通讯编程

开发平台：
Visual C++

rtqueue.cc：源码内容
							#include <assert.h>
#include <rtqueue.h>
#include <cmu-trace.h>
#define CURRENT_TIME    Scheduler::instance().clock()
#define DEBUG
/* ======================================================================
   Packet Queue used by TORA and AODV.
   ===================================================================== */
rtqueue::rtqueue()
{
        head_ = tail_ = 0;
        len_ = 0;
        limit_ = RTQ_MAX_LEN;
        timeout_ = RTQ_TIMEOUT;
}
void
rtqueue::enque(Packet *p)
{
        struct hdr_cmn *ch = HDR_CMN(p);
 
	p->next_ = 0;
        ch->ts_ = CURRENT_TIME + timeout_;
        if (len_ == limit_) {
		Packet *p0 = remove_head();	// decrements len_
		assert(p0);
                if(HDR_CMN(p0)->ts_ > CURRENT_TIME) {
		        drop(p0, DROP_RTR_QFULL);
                }
                else {
                        drop(p0, DROP_RTR_QTIMEOUT);
                }
        }
        if(head_ == 0) {
                head_ = tail_ = p;
        }
        else {
                tail_->next_ = p;
                tail_ = p;
        }
        len_++;
#ifdef DEBUG
	verifyQueue();
#endif
}
                
Packet*
rtqueue::deque()
{
	Packet *p;
        /*
         * Purge any packets that have timed out.
         */
        purge();
	p = remove_head();
#ifdef DEBUG
	verifyQueue();
#endif
	return p;
}
Packet*
rtqueue::deque(nsaddr_t dst)
{
        Packet *p, *prev;
        /*
         * Purge any packets that have timed out.
         */
        purge();
	findPacketWithDst(dst, p, prev);
	assert(p == 0 || (p == head_ && prev == 0) || (prev->next_ == p));
	if(p == 0) return 0;
        if (p == head_) {
		p = remove_head();
        }
        else if (p == tail_) {
                prev->next_ = 0;
                tail_ = prev;
                len_--;
        }
        else {
                prev->next_ = p->next_;
                len_--;
        }
#ifdef DEBUG
	verifyQueue();
#endif
	return p;
}
char 
rtqueue::find(nsaddr_t dst)
{
        Packet *p, *prev;  
	findPacketWithDst(dst, p, prev);
	if (0 == p)
	       return 0;
	else
	       return 1;
}
	
	
/* ======================================================================
   Private Routines
   ====================================================================== */
Packet*
rtqueue::remove_head()
{
        Packet *p = head_;
        
        if(head_ == tail_) {
                head_ = tail_ = 0;
        }
        else {
                head_ = head_->next_;
        }
        if(p) len_--;
        return p;
}
void
rtqueue::purge()
{
        Packet *p;
        while((p = head_) && HDR_CMN(p)->ts_ < CURRENT_TIME) {
                Packet *temp;
		temp = remove_head();     
                assert(p == temp);     
                drop(p, DROP_RTR_QTIMEOUT);
        }
}
void
rtqueue::findPacketWithDst(nsaddr_t dst, Packet*& p, Packet*& prev)
{
	p = prev = 0;
	for(p = head_; p; p = p->next_) {
	  //		if(HDR_IP(p)->dst() == dst) {
	       if(HDR_IP(p)->daddr() == dst) {
			return;
		}
		prev = p;
	}
	if(p == 0) prev = 0;	// not found
}
void
rtqueue::verifyQueue()
{
	Packet *p, *prev = 0;
	int cnt = 0;
	for(p = head_; p; p = p->next_) {
		cnt++;
		prev = p;
	}
	assert(cnt == len_);
	assert(prev == tail_);
}

						