = {
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256 'dataType' : dataType,
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257 'crcType' : crcType,
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258 'name' : functionName,
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259 'crcAlgor' : crcAlgor % dataType,
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260 'crcTable' : ''.join(lst),
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261 'poly' : poly,
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262 'preCondition' : preCondition,
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263 'postCondition' : postCondition,
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264 }
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265 out.write(_codeTemplate % parms)
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266
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267 #-----------------------------------------------------------------------------
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268 def mkCrcFun(poly, initCrc=~0, rev=True, xorOut=0):
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269 '''Return a function that computes the CRC using the specified polynomial.
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270
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271 poly -- integer representation of the generator polynomial
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272 initCrc -- default initial CRC value
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273 rev -- when true, indicates that the data is processed bit reversed.
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274 xorOut -- the final XOR value
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275
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276 The returned function has the following user interface
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277 def crcfun(data, crc=initCrc):
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278 '''
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279
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280 # First we must verify the params
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281 (sizeBits, initCrc, xorOut) = _verifyParams(poly, initCrc, xorOut)
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282 # Make the function (and table), return the function
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283 return _mkCrcFun(poly, sizeBits, initCrc, rev, xorOut)[0]
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284
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285 #-----------------------------------------------------------------------------
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286 # Naming convention:
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287 # All function names ending with r are bit reverse variants of the ones
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288 # without the r.
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289
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parents:
diff changeset
290 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
291 # Check the polynomial to make sure that it is acceptable and return the number
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
292 # of bits in the CRC.
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parents:
diff changeset
293
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
294 def _verifyPoly(poly):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
295 msg = 'The degree of the polynomial must be 8, 16, 24, 32 or 64'
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
296 for n in (8,16,24,32,64):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
297 low = 1<<n
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
298 high = low*2
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
299 if low <= poly < high:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
300 return n
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
301 raise ValueError(msg)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
302
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
303 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
304 # Bit reverse the input value.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
305
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
306 def _bitrev(x, n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
307 y = 0
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
308 for i in range(n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
309 y = (y << 1) | (x & 1)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
310 x = x >> 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
311 return y
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
312
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
313 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
314 # The following functions compute the CRC for a single byte. These are used
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
315 # to build up the tables needed in the CRC algorithm. Assumes the high order
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
316 # bit of the polynomial has been stripped off.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
317
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
318 def _bytecrc(crc, poly, n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
319 mask = 1<<(n-1)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
320 for i in range(8):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
321 if crc & mask:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
322 crc = (crc << 1) ^ poly
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
323 else:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
324 crc = crc << 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
325 mask = (1<<n) - 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
326 crc = crc & mask
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
327 return crc
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
328
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
329 def _bytecrc_r(crc, poly, n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
330 for i in range(8):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
331 if crc & 1:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
332 crc = (crc >> 1) ^ poly
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
333 else:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
334 crc = crc >> 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
335 mask = (1<<n) - 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
336 crc = crc & mask
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
337 return crc
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
338
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
339 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
340 # The following functions compute the table needed to compute the CRC. The
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
341 # table is returned as a list. Note that the array module does not support
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
342 # 64-bit integers on a 32-bit architecture as of Python 2.3.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
343 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
344 # These routines assume that the polynomial and the number of bits in the CRC
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
345 # have been checked for validity by the caller.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
346
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
347 def _mkTable(poly, n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
348 mask = (1<<n) - 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
349 poly = poly & mask
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
350 table = [_bytecrc(i<<(n-8),poly,n) for i in range(256)]
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
351 return table
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
352
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
353 def _mkTable_r(poly, n):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
354 mask = (1<<n) - 1
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
355 poly = _bitrev(poly & mask, n)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
356 table = [_bytecrc_r(i,poly,n) for i in range(256)]
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
357 return table
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
358
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
359 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
360 # Map the CRC size onto the functions that handle these sizes.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
361
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
362 _sizeMap = {
