100 lines
3.5 KiB
Java
100 lines
3.5 KiB
Java
/*
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* Copyright (c) 2014, Friedrich-Alexander University Erlangen-Nuremberg.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the university nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*/
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package org.contikios.cooja;
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import java.util.Random;
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/**
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* This ensures that the functions of the random number generator are
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* only called by the the thread initializing a simulation or the
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* simulation thread itself.
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* Rationale: By allowing another thread to use the random number
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* generator concurrency is introduced, thus it can not be guaranteed
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* that simulations are reproducible.
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*
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*/
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public class SafeRandom extends Random {
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Simulation sim = null;
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Thread initThread = null;
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Boolean simStarted = false;
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private void assertSimThread() {
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// sim can be null, because setSeed is called by the super-constructor.
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if(sim == null) return;
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// If we are in the simulation thread, everything is fine (the default)
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if(sim.isSimulationThread()) {
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simStarted = true;
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return;
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}
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// Simulation has not started yet. Allow one initialisation thread.
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if(!simStarted) {
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if(initThread == null) initThread = Thread.currentThread();
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if(Thread.currentThread() == initThread ) return;
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}
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//This is done via the GUI - reproducibility is lost anyway!
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if(javax.swing.SwingUtilities.isEventDispatchThread()) return;
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// Some other threads seems to access the PNRG. This must not happen.
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throw new RuntimeException("A random-function was not called from the simulation thread. This can break things!");
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}
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public SafeRandom(Simulation sim) {
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// assertSimThread is called by the super-constructor.
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super();
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this.sim = sim;
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}
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public SafeRandom(Simulation sim, long seed) {
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// assertSimThread is called by the super-constructor.
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super(seed);
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this.sim = sim;
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}
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synchronized public void setSeed(long seed) {
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assertSimThread();
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super.setSeed(seed);
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}
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/*
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* This function is called by all functions returning random numbers
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* @see java.util.Random#next(int)
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*/
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protected int next(int bits) {
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assertSimThread();
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return super.next(bits);
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}
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}
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