git.zerfleddert.de Git - proxmark3-svn/blob - common/crc.c

   1 /*
   2  * crc.c
   3  *
   4  * Generic CRC calculation code.
   5  *
   6  */
   7
   8 #include "crc.h"
   9
  10 void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
  11 {
  12         crc->order = order;
  13         crc->polynom = polynom;
  14         crc->initial_value = initial_value;
  15         crc->final_xor = final_xor;
  16         crc->mask = (1L<<order)-1;
  17         crc_clear(crc);
  18 }
  19
  20 void crc_update(crc_t *crc, uint32_t data, int data_width)
  21 {
  22         int i;
  23         for(i=0; i<data_width; i++) {
  24                 int oldstate = crc->state;
  25                 crc->state = crc->state >> 1;
  26                 if( (oldstate^data) & 1 ) {
  27                         crc->state ^= crc->polynom;
  28                 }
  29                 data >>= 1;
  30         }
  31 }
  32
  33 void crc_clear(crc_t *crc)
  34 {
  35         crc->state = crc->initial_value & crc->mask;
  36 }
  37
  38 uint32_t crc_finish(crc_t *crc)
  39 {
  40         return ( crc->state ^ crc->final_xor ) & crc->mask;
  41 }