itempayloadinternals_p.h

/*
    Copyright (c) 2007 Till Adam <adam@kde.org>

    This library is free software; you can redistribute it and/or modify it
    under the terms of the GNU Library General Public License as published by
    the Free Software Foundation; either version 2 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 Library General Public
    License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to the
    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301, USA.
*/

#ifndef ITEMPAYLOADINTERNALS_P_H
#define ITEMPAYLOADINTERNALS_P_H

#include <kpimutils/supertrait.h>

#include <QtCore/QtGlobal>
#include <QtCore/QSharedPointer>
#include <QtCore/QMetaType>

#include <boost/shared_ptr.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/utility/enable_if.hpp>

#include <typeinfo>

#include "exception.h"

//@cond PRIVATE Doxygen 1.7.1 hangs processing this file. so skip it.
//for more info, see https://bugzilla.gnome.org/show_bug.cgi?id=531637

/* WARNING
 * The below is an implementation detail of the Item class. It is not to be
 * considered public API, and subject to change without notice
 */

namespace Akonadi {
namespace Internal {

template <typename T>
struct has_clone_method {
private:
    template <typename S, S * (S::*)() const> struct sfinae
    {
    };
    struct No
    {
    };
    struct Yes
    {
        No no[2];
    };
    template <typename S> static No  test(...);
    template <typename S> static Yes test(sfinae<S, &S::clone> *);
public:
    static const bool value = sizeof (test<T>(0)) == sizeof (Yes) ;
};

template <typename T, bool b>
struct clone_traits_helper {
    // runtime error (commented in) or compiletime error (commented out)?
    // ### runtime error, until we check has_clone_method in the
    // ### Item::payload<T> impl directly...
    template <typename U>
    static T *clone(U)
    {
        return 0;
    }
};

template <typename T>
struct clone_traits_helper<T, true>
{
    static T *clone(T *t)
    {
        return t ? t->clone() : 0 ;
    }
};

template <typename T>
struct clone_traits : clone_traits_helper<T, has_clone_method<T>::value> {};

template <typename T>
struct shared_pointer_traits
{
    static const bool defined = false;
};

template <typename T>
struct shared_pointer_traits< boost::shared_ptr<T> >
{
    static const bool defined = true;
    typedef T element_type;
    template <typename S>
    struct make {
        typedef boost::shared_ptr<S> type;
    };
    typedef QSharedPointer<T> next_shared_ptr;
};

template <typename T>
struct shared_pointer_traits< QSharedPointer<T> >
{
    static const bool defined = true;
    typedef T element_type;
    template <typename S>
    struct make {
        typedef QSharedPointer<S> type;
    };
    typedef boost::shared_ptr<T> next_shared_ptr;
};

template <typename T>
struct is_shared_pointer
{
    static const bool value = shared_pointer_traits<T>::defined;
};

template <typename T>
struct get_hierarchy_root;

template <typename T, typename S>
struct get_hierarchy_root_recurse
    : get_hierarchy_root<S>
{
};

template <typename T>
struct get_hierarchy_root_recurse<T, T>
    : boost::mpl::identity<T>
{
};

template <typename T>
struct get_hierarchy_root
    : get_hierarchy_root_recurse< T, typename ::KPIMUtils::SuperClass<T>::Type >
{
};

template <typename T>
struct get_hierarchy_root< boost::shared_ptr<T> >
{
    typedef boost::shared_ptr< typename get_hierarchy_root<T>::type > type;
};

template <typename T>
struct get_hierarchy_root< QSharedPointer<T> >
{
    typedef QSharedPointer< typename get_hierarchy_root<T>::type > type;
};

template <typename T> struct PayloadTrait
{
    typedef T ElementType;
    // the metatype id for the element type, or for pointer-to-element
    // type, if in a shared pointer
    static int elementMetaTypeId()
    {
        return qMetaTypeId<T>();
    }
    typedef typename KPIMUtils::SuperClass<T>::Type SuperElementType;
    typedef T Type;
    typedef typename KPIMUtils::SuperClass<T>::Type SuperType;
    static const bool isPolymorphic = false;
    static inline bool isNull(const Type &p)
    {
        Q_UNUSED(p);
        return true;
    }
    template <typename U> static inline Type castFrom(const U &)
    {
        throw PayloadException("you should never get here");
    }
    template <typename U> static inline bool canCastFrom(const U &)
    {
        return false;
    }
    template <typename U> static inline U castTo(const Type &)
    {
        throw PayloadException("you should never get here");
    }
    template <typename U> static T clone(const U &)
    {
        throw PayloadException("clone: you should never get here");
    }
    static const unsigned int sharedPointerId = 0;
};

