ClickHouse/base/poco/Foundation/include/Poco/SharedPtr.h

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


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()
    {
        try
        {
            release();
        }
        catch (...)
        {
            poco_unexpected();
        }
    } // NOLINT

    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;
    }

    void reset() { assign(0); }

    void reset(C * ptr) { assign(ptr); }

    void reset(const SharedPtr & ptr) { assign(ptr); }

    template <class Other, class OtherRP>
    void reset(const SharedPtr<Other, RC, OtherRP> & ptr)
    {
        assign<Other, OtherRP>(ptr);
    }

    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