utils/rk27utils/rk27load/checksum.c

   1 #include <stdint.h>
   2 #include "checksum.h"
   3
   4 uint16_t checksum(void *buff, uint32_t size)
   5 {
   6         uint32_t r2 = 0xffff;
   7         uint32_t r3 = 0;
   8         uint32_t i, j;
   9
  10         for (i=0; i<size; i++) {
  11                 r3 = 0x80;
  12                 for (j=0; j<8; j++) {
  13                         if ((r2 & 0x8000) != 0) {
  14                                 r2 <<= 17;
  15                                 r2 >>= 16;
  16                                 r2 ^= 0x1000;
  17                                 r2 ^= 0x21;
  18                         }
  19                         else {
  20                                 r2 <<= 17;
  21                                 r2 >>= 16;
  22                         }
  23
  24                         if ((((uint8_t *)buff)[i] & r3) != 0) {
  25                                 r2 ^= 0x1000;
  26                                 r2 ^= 0x21;
  27                         }
  28
  29                         r3 >>= 1;
  30                 }
  31         }
  32
  33         return r2 & 0xffff;
  34 }
  35