drop-tail.cc

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/* -*-  Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 1994 Regents of the University of California.
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 *    notice, this list of conditions and the following disclaimer in the
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 *    must display the following acknowledgement:
 *  This product includes software developed by the Computer Systems
 *  Engineering Group at Lawrence Berkeley Laboratory.
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#ifndef lint
static const char rcsid[] =
    "@(#) $Header: /nfs/jade/vint/CVSROOT/ns-2/queue/drop-tail.cc,v 1.17 2004/10/28 23:35:37 haldar Exp $ (LBL)";
#endif

#include "drop-tail.h"

static class DropTailClass : public TclClass {
 public:
    DropTailClass() : TclClass("Queue/DropTail") {}
    TclObject* create(int, const char*const*) {
        return (new DropTail);
    }
} class_drop_tail;

void DropTail::reset()
{
    Queue::reset();
}

int 
DropTail::command(int argc, const char*const* argv) 
{
    if (argc==2) {
        if (strcmp(argv[1], "printstats") == 0) {
            print_summarystats();
            return (TCL_OK);
        }
        if (strcmp(argv[1], "shrink-queue") == 0) {
            shrink_queue();
            return (TCL_OK);
        }
    }
    if (argc == 3) {
        if (!strcmp(argv[1], "packetqueue-attach")) {
            delete q_;
            if (!(q_ = (PacketQueue*) TclObject::lookup(argv[2])))
                return (TCL_ERROR);
            else {
                pq_ = q_;
                return (TCL_OK);
            }
        }
    }
    return Queue::command(argc, argv);
}

/*
 * drop-tail
 */
void DropTail::enque(Packet* p)
{
    if (summarystats) {
                Queue::updateStats(qib_?q_->byteLength():q_->length());
    }

    int qlimBytes = qlim_ * mean_pktsize_;
    if ((!qib_ && (q_->length() + 1) >= qlim_) ||
    (qib_ && (q_->byteLength() + hdr_cmn::access(p)->size()) >= qlimBytes)){
        // if the queue would overflow if we added this packet...
        if (drop_front_) { /* remove from head of queue */
            q_->enque(p);
            Packet *pp = q_->deque();
            drop(pp);
        } else {
            drop(p);
        }
    } else {
        q_->enque(p);
    }
}

//AG if queue size changes, we drop excessive packets...
void DropTail::shrink_queue() 
{
        int qlimBytes = qlim_ * mean_pktsize_;
    if (debug_)
        printf("shrink-queue: time %5.2f qlen %d, qlim %d\n",
            Scheduler::instance().clock(),
            q_->length(), qlim_);
        while ((!qib_ && q_->length() > qlim_) || 
            (qib_ && q_->byteLength() > qlimBytes)) {
                if (drop_front_) { /* remove from head of queue */
                        Packet *pp = q_->deque();
                        drop(pp);
                } else {
                        Packet *pp = q_->tail();
                        q_->remove(pp);
                        drop(pp);
                }
        }
}

Packet* DropTail::deque()
{
        if (summarystats && &Scheduler::instance() != NULL) {
                Queue::updateStats(qib_?q_->byteLength():q_->length());
        }
    return q_->deque();
}

void DropTail::print_summarystats()
{
    //double now = Scheduler::instance().clock();
        printf("True average queue: %5.3f", true_ave_);
        if (qib_)
                printf(" (in bytes)");
        printf(" time: %5.3f\n", total_time_);
}

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