83 lines
2.1 KiB
Java
83 lines
2.1 KiB
Java
// Time-stamp: <08 Apr 2008 11:35 queinnec@enseeiht.fr>
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import java.util.concurrent.locks.Condition;
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import java.util.concurrent.locks.Lock;
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import java.util.concurrent.locks.ReentrantLock;
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/**
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* Lecteurs/rédacteurs stratégie d'ordonnancement: priorité FIFO, implantation:
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* avec un moniteur.
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*/
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public class LectRed_FIFO implements LectRed {
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Lock lock;
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Condition requestAccess;
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Condition SAS;
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boolean activeWriter;
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int activeReaders;
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boolean SASoccupied;
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int FIFOsize;
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public LectRed_FIFO() {
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lock = new ReentrantLock();
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requestAccess = lock.newCondition();
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SAS = lock.newCondition();
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activeWriter = false;
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activeReaders = 0;
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SASoccupied = false;
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FIFOsize = 0;
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}
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public void demanderLecture() throws InterruptedException {
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lock.lock();
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if (activeWriter || FIFOsize > 0) {
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FIFOsize++;
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requestAccess.await();
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FIFOsize--;
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}
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activeReaders++;
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requestAccess.signal();
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lock.unlock();
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}
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public void terminerLecture() throws InterruptedException {
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lock.lock();
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activeReaders--;
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if (activeReaders == 0) {
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if (SASoccupied) {
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SAS.signal();
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} else {
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requestAccess.signal();
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}
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}
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lock.unlock();
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}
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public void demanderEcriture() throws InterruptedException {
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lock.lock();
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if (activeWriter || activeReaders > 0 || FIFOsize > 0 || SASoccupied) {
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FIFOsize++;
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requestAccess.await();
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FIFOsize--;
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}
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if (activeReaders > 0) {
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SASoccupied = true;
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SAS.await();
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SASoccupied = false;
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}
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activeWriter = true;
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lock.unlock();
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}
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public void terminerEcriture() throws InterruptedException {
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lock.lock();
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activeWriter = false;
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requestAccess.signal();
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lock.unlock();
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}
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public String nomStrategie() {
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return "Stratégie: Moniteur, prio FIFO.";
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}
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}
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