poco/Foundation/include/Poco/SharedPtr.h

423 lines
7.4 KiB
C++

//
// SharedPtr.h
//
// $Id: //poco/1.4/Foundation/include/Poco/SharedPtr.h#1 $
//
// Library: Foundation
// Package: Core
// Module: SharedPtr
//
// Definition of the SharedPtr template class.
//
// Copyright (c) 2005-2008, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#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)
try:
_pCounter(new RC),
_ptr(ptr)
{
}
catch (...)
{
RP::release(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)
{
SharedPtr tmp(ptr);
swap(tmp);
}
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