source: XMLIO_V2/external/include/Poco/SharedPtr.h @ 80

//
// SharedPtr.h
//
// $Id: //poco/1.3/Foundation/include/Poco/SharedPtr.h#8 $
//
// Library: Foundation
// Package: Core
// Module:  SharedPtr
//
// Definition of the SharedPtr template class.
//
// Copyright (c) 2005-2008, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// 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 PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_SharedPtr_INCLUDED
#define Foundation_SharedPtr_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/AtomicCounter.h"
#include <algorithm>


namespace Poco {


class ReferenceCounter
        /// Simple ReferenceCounter object, does not delete itself when count reaches 0.
{
public:
        ReferenceCounter(): _cnt(1)
        {
        }

        void duplicate()
        {
                ++_cnt;
        }

        int release()
        {
                return --_cnt;
        }
        
        int referenceCount() const
        {
                return _cnt.value();
        }

private:
        AtomicCounter _cnt;
};


template <class C>
class ReleasePolicy
        /// The default release policy for SharedPtr, which
        /// simply uses the delete operator to delete an object.
{
public:
        static void release(C* pObj)
                /// Delete the object.
                /// Note that pObj can be 0.
        {
                delete pObj;
        }
};


template <class C>
class ReleaseArrayPolicy
        /// The release policy for SharedPtr holding arrays.
{
public:
        static void release(C* pObj)
                /// Delete the object.
                /// Note that pObj can be 0.
        {
                delete [] pObj;
        }
};


template <class C, class RC = ReferenceCounter, class RP = ReleasePolicy<C> >
class SharedPtr
        /// SharedPtr is a "smart" pointer for classes implementing
        /// reference counting based garbage collection.
        /// SharedPtr is thus similar to AutoPtr. Unlike the
        /// AutoPtr template, which can only be used with
        /// classes that support reference counting, SharedPtr
        /// can be used with any class. For this to work, a
        /// SharedPtr manages a reference count for the object
        /// it manages.
        /// 
        /// SharedPtr works in the following way:
        /// If an SharedPtr is assigned an ordinary pointer to
        /// an object (via the constructor or the assignment operator),
        /// it takes ownership of the object and the object's reference 
        /// count is initialized to one.
        /// If the SharedPtr is assigned another SharedPtr, the
        /// object's reference count is incremented by one.
        /// The destructor of SharedPtr decrements the object's
        /// reference count by one and deletes the object if the
        /// reference count reaches zero.
        /// SharedPtr supports dereferencing with both the ->
        /// and the * operator. An attempt to dereference a null
        /// SharedPtr results in a NullPointerException being thrown.
        /// SharedPtr also implements all relational operators and
        /// a cast operator in case dynamic casting of the encapsulated data types
        /// is required.
{
public:
        SharedPtr(): _pCounter(new RC), _ptr(0)
        {
        }

        SharedPtr(C* ptr): _pCounter(new RC), _ptr(ptr)
        {
        }

        template <class Other, class OtherRP> 
        SharedPtr(const SharedPtr<Other, RC, OtherRP>& ptr): _pCounter(ptr._pCounter), _ptr(const_cast<Other*>(ptr.get()))
        {
                _pCounter->duplicate();
        }

        SharedPtr(const SharedPtr& ptr): _pCounter(ptr._pCounter), _ptr(ptr._ptr)
        {
                _pCounter->duplicate();
        }

        ~SharedPtr()
        {
                release();
        }

        SharedPtr& assign(C* ptr)
        {
                if (get() != ptr)
                {
                        RC* pTmp = new RC;
                        release();
                        _pCounter = pTmp;
                        _ptr = ptr;
                }
                return *this;
        }
        
        SharedPtr& assign(const SharedPtr& ptr)
        {
                if (&ptr != this)
                {
                        SharedPtr tmp(ptr);
                        swap(tmp);
                }
                return *this;
        }
        
        template <class Other, class OtherRP>
        SharedPtr& assign(const SharedPtr<Other, RC, OtherRP>& ptr)
        {
                if (ptr.get() != _ptr)
                {
                        SharedPtr tmp(ptr);
                        swap(tmp);
                }
                return *this;
        }

        SharedPtr& operator = (C* ptr)
        {
                return assign(ptr);
        }

