-/*
- * Copyright (c) 2003-2005 The BISON Project
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- *
- */
-
-package peersim.transport;
-
-import peersim.config.*;
-import peersim.core.*;
-
-
-/**
- * This transport protocol can be combined with other transports
- * to simulate message losses. Its behavior is the following: each message
- * can be dropped based on the configured probability, or it will be sent
- * using the underlying transport protocol.
- * <p>
- * The memory requirements are minimal, as a single instance is created and
- * inserted in the protocol array of all nodes (because instances have no state
- * that depends on the hosting node).
- *
- * @author Alberto Montresor
- * @version $Revision: 1.13 $
- */
-public final class UnreliableTransport implements Transport
-{
-
-//---------------------------------------------------------------------
-//Parameters
-//---------------------------------------------------------------------
-
-/**
- * The name of the underlying transport protocol. This transport is
- * extended with dropping messages.
- * @config
- */
-private static final String PAR_TRANSPORT = "transport";
-
-/**
- * String name of the parameter used to configure the probability that a
- * message sent through this transport is lost.
- * @config
- */
-private static final String PAR_DROP = "drop";
-
-
-//---------------------------------------------------------------------
-//Fields
-//---------------------------------------------------------------------
-
-/** Protocol identifier for the support transport protocol */
-private final int transport;
-
-/** Probability of dropping messages */
-private final float loss;
-
-//---------------------------------------------------------------------
-//Initialization
-//---------------------------------------------------------------------
-
-/**
- * Reads configuration parameter.
- */
-public UnreliableTransport(String prefix)
-{
- transport = Configuration.getPid(prefix+"."+PAR_TRANSPORT);
- loss = (float) Configuration.getDouble(prefix+"."+PAR_DROP);
-}
-
-//---------------------------------------------------------------------
-
-/**
-* Returns <code>this</code>. This way only one instance exists in the system
-* that is linked from all the nodes. This is because this protocol has no
-* state that depends on the hosting node.
- */
-public Object clone()
-{
- return this;
-}
-
-//---------------------------------------------------------------------
-//Methods
-//---------------------------------------------------------------------
-
-/** Sends the message according to the underlying transport protocol.
-* With the configured probability, the message is not sent (i.e. the method does
-* nothing).
-*/
-public void send(Node src, Node dest, Object msg, int pid)
-{
- try
- {
- if (CommonState.r.nextFloat() >= loss)
- {
- // Message is not lost
- Transport t = (Transport) src.getProtocol(transport);
- t.send(src, dest, msg, pid);
- }
- }
- catch(ClassCastException e)
- {
- throw new IllegalArgumentException("Protocol " +
- Configuration.lookupPid(transport) +
- " does not implement Transport");
- }
-}
-
-/** Returns the latency of the underlying protocol.*/
-public long getLatency(Node src, Node dest)
-{
- Transport t = (Transport) src.getProtocol(transport);
- return t.getLatency(src, dest);
-}
-
-}
