common/crc32.c

   1 //-----------------------------------------------------------------------------
   2 // Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
   3 //
   4 // This program is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // This program is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // See LICENSE.txt for the text of the license.
  15 //-----------------------------------------------------------------------------
  16 #include "crc32.h"
  17
  18 #define htole32(x) (x)
  19 #define CRC32_PRESET 0xFFFFFFFF
  20
  21 static void crc32_byte(uint32_t *crc, const uint8_t value);
  22
  23 static void crc32_byte(uint32_t *crc, const uint8_t value) {
  24     /* x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1 */
  25     const uint32_t poly = 0xEDB88320;
  26
  27     *crc ^= value;
  28     for (int current_bit = 7; current_bit >= 0; current_bit--) {
  29         int bit_out = (*crc) & 0x00000001;
  30         *crc >>= 1;
  31         if (bit_out)
  32             *crc ^= poly;
  33     }
  34 }
  35
  36 void crc32_ex(const uint8_t *d, const size_t n, uint8_t *crc) {
  37     uint32_t c = CRC32_PRESET;
  38     for (size_t i = 0; i < n; i++) {
  39         crc32_byte(&c, d[i]);
  40     }
  41     crc[0] = (uint8_t) c;
  42     crc[1] = (uint8_t)(c >> 8);
  43     crc[2] = (uint8_t)(c >> 16);
  44     crc[3] = (uint8_t)(c >> 24);
  45 }
  46
  47
  48 void crc32_append(uint8_t *d, const size_t n) {
  49     crc32_ex(d, n, d + n);
  50 }