        SharedPtr& operator = (const SharedPtr& ptr)
        {
                return assign(ptr);
        }

        template <class Other, class OtherRP>
        SharedPtr& operator = (const SharedPtr<Other, RC, OtherRP>& ptr)
        {
                return assign<Other>(ptr);
        }

        void swap(SharedPtr& ptr)
        {
                std::swap(_ptr, ptr._ptr);
                std::swap(_pCounter, ptr._pCounter);
        }

        template <class Other> 
        SharedPtr<Other, RC, RP> cast() const
                /// Casts the SharedPtr via a dynamic cast to the given type.
                /// Returns an SharedPtr containing NULL if the cast fails.
                /// Example: (assume class Sub: public Super)
                ///    SharedPtr<Super> super(new Sub());
                ///    SharedPtr<Sub> sub = super.cast<Sub>();
                ///    poco_assert (sub.get());
        {
                Other* pOther = dynamic_cast<Other*>(_ptr);
                if (pOther)
                        return SharedPtr<Other, RC, RP>(_pCounter, pOther);
                return SharedPtr<Other, RC, RP>();
        }

        template <class Other> 
        SharedPtr<Other, RC, RP> unsafeCast() const
                /// Casts the SharedPtr via a static cast to the given type.
                /// Example: (assume class Sub: public Super)
                ///    SharedPtr<Super> super(new Sub());
                ///    SharedPtr<Sub> sub = super.unsafeCast<Sub>();
                ///    poco_assert (sub.get());
        {
                Other* pOther = static_cast<Other*>(_ptr);
                return SharedPtr<Other, RC, RP>(_pCounter, pOther);
        }

        C* operator -> ()
        {
                return deref();
        }

        const C* operator -> () const
        {
                return deref();
        }

        C& operator * ()
        {
                return *deref();
        }

        const C& operator * () const
        {
                return *deref();
        }

        C* get()
        {
                return _ptr;
        }

        const C* get() const
        {
                return _ptr;
        }

        operator C* ()
        {
                return _ptr;
        }
        
        operator const C* () const
        {
                return _ptr;
        }

        bool operator ! () const
        {
                return _ptr == 0;
        }

        bool isNull() const
        {
                return _ptr == 0;
        }

        bool operator == (const SharedPtr& ptr) const
        {
                return get() == ptr.get();
        }

        bool operator == (const C* ptr) const
        {
                return get() == ptr;
        }

        bool operator == (C* ptr) const
        {
                return get() == ptr;
        }

        bool operator != (const SharedPtr& ptr) const
        {
                return get() != ptr.get();
        }

        bool operator != (const C* ptr) const
        {
                return get() != ptr;
        }

        bool operator != (C* ptr) const
        {
                return get() != ptr;
        }

        bool operator < (const SharedPtr& ptr) const
        {
                return get() < ptr.get();
        }

        bool operator < (const C* ptr) const
        {
                return get() < ptr;
        }

        bool operator < (C* ptr) const
        {
                return get() < ptr;
        }

        bool operator <= (const SharedPtr& ptr) const
        {
                return get() <= ptr.get();
        }

        bool operator <= (const C* ptr) const
        {
                return get() <= ptr;
        }

        bool operator <= (C* ptr) const
        {
                return get() <= ptr;
        }

        bool operator > (const SharedPtr& ptr) const
        {
                return get() > ptr.get();
        }

        bool operator > (const C* ptr) const
        {
                return get() > ptr;
        }

        bool operator > (C* ptr) const
        {
                return get() > ptr;
        }

        bool operator >= (const SharedPtr& ptr) const
        {
                return get() >= ptr.get();
        }

        bool operator >= (const C* ptr) const
        {
                return get() >= ptr;
        }

        bool operator >= (C* ptr) const
        {
                return get() >= ptr;
        }
        
        int referenceCount() const
        {
                return _pCounter->referenceCount();
        }

private:
        C* deref() const
        {
                if (!_ptr)
                        throw NullPointerException();

                return _ptr;
        }

        void release()
        {
                poco_assert_dbg (_pCounter);
                int i = _pCounter->release();
                if (i == 0)
                {
                        RP::release(_ptr);
                        _ptr = 0;

                        delete _pCounter;
                        _pCounter = 0;
                }
        }

        SharedPtr(RC* pCounter, C* ptr): _pCounter(pCounter), _ptr(ptr)
                /// for cast operation
        {
                poco_assert_dbg (_pCounter);
                _pCounter->duplicate();
        }

private:
        RC* _pCounter;
        C*  _ptr;

        template <class OtherC, class OtherRC, class OtherRP> friend class SharedPtr;
};


template <class C, class RC, class RP>
inline void swap(SharedPtr<C, RC, RP>& p1, SharedPtr<C, RC, RP>& p2)
{
        p1.swap(p2);
}


} // namespace Poco


#endif // Foundation_SharedPtr_INCLUDED