mirror of
https://github.com/pocoproject/poco.git
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423 lines
7.4 KiB
C++
423 lines
7.4 KiB
C++
//
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// SharedPtr.h
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//
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// $Id: //poco/1.4/Foundation/include/Poco/SharedPtr.h#1 $
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//
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// Library: Foundation
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// Package: Core
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// Module: SharedPtr
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//
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// Definition of the SharedPtr template class.
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//
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// Copyright (c) 2005-2008, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_SharedPtr_INCLUDED
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#define Foundation_SharedPtr_INCLUDED
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#include "Poco/Foundation.h"
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#include "Poco/Exception.h"
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#include "Poco/AtomicCounter.h"
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#include <algorithm>
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namespace Poco {
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class ReferenceCounter
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/// Simple ReferenceCounter object, does not delete itself when count reaches 0.
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{
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public:
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ReferenceCounter(): _cnt(1)
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{
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}
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void duplicate()
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{
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++_cnt;
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}
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int release()
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{
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return --_cnt;
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}
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int referenceCount() const
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{
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return _cnt.value();
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}
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private:
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AtomicCounter _cnt;
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};
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template <class C>
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class ReleasePolicy
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/// The default release policy for SharedPtr, which
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/// simply uses the delete operator to delete an object.
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{
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public:
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static void release(C* pObj)
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/// Delete the object.
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/// Note that pObj can be 0.
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{
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delete pObj;
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}
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};
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template <class C>
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class ReleaseArrayPolicy
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/// The release policy for SharedPtr holding arrays.
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{
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public:
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static void release(C* pObj)
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/// Delete the object.
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/// Note that pObj can be 0.
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{
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delete [] pObj;
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}
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};
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template <class C, class RC = ReferenceCounter, class RP = ReleasePolicy<C> >
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class SharedPtr
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/// SharedPtr is a "smart" pointer for classes implementing
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/// reference counting based garbage collection.
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/// SharedPtr is thus similar to AutoPtr. Unlike the
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/// AutoPtr template, which can only be used with
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/// classes that support reference counting, SharedPtr
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/// can be used with any class. For this to work, a
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/// SharedPtr manages a reference count for the object
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/// it manages.
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///
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/// SharedPtr works in the following way:
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/// If an SharedPtr is assigned an ordinary pointer to
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/// an object (via the constructor or the assignment operator),
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/// it takes ownership of the object and the object's reference
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/// count is initialized to one.
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/// If the SharedPtr is assigned another SharedPtr, the
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/// object's reference count is incremented by one.
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/// The destructor of SharedPtr decrements the object's
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/// reference count by one and deletes the object if the
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/// reference count reaches zero.
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/// SharedPtr supports dereferencing with both the ->
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/// and the * operator. An attempt to dereference a null
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/// SharedPtr results in a NullPointerException being thrown.
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/// SharedPtr also implements all relational operators and
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/// a cast operator in case dynamic casting of the encapsulated data types
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/// is required.
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{
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public:
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SharedPtr(): _pCounter(new RC), _ptr(0)
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{
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}
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SharedPtr(C* ptr)
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try:
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_pCounter(new RC),
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_ptr(ptr)
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{
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}
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catch (...)
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{
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RP::release(ptr);
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}
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template <class Other, class OtherRP>
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SharedPtr(const SharedPtr<Other, RC, OtherRP>& ptr): _pCounter(ptr._pCounter), _ptr(const_cast<Other*>(ptr.get()))
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{
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_pCounter->duplicate();
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}
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SharedPtr(const SharedPtr& ptr): _pCounter(ptr._pCounter), _ptr(ptr._ptr)
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{
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_pCounter->duplicate();
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}
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~SharedPtr()
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{
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release();
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}
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SharedPtr& assign(C* ptr)
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{
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if (get() != ptr)
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{
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SharedPtr tmp(ptr);
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swap(tmp);
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}
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return *this;
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}
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SharedPtr& assign(const SharedPtr& ptr)
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{
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if (&ptr != this)
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{
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SharedPtr tmp(ptr);
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swap(tmp);
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}
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return *this;
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}
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template <class Other, class OtherRP>
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SharedPtr& assign(const SharedPtr<Other, RC, OtherRP>& ptr)
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{
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if (ptr.get() != _ptr)
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{
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SharedPtr tmp(ptr);
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swap(tmp);
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}
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return *this;
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}
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SharedPtr& operator = (C* ptr)
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{
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return assign(ptr);
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}
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SharedPtr& operator = (const SharedPtr& ptr)
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{
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return assign(ptr);
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}
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template <class Other, class OtherRP>
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SharedPtr& operator = (const SharedPtr<Other, RC, OtherRP>& ptr)
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{
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return assign<Other>(ptr);
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}
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void swap(SharedPtr& ptr)
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{
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std::swap(_ptr, ptr._ptr);
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std::swap(_pCounter, ptr._pCounter);
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}
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template <class Other>
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SharedPtr<Other, RC, RP> cast() const
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/// Casts the SharedPtr via a dynamic cast to the given type.
