OpenSpace/include/openspace/util/syncdata.h

/*****************************************************************************************
 *                                                                                       *
 * OpenSpace                                                                             *
 *                                                                                       *
 * Copyright (c) 2014-2016                                                               *
 *                                                                                       *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this  *
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 * without restriction, including without limitation the rights to use, copy, modify,    *
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 * permit persons to whom the Software is furnished to do so, subject to the following   *
 * conditions:                                                                           *
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 * The above copyright notice and this permission notice shall be included in all copies *
 * or substantial portions of the Software.                                              *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,   *
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A         *
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#ifndef __OPENSPACE_CORE___SYNCDATA___H__
#define __OPENSPACE_CORE___SYNCDATA___H__

#include <memory>
#include <mutex>

#include <ghoul/misc/assert.h>
#include <openspace/util/syncbuffer.h>

namespace openspace {

/**
 * Interface for synchronizable data
 *
 * Used by <code>SyncEngine</code>
 */
class Syncable {
public:
    virtual ~Syncable() {};

protected:
    // Allowing SyncEngine synchronization methods and at the same time hiding them
    // from the used of implementations of the interface
    friend class SyncEngine;
    virtual void presync(bool isMaster) {};
    virtual void encode(SyncBuffer* syncBuffer) = 0;
    virtual void decode(SyncBuffer* syncBuffer) = 0;
    virtual void postsync(bool isMaster) {};
};

/**
 * A double buffered implementation of the Syncable interface. 
 * Users are encouraged to used this class as a default way to synchronize different 
 * C++ data types using the <code>SyncEngine</code>
 *
 * This class aims to handle the synchronization parts and yet act like a regular  
 * instance of T. Implicit casts are supported, however, when accessing member functions or
 * or variables, user may have to do explicit casts. 
 *
 * ((T&) t).method();
 *
 */
template<class T>
class SyncData : public Syncable {
public:

    SyncData() {};
    SyncData(const T& val) : data(val) {};
    SyncData(const SyncData<T>& o) : data(o.data) {
        // Should not have to be copied! 
    };

    /**
     * Allowing assignment of data as if
     */
    SyncData& operator=(const T& rhs) {
        data = rhs;
        return *this;
    }

    /**
     * Allow implicit cast to referenced T
     */
    operator T&() {
        return data;
    }

    /**
     * Allow implicit cast to const referenced T
     */
    operator const T&() const {
        return data;
    }

protected:
    virtual void encode(SyncBuffer* syncBuffer) {
        _mutex.lock();
        syncBuffer->encode(data);
        _mutex.unlock();
    }

    virtual void decode(SyncBuffer* syncBuffer) {
        _mutex.lock();
        syncBuffer->decode(doubleBufferedData);
        _mutex.unlock();
    }

    virtual void postsync(bool isMaster) {
        // apply synced update
        if (!isMaster) {
            _mutex.lock();
            data = doubleBufferedData;
            _mutex.unlock();
        }
    };

    T data;
    T doubleBufferedData;
    std::mutex _mutex;

};

} // namespace openspace

#endif // __OPENSPACE_CORE___SYNCDATA___H__