plugins/epan/wimax/crc.c

   1 /* crc.c
   2  * crc checksum generation and calculation functions: crc.c
   3  *
   4  * Copyright (c) 2007 by Intel Corporation.
   5  *
   6  * Author: Mike Harvey <michael.harvey@intel.com>
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@wireshark.org>
  10  * Copyright 1999 Gerald Combs
  11  *
  12  * SPDX-License-Identifier: GPL-2.0-or-later
  13  */
  14
  15 #include "crc.h"
  16
  17 #define WMAX_MAC_CRC32_POLYNOMIAL 0x04c11db7U /* polynomial used in calculating the CRC-32 checksum */
  18 #define CCITT_X25_CRC16_POLYNOMIAL 0x1021     /* polynomial used in calculating the CRC-16 checksum */
  19 #define WMAX_MAC_CRC8_POLYNOMIAL  0x07        /* polynomial used in calculating the CRC-8 checksum */
  20 #define CRC32_INITIAL_VALUE       0xFFFFFFFF
  21 #define CRC16_INITIAL_VALUE       0xFFFF
  22
  23 #ifndef STATIC_DATA
  24 static uint8_t crc8_table[256];
  25 static uint32_t crc32_table[256];
  26
  27 extern uint16_t crc16_table[256];
  28
  29 /*
  30   void wimax_mac_gen_crc32_table(void)
  31
  32   REQUIRES: The functions must be called only once to initialze CRC table
  33
  34   DESCRIPTION:  Generate the table of CRC remainders
  35                 for all possible bytes
  36
  37   ARGS:
  38
  39   RETURNS:
  40
  41   SIDE EFFECTS:
  42
  43 */
  44 void wimax_mac_gen_crc32_table(void)
  45 {
  46   uint32_t i, bit;
  47   uint32_t crc;
  48
  49   /* little-endian (reflected) algorithm */
  50   for ( i = 0;  i < G_N_ELEMENTS(crc32_table);  i++ )
  51   {
  52     crc = ( i << 24 );
  53     for ( bit = 0;  bit < 8;  bit++ )
  54     {
  55       if ( crc & 0x80000000U )
  56         crc = ( crc << 1 ) ^ WMAX_MAC_CRC32_POLYNOMIAL;
  57       else
  58         crc = ( crc << 1 );
  59     }
  60     crc32_table[i] = crc;
  61   }
  62 }
  63
  64 /*
  65   void wimax_mac_gen_crc8_table(void)
  66
  67   REQUIRES: The functions must be called only once to initialze CRC table
  68
  69   DESCRIPTION:  Generate the table of CRC remainders
  70                 for all possible bytes
  71
  72   ARGS:
  73
  74   RETURNS:
  75
  76   SIDE EFFECTS:
  77
  78 */
  79 void wimax_mac_gen_crc8_table(void)
  80 {
  81   unsigned  i, bit;
  82   uint8_t crc;
  83
  84   for ( i = 0;  i < G_N_ELEMENTS(crc8_table);  i++ )
  85   {
  86     crc = i;
  87     for ( bit = 0;  bit < 8;  bit++ )
  88     {
  89       if ( crc & 0x80 )
  90         crc = ( crc << 1 ) ^ WMAX_MAC_CRC8_POLYNOMIAL;
  91       else
  92         crc = ( crc << 1 );
  93     }
  94     crc8_table[i] = crc;
  95   }
  96 }
  97 #endif
  98
  99 /*
 100
 101   uint32_t wimax_mac_calc_crc32(uint8_t *data, unsigned data_len)
 102
 103   REQUIRES: wimax_mac_gen_crc32_table() must be called before
 104
 105   DESCRIPTION: Calculate the 32-bit CRC from a given data block
 106
 107   ARGS:  data - pointer to data
 108          data_len - length of data (in bytes)
 109
 110   RETURNS:  calculated crc32
 111
 112   SIDE EFFECTS:
 113
 114 */
 115 uint32_t wimax_mac_calc_crc32(const uint8_t *data, unsigned data_len)
 116 {
 117   uint32_t crc=CRC32_INITIAL_VALUE;
 118   unsigned i, j;
 119
 120   for ( j = 0;  j < data_len;  j++ )
 121   {
 122     i = ( (uint8_t)(crc>>24) ^ data[j] ) & 0xff;
 123     crc = ( crc<<8 ) ^ crc32_table[i];
 124   }
 125   return ~crc;
 126 }
 127
 128 /*
 129
 130   uint16_t wimax_mac_calc_crc16(uint8_t *data, unsigned data_len)
 131
 132   REQUIRES: crc16_table[] in crc_data.c
 133
 134   DESCRIPTION: Calculate the 16-bit CRC from a given data block
 135
 136   ARGS:  data - pointer to data
 137          data_len - length of data (in bytes)
 138
 139   RETURNS:  calculated crc16
 140
 141   SIDE EFFECTS:
 142
 143 */
 144 uint16_t wimax_mac_calc_crc16(const uint8_t *data, unsigned data_len)
 145 {
 146   uint32_t crc=CRC16_INITIAL_VALUE;
 147   unsigned j;
 148
 149   for ( j = 0;  j < data_len;  j++ )
 150   {
 151     crc ^= data[j] << 8;
 152     crc = (crc << 8) ^ crc16_table[(crc & 0xff00) >> 8];
 153   }
 154   crc ^= 0xFFFF;        /* Invert the output. */
 155   crc &= 0xFFFF;
 156   return crc;
 157 }
 158
 159 /*
 160
 161   uint8_t wimax_mac_calc_crc8(uint8_t *data, unsigned data_len)
 162
 163   REQUIRES: wimax_mac_gen_crc8_table() must be called before
 164
 165   DESCRIPTION: Calculate the 8-bit CRC from a given data block
 166
 167   ARGS:  data - pointer to data
 168          data_len - length of data (in bytes)
 169
 170   RETURNS:  calculated crc8
 171
 172   SIDE EFFECTS:
 173
 174 */
 175 uint8_t wimax_mac_calc_crc8(const uint8_t *data, unsigned data_len)
 176 {
 177   uint8_t crc=0;
 178   unsigned i;
 179
 180   for(i = 0; i < data_len; i++)
 181   {
 182     crc = crc8_table[data[i]^crc];
 183   }
 184   return crc;
 185 }
 186
 187 /*
 188  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 189  *
 190  * Local Variables:
 191  * c-basic-offset: 2
 192  * tab-width: 8
 193  * indent-tabs-mode: nil
 194  * End:
 195  *
 196  * ex: set shiftwidth=2 tabstop=8 expandtab:
 197  * :indentSize=2:tabSize=8:noTabs=true:
 198  */