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annotate cutils/crcmod/python3/crcmod.py @ 186:5c5c0c5a7402

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Sync with latest crcmod2
author Franz Glasner <fzglas.hg@dom66.de>
date Tue, 14 Jan 2025 13:31:39 +0100
parents d038f0a9ba49
children
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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 # Copyright (c) 2025 Franz Glasner
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5 #
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6 # Permission is hereby granted, free of charge, to any person obtaining a copy
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7 # of this software and associated documentation files (the "Software"), to deal
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8 # in the Software without restriction, including without limitation the rights
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9 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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10 # copies of the Software, and to permit persons to whom the Software is
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11 # furnished to do so, subject to the following conditions:
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12 #
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13 # The above copyright notice and this permission notice shall be included in
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14 # all copies or substantial portions of the Software.
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15 #
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16 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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17 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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18 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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19 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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20 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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21 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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22 # SOFTWARE.
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23 #-----------------------------------------------------------------------------
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24 '''crcmod is a Python module for gererating objects that compute the Cyclic
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25 Redundancy Check. Any 8, 16, 24, 32, or 64 bit polynomial can be used.
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26
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27 The following are the public components of this module.
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29 Crc -- a class that creates instances providing the same interface as the
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30 algorithms in the hashlib module in the Python standard library. These
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31 instances also provide a method for generating a C/C++ function to compute
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32 the CRC.
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34 mkCrcFun -- create a Python function to compute the CRC using the specified
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35 polynomial and initial value. This provides a much simpler interface if
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36 all you need is a function for CRC calculation.
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37 '''
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38
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39 __all__ = '''mkCrcFun Crc'''.split()
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40
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41 # Select the appropriate set of low-level CRC functions for this installation.
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42 # If the extension module was not built, drop back to the Python implementation
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43 # even though it is significantly slower.
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44 try:
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45 from . import _crcfunext as _crcfun
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46 _usingExtension = True
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47 except ImportError:
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48 from . import _crcfunpy as _crcfun
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49 _usingExtension = False
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50
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51 import sys, struct
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52
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53 #-----------------------------------------------------------------------------
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54 class Crc:
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55 '''Compute a Cyclic Redundancy Check (CRC) using the specified polynomial.
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57 Instances of this class have the same interface as the algorithms in the
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58 hashlib module in the Python standard library. See the documentation of
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59 this module for examples of how to use a Crc instance.
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60
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61 The string representation of a Crc instance identifies the polynomial,
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62 initial value, XOR out value, and the current CRC value. The print
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63 statement can be used to output this information.
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64
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65 If you need to generate a C/C++ function for use in another application,
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66 use the generateCode method. If you need to generate code for another
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67 language, subclass Crc and override the generateCode method.
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68
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69 The following are the parameters supplied to the constructor.
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70
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71 poly -- The generator polynomial to use in calculating the CRC. The value
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72 is specified as a Python integer. The bits in this integer are the
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73 coefficients of the polynomial. The only polynomials allowed are those
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74 that generate 8, 16, 24, 32, or 64 bit CRCs.
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75
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76 initCrc -- Initial value used to start the CRC calculation. This initial
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77 value should be the initial shift register value XORed with the final XOR
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78 value. That is equivalent to the CRC result the algorithm should return for
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79 a zero-length string. Defaults to all bits set because that starting value
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80 will take leading zero bytes into account. Starting with zero will ignore
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81 all leading zero bytes.
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82
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83 rev -- A flag that selects a bit reversed algorithm when True. Defaults to
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84 True because the bit reversed algorithms are more efficient.
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85
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86 xorOut -- Final value to XOR with the calculated CRC value. Used by some
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87 CRC algorithms. Defaults to zero.
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88 '''
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89 def __init__(self, poly, initCrc=~0, rev=True, xorOut=0, initialize=True):
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90 if not initialize:
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91 # Don't want to perform the initialization when using new or copy
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92 # to create a new instance.
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93 return
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94
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95 (sizeBits, initCrc, xorOut) = _verifyParams(poly, initCrc, xorOut)
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diff changeset
96 self.digest_size = sizeBits//8
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97 self.initCrc = initCrc
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diff changeset
98 self.xorOut = xorOut
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99
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100 self.poly = poly
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101 self.reverse = rev
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102
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103 (crcfun, table) = _mkCrcFun(poly, sizeBits, initCrc, rev, xorOut)
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104 self._crc = crcfun
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105 self.table = table
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106
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diff changeset
107 self.crcValue = self.initCrc
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108
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diff changeset
109 def __str__(self):
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110 lst = []
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111 lst.append('poly = 0x%X' % self.poly)
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112 lst.append('reverse = %s' % self.reverse)
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113 fmt = '0x%%0%dX' % (self.digest_size*2)
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114 lst.append('initCrc = %s' % (fmt % self.initCrc))
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115 lst.append('xorOut = %s' % (fmt % self.xorOut))
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116 lst.append('crcValue = %s' % (fmt % self.crcValue))
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117 return '\n'.join(lst)
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118
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119 def new(self, arg=None):
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120 '''Create a new instance of the Crc class initialized to the same
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121 values as the original instance. The current CRC is set to the initial
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122 value. If a string is provided in the optional arg parameter, it is
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123 passed to the update method.
