datahandle.h 4.08 KB
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// ================================================================================================
// 
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// This file is part of the CAMPVis Software Framework.
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// 
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// If not explicitly stated otherwise: Copyright (C) 2012-2013, all rights reserved,
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//      Christian Schulte zu Berge <christian.szb@in.tum.de>
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//      Chair for Computer Aided Medical Procedures
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//      Technische Universität München
//      Boltzmannstr. 3, 85748 Garching b. München, Germany
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// 
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// For a full list of authors and contributors, please refer to the file "AUTHORS.txt".
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// 
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file 
// except in compliance with the License. You may obtain a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0
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// 
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// Unless required by applicable law or agreed to in writing, software distributed under the 
// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
// either express or implied. See the License for the specific language governing permissions 
// and limitations under the License.
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// 
// ================================================================================================

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#ifndef datahandle_h__
#define datahandle_h__

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#include <ctime>

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namespace campvis {
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    class AbstractData;
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    /**
     * A DataHandle is responsible to manage the lifetime of an AbstractData instance.
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     * Therefore, it implements a reference counting technique in cooperation with AbstractData.
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     * 
     * This class can be considered as thread safe under the following conditions:
     *  * A single DataHandle instance must not be accessed from different threads.
     *  * Concurrent access to the same AbstractData instance via different DataHandles is safe.
     * 
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     * \note    For clarity: An AbstractData instance can be referenced by multiple DataHandles. As soon 
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     *          as it is afterwards reference by 0 DataHandles, the AbstractData instance will be destroyed.
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     *          Also remember that a DataHandle takes ownership of the given AbstractData instance. So do
     *          not delete it once it has been assigned to a DataHandle (respectively DataContainer) or mess
     *          with its reference counting!
     * \note    Reference counting implementation inspired from Scott Meyers: More Effective C++, Item 29
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     */
    class DataHandle {
    public:
        /**
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         * Creates a new DataHandle for the given data.
         * \note    By passing the data to DataHandle you will transfer its ownership to the reference
         *          counting mechanism. Make sure not to interfere with it or delete \a data yourself!
         * \param   data    Data for the DataHandle
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         */
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        explicit DataHandle(AbstractData* data = 0);
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        /**
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         * Copy-constructor
         * \note    If \a rhs is not shareable, this implies a copy of the data!
         * \param   rhs     Source DataHandle
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         */
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        DataHandle(const DataHandle& rhs);
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        /**
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         * Assignment operator
         * \note    If \a rhs is not shareable, this implies a copy of the data!
         * \param   rhs     source DataHandle
         * \return  *this
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         */
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        DataHandle& operator=(const DataHandle& rhs);
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        /**
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         * Destructor, decrease the reference count of the managed AbstractData.
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         */
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        virtual ~DataHandle();
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        /**
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         * Grants const access to the managed AbstractData instance.
         * \return  _data;
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         */
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        const AbstractData* getData() const;
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        /**
         * Gets the timestamp when this data has been created.
         * \return _timestamp
         */
        clock_t getTimestamp() const;

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    private:
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        /**
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         * Initializes the reference counting for the data.
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         */
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        void init();
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        AbstractData* _data;                    ///< managed data
        clock_t _timestamp;                     ///< Timestamp when this data has been created
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    };

}

#endif // datahandle_h__