/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2007 University of Washington

 * All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

#include "ns3/log.h"

#include "drop-tail-queue.h"

NS_LOG_COMPONENT_DEFINE ("DropTailQueue");

namespace ns3 {

DropTailQueue::DropTailQueue () :

  Queue (),

  m_packets (),

  m_maxPackets(DTQ_NPACKETS_MAX_DEFAULT)

{

  NS_LOG_FUNCTION;

}

DropTailQueue::~DropTailQueue ()

{

  NS_LOG_FUNCTION;

}

void 

DropTailQueue::SetMaxPackets (uint32_t npackets)

{

  NS_LOG_FUNCTION;

  NS_LOG_PARAMS (this << npackets);

  m_maxPackets = npackets;

}

uint32_t 

DropTailQueue::GetMaxPackets (void)

{

  NS_LOG_FUNCTION;

  NS_LOG_LOGIC ("returns " << m_maxPackets);

  return m_maxPackets;

}

bool 

DropTailQueue::DoEnqueue (Ptr<Packet> p)

{

  NS_LOG_FUNCTION;

  NS_LOG_PARAMS (this << p);

  if (m_packets.size () >= m_maxPackets)

    {

      NS_LOG_LOGIC ("Queue full -- droppping pkt");

      Drop (p);

      return false;

    }

  m_packets.push(p);

  return true;

}

Ptr<Packet>

DropTailQueue::DoDequeue (void)

{

  NS_LOG_FUNCTION;

  NS_LOG_PARAMS (this);

  if (m_packets.empty()) 

    {

      NS_LOG_LOGIC ("Queue empty");

      return false;

    }

  Ptr<Packet> p = m_packets.front ();

  m_packets.pop ();

  NS_LOG_LOGIC ("Popped " << p);

  return p;

}

Ptr<Packet>

DropTailQueue::DoPeek (void) const

{

  NS_LOG_FUNCTION;

  NS_LOG_PARAMS (this);

  if (m_packets.empty()) 

    {

      NS_LOG_LOGIC ("Queue empty");

      return false;

    }

  Ptr<Packet> p = m_packets.front ();

  return p;

}

} // namespace ns3

#ifdef RUN_SELF_TESTS

#include "ns3/test.h"

namespace ns3 {

class DropTailQueueTest: public Test {

public:

  virtual bool RunTests (void);

  DropTailQueueTest ();

};

DropTailQueueTest::DropTailQueueTest ()

  : Test ("DropTailQueue") {}

bool

DropTailQueueTest::RunTests (void)

{

  bool result = true;

  DropTailQueue queue;

  queue.SetMaxPackets (3);

  Ptr<Packet> p1, p2, p3, p4;

  p1 = Create<Packet> ();

  p2 = Create<Packet> ();

  p3 = Create<Packet> ();

  p4 = Create<Packet> ();

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 0);

  queue.Enqueue (p1);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 1);

  queue.Enqueue (p2);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 2);

  queue.Enqueue (p3);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 3);

  queue.Enqueue (p4); // will be dropped

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 3);

  Ptr<Packet> p;

  p = queue.Dequeue ();

  NS_TEST_ASSERT (p != 0);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 2);

  NS_TEST_ASSERT_EQUAL (p->GetUid (), p1->GetUid ());

  p = queue.Dequeue ();

  NS_TEST_ASSERT (p != 0);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 1);

  NS_TEST_ASSERT_EQUAL (p->GetUid (), p2->GetUid ());

  p = queue.Dequeue ();

  NS_TEST_ASSERT (p != 0);

  NS_TEST_ASSERT_EQUAL (queue.GetNPackets (), 0);

  NS_TEST_ASSERT_EQUAL (p->GetUid (), p3->GetUid ());

  p = queue.Dequeue ();

  NS_TEST_ASSERT (p == 0);

  return result;

}

static DropTailQueueTest gDropTailQueueTest;

}; // namespace ns3

#endif /* RUN_SELF_TESTS */