checkbyte.c

来自「spice中支持多层次元件模型仿真的可单独运行的插件源码」· C语言 代码 · 共 24 行

/* $Header: /home/harrison/c/tcgmsg/ipcv4.0/RCS/checkbyte.c,v 1.1 91/12/06 17:26:14 harrison Exp Locker: harrison $ */

unsigned char CheckByte(c, n)
    unsigned char *c;
    long n;
{
/*
  unsigned char sum = (char) 0;
  while (n-- > 0)
    sum  = sum ^ *c++;

  return sum;
*/

  unsigned int sum = 0;
  unsigned int mask = 0xff;

  while (n-- > 0)
    sum += (int) *c++;

  sum = (sum + (sum>>8) + (sum>>16) + (sum>>24)) & mask;
  return (unsigned char) sum;
}