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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of Qt 3D Studio.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QT3DRENDER_DRAGON_MUTABLE_P_H
#define QT3DRENDER_DRAGON_MUTABLE_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists for the convenience
// of other Qt classes. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <functional>
#include <sstream>
#include <memory>
#include <type_traits>
#include <QDebug>
QT_BEGIN_NAMESPACE
/*!
* The Mutable class is a reference-counting container that invalidates copies when modified.
*
* This class was designed to handle types that are not suitable to be stored in an Immutable
* container, such as OpenGL buffers, textures, and shaders.
* These types are expensive to copy, are referenced in multiple places, and need to be modified.
* However, we do not want objects that can be modified in one place, only to have the changes
* suddenly affect other parts of our code.
* To make sure changes need to be properly propagated throughout the code,
* copies of Mutable objects are invalidated once changed.
*
* TODO: Consider making the Mutable object non-copyable and introduce a MutableReference that is
* read-only.
*/
template <typename T>
struct Mutable
{
Mutable()
: container(std::make_shared<T>())
{
}
// Copy constructors
Mutable(const Mutable<T> &other)
: container(other.container)
{}
Mutable(const T& arg)
: container(std::make_shared<T>(arg))
{
}
// Move constructors
Mutable(Mutable<T> &&other)
: container(std::move(other.container))
{
}
Mutable(T &&value)
: container(std::make_shared<T>(std::forward<T>(value)))
{
}
// Copy assignment
Mutable &operator=(const Mutable<T> &other)
{
container = other.container;
return *this;
}
Mutable &operator=(const T &value)
{
container = std::make_shared<T>(value);
return *this;
}
// Move assignment
// ImmutableResource &operator=(ImmutableResource<T> &&other)
// {
// container = std::make_shared<T>(std::move<std::shared_ptr<T>>(*other.container));
// return *this;
// }
Mutable &operator=(T &&value)
{
container = std::make_shared<T>(std::forward<T>(value));
return *this;
}
const T &operator*() const
{
return *container;
}
// TODO consider using a reference
Mutable<T> take(std::function<T(T)> modifyFunction)
{
Q_ASSERT(*m_valid == true);
Q_ASSERT(container != nullptr);
Mutable<T> result;
result.container = container;
// Make all others know that they have been invalidated
*m_valid = false;
container.reset();
*(result.container) = modifyFunction(std::move(*(result.container)));
return result;
}
const T *operator->() const
{
// Note: These asserts are fine as debug-only as long as this is an internal class.
// However, an exception is also in release builds if this class ever gets promoted
// to a public Qt class. Otherwise, this class serves little purpose.
Q_ASSERT(*m_valid == true);
Q_ASSERT(container != nullptr);
return container.get();
}
bool operator==(const Mutable<T> &other)
{
return *container == *other.container;
}
bool operator!=(const Mutable<T> &other)
{
return *container != *other.container;
}
private:
std::shared_ptr<bool> m_valid = std::make_shared<bool>(true);
std::shared_ptr<T> container;
template<typename U>
friend struct Mutable;
};
QT_END_NAMESPACE
#endif // QT3DRENDER_DRAGON_MUTABLE_P_H
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