short dohash(const char* thecall)
{
   char rootcall[10];     // need to copy call to remove ssid from parse
   char *p1 = rootcall;
  while ((*thecall != '-') && (*thecall != 0)) *p1++ = toupper(*thecall++);
     *p1 = 0;
  short hash = kkey;     // initialize with the key value
   short i = 0;
   short len = strlen(rootcall);
   char *ptr = rootcall;
  
  while (i < len) {         // loop through the string two bytes at a time
     hash ^= (*ptr++)<<8;   // xor high byte with accumulated hash
     hash ^= (*ptr++);     // xor low byte with accumulated hash
     i += 2;
   }
   return hash & 0x7fff;     // mask off the high bit so number is always positive
}


我理解的大概意思是THECALL=5位ASCII码的组合，但是thecall怎么计算呢，求执行方法或讲解