/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2008 University of Washington
*
* 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
*
* Author: Tom Henderson <tomh@tomh.org>
*/
#include "ns3/log.h"
#include "ns3/command-line.h"
#include "ns3/ptr.h"
#include "ns3/config.h"
#include "ns3/uinteger.h"
#include "ns3/string.h"
#include "ns3/pointer.h"
#include "ns3/simulator.h"
#include "ns3/node.h"
#include "ns3/queue.h"
#include "ns3/drop-tail-queue.h"
#include "ns3/point-to-point-net-device.h"
using namespace ns3;
NS_LOG_COMPONENT_DEFINE ("AttributeValueSample");
//
// This is a basic example of how to use the attribute system to
// set and get a value in the underlying system; namely, an unsigned
// integer of the maximum number of packets in a queue
//
int
main (int argc, char *argv[])
{
LogComponentEnable ("AttributeValueSample", LOG_LEVEL_INFO);
// By default, the MaxPackets attribute has a value of 100 packets
// (this default can be observed in the function DropTailQueue::GetTypeId)
//
// Here, we set it to 80 packets. We could use one of two value types:
// a string-based value or a UintegerValue value
Config::SetDefault ("ns3::DropTailQueue::MaxPackets", StringValue ("80"));
// The below function call is redundant
Config::SetDefault ("ns3::DropTailQueue::MaxPackets", UintegerValue (80));
// Allow the user to override any of the defaults and the above
// SetDefaults() at run-time, via command-line arguments
CommandLine cmd;
cmd.Parse (argc, argv);
// Now, we will create a few objects using the low-level API
Ptr<Node> n0 = CreateObject<Node> ();
Ptr<PointToPointNetDevice> net0 = CreateObject<PointToPointNetDevice> ();
n0->AddDevice (net0);
Ptr<Queue> q = CreateObject<DropTailQueue> ();
net0->SetQueue(q);
// At this point, we have created a single node (Node 0) and a
// single PointToPointNetDevice (NetDevice 0) and added a
// DropTailQueue to it.
// Now, we can manipulate the MaxPackets value of the already
// instantiated DropTailQueue. Here are various ways to do that.
// We assume that a smart pointer (Ptr) to a relevant network device
// is in hand; here, it is the net0 pointer.
// 1. Pointer-based access
//
// One way to change the value is to access a pointer to the
// underlying queue and modify its attribute.
//
// First, we observe that we can get a pointer to the (base class)
// queue via the PointToPointNetDevice attributes, where it is called
// TxQueue
PointerValue ptr;
net0->GetAttribute ("TxQueue", ptr);
Ptr<Queue> txQueue = ptr.Get<Queue> ();
// Using the GetObject function, we can perform a safe downcast
// to a DropTailQueue, where MaxPackets is a member
Ptr<DropTailQueue> dtq = txQueue->GetObject <DropTailQueue> ();
NS_ASSERT (dtq);
// Next, we can get the value of an attribute on this queue
// We have introduced wrapper "Value" classes for the underlying
// data types, similar to Java wrappers around these types, since
// the attribute system stores values and not disparate types.
// Here, the attribute value is assigned to a Uinteger, and
// the Get() method on this value produces the (unwrapped) uint32_t.
UintegerValue limit;
dtq->GetAttribute ("MaxPackets", limit);
NS_LOG_INFO ("1. dtq limit: " << limit.Get () << " packets");
// Note that the above downcast is not really needed; we could have
// done the same using the Ptr<Queue> even though the attribute
// is a member of the subclass
txQueue->GetAttribute ("MaxPackets", limit);
NS_LOG_INFO ("2. txQueue limit: " << limit.Get () << " packets");
// Now, let's set it to another value (60 packets)
txQueue->SetAttribute("MaxPackets", UintegerValue (60));
txQueue->GetAttribute ("MaxPackets", limit);
NS_LOG_INFO ("3. txQueue limit changed: " << limit.Get () << " packets");
// 2. Namespace-based access
//
// An alternative way to get at the attribute is to use the configuration
// namespace. Here, this attribute resides on a known path in this
// namespace; this approach is useful if one doesn't have access to
// the underlying pointers and would like to configure a specific
// attribute with a single statement.
Config::Set ("/NodeList/0/DeviceList/0/TxQueue/MaxPackets", UintegerValue (25));
txQueue->GetAttribute ("MaxPackets", limit);
NS_LOG_INFO ("4. txQueue limit changed through namespace: " <<
limit.Get () << " packets");
// we could have also used wildcards to set this value for all nodes
// and all net devices (which in this simple example has the same
// effect as the previous Set())
Config::Set ("/NodeList/*/DeviceList/*/TxQueue/MaxPackets", UintegerValue (15));
txQueue->GetAttribute ("MaxPackets", limit);
NS_LOG_INFO ("5. txQueue limit changed through wildcarded namespace: " <<
limit.Get () << " packets");
Simulator::Destroy ();
}