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124 '''
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125 n = Crc(poly=None, initialize=False)
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126 n._crc = self._crc
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127 n.digest_size = self.digest_size
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128 n.initCrc = self.initCrc
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129 n.xorOut = self.xorOut
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130 n.table = self.table
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131 n.crcValue = self.initCrc
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132 n.reverse = self.reverse
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133 n.poly = self.poly
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134 if arg is not None:
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135 n.update(arg)
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136 return n
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137
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138 def copy(self):
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139 '''Create a new instance of the Crc class initialized to the same
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diff changeset
140 values as the original instance. The current CRC is set to the current
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141 value. This allows multiple CRC calculations using a common initial
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142 string.
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143 '''
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144 c = self.new()
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145 c.crcValue = self.crcValue
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146 return c
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147
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148 def update(self, data):
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149 '''Update the current CRC value using the string specified as the data
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150 parameter.
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151 '''
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152 self.crcValue = self._crc(data, self.crcValue)
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153
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154 def digest(self):
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155 '''Return the current CRC value as a string of bytes. The length of
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diff changeset
156 this string is specified in the digest_size attribute.
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157 '''
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158 n = self.digest_size
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159 crc = self.crcValue
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160 lst = []
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161 while n > 0:
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162 lst.append(crc & 0xFF)
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163 crc = crc >> 8
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164 n -= 1
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165 lst.reverse()
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166 return bytes(lst)
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167
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168 def hexdigest(self):
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169 '''Return the current CRC value as a string of hex digits. The length
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170 of this string is twice the digest_size attribute.
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171 '''
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172 n = self.digest_size
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173 crc = self.crcValue
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174 lst = []
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175 while n > 0:
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176 lst.append('%02X' % (crc & 0xFF))
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177 crc = crc >> 8
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178 n -= 1
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179 lst.reverse()
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180 return ''.join(lst)
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181
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182 def generateCode(self, functionName, out, dataType=None, crcType=None):
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183 '''Generate a C/C++ function.
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184
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diff changeset
185 functionName -- String specifying the name of the function.
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186
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187 out -- An open file-like object with a write method. This specifies
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188 where the generated code is written.
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189
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190 dataType -- An optional parameter specifying the data type of the input
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191 data to the function. Defaults to UINT8.
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192
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193 crcType -- An optional parameter specifying the data type of the CRC
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194 value. Defaults to one of UINT8, UINT16, UINT32, or UINT64 depending
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195 on the size of the CRC value.
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196 '''
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197 if dataType is None:
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198 dataType = 'UINT8'
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199
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200 if crcType is None:
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201 size = 8*self.digest_size
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202 if size == 24:
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203 size = 32
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204 crcType = 'UINT%d' % size
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205
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206 if self.digest_size == 1:
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207 # Both 8-bit CRC algorithms are the same
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208 crcAlgor = 'table[*data ^ (%s)crc]'
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209 elif self.reverse:
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210 # The bit reverse algorithms are all the same except for the data
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211 # type of the crc variable which is specified elsewhere.
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212 crcAlgor = 'table[*data ^ (%s)crc] ^ (crc >> 8)'
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213 else:
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214 # The forward CRC algorithms larger than 8 bits have an extra shift
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215 # operation to get the high byte.
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216 shift = 8*(self.digest_size - 1)
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217 crcAlgor = 'table[*data ^ (%%s)(crc >> %d)] ^ (crc << 8)' % shift
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218
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219 fmt = '0x%%0%dX' % (2*self.digest_size)
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220 if self.digest_size <= 4:
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221 fmt = fmt + 'U,'
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222 else:
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223 # Need the long long type identifier to keep gcc from complaining.
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224 fmt = fmt + 'ULL,'
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225
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226 # Select the number of entries per row in the output code.
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227 n = {1:8, 2:8, 3:4, 4:4, 8:2}[self.digest_size]
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228
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229 lst = []
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230 for i, val in enumerate(self.table):
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231 if (i % n) == 0:
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232 lst.append('\n ')
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233 lst.append(fmt % val)
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234
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235 poly = 'polynomial: 0x%X' % self.poly
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236 if self.reverse:
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237 poly = poly + ', bit reverse algorithm'
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238
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239 if self.xorOut:
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240 # Need to remove the comma from the format.
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241 preCondition = '\n crc = crc ^ %s;' % (fmt[:-1] % self.xorOut)
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242 postCondition = preCondition
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243 else:
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244 preCondition = ''
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245 postCondition = ''
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246
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247 if self.digest_size == 3:
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248 # The 24-bit CRC needs to be conditioned so that only 24-bits are
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249 # used from the 32-bit variable.
