libnids源码分析rcv->offset和循环读取数据这部分不太明白

likuan880506

//常规数据
  if (rcv->collect) {
    if (rcv == &a_tcp->client)
      mask = COLLECT_cc;
    else
      mask = COLLECT_sc;
   do {
        int total;
        a_tcp->read = rcv->count - rcv->offset;
        total = a_tcp->read;

        ride_lurkers(a_tcp, mask);
        if (a_tcp->read>total-rcv->count_new)
            rcv->count_new=total-a_tcp->read;

                if (a_tcp->read > 0) {
          memmove(rcv->data, rcv->data + a_tcp->read, rcv->count - rcv->offset - a_tcp->read);
          //最终rcv->offset == rcv->count
          rcv->offset += a_tcp->read;
        }
    }while (nids_params.one_loop_less && a_tcp->read>0 && rcv->count_new);
// we know that if one_loop_less!=0, we have only one callback to notify
   rcv->count_new=0;
  }

do{

}while里面的不太理解，求高手指教