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38
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1 ///////////////////////////////////////////////////////////////////////////////
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2 /// -*- coding: UTF-8 -*-
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3 ///
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4 /// \file Discovery/Inc/crcmodel.h
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5 /// \brief Rocksoft CRC Model Algorithm
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6 /// \author Ross Williams (ross@guest.adelaide.edu.au.) and Heinrichs Weikamp
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7 /// \date 3 June 1993
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8 ///
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9 /// \details
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10 ///
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11 /// This is the header (.h) file for the reference
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12 /// implementation of the Rocksoft^tm Model CRC Algorithm. For more
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13 /// information on the Rocksoft^tm Model CRC Algorithm, see the document
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14 /// titled "A Painless Guide to CRC Error Detection Algorithms" by Ross
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15 /// Williams (ross@guest.adelaide.edu.au.). This document is likely to be in
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16 /// "ftp.adelaide.edu.au/pub/rocksoft".
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17 ///
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18 /// Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia.
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19 ///
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20 /// $Id$
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21 ///////////////////////////////////////////////////////////////////////////////
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22 /// \par Copyright (c) 2014-2018 Heinrichs Weikamp gmbh
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23 ///
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24 /// This program is free software: you can redistribute it and/or modify
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25 /// it under the terms of the GNU General Public License as published by
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26 /// the Free Software Foundation, either version 3 of the License, or
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27 /// (at your option) any later version.
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28 ///
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29 /// This program is distributed in the hope that it will be useful,
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30 /// but WITHOUT ANY WARRANTY; without even the implied warranty of
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31 /// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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32 /// GNU General Public License for more details.
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33 ///
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34 /// You should have received a copy of the GNU General Public License
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35 /// along with this program. If not, see <http://www.gnu.org/licenses/>.
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36 //////////////////////////////////////////////////////////////////////////////
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37
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38 /******************************************************************************/
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39 /* Start of crcmodel.h */
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40 /******************************************************************************/
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41 /* */
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42 /* Author : Ross Williams (ross@guest.adelaide.edu.au.). */
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43 /* Date : 3 June 1993. */
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44 /* Status : Public domain. */
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45 /* */
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46 /* Description : This is the header (.h) file for the reference */
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47 /* implementation of the Rocksoft^tm Model CRC Algorithm. For more */
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48 /* information on the Rocksoft^tm Model CRC Algorithm, see the document */
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49 /* titled "A Painless Guide to CRC Error Detection Algorithms" by Ross */
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50 /* Williams (ross@guest.adelaide.edu.au.). This document is likely to be in */
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51 /* "ftp.adelaide.edu.au/pub/rocksoft". */
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52 /* */
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53 /* Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia. */
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54 /* */
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55 /******************************************************************************/
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56 /* */
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57 /* How to Use This Package */
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58 /* ----------------------- */
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59 /* Step 1: Declare a variable of type cm_t. Declare another variable */
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60 /* (p_cm say) of type p_cm_t and initialize it to point to the first */
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61 /* variable (e.g. p_cm_t p_cm = &cm_t). */
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62 /* */
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63 /* Step 2: Assign values to the parameter fields of the structure. */
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64 /* If you don't know what to assign, see the document cited earlier. */
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65 /* For example: */
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66 /* p_cm->cm_width = 16; */
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67 /* p_cm->cm_poly = 0x8005L; */
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68 /* p_cm->cm_init = 0L; */
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69 /* p_cm->cm_refin = TRUE; */
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70 /* p_cm->cm_refot = TRUE; */
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71 /* p_cm->cm_xorot = 0L; */
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72 /* Note: Poly is specified without its top bit (18005 becomes 8005). */
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73 /* Note: Width is one bit less than the raw poly width. */
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74 /* */
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75 /* Step 3: Initialize the instance with a call cm_ini(p_cm); */
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76 /* */
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77 /* Step 4: Process zero or more message bytes by placing zero or more */
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78 /* successive calls to cm_nxt. Example: cm_nxt(p_cm,ch); */
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79 /* */
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80 /* Step 5: Extract the CRC value at any time by calling crc = cm_crc(p_cm); */
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81 /* If the CRC is a 16-bit value, it will be in the bottom 16 bits. */
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82 /* */
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83 /******************************************************************************/
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84 /* */
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85 /* Design Notes */
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86 /* ------------ */
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87 /* PORTABILITY: This package has been coded very conservatively so that */
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88 /* it will run on as many machines as possible. For example, all external */
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89 /* identifiers have been restricted to 6 characters and all internal ones to */
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90 /* 8 characters. The prefix cm (for Crc Model) is used as an attempt to avoid */
