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/************************************************************************
*
* Copyright (C) 2021-2024 IRCAD France
* Copyright (C) 2021 IHU Strasbourg
*
* This file is part of Sight.
*
* Sight 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 3 of the License, or
* (at your option) any later version.
*
* Sight 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 for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Sight. If not, see <https://www.gnu.org/licenses/>.
*
***********************************************************************/
#pragma once
#include <memory>
namespace sight::service
{
class base;
} // namespace sight::service
namespace sight::activity
{
class launcher;
} // namespace sight::activity
namespace sight::data::mt
{
template<class DATATYPE>
class locked_ptr;
/**
* @brief This class holds a non-owning ("weak") reference on a data object.
*
* This class main purpose is to be used as class member to avoid continuous lookup in service tables.
*
* In a `base`, the `weak_ptr` member could be initialized in the `starting()` and then 'locked'
* and used in the `updating()` method. It will spare the lookup, and only lock the data in the `updating()`
* which may have an impact when `updating()` is called very often.
*
* It must be converted to a locked_ptr in order to access the referenced object.
*/
template<class DATATYPE>
class weak_ptr
{
public:
/// Constructor
inline explicit weak_ptr(const std::weak_ptr<DATATYPE>& _data) noexcept :
m_data(_data)
{
}
/// Constructor
inline explicit weak_ptr(const std::shared_ptr<DATATYPE>& _data) noexcept :
m_data(_data)
{
}
/// Constructor
inline explicit weak_ptr(const locked_ptr<DATATYPE>& _data) noexcept :
m_data(_data.get_shared())
{
}
/// Assignment operator
inline weak_ptr& operator=(const std::weak_ptr<DATATYPE>& _data) noexcept
{
m_data = _data;
return *this;
}
/// Assignment operator
inline weak_ptr& operator=(const locked_ptr<DATATYPE>& _data) noexcept
{
m_data = _data.get_shared();
return *this;
}
/// Default constructors, destructor and assignment operators
weak_ptr() = default;
weak_ptr(const weak_ptr&) = default;
weak_ptr(weak_ptr&&) noexcept = default;
weak_ptr& operator=(const weak_ptr&) = default;
weak_ptr& operator=(weak_ptr&&) noexcept = default;
~weak_ptr() = default;
[[nodiscard]] locked_ptr<DATATYPE> lock() const noexcept;
[[nodiscard]] locked_ptr<std::add_const_t<DATATYPE> > const_lock() const noexcept;
/// Returns true if the weak pointer has expired
[[nodiscard]] inline bool expired() const noexcept
{
return m_data.expired();
}
/// Resets the pointer to null
inline void reset() noexcept
{
m_data.reset();
}
/// Convenience function that mimic std::dynamic_pointer_cast()
template<class CASTED_DATATYPE>
inline weak_ptr<CASTED_DATATYPE> dynamic_pointer_cast() const noexcept
{
return weak_ptr<CASTED_DATATYPE>(std::dynamic_pointer_cast<CASTED_DATATYPE>(m_data.lock()));
}
protected:
/// @todo remove me when base will be ready to use lock()
friend class service::base;
/// Convenience getter for weak_ptr
/// @todo remove me when base will be ready to use lock()
[[nodiscard]] inline std::weak_ptr<DATATYPE> get_weak() const noexcept
{
return m_data;
}
/// Convenience getter shared_ptr
/// @todo remove me when base and ObjectService will be ready to use lock()
[[nodiscard]] inline std::shared_ptr<DATATYPE> get_shared() const noexcept
{
return m_data.lock();
}
private:
/// The data to guard
std::weak_ptr<DATATYPE> m_data;
};
//-----------------------------------------------------------------------------
template<class DATATYPE>
inline locked_ptr<DATATYPE> weak_ptr<DATATYPE>::lock() const noexcept
{
return locked_ptr<DATATYPE>(m_data);
}
//-----------------------------------------------------------------------------
template<class DATATYPE>
inline locked_ptr<std::add_const_t<DATATYPE> > weak_ptr<DATATYPE>::const_lock() const noexcept
{
return locked_ptr<std::add_const_t<DATATYPE> >(m_data);
}
//-----------------------------------------------------------------------------
} // namespace sight::data::mt
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