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
363 8 : [_crcfun._crc8, _crcfun._crc8r],
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
364 16 : [_crcfun._crc16, _crcfun._crc16r],
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
365 24 : [_crcfun._crc24, _crcfun._crc24r],
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
366 32 : [_crcfun._crc32, _crcfun._crc32r],
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
367 64 : [_crcfun._crc64, _crcfun._crc64r],
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
368 }
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
369
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
370 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
371 # Build a mapping of size to struct module type code. This table is
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
372 # constructed dynamically so that it has the best chance of picking the best
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
373 # code to use for the platform we are running on. This should properly adapt
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
374 # to 32 and 64 bit machines.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
375
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
376 _sizeToTypeCode = {}
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
377
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
378 for typeCode in 'B H I L Q'.split():
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
379 size = {1:8, 2:16, 4:32, 8:64}.get(struct.calcsize(typeCode),None)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
380 if size is not None and size not in _sizeToTypeCode:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
381 _sizeToTypeCode[size] = '256%s' % typeCode
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
382
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
383 _sizeToTypeCode[24] = _sizeToTypeCode[32]
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
384
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
385 del typeCode, size
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
386
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
387 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
388 # The following function validates the parameters of the CRC, namely,
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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389 # poly, and initial/final XOR values.
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390 # It returns the size of the CRC (in bits), and "sanitized" initial/final XOR values.
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391
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392 def _verifyParams(poly, initCrc, xorOut):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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393 sizeBits = _verifyPoly(poly)
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394
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395 mask = (1<<sizeBits) - 1
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396
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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397 # Adjust the initial CRC to the correct data type (unsigned value).
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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398 initCrc = initCrc & mask
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399
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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400 # Similar for XOR-out value.
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diff changeset
401 xorOut = xorOut & mask
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402
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
403 return (sizeBits, initCrc, xorOut)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
404
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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405 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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406 # The following function returns a Python function to compute the CRC.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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407 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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408 # It must be passed parameters that are already verified & sanitized by
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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409 # _verifyParams().
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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410 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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411 # The returned function calls a low level function that is written in C if the
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
412 # extension module could be loaded. Otherwise, a Python implementation is
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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413 # used.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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414 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
415 # In addition to this function, a list containing the CRC table is returned.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
416
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
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diff changeset
417 def _mkCrcFun(poly, sizeBits, initCrc, rev, xorOut):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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418 if rev:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
419 tableList = _mkTable_r(poly, sizeBits)
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diff changeset
420 _fun = _sizeMap[sizeBits][1]
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diff changeset
421 else:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
422 tableList = _mkTable(poly, sizeBits)
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diff changeset
423 _fun = _sizeMap[sizeBits][0]
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diff changeset
424
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
425 _table = tableList
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diff changeset
426 if _usingExtension:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
427 _table = struct.pack(_sizeToTypeCode[sizeBits], *tableList)
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diff changeset
428
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
429 if xorOut == 0:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
430 def crcfun(data, crc=initCrc, table=_table, fun=_fun):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
431 return fun(data, crc, table)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
432 else:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
433 def crcfun(data, crc=initCrc, table=_table, fun=_fun):
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
434 return xorOut ^ fun(data, xorOut ^ crc, table)
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parents:
diff changeset
435
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
436 return crcfun, tableList
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
437
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
438 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
439 _codeTemplate = '''// Automatically generated CRC function
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
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diff changeset
440 // %(poly)s
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diff changeset
441 %(crcType)s
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diff changeset
442 %(name)s(%(dataType)s *data, int len, %(crcType)s crc)
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diff changeset
443 {
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
444 static const %(crcType)s table[256] = {%(crcTable)s
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
445 };
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
446 %(preCondition)s
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
447 while (len > 0)
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
448 {
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
449 crc = %(crcAlgor)s;
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
450 data++;
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
451 len--;
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
452 }%(postCondition)s
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
453 return crc;
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
454 }
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
455 '''
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
456