git.zerfleddert.de Git - proxmark3-svn/blob - common/iso14443crc.c

   1 #include "iso14443crc.h"
   2
   3 static unsigned short UpdateCrc14443(unsigned char ch, unsigned short *lpwCrc)
   4 {
   5     ch = (ch ^ (unsigned char) ((*lpwCrc) & 0x00FF));
   6     ch = (ch ^ (ch << 4));
   7     *lpwCrc = (*lpwCrc >> 8) ^ ((unsigned short) ch << 8) ^
   8               ((unsigned short) ch << 3) ^ ((unsigned short) ch >> 4);
   9     return (*lpwCrc);
  10 }
  11
  12 void ComputeCrc14443(int CrcType,
  13                      unsigned char *Data, int Length,
  14                      unsigned char *TransmitFirst,
  15                      unsigned char *TransmitSecond)
  16 {
  17     unsigned char chBlock;
  18     unsigned short wCrc=CrcType;
  19
  20   do {
  21         chBlock = *Data++;
  22         UpdateCrc14443(chBlock, &wCrc);
  23     } while (--Length);
  24
  25     if (CrcType == CRC_14443_B)
  26         wCrc = ~wCrc;                /* ISO/IEC 13239 (formerly ISO/IEC 3309) */
  27
  28     *TransmitFirst = (unsigned char) (wCrc & 0xFF);
  29     *TransmitSecond = (unsigned char) ((wCrc >> 8) & 0xFF);
  30     return;
  31 }