projet-donnees-reparties/linda/shm/CentralizedLinda.java

package linda.shm;

import linda.Callback;
import linda.Linda;
import linda.Tuple;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/** Shared memory implementation of Linda. */
public class CentralizedLinda implements Linda {

    List<Tuple> tuples;

    Lock moniteur;
    Condition accessDemand;
    Condition SAS;

    int nbReaders;
    int nbWaiting;
    boolean writing;
    boolean SASused;

    public CentralizedLinda() {
        nbReaders = 0;
        nbWaiting = 0;
        writing = false;
        SASused = false;
        moniteur = new ReentrantLock();
        accessDemand = moniteur.newCondition();
        SAS = moniteur.newCondition();
        tuples = new ArrayList<Tuple>();
    }

    public void write(Tuple t) {
        try {
            // Wait for writing access
            requestWriting();

            // Add the new tuple
            tuples.add(t);

            // End writing
            endWriting();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public Tuple take(Tuple template) {
        Tuple result = null;
        boolean found = false;
        int index;

        try {

            while (!found) {
                // Wait for writing access
                requestWriting();

                // Find the tuple in the tuple list
                for (index = 0; index < tuples.size(); index++) {
                    if (tuples.get(index).matches(template)) {
                        found = true;
                        break;
                    }
                }

                if (found) {
                    // Result found, remove it from the tuple list
                    result = tuples.remove(index);
                }

                // End writing
                endWriting();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return result;
    }

    public Tuple read(Tuple template) {
        Tuple result = null;
        boolean found = false;
        int index;

        try {
            while (!found) {
                // Waiting for reading access
                requestReading();

                // Find the tuple in the tuple list
                for (index = 0; index < tuples.size(); index++) {
                    if (tuples.get(index).matches(template)) {
                        found = true;
                        break;
                    }
                }

                if (found) {
                    // Result found, get it from the tuple list
                    result = tuples.get(index);
                }

                // End reading
                endReading();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return result;
    }

    public Tuple tryTake(Tuple template) {
        Tuple result = null;
        int index;

        try {
            // Wait for writing access
            requestWriting();

            // Extract the tuple in the tuple list
            for (index = 0; index < tuples.size(); index++) {
                if (tuples.get(index).matches(template)) {
                    result = tuples.remove(index);
                    break;
                }
            }

            // End writing
            endWriting();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return result;
    }

    public Tuple tryRead(Tuple template) {
        Tuple result = null;
        int index;

        try {
            // Waiting for reading access
            requestReading();

            // Find the tuple in the tuple list
            for (index = 0; index < tuples.size(); index++) {
                if (tuples.get(index).matches(template)) {
                    result = tuples.get(index);
                    break;
                }
            }

            // End reading
            endReading();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return result;
    }

    public Collection<Tuple> takeAll(Tuple template) {
        List<Tuple> results = new ArrayList<Tuple>();
        int index;

        try {
            // Wait for writing access
            requestWriting();

            // Extract the tuples in the tuple list
            for (index = 0; index < tuples.size(); index++) {
                if (tuples.get(index).matches(template)) {
                    results.add(tuples.remove(index));
                }
            }

            // End writing
            endWriting();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return results;
    }

    public Collection<Tuple> readAll(Tuple template) {
        List<Tuple> results = new ArrayList<Tuple>();
        int index;

        try {
            // Waiting for reading access
            requestReading();

            // Find the tuples in the tuple list
            for (index = 0; index < tuples.size(); index++) {
                if (tuples.get(index).matches(template)) {
                    results.add(tuples.get(index));
                }
            }

            // End reading
            endReading();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return results;
    }

    public void eventRegister(eventMode mode, eventTiming timing, Tuple template, Callback callback) {
        new Thread() {
            public void run() {
                Tuple result = null;
                boolean found = false;
                int index;

                // Get known tuples for FUTURE timing
                List<Tuple> knownTuples = (List<Tuple>) readAll(template);

                try {
                    while (!found) {
                        // Waiting for reading access
                        requestReading();

                        // Find the tuple in the tuple list
                        for (index = 0; index < tuples.size(); index++) {
                            if (tuples.get(index).matches(template)) {

                                // Tuple matching

                                switch (timing) {
                                    case IMMEDIATE:
                                        // Tuple found
                                        found = true;
                                        break;

                                    case FUTURE:
                                        // Is tuple unknown
                                        for (Tuple knownTuple : knownTuples) {
                                            if (knownTuple != tuples.get(index)) {
                                                found = true;
                                                break;
                                            }
                                        }
                                        break;
                                }

                                // Rebreak to end searching
                                if (found) {
                                    break;
                                }
                            }
                        }

                        if (found) {
                            // Result found
                            switch (mode) {
                                case READ:
                                    // Get it from the tuple list
                                    result = tuples.get(index);
                                    break;

                                case TAKE:
                                    // Remove it from the tuple list
                                    result = tuples.remove(index);
                                    break;
                            }
                        }

                        // End reading
                        endReading();
                    }

                    // Callback with the result tuple
                    callback.call(result);

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }

    public void debug(String prefix) {
        System.out.println(prefix + tuples);
    }

    private void requestReading() throws InterruptedException {
        moniteur.lock();

        if (!(!writing && nbWaiting == 0)) {
            nbWaiting++;
            accessDemand.await();
            nbWaiting--;
        }
        nbReaders++;
        accessDemand.signal();

        moniteur.unlock();
    }

    private void endReading() throws InterruptedException {
        moniteur.lock();

        nbReaders--;
        if (nbReaders == 0) {
            if (SASused) {
                SAS.signal();
            } else {
                accessDemand.signal();
            }
        }

        moniteur.unlock();
    }

    private void requestWriting() throws InterruptedException {
        moniteur.lock();

        if (!(!writing && nbReaders == 0 && !SASused && nbWaiting == 0)) {
            nbWaiting++;
            accessDemand.await();
            nbWaiting--;
        }
        if (nbReaders > 0) {
            SASused = true;
            SAS.await();
            SASused = false;
        }
        writing = true;

        moniteur.unlock();
    }

    private void endWriting() throws InterruptedException {
        moniteur.lock();

        writing = false;
        accessDemand.signal();

        moniteur.unlock();
    }

}