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250 if self.reverse:
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251 preCondition += '\n crc = crc & 0xFFFFFFU;'
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252 else:
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253 postCondition += '\n crc = crc & 0xFFFFFFU;'
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254
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255
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256 parms = {
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257 'dataType' : dataType,
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258 'crcType' : crcType,
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259 'name' : functionName,
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260 'crcAlgor' : crcAlgor % dataType,
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261 'crcTable' : ''.join(lst),
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262 'poly' : poly,
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263 'preCondition' : preCondition,
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264 'postCondition' : postCondition,
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265 }
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266 out.write(_codeTemplate % parms)
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267
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268 #-----------------------------------------------------------------------------
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269 def mkCrcFun(poly, initCrc=~0, rev=True, xorOut=0):
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270 '''Return a function that computes the CRC using the specified polynomial.
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271
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272 poly -- integer representation of the generator polynomial
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273 initCrc -- default initial CRC value
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274 rev -- when true, indicates that the data is processed bit reversed.
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275 xorOut -- the final XOR value
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276
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277 The returned function has the following user interface
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278 def crcfun(data, crc=initCrc):
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279 '''
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280
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281 # First we must verify the params
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282 (sizeBits, initCrc, xorOut) = _verifyParams(poly, initCrc, xorOut)
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283 # Make the function (and table), return the function
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284 return _mkCrcFun(poly, sizeBits, initCrc, rev, xorOut)[0]
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285
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286 #-----------------------------------------------------------------------------
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287 # Naming convention:
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288 # All function names ending with r are bit reverse variants of the ones
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289 # without the r.
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290
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parents:
diff changeset
291 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
292 # 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
293 # of bits in the CRC.
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parents:
diff changeset
294
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
295 def _verifyPoly(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
296 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
297 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
298 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
299 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
300 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
301 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
302 raise ValueError(msg)
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 #-----------------------------------------------------------------------------
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 # 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
306
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 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
308 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
309 for i in range(n):
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
310 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
311 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
312 return y
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 #-----------------------------------------------------------------------------
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 # 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
316 # 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
317 # 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.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
318
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 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
320 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
321 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
322 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
323 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
324 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
325 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
326 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
327 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
328 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
329
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 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
331 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
332 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
333 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
334 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
335 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
336 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
337 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
338 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
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 #-----------------------------------------------------------------------------
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 # 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
342 # 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
343 # 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
344 #
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 # 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
346 # 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.
Franz Glasner <fzglas.hg@dom66.de>
parents:
diff changeset
347
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 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
349 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
350 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
351 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
352 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
353
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 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
355 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
356 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
357 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
358 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
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 #-----------------------------------------------------------------------------
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 # 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
362
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 _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
364 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
365 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
366 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
367 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
368 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
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 #-----------------------------------------------------------------------------
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 # 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
373 # 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
374 # 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
375 # 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
376
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 _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
378
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 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
380 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
381 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
382 _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
383
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 _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
385
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 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
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 #-----------------------------------------------------------------------------
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
389 # 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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390 # poly, and initial/final XOR values.
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391 # It returns the size of the CRC (in bits), and "sanitized" initial/final XOR values.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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392
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393 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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394 sizeBits = _verifyPoly(poly)
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395
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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396 mask = (1<<sizeBits) - 1
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397
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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398 # 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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399 initCrc = initCrc & mask
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400
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
401 # Similar for XOR-out value.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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402 xorOut = xorOut & mask
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diff changeset
403
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
404 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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405
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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406 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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407 # 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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408 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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409 # 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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410 # _verifyParams().
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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411 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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412 # 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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413 # 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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diff changeset
414 # used.
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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415 #
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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416 # 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
417
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diff changeset
418 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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419 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
420 tableList = _mkTable_r(poly, sizeBits)
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diff changeset
421 _fun = _sizeMap[sizeBits][1]
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diff changeset
422 else:
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
423 tableList = _mkTable(poly, sizeBits)
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diff changeset
424 _fun = _sizeMap[sizeBits][0]
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diff changeset
425
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
426 _table = tableList
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parents:
diff changeset
427 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
428 _table = struct.pack(_sizeToTypeCode[sizeBits], *tableList)
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diff changeset
429
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
430 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
431 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
432 return fun(data, crc, table)
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diff changeset
433 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
434 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
435 return xorOut ^ fun(data, xorOut ^ crc, table)
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parents:
diff changeset
436
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 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
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 #-----------------------------------------------------------------------------
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
440 _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
441 // %(poly)s
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diff changeset
442 %(crcType)s
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diff changeset
443 %(name)s(%(dataType)s *data, int len, %(crcType)s crc)
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diff changeset
444 {
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
445 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
446 };
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
447 %(preCondition)s
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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diff changeset
448 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
449 {
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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parents:
diff changeset
450 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
451 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
452 len--;
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 }%(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
454 return crc;
d038f0a9ba49 Vendored crcmod2 into sub-package "cutils.crcmod" as pure-Python implementation of additional "digests": CRC sums.
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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 '''
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
457