smart_i.h

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/** @file
 *  @author Bram de Greve (bramz@users.sourceforge.net)
 *  @author Tom De Muer (tomdemuer@users.sourceforge.net)
 *
 *  *** BEGIN LICENSE INFORMATION ***
 *  
 *  The contents of this file are subject to the Common Public Attribution License 
 *  Version 1.0 (the "License"); you may not use this file except in compliance with 
 *  the License. You may obtain a copy of the License at 
 *  http://lass.sourceforge.net/cpal-license. The License is based on the 
 *  Mozilla Public License Version 1.1 but Sections 14 and 15 have been added to cover 
 *  use of software over a computer network and provide for limited attribution for 
 *  the Original Developer. In addition, Exhibit A has been modified to be consistent 
 *  with Exhibit B.
 *  
 *  Software distributed under the License is distributed on an "AS IS" basis, WITHOUT 
 *  WARRANTY OF ANY KIND, either express or implied. See the License for the specific 
 *  language governing rights and limitations under the License.
 *  
 *  The Original Code is LASS - Library of Assembled Shared Sources.
 *  
 *  The Initial Developer of the Original Code is Bram de Greve and Tom De Muer.
 *  The Original Developer is the Initial Developer.
 *  
 *  All portions of the code written by the Initial Developer are:
 *  Copyright (C) 2004-2007 the Initial Developer.
 *  All Rights Reserved.
 *  
 *  Contributor(s):
 *
 *  Alternatively, the contents of this file may be used under the terms of the 
 *  GNU General Public License Version 2 or later (the GPL), in which case the 
 *  provisions of GPL are applicable instead of those above.  If you wish to allow use
 *  of your version of this file only under the terms of the GPL and not to allow 
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 *  deleting the provisions above and replace them with the notice and other 
 *  provisions required by the GPL License. If you do not delete the provisions above,
 *  a recipient may use your version of this file under either the CPAL or the GPL.
 *  
 *  *** END LICENSE INFORMATION ***
 */

/** @class lass::util::SmartI
 *  @ingroup SmartPtr
 *  @brief smart pointer to COM interfaces
 *  @author Bram de Greve [Bramz]
 *
 *  @section interface_requirements Requirements for COM interface
 *
 *  COM interface @a I must implement two methods @c AddRef() and @c Release():
 *  - @c AddRef() should increase reference count to interface
 *  - @c Release() should decrease reference count
 */

#ifndef LASS_GUARDIAN_OF_INCLUSION_UTIL_SMART_I_H
#define LASS_GUARDIAN_OF_INCLUSION_UTIL_SMART_I_H

#include "util_common.h"
#include "../num/safe_bool.h"

namespace lass
{
namespace util
{

template <typename I>
class SmartI
{
public:


    typedef SmartI<I> TSelf;   /**< type of @c *this */

    typedef I TInterface;
    typedef I* TPointer;
    typedef I** TAddress;

    /** Rebind to another interface type.
     */
    template <typename I>
    struct Rebind
    {
        typedef SmartI<I> Type;
    };



    /** Default constructor initializes to NULL interface.
     */
    SmartI():
        interface_(0)
    {
    }

    /** Constructor won't do an extra AddRef() on construction but will Release() on destruction.
     */
    explicit SmartI(TInterface* iInterface):
        interface_(iInterface)
    {
    }

    /** Copy constructor performs AddRef() on interface.
     */
    SmartI(const TSelf& iOther):
        interface_(iOther.interface_)
    {
        safeAddRef();
    }

    /** Destructor performs Release() on interface.
     */
    ~SmartI()
    {
        safeRelease();
    }

    /** Reinitialize to NULL interface.
     *  Performs Release() on old interface.
     */
    void reset()
    {
        TSelf temp;
        swap(temp);
    }

    /** Reinitialize to an interface, performs no AddRef on new interface, but will Release() it
     *  in destructor.
     *  Performs Release() on old interface.
     */
    void reset(TInterface* iInterface)
    {
        TSelf temp(iInterface);
        swap(temp);
    }

    /** assign the SmartI to another one, performing AddRef() on interface.
     */
    TSelf& operator=(const TSelf& iOther)
    {
        TSelf temp(iOther);
        swap(temp);
        return *this;
    }

    /** return pointer to interface
     */
    TPointer get() const
    {
        return interface_;
    }

    /** access pointee as a pointer
     */
    TPointer operator->() const
    {
        LASS_ASSERT(interface_);
        return interface_;
    }

    /** access address of interface pointer.
     */
    TAddress address()
    {
        return &interface_;
    }

    /** return true if pointer doesn't own any interface.
     *  @return this->get() == 0
     */
    bool isEmpty() const
    {
        return interface_ == 0;
    }

    /** return true if pointer doesn't own any interface (same as isEmpty).
     *  @return this->get() == 0.
     */
    bool operator!() const
    {
        return interface_ == 0;
    }

    /** evaluates to true if pointer owns an interface (only in boolean context)
     *  @return this->get() != 0.
     *  @sa num::SafeBool
     */
    operator num::SafeBool() const
    {
        return interface_ ? num::safeTrue : num::safeFalse;
    }

    /** exchange the pointees (and there reference counts) between two shared pointers
     */
    void swap(TSelf& iOther)
    {
        std::swap(interface_, iOther.interface_);
    }

private:

    void safeAddRef()
    {
        if (interface_)
        {
            interface_->AddRef();
        }
    }

    void safeRelease()
    {
        if (interface_)
        {
            interface_->Release();
            interface_ = 0;
        }
    }

    TPointer interface_;
};

}

}

#endif

// EOF