C++ VC strstr函数的仿真

 char *strstr(register char *buf, register char *sub)
{
  register char *bp;
  if (!*sub) return buf;
  for (;;) 
  {
    if (!*buf)  break;
    bp = buf;
    for (;;)
    {
      if (!*sub) return buf;
      if (*bp++ != *sub++) break;
    }
    sub -= (unsigned long) bp;
    sub += (unsigned long) buf;
    buf += 1;
  }
  return 0;
}