utils/Install/packace/uac_crc.c

   1 /* ------------------------------------------------------------------------ */
   2 /*                                                                          */
   3 /*      CRC-calculation routines.                                           */
   4 /*                                                                          */
   5 /* ------------------------------------------------------------------------ */
   6
   7 #include "uac_crc.h"
   8
   9
  10 ULONG crctable[256];
  11 ULONG rd_crc=0;
  12
  13
  14 void make_crctable(void)   // initializes CRC table
  15 {
  16         ULONG r,
  17         i,
  18         j;
  19
  20         for (i = 0; i <= 255; i++)
  21         {
  22                 for (r = i, j = 8; j; j--)
  23                         r = (r & 1) ? (r >> 1) ^ CRCPOLY : (r >> 1);
  24                 crctable[i] = r;
  25         }
  26 }
  27
  28 // Updates crc from addr till addr+len-1
  29 //
  30 ULONG getcrc(ULONG crc, UCHAR * addr, INT len)
  31 {
  32         while (len--)
  33                 crc = crctable[(unsigned char) crc ^ (*addr++)] ^ (crc >> 8);
  34         return (crc);
  35 }
  36