source: Sophya/trunk/SophyaExt/JThreadsC++/Examples/conprod.cc@ 1224

// **********************************************************************
//
// Copyright (c) 2000
// Object Oriented Concepts, Inc.
// Billerica, MA, USA
//
// All Rights Reserved
//
// **********************************************************************

#include <JTC/JTC.h>

#include <stdlib.h>

#ifdef HAVE_STD_IOSTREAM
using namespace std;
#endif

//
// This example is a port of the CubbyHole example in the java tutorial.
// See: http://java.sun.com/tutorial.
//
// This class acts as a cubby hole for producers and consumers.
// A producer may not put another item in the cubby until a consumer
// has retrieved the item.  A consumer may not retrieve an item
// until a producer has placed a new item in the hole.
//
class CubbyHole
{
    bool available_; // Item available?
    int value_; // If so, what is the value of the item?
    int ref_; // Number of times the cubby hole is referenced.
    JTCMonitor mon_; // Associated monitor.

public:

    //
    // Constructor.
    //
    CubbyHole()
        : available_(false), ref_(0)
    {
    }

    //
    // Increment reference count.
    //
    void reference()
    {
        ++ref_;
    }

    //
    // Decrement reference count.  Delete the cubby if the reference
    // count drops to zero.
    //
    void dereference()
    {
        if(--ref_ == 0)
        {
            delete this;
        }
    }

    //
    // Place a new item in the hole.  If the hole is currently
    // occupied, then block until the hole is empty.
    //
    void put(int v, int client)
    {
        JTCSynchronized sync(mon_);

        //
        // Loop while the hole is filled.
        //
        while(available_)
        {
            //
            // Wait to be notified.  The monitor is notified when
            // the hole is filled, or emptied.
            //
            try
            {
                mon_.wait();
            }
            catch(const JTCInterruptedException&)
            {
            }
        }
        //
        // The hole is now filled, with associated value.
        // Wake any waiting consumers.
        //
        available_ = true;
        value_ = v;
        mon_.notifyAll();

        //
        // We put this display in here to avoid problems with
        // corrupting the output stream.
        //
        cout << "Producer #" << client << " put: " << value_ << endl;
    }

    //
    // Retrieve an element store in the cubby hole.  If no element
    // is available for retrieval then wait.
    //
    int get(int client)
    {
        JTCSynchronized sync(mon_);
        //
        // While no element is available for retrieval wait.
        //
        while(!available_)
        {
            try
            {
                mon_.wait();
            }
            catch(const JTCInterruptedException&)
            {
            }
        }
        //
        // Retrieve the element.  Mark the state as "no element available".
        // Notify any waiting producers.
        //
        available_ = false;
        mon_.notifyAll();
        //
        // Display the value while the monitor is still locked, since
        // this will prevent corruption of the output stream.
        //
        cout << "Consumer #" << client << " get: " << value_ << endl;
        
        return value_;
    }
};

//
// This class represents a consumer thread.  This class is responsible
// for retrieving elements from the cubby hole.
//
class Consumer : public JTCThread
{
    CubbyHole* cubby_; // Pointer to the cubby hole.
    int number_; // The client number, for debugging.
public:
    //
    // Constructor.
    //
    Consumer(CubbyHole* c, int which)
        : JTCThread("consumer"), cubby_(c), number_(which)
    {
        cubby_ -> reference();
    }

    //
    // Destructor.
    //
    virtual ~Consumer()
    {
        cubby_ -> dereference();
    }

    //
    // This method is called when start is invoked on the thread.
    //
    virtual void run()
    {
        //
        // Retrieve 10 numbers from the cubby hole.
        //
        for(int i = 0; i < 10; ++i)
        {
            cubby_ -> get(number_);
        }
    }
};

//
// This class represents the producer thread.  This thread places objects
// in the cubbyhole for a consumer to retrieve.
//
class Producer : public JTCThread
{
    CubbyHole* cubby_; // The cubby hole object.
    int number_; // The client number, for debugging.

public:
    //
    // Constructor.
    //
    Producer(CubbyHole* c, int which)
        : JTCThread("producer"), cubby_(c), number_(which)
    {
        cubby_ -> reference();
    }

    //
    // Destructor.
    //
    virtual ~Producer()
    {
        cubby_ -> dereference();
    }

    //
    // This method represents the main loop for this thread.
    // It places 10 numbers in the cubby hole.
    //
    virtual void run()
    {
        for(int i = 0; i < 10; ++i)
        {
            cubby_ -> put(i, number_);
        }
    }
};

int
main(int argc, char** argv)
{
    try
    {
        //
        // A user of the JTC library must create an instance of this
        // class to initialize the library.
        //
        JTCInitialize bootJTC(argc, argv);

        //
        // Create an instance of the CubbyHole class.
        //
        CubbyHole* c = new CubbyHole;

        //
        // Create the producer and the consumer.
        //
        JTCThreadHandle producer = new Producer(c, 0);
        JTCThreadHandle consumer = new Consumer(c, 1);

        //
        // Start the threads.
        //
        producer -> start();

        consumer -> start();
        //
        // The instance of the JTCInitialize class will ensure that
        // this block is not exited until all threads terminate.
        //
    }
    catch(const JTCException& e)
    {
        cerr << "JTCException: " << e.getMessage() << endl;
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}