AutoPtr.h

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//
// AutoPtr.h
//
// Library: Foundation
// Package: Core
// Module:  AutoPtr
//
// Definition of the AutoPtr template class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
 
 
#ifndef Foundation_AutoPtr_INCLUDED
#define Foundation_AutoPtr_INCLUDED
 
 
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include <algorithm>
#include <cstddef>
 
 
namespace Poco {
 
 
template <class C>
class AutoPtr
    /// AutoPtr is a "smart" pointer for classes implementing
    /// reference counting based garbage collection.
    /// To be usable with the AutoPtr template, a class must
    /// implement the following behaviour:
    /// A class must maintain a reference count.
    /// The constructors of the object initialize the reference
    /// count to one.
    /// The class must implement a public duplicate() method:
    ///     void duplicate();
    /// that increments the reference count by one.
    /// The class must implement a public release() method:
    ///     void release()
    /// that decrements the reference count by one, and,
    /// if the reference count reaches zero, deletes the
    /// object.
    ///
    /// AutoPtr works in the following way:
    /// If an AutoPtr 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 remains unchanged.
    /// If the AutoPtr is assigned another AutoPtr, the
    /// object's reference count is incremented by one by
    /// calling duplicate() on its object.
    /// The destructor of AutoPtr calls release() on its
    /// object.
    /// AutoPtr supports dereferencing with both the ->
    /// and the * operator. An attempt to dereference a null
    /// AutoPtr results in a NullPointerException being thrown.
    /// AutoPtr also implements all relational operators.
    /// Note that AutoPtr allows casting of its encapsulated data types.
{
public:
    AutoPtr(): _ptr(nullptr)
    {
    }
 
    AutoPtr(C* ptr): _ptr(ptr)
    {
    }
 
    AutoPtr(C* ptr, bool shared): _ptr(ptr)
    {
        if (shared && _ptr) _ptr->duplicate();
    }
 
    AutoPtr(const AutoPtr& ptr): _ptr(ptr._ptr)
    {
        if (_ptr) _ptr->duplicate();
    }
 
    AutoPtr(AutoPtr&& ptr) noexcept: _ptr(std::move(ptr._ptr))
    {
        ptr._ptr = nullptr;
    }
 
    template <class Other>
    AutoPtr(const AutoPtr<Other>& ptr): _ptr(const_cast<Other*>(ptr.get()))
    {
        if (_ptr) _ptr->duplicate();
    }
 
    ~AutoPtr()
    {
        if (_ptr) _ptr->release();
    }
 
    AutoPtr& assign(C* ptr)
    {
        if (_ptr != ptr)
        {
            if (_ptr) _ptr->release();
            _ptr = ptr;
        }
        return *this;
    }
 
    AutoPtr& assign(C* ptr, bool shared)
    {
        if (_ptr != ptr)
        {
            if (_ptr) _ptr->release();
            _ptr = ptr;
            if (shared && _ptr) _ptr->duplicate();
        }
        return *this;
    }
 
    AutoPtr& assign(const AutoPtr& ptr)
    {
        if (&ptr != this)
        {
            if (_ptr) _ptr->release();
            _ptr = ptr._ptr;
            if (_ptr) _ptr->duplicate();
        }
        return *this;
    }
 
    template <class Other>
    AutoPtr& assign(const AutoPtr<Other>& ptr)
    {
        if (ptr.get() != _ptr)
        {
            if (_ptr) _ptr->release();
            _ptr = const_cast<Other*>(ptr.get());
            if (_ptr) _ptr->duplicate();
        }
        return *this;
    }
 
    void reset()
    {
        if (_ptr)
        {
            _ptr->release();
            _ptr = nullptr;
        }
    }
 
    void reset(C* ptr)
    {
        assign(ptr);
    }
 
    void reset(C* ptr, bool shared)
    {
        assign(ptr, shared);
    }
 
    void reset(const AutoPtr& ptr)
    {
        assign(ptr);
    }
 
    template <class Other>
    void reset(const AutoPtr<Other>& ptr)
    {
        assign<Other>(ptr);
    }
 
