370 lines
10 KiB
Java
370 lines
10 KiB
Java
package linda.shm;
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import linda.Callback;
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import linda.Linda;
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import linda.Tuple;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.List;
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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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/** Shared memory implementation of Linda. */
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public class CentralizedLinda implements Linda {
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List<Tuple> tuples;
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Lock moniteur;
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Condition accessDemand;
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Condition SAS;
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int nbReaders;
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int nbWaiting;
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boolean writing;
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boolean SASused;
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public CentralizedLinda() {
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nbReaders = 0;
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nbWaiting = 0;
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writing = false;
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SASused = false;
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moniteur = new ReentrantLock();
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accessDemand = moniteur.newCondition();
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SAS = moniteur.newCondition();
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tuples = new ArrayList<Tuple>();
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}
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public void write(Tuple t) {
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try {
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// Wait for writing access
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requestWriting();
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// Add the new tuple
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tuples.add(t);
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// End writing
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endWriting();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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public Tuple take(Tuple template) {
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Tuple result = null;
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boolean found = false;
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int index;
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try {
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while (!found) {
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// Wait for writing access
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requestWriting();
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// Find the tuple in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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found = true;
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break;
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}
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}
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if (found) {
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// Result found, remove it from the tuple list
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result = tuples.remove(index);
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}
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// End writing
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endWriting();
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}
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return result;
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}
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public Tuple read(Tuple template) {
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Tuple result = null;
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boolean found = false;
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int index;
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try {
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while (!found) {
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// Waiting for reading access
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requestReading();
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// Find the tuple in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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found = true;
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break;
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}
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}
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if (found) {
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// Result found, get it from the tuple list
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result = tuples.get(index);
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}
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// End reading
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endReading();
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}
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return result;
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}
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public Tuple tryTake(Tuple template) {
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Tuple result = null;
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int index;
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try {
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// Wait for writing access
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requestWriting();
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// Extract the tuple in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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result = tuples.remove(index);
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break;
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}
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}
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// End writing
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endWriting();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return result;
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}
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public Tuple tryRead(Tuple template) {
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Tuple result = null;
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int index;
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try {
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// Waiting for reading access
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requestReading();
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// Find the tuple in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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result = tuples.get(index);
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break;
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}
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}
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// End reading
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endReading();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return result;
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}
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public Collection<Tuple> takeAll(Tuple template) {
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List<Tuple> results = new ArrayList<Tuple>();
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int index;
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try {
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// Wait for writing access
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requestWriting();
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// Extract the tuples in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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results.add(tuples.remove(index));
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}
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}
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// End writing
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endWriting();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return results;
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}
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public Collection<Tuple> readAll(Tuple template) {
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List<Tuple> results = new ArrayList<Tuple>();
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int index;
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try {
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// Waiting for reading access
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requestReading();
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// Find the tuples in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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results.add(tuples.get(index));
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}
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}
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// End reading
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endReading();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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return results;
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}
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public void eventRegister(eventMode mode, eventTiming timing, Tuple template, Callback callback) {
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new Thread() {
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public void run() {
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Tuple result = null;
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boolean found = false;
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int index;
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// Get known tuples for FUTURE timing
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List<Tuple> knownTuples = (List<Tuple>) readAll(template);
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try {
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while (!found) {
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// Waiting for access
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switch (mode) {
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case READ:
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requestReading();
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break;
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case TAKE:
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requestWriting();
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break;
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}
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// Find the tuple in the tuple list
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for (index = 0; index < tuples.size(); index++) {
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if (tuples.get(index).matches(template)) {
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// Tuple matching
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if (timing == eventTiming.IMMEDIATE || knownTuples.isEmpty()) {
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found = true;
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} else {
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for (Tuple knownTuple : knownTuples) {
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if (knownTuple != tuples.get(index)) {
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found = true;
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break;
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}
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}
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}
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// Rebreak to end searching
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if (found) {
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break;
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}
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}
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}
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if (found) {
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// Result found
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switch (mode) {
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case READ:
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// Get it from the tuple list
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result = tuples.get(index);
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break;
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case TAKE:
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// Remove it from the tuple list
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result = tuples.remove(index);
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break;
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}
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}
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// End access
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switch (mode) {
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case READ:
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endReading();
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break;
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case TAKE:
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endWriting();
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break;
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}
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}
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// Callback with the result tuple
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callback.call(result);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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}.start();
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}
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public void debug(String prefix) {
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try {
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// Waiting for reading access
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requestReading();
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System.out.println(prefix + tuples);
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// End reading
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endReading();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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private void requestReading() throws InterruptedException {
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moniteur.lock();
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if (!(!writing && nbWaiting == 0)) {
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nbWaiting++;
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accessDemand.await();
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nbWaiting--;
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}
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nbReaders++;
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accessDemand.signal();
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moniteur.unlock();
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}
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private void endReading() throws InterruptedException {
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moniteur.lock();
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nbReaders--;
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if (nbReaders == 0) {
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if (SASused) {
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SAS.signal();
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} else {
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accessDemand.signal();
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}
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}
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moniteur.unlock();
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}
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private void requestWriting() throws InterruptedException {
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moniteur.lock();
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if (!(!writing && nbReaders == 0 && !SASused && nbWaiting == 0)) {
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nbWaiting++;
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accessDemand.await();
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nbWaiting--;
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}
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if (nbReaders > 0) {
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SASused = true;
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SAS.await();
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SASused = false;
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}
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writing = true;
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moniteur.unlock();
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}
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private void endWriting() throws InterruptedException {
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moniteur.lock();
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writing = false;
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accessDemand.signal();
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moniteur.unlock();
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}
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}
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