ResInsight/Fwk/AppFwk/cafProjectDataModel/cafPdmCore/cafPdmPointer.h

//##################################################################################################
//
//   Custom Visualization Core library
//   Copyright (C) 2011-2013 Ceetron AS
//
//   This library may be used under the terms of either the GNU General Public License or
//   the GNU Lesser General Public License as follows:
//
//   GNU General Public License Usage
//   This library is free software: you can redistribute it and/or modify
//   it under the terms of the GNU General Public License as published by
//   the Free Software Foundation, either version 3 of the License, or
//   (at your option) any later version.
//
//   This library is distributed in the hope that it will be useful, but WITHOUT ANY
//   WARRANTY; without even the implied warranty of MERCHANTABILITY or
//   FITNESS FOR A PARTICULAR PURPOSE.
//
//   See the GNU General Public License at <<http://www.gnu.org/licenses/gpl.html>>
//   for more details.
//
//   GNU Lesser General Public License Usage
//   This library is free software; you can redistribute it and/or modify
//   it under the terms of the GNU Lesser General Public License as published by
//   the Free Software Foundation; either version 2.1 of the License, or
//   (at your option) any later version.
//
//   This library is distributed in the hope that it will be useful, but WITHOUT ANY
//   WARRANTY; without even the implied warranty of MERCHANTABILITY or
//   FITNESS FOR A PARTICULAR PURPOSE.
//
//   See the GNU Lesser General Public License at <<http://www.gnu.org/licenses/lgpl-2.1.html>>
//   for more details.
//
//##################################################################################################

#pragma once

#include <cstddef>

namespace caf
{
class PdmObjectHandle;

//==================================================================================================
/// Helper class for the PdmPointer class
/// The add and removing of references is put into a pure static class to
/// resolve circular include problems.
//
/// Overall idea of the referencing system:
/// The addressToObjectPointer is added to a std::set in the object pointed to.
/// when the object pointed to is deleted, its destructor sets the object pointers
/// it has addresses to to NULL
//==================================================================================================

class PdmPointerImpl
{
private:
    template <class T>
    friend class PdmPointer;
    static void addReference( PdmObjectHandle** addressToObjectPointer );
    static void removeReference( PdmObjectHandle** addressToObjectPointer );
};

//==================================================================================================
/// Guarded pointer class to point at PdmObjects
/// Use a PdmPointer<SomePdmObject> in the same way as a normal pointer.
/// The guarding sets the pointer to NULL if the object pointed to dies
///
/// NOTE: This is not reference counting. The user is responsible to delete the objects pointed to.
///       It _can_ be used together with the cvf::ref system if necessary (this is no recommendation)
//==================================================================================================

template <class T>
class PdmPointer
{
    PdmObjectHandle* m_object;

public:
    inline PdmPointer()
        : m_object( nullptr )
    {
    }
    inline PdmPointer( T* p )
        : m_object( p )
    {
        PdmPointerImpl::addReference( &m_object );
    }
    inline PdmPointer( const PdmPointer<T>& p )
        : m_object( p.m_object )
    {
        PdmPointerImpl::addReference( &m_object );
    }
    inline ~PdmPointer() { PdmPointerImpl::removeReference( &m_object ); }

    T*   p() const { return static_cast<T*>( const_cast<PdmObjectHandle*>( m_object ) ); }
    bool isNull() const { return !m_object; }
    bool notNull() const { return !isNull(); }
    operator T*() const { return static_cast<T*>( const_cast<PdmObjectHandle*>( m_object ) ); }
    T&             operator*() const { return *static_cast<T*>( const_cast<PdmObjectHandle*>( m_object ) ); }
    T*             operator->() const { return static_cast<T*>( const_cast<PdmObjectHandle*>( m_object ) ); }
    PdmPointer<T>& operator=( const PdmPointer<T>& p )
    {
        if ( this != &p ) PdmPointerImpl::removeReference( &m_object );
        m_object = p.m_object;
        PdmPointerImpl::addReference( &m_object );
        return *this;
    }
    PdmPointer<T>& operator=( T* p )
    {
        if ( m_object != p ) PdmPointerImpl::removeReference( &m_object );
        m_object = p;
        PdmPointerImpl::addReference( &m_object );
        return *this;
    }
    template <class S>
    bool operator==( const PdmPointer<S>& rhs ) const
    {
        return m_object == rhs.rawPtr();
    }
    // Private methods used by PdmField<T*> and PdmPointersField<T*>. Do not use unless you mean it !
    PdmObjectHandle* rawPtr() const { return m_object; }
    void             setRawPtr( PdmObjectHandle* p )
    {
        if ( m_object != p ) PdmPointerImpl::removeReference( &m_object );
        m_object = p;
        PdmPointerImpl::addReference( &m_object );
    }
};

//==================================================================================================
/// Guarded const pointer to a PdmObject.
///
/// Same lifetime-guarding behavior as PdmPointer<T>, but exposes only const access to the target.
/// Use for non-owning read-only observers (text providers, renderers, part managers) that hold
/// a reference to a logically-const PdmObject. Construction from a const T* does not require
/// the caller to const_cast.
//==================================================================================================

template <class T>
class PdmConstPointer
{
    PdmPointer<T> m_ptr;

public:
    inline PdmConstPointer() = default;
    inline PdmConstPointer( const T* p )
        : m_ptr( const_cast<T*>( p ) )
    {
    }
    inline PdmConstPointer( const PdmConstPointer<T>& p )               = default;
    inline PdmConstPointer<T>& operator=( const PdmConstPointer<T>& p ) = default;

    inline PdmConstPointer( const PdmPointer<T>& p )
        : m_ptr( p )
    {
    }

    const T* p() const { return m_ptr.p(); }
    bool     isNull() const { return m_ptr.isNull(); }
    bool     notNull() const { return m_ptr.notNull(); }
    operator const T*() const { return m_ptr.p(); }
    const T& operator*() const { return *m_ptr.p(); }
    const T* operator->() const { return m_ptr.p(); }

    PdmConstPointer<T>& operator=( const T* p )
    {
        m_ptr = const_cast<T*>( p );
        return *this;
    }

    template <class S>
    bool operator==( const PdmConstPointer<S>& rhs ) const
    {
        return m_ptr.rawPtr() == rhs.rawPtr();
    }

    PdmObjectHandle* rawPtr() const { return m_ptr.rawPtr(); }
};

} // End of namespace caf

#include <QMetaType>
Q_DECLARE_METATYPE( caf::PdmPointer<caf::PdmObjectHandle> );

#include "cafPdmFieldTraits.h"

#include <QVariant>

namespace caf
{

template <typename T>
QVariant pdmToVariant( const PdmPointer<T>& value )
{
    return QVariant::fromValue( PdmPointer<PdmObjectHandle>( value.rawPtr() ) );
}

template <typename T>
void pdmFromVariant( const QVariant& v, PdmPointer<T>& out )
{
    out.setRawPtr( v.value<PdmPointer<PdmObjectHandle>>().rawPtr() );
}

template <typename T>
struct PdmVariantEqualImpl<PdmPointer<T>>
{
    static bool equal( const QVariant& a, const QVariant& b )
    {
        return a.value<PdmPointer<PdmObjectHandle>>() == b.value<PdmPointer<PdmObjectHandle>>();
    }
};

} // namespace caf