    AutoPtr& operator = (C* ptr)
    {
        return assign(ptr);
    }
 
    AutoPtr& operator = (const AutoPtr& ptr)
    {
        return assign(ptr);
    }
 
    AutoPtr& operator = (AutoPtr&& ptr) noexcept
    {
        if (_ptr) _ptr->release();
        _ptr = ptr._ptr;
        ptr._ptr = nullptr;
        return *this;
    }
 
    template <class Other>
    AutoPtr& operator = (const AutoPtr<Other>& ptr)
    {
        return assign<Other>(ptr);
    }
 
    void swap(AutoPtr& ptr)
    {
        std::swap(_ptr, ptr._ptr);
    }
 
    template <class Other>
    AutoPtr<Other> cast() const
        /// Casts the AutoPtr via a dynamic cast to the given type.
        /// Returns an AutoPtr containing NULL if the cast fails.
        /// Example: (assume class Sub: public Super)
        ///    AutoPtr<Super> super(new Sub());
        ///    AutoPtr<Sub> sub = super.cast<Sub>();
        ///    poco_assert (sub.get());
    {
        Other* pOther = dynamic_cast<Other*>(_ptr);
        return AutoPtr<Other>(pOther, true);
    }
 
    template <class Other>
    AutoPtr<Other> unsafeCast() const
        /// Casts the AutoPtr via a static cast to the given type.
        /// Example: (assume class Sub: public Super)
        ///    AutoPtr<Super> super(new Sub());
        ///    AutoPtr<Sub> sub = super.unsafeCast<Sub>();
        ///    poco_assert (sub.get());
    {
        Other* pOther = static_cast<Other*>(_ptr);
        return AutoPtr<Other>(pOther, true);
    }
 
    C* operator -> ()
    {
        if (_ptr)
            return _ptr;
        else
            throw NullPointerException();
    }
 
    const C* operator -> () const
    {
        if (_ptr)
            return _ptr;
        else
            throw NullPointerException();
    }
 
    C& operator * ()
    {
        if (_ptr)
            return *_ptr;
        else
            throw NullPointerException();
    }
 
    const C& operator * () const
    {
        if (_ptr)
            return *_ptr;
        else
            throw NullPointerException();
    }
 
    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 == nullptr;
    }
 
    bool isNull() const
    {
        return _ptr == nullptr;
    }
 
    C* duplicate()
    {
        if (_ptr) _ptr->duplicate();
        return _ptr;
    }
 
    bool operator == (const AutoPtr& ptr) const
    {
        return _ptr == ptr._ptr;
    }
 
    bool operator == (const C* ptr) const
    {
        return _ptr == ptr;
    }
 
    bool operator == (C* ptr) const
    {
        return _ptr == ptr;
    }
 
    bool operator == (std::nullptr_t ptr) const
    {
        return _ptr == ptr;
    }
 
    bool operator != (const AutoPtr& ptr) const
    {
        return _ptr != ptr._ptr;
    }
 
    bool operator != (const C* ptr) const
    {
        return _ptr != ptr;
    }
 
    bool operator != (C* ptr) const
    {
        return _ptr != ptr;
    }
 
    bool operator != (std::nullptr_t ptr) const
    {
        return _ptr != ptr;
    }
 
    bool operator < (const AutoPtr& ptr) const
    {
        return _ptr < ptr._ptr;
    }
 
    bool operator < (const C* ptr) const
    {
        return _ptr < ptr;
    }
 
    bool operator < (C* ptr) const
    {
        return _ptr < ptr;
    }
 
    bool operator <= (const AutoPtr& ptr) const
    {
        return _ptr <= ptr._ptr;
    }
 
    bool operator <= (const C* ptr) const
    {
        return _ptr <= ptr;
    }
 
    bool operator <= (C* ptr) const
    {
        return _ptr <= ptr;
    }
 
    bool operator > (const AutoPtr& ptr) const
    {
        return _ptr > ptr._ptr;
    }
 
    bool operator > (const C* ptr) const
    {
        return _ptr > ptr;
    }
 
    bool operator > (C* ptr) const
    {
        return _ptr > ptr;
    }
 
    bool operator >= (const AutoPtr& ptr) const
    {
        return _ptr >= ptr._ptr;
    }
 
    bool operator >= (const C* ptr) const
    {
        return _ptr >= ptr;
    }
 
    bool operator >= (C* ptr) const
    {
        return _ptr >= ptr;
    }
 
private:
    C* _ptr;
};
 
 
template <class C>
inline void swap(AutoPtr<C>& p1, AutoPtr<C>& p2)
{
    p1.swap(p2);
}
 
 
template<typename T, typename... Args>
AutoPtr<T> makeAuto(Args&&... args)
{
    return AutoPtr<T>(new T(std::forward<Args>(args)...));
}
 
 
} // namespace Poco
 
 
#endif // Foundation_AutoPtr_INCLUDED