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/// Returns an SharedPtr containing NULL if the cast fails.
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/// Example: (assume class Sub: public Super)
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/// SharedPtr<Super> super(new Sub());
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/// SharedPtr<Sub> sub = super.cast<Sub>();
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/// poco_assert (sub.get());
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{
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Other* pOther = dynamic_cast<Other*>(_ptr);
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if (pOther)
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return SharedPtr<Other, RC, RP>(_pCounter, pOther);
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return SharedPtr<Other, RC, RP>();
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}
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template <class Other>
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SharedPtr<Other, RC, RP> unsafeCast() const
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/// Casts the SharedPtr via a static cast to the given type.
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/// Example: (assume class Sub: public Super)
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/// SharedPtr<Super> super(new Sub());
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/// SharedPtr<Sub> sub = super.unsafeCast<Sub>();
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/// poco_assert (sub.get());
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{
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Other* pOther = static_cast<Other*>(_ptr);
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return SharedPtr<Other, RC, RP>(_pCounter, pOther);
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}
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C* operator -> ()
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{
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return deref();
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}
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const C* operator -> () const
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{
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return deref();
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}
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C& operator * ()
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{
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return *deref();
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}
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const C& operator * () const
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{
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return *deref();
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}
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C* get()
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{
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return _ptr;
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}
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const C* get() const
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{
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return _ptr;
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}
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operator C* ()
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{
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return _ptr;
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}
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operator const C* () const
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{
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return _ptr;
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}
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bool operator ! () const
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{
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return _ptr == 0;
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}
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bool isNull() const
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{
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return _ptr == 0;
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}
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bool operator == (const SharedPtr& ptr) const
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{
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return get() == ptr.get();
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}
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bool operator == (const C* ptr) const
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{
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return get() == ptr;
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}
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bool operator == (C* ptr) const
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{
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return get() == ptr;
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}
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bool operator != (const SharedPtr& ptr) const
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{
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return get() != ptr.get();
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}
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bool operator != (const C* ptr) const
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{
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return get() != ptr;
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}
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bool operator != (C* ptr) const
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{
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return get() != ptr;
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}
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bool operator < (const SharedPtr& ptr) const
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{
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return get() < ptr.get();
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}
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bool operator < (const C* ptr) const
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{
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return get() < ptr;
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}
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bool operator < (C* ptr) const
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{
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return get() < ptr;
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}
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bool operator <= (const SharedPtr& ptr) const
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{
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return get() <= ptr.get();
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}
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bool operator <= (const C* ptr) const
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{
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return get() <= ptr;
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}
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bool operator <= (C* ptr) const
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{
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return get() <= ptr;
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}
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bool operator > (const SharedPtr& ptr) const
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{
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return get() > ptr.get();
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}
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bool operator > (const C* ptr) const
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{
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return get() > ptr;
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}
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bool operator > (C* ptr) const
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{
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return get() > ptr;
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}
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bool operator >= (const SharedPtr& ptr) const
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{
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return get() >= ptr.get();
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}
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bool operator >= (const C* ptr) const
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{
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return get() >= ptr;
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}
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bool operator >= (C* ptr) const
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{
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return get() >= ptr;
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}
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int referenceCount() const
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{
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return _pCounter->referenceCount();
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}
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private:
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C* deref() const
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{
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if (!_ptr)
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throw NullPointerException();
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return _ptr;
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}
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void release()
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{
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poco_assert_dbg (_pCounter);
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int i = _pCounter->release();
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if (i == 0)
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{
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RP::release(_ptr);
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_ptr = 0;
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delete _pCounter;
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_pCounter = 0;
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}
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}
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SharedPtr(RC* pCounter, C* ptr): _pCounter(pCounter), _ptr(ptr)
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/// for cast operation
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{
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poco_assert_dbg (_pCounter);
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_pCounter->duplicate();
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}
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private:
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RC* _pCounter;
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C* _ptr;
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template <class OtherC, class OtherRC, class OtherRP> friend class SharedPtr;
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};
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template <class C, class RC, class RP>
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inline void swap(SharedPtr<C, RC, RP>& p1, SharedPtr<C, RC, RP>& p2)
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{
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p1.swap(p2);
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}
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} // namespace Poco
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#endif // Foundation_SharedPtr_INCLUDED
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