template <typename T> struct PayloadTrait<boost::shared_ptr<T> >
{
    typedef T ElementType;
    static int elementMetaTypeId()
    {
        return qMetaTypeId<T *>();
    }
    typedef typename KPIMUtils::SuperClass<T>::Type SuperElementType;
    typedef boost::shared_ptr<ElementType> Type;
    typedef boost::shared_ptr<SuperElementType> SuperType;
    static const bool isPolymorphic = !boost::is_same<ElementType, SuperElementType>::value;
    static inline bool isNull(const Type &p)
    {
        return p.get() == 0;
    }
    template <typename U> static inline Type castFrom(const boost::shared_ptr<U> &p)
    {
        const Type sp = boost::dynamic_pointer_cast<T, U>(p);
        if (sp.get() != 0 || p.get() == 0) {
            return sp;
        }
        throw PayloadException("boost::dynamic_pointer_cast failed");
    }
    template <typename U> static inline bool canCastFrom(const boost::shared_ptr<U> &p)
    {
        const Type sp = boost::dynamic_pointer_cast<T, U>(p);
        return sp.get() != 0 || p.get() == 0;
    }
    template <typename U> static inline boost::shared_ptr<U> castTo(const Type &p)
    {
        const boost::shared_ptr<U> sp = boost::dynamic_pointer_cast<U>(p);
        return sp;
    }
    static boost::shared_ptr<T> clone(const QSharedPointer<T> &t) {
        if (T *nt = clone_traits<T>::clone(t.data())) {
            return boost::shared_ptr<T>(nt);
        } else {
            return boost::shared_ptr<T>();
        }
    }
    static const unsigned int sharedPointerId = 1;
};

template <typename T> struct PayloadTrait<QSharedPointer<T> >
{
    typedef T ElementType;
    static int elementMetaTypeId()
    {
        return qMetaTypeId<T *>();
    }
    typedef typename KPIMUtils::SuperClass<T>::Type SuperElementType;
    typedef QSharedPointer<T> Type;
    typedef QSharedPointer<SuperElementType> SuperType;
    static const bool isPolymorphic = !boost::is_same<ElementType, SuperElementType>::value;
    static inline bool isNull(const Type &p)
    {
        return p.isNull();
    }
    template <typename U> static inline Type castFrom(const QSharedPointer<U> &p)
    {
        const Type sp = qSharedPointerDynamicCast<T, U>(p);
        if (!sp.isNull() || p.isNull()) {
            return sp;
        }
        throw PayloadException("qSharedPointerDynamicCast failed");
    }
    template <typename U> static inline bool canCastFrom(const QSharedPointer<U> &p)
    {
        const Type sp = qSharedPointerDynamicCast<T, U>(p);
        return !sp.isNull() || p.isNull();
    }
    template <typename U> static inline QSharedPointer<U> castTo(const Type &p)
    {
        const QSharedPointer<U> sp = qSharedPointerDynamicCast<U, T>(p);
        return sp;
    }
    static QSharedPointer<T> clone(const boost::shared_ptr<T> &t) {
        if (T *nt = clone_traits<T>::clone(t.get())) {
            return QSharedPointer<T>(nt);
        } else {
            return QSharedPointer<T>();
        }
    }
    static const unsigned int sharedPointerId = 2;
};

}

struct PayloadBase
{
    virtual ~PayloadBase()
    {
    }
    virtual PayloadBase *clone() const = 0;
    virtual const char *typeName() const = 0;
};

template <typename T>
struct Payload : public PayloadBase
{
    Payload()
    {
    }
    Payload(const T &p)
        : payload(p)
    {
    }

    PayloadBase *clone() const
    {
        return new Payload<T>(const_cast<Payload<T>* >(this)->payload);
    }

    const char *typeName() const
    {
        return typeid (const_cast<Payload<T>*>(this)).name();
    }

    T payload;
};

template <typename T>
struct Payload<T *> : public PayloadBase
{
};

namespace Internal {

template <typename T> inline Payload<T> *payload_cast(PayloadBase *payloadBase)
{
    Payload<T> *p = dynamic_cast<Payload<T>*>(payloadBase);
    // try harder to cast, workaround for some gcc issue with template instances in multiple DSO's
    if (!p && payloadBase && strcmp(payloadBase->typeName(), typeid (p).name()) == 0) {
        p = static_cast<Payload<T>*>(payloadBase);
    }
    return p;
}

}

}
//@endcond

#endif