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91 /* namespace collisions. This package is endian independent. */
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92 /* */
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93 /* EFFICIENCY: This package (and its interface) is not designed for */
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94 /* speed. The purpose of this package is to act as a well-defined reference */
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95 /* model for the specification of CRC algorithms. If you want speed, cook up */
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96 /* a specific table-driven implementation as described in the document cited */
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97 /* above. This package is designed for validation only; if you have found or */
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98 /* implemented a CRC algorithm and wish to describe it as a set of parameters */
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99 /* to the Rocksoft^tm Model CRC Algorithm, your CRC algorithm implementation */
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100 /* should behave identically to this package under those parameters. */
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101 /* */
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102 /******************************************************************************/
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103
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104 #ifndef CRC_MODEL_H
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105 #define CRC_MODEL_H
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106
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107 /******************************************************************************/
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108
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109 /* The following definitions are extracted from my style header file which */
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110 /* would be cumbersome to distribute with this package. The DONE_STYLE is the */
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111 /* idempotence symbol used in my style header file. */
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112
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113 #ifndef DONE_STYLE
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114
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115 typedef unsigned long ulong;
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116 typedef unsigned bool;
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117 typedef unsigned char * p_ubyte_;
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118
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119 #ifndef TRUE
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120 #define FALSE 0
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121 #define TRUE 1
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122 #endif
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123
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124 /* Change to the second definition if you don't have prototypes. */
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125 #define P_(A) A
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126 /* #define P_(A) () */
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127
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128 /* Uncomment this definition if you don't have void. */
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129 /* typedef int void; */
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130
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131 #endif
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132
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133 /******************************************************************************/
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134
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135 /* CRC Model Abstract Type */
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136 /* ----------------------- */
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137 /* The following type stores the context of an executing instance of the */
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138 /* model algorithm. Most of the fields are model parameters which must be */
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139 /* set before the first initializing call to cm_ini. */
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140 typedef struct
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141 {
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142 int cm_width; /* Parameter: Width in bits [8,32]. */
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143 ulong cm_poly; /* Parameter: The algorithm's polynomial. */
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144 ulong cm_init; /* Parameter: Initial register value. */
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145 bool cm_refin; /* Parameter: Reflect input bytes? */
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146 bool cm_refot; /* Parameter: Reflect output CRC? */
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147 ulong cm_xorot; /* Parameter: XOR this to output CRC. */
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148
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149 ulong cm_reg; /* Context: Context during execution. */
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150 } cm_t;
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151 typedef cm_t *p_cm_t;
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152
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153 /******************************************************************************/
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154
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155 /* Functions That Implement The Model */
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156 /* ---------------------------------- */
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157 /* The following functions animate the cm_t abstraction. */
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158
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159 void cm_ini P_((p_cm_t p_cm));
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160 /* Initializes the argument CRC model instance. */
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161 /* All parameter fields must be set before calling this. */
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162
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163 void cm_nxt P_((p_cm_t p_cm,int ch));
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164 /* Processes a single message byte [0,255]. */
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165
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166 void cm_blk P_((p_cm_t p_cm,p_ubyte_ blk_adr,ulong blk_len));
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167 /* Processes a block of message bytes. */
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168
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169 ulong cm_crc P_((p_cm_t p_cm));
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170 /* Returns the CRC value for the message bytes processed so far. */
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171
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172 /******************************************************************************/
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173
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174 /* Functions For Table Calculation */
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175 /* ------------------------------- */
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176 /* The following function can be used to calculate a CRC lookup table. */
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177 /* It can also be used at run-time to create or check static tables. */
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178
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179 ulong cm_tab P_((p_cm_t p_cm,int index));
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180 /* Returns the i'th entry for the lookup table for the specified algorithm. */
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181 /* The function examines the fields cm_width, cm_poly, cm_refin, and the */
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182 /* argument table index in the range [0,255] and returns the table entry in */
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183 /* the bottom cm_width bytes of the return value. */
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184
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185 /******************************************************************************/
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186
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187 #endif // CRC_MODEL_H
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