ownership.cpp

Ownership example application.

This example illustrates how to use ownership of attributes in GizmoDistribution. Two clients request ownership and try to update attributes on objects. Only the current owner will succeed in updating attributes.

The source code can also be found in the examples directory of the GizmoDistribution installation.

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//*****************************************************************************
// File         : ownership.cpp
// Module       : ownership
// Description  : ownership (example application)
// Author       : Anders Sandblad       
// Product      : GizmoDistribution
//      
// Copyright © 2004- Saab Training Systems AB, Sweden
//          
// NOTE:    GizmoDistribution is a toolkit used for implementing distributed 
//          objects and events in C++
//
//
// Revision History...                          
//                                  
// Who  Date    Description                     
//                                  
// XAA  040421  Created file    
//
//*****************************************************************************

// Includes
#include <stdio.h>
#include "gzBaseLibrary.h"
#include "gzDistLibrary.h"


// Common constants
static const gzString EXAMPLE_SESSION = "EXAMPLE_SESSION";
static const gzString EXAMPLE_ATTRIBUTE = "EXAMPLE_ATTRIB";
static const gzString NAME_A = "A";
static const gzString NAME_B = "B";
static const gzString CLIENT_PREFIX = "CLIENT_";
static const gzString OBJECT_PREFIX = "OBJECT_";


//-----------------------------------------------------------------------------

// Example owner client
class Client : public gzDistClientInterface
{
    public:

        Client(const gzString& name);

        virtual ~Client();


    private:

        // callbacks

        gzVoid onClientTick();

        gzVoid onNewObject(gzDistObject* object, gzDistSession* session);

        gzVoid onRemoveObject(gzDistObject* object, gzDistSession* session);

        gzVoid onUpdateAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session);

        gzVoid onGrantOwnership(const gzString& attributeName, gzDistObject* object, gzDistSession* session);

        gzVoid onDropOwnership(const gzString& attributeName, gzDistObject* object, gzDistSession* session);

        gzVoid onRequestOwnership(const gzString& attributeName, gzDistObject* object, const gzDistClientID& requester, gzDistSession* session);

        gzVoid onSystemShutdown();


    private:

        // members

        gzDistSessionPtr m_session;

        gzRefList<gzDistObject> m_objects;

        gzULong m_tickCount;

};


Client::Client(const gzString& name)
 :  gzDistClientInterface(CLIENT_PREFIX + name),
    m_tickCount(0)
{
    // initialize client
    initialize(2);

    // create and join session
    m_session = getSession(EXAMPLE_SESSION, TRUE);
    joinSession(m_session);

    // subscribe for objects
    subscribeObjects(gzDistObject::getClassType(), m_session, TRUE);

    // add an object using my own name
    gzDistObjectPtr object = new gzDistObject(OBJECT_PREFIX + name);
    object->setAttributeValue(EXAMPLE_ATTRIBUTE, GZ_EMPTY_STRING);
    addObject(object, m_session);

}


Client::~Client()
{
    // unsubscribe objects
    unsubscribeObjects(gzDistObject::getClassType(), m_session);

    // resign the session
    resignSession(m_session);

    // uninitialize client
    uninitialize();
}


gzVoid Client::onClientTick()
{
    gzListIterator<gzDistObject> iter(m_objects);
    gzDistObject* object;
    
    while (object = iter())
    {
        if (!updateObject(EXAMPLE_ATTRIBUTE, getID().name + gzString(m_tickCount), object, GZ_DIST_SYNCHRONOUS))
        {
            GZMESSAGE(GZ_MESSAGE_NOTICE, "'%s' failed to update '%s' on '%s'",
                        (const char*)getID().name, (const char*)EXAMPLE_ATTRIBUTE, (const char*)object->getName());
        }

        if (!object->isOwnerOf(EXAMPLE_ATTRIBUTE, getID()))
        {
            requestOwnership(EXAMPLE_ATTRIBUTE, object);
        }

    }

    ++m_tickCount;

}


gzVoid Client::onNewObject(gzDistObject* object, gzDistSession* session)
{
    m_objects.insert(object);

    if (object->getName() == getID().name)
    {
        requestOwnership(EXAMPLE_ATTRIBUTE, object);
        subscribeAttributeValue(EXAMPLE_ATTRIBUTE, object);
    }
}


gzVoid Client::onRemoveObject(gzDistObject* object, gzDistSession* session)
{
    m_objects.remove(object);
}


gzVoid Client::onUpdateAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session)
{
    gzDistNotificationSetIterator iter(attributes);
    gzDistNotificationData* data;

    while (data = iter())
    {
        GZMESSAGE(GZ_MESSAGE_NOTICE, "'%s' on '%s' was updated to '%s'",
                    (const char*)data->getAttributeName(), (const char*)object->getName(),
                    (const char*)data->getAttributeValue().getString());
    }
    
}

        
gzVoid Client::onGrantOwnership(const gzString& attributeName, gzDistObject* object, gzDistSession* session)
{
    // ownership was granted
    GZMESSAGE(GZ_MESSAGE_NOTICE, "Ownership of '%s' on '%s' was granted to '%s'",
                (const char*)attributeName, (const char*)object->getName(), (const char*)getID().name);
}


gzVoid Client::onDropOwnership(const gzString& attributeName, gzDistObject* object, gzDistSession* session)
{
    // ownership was dropped
    GZMESSAGE(GZ_MESSAGE_NOTICE, "'%s' dropped ownership of '%s' on '%s'",
                (const char*)getID().name, (const char*)attributeName, (const char*)object->getName());
}


gzVoid Client::onRequestOwnership(const gzString& attributeName, gzDistObject* object, const gzDistClientID& requester, gzDistSession* session)
{
    // someone has requested ownership of my attribute
    GZMESSAGE(GZ_MESSAGE_NOTICE, "'%s' requested ownership of '%s' on '%s'",
                (const char*)requester.name, (const char*)attributeName, (const char*)object->getName());
}


gzVoid Client::onSystemShutdown()
{
    // in case of pre-mature shutdown
    m_objects.clear();
    m_session = NULL;   
}


//-----------------------------------------------------------------------------

// Application entry point
int main(int argc, char* argv[])
{
    // setup default message receiver
    gzMessage::setMessageLevel(GZ_MESSAGE_NOTICE);

    // create manager and start
    gzDistManagerPtr manager = gzDistManager::getManager(TRUE);
    manager->start();

    GZMESSAGE(GZ_MESSAGE_NOTICE, "Hit return to quit!\n");
    
    // create clients
    gzDistClientInterface* clientA = new Client(NAME_A);
    gzDistClientInterface* clientB = new Client(NAME_B);


    // wait for return
    getchar();
    

    // delete clients
    delete clientA;
    delete clientB;

    // shut down and release manager
    manager->shutDown();
    manager = NULL;

    gzSleep(GZ_SLEEP_SECOND);

    return 0;

}

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