delibs/decpp/deSharedPtr.hpp

#ifndef _DESHAREDPTR_HPP
#define _DESHAREDPTR_HPP
/*-------------------------------------------------------------------------
 * drawElements C++ Base Library
 * -----------------------------
 *
 * Copyright 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *//*!
 * \file
 * \brief Shared pointer.
 *//*--------------------------------------------------------------------*/

#include "deDefs.hpp"
#include "deAtomic.h"

#include <exception>
#include <algorithm>

namespace de
{

//! Shared pointer self-test.
void SharedPtr_selfTest (void);

class DeadReferenceException : public std::exception
{
public:
				DeadReferenceException	(void) throw()
		: std::exception()
	{
	}

	const char*	what					(void) const throw()
	{
		return "DeadReferenceException";
	}
};

struct SharedPtrStateBase
{
	SharedPtrStateBase (void)
		: strongRefCount	(0)
		, weakRefCount		(0)
	{
	}

	virtual				~SharedPtrStateBase	(void) throw() {}
	virtual void		deletePtr			(void) throw() = 0;

	volatile deInt32	strongRefCount;
	volatile deInt32	weakRefCount;		//!< WeakPtr references + StrongPtr references.
};

template<typename Type, typename Deleter>
struct SharedPtrState : public SharedPtrStateBase
{
	SharedPtrState (Type* ptr, Deleter deleter)
		: m_ptr		(ptr)
		, m_deleter	(deleter)
	{
	}

	virtual ~SharedPtrState (void) throw()
	{
		DE_ASSERT(!m_ptr);
	}

	virtual void deletePtr (void) throw()
	{
		m_deleter(m_ptr);
		m_ptr = DE_NULL;
	}

private:
	Type*		m_ptr;
	Deleter		m_deleter;
};

template<typename T>
class SharedPtr;

template<typename T>
class WeakPtr;

/*--------------------------------------------------------------------*//*!
 * \brief Shared pointer
 *
 * SharedPtr is smart pointer for managing shared ownership to a pointer.
 * Multiple SharedPtrs can maintain ownership to the pointer and it is
 * destructed when last SharedPtr is destroyed.
 *
 * SharedPtr can also be NULL.
 *//*--------------------------------------------------------------------*/
template<typename T>
class SharedPtr
{
public:
								SharedPtr			(void);
								SharedPtr			(const SharedPtr<T>& other);
	explicit					SharedPtr			(T* ptr);

	template<typename Deleter>
								SharedPtr			(T* ptr, Deleter deleter);

	template<typename Y>
	explicit					SharedPtr			(const SharedPtr<Y>& other);

	template<typename Y>
	explicit					SharedPtr			(const WeakPtr<Y>& other);

								~SharedPtr			(void);

	template<typename Y>
	SharedPtr&					operator=			(const SharedPtr<Y>& other);
	SharedPtr&					operator=			(const SharedPtr<T>& other);

	template<typename Y>
	SharedPtr&					operator=			(const WeakPtr<Y>& other);

	T*							get					(void) const throw() { return m_ptr;	}	//!< Get stored pointer.
	T*							operator->			(void) const throw() { return m_ptr;	}	//!< Get stored pointer.
	T&							operator*			(void) const throw() { return *m_ptr;	}	//!< De-reference pointer.

	operator					bool				(void) const throw() { return !!m_ptr;	}

	void						swap				(SharedPtr<T>& other);

	void						clear				(void);

	template<typename Y>
	operator SharedPtr<Y>		(void) const;

private:
	void						acquire				(void);
	void						acquireFromWeak		(const WeakPtr<T>& other);
	void						release				(void);

	T*							m_ptr;
	SharedPtrStateBase*			m_state;

	friend class WeakPtr<T>;

	template<typename U>
	friend class SharedPtr;
};

/*--------------------------------------------------------------------*//*!
 * \brief Weak pointer
 *
 * WeakPtr manages weak references to objects owned by SharedPtr. Shared
 * pointer can be converted to weak pointer and vice versa. Weak pointer
 * differs from SharedPtr by not affecting the lifetime of the managed
 * object.
 *
 * WeakPtr can be converted back to SharedPtr but that operation can fail
 * if the object is no longer live. In such case DeadReferenceException
 * will be thrown.
 *//*--------------------------------------------------------------------*/
template<typename T>
class WeakPtr
{
public:
						WeakPtr		(void);
						WeakPtr		(const WeakPtr<T>& other);

	explicit			WeakPtr		(const SharedPtr<T>& other);
						~WeakPtr	(void);

	WeakPtr&			operator=	(const WeakPtr<T>& other);
	WeakPtr&			operator=	(const SharedPtr<T>& other);

	SharedPtr<T>		lock		(void);

private:
	void				acquire		(void);
	void				release		(void);

	T*					m_ptr;
	SharedPtrStateBase*	m_state;

	friend class SharedPtr<T>;
};

// SharedPtr template implementation.

/*--------------------------------------------------------------------*//*!
 * \brief Construct empty shared pointer.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline SharedPtr<T>::SharedPtr (void)
	: m_ptr		(DE_NULL)
	, m_state	(DE_NULL)
{
}

/*--------------------------------------------------------------------*//*!
 * \brief Construct shared pointer from pointer.
 * \param ptr Pointer to be managed.
 *
 * Ownership of the pointer will be transferred to SharedPtr and future
 * SharedPtr's initialized or assigned from this SharedPtr.
 *
 * If allocation of shared state fails. The "ptr" argument will not be
 * released.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline SharedPtr<T>::SharedPtr (T* ptr)
	: m_ptr		(DE_NULL)
	, m_state	(DE_NULL)
{
	try
	{
		m_ptr	= ptr;
		m_state	= new SharedPtrState<T, DefaultDeleter<T> >(ptr, DefaultDeleter<T>());
		m_state->strongRefCount	= 1;
		m_state->weakRefCount	= 1;
	}
	catch (...)
	{
		// \note ptr is not released.
		delete m_state;
		throw;
	}
}

/*--------------------------------------------------------------------*//*!
 * \brief Construct shared pointer from pointer.
 * \param ptr Pointer to be managed.
 *
 * Ownership of the pointer will be transferred to SharedPtr and future
 * SharedPtr's initialized or assigned from this SharedPtr.
 *
 * Deleter must be callable type and deleter is called with the pointer
 * argument when the reference count becomes 0.
 *
 * If allocation of shared state fails. The "ptr" argument will not be
 * released.
 *
 * Calling deleter or calling destructor for deleter should never throw.
 *//*--------------------------------------------------------------------*/
template<typename T>
template<typename Deleter>
inline SharedPtr<T>::SharedPtr (T* ptr, Deleter deleter)
	: m_ptr		(DE_NULL)
	, m_state	(DE_NULL)
{
	try
	{
		m_ptr	= ptr;
		m_state	= new SharedPtrState<T, Deleter>(ptr, deleter);
		m_state->strongRefCount	= 1;
		m_state->weakRefCount	= 1;
	}
	catch (...)
	{
		// \note ptr is not released.
		delete m_state;
		throw;
	}
}

/*--------------------------------------------------------------------*//*!
 * \brief Initialize shared pointer from another SharedPtr.
 * \param other Pointer to be shared.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline SharedPtr<T>::SharedPtr (const SharedPtr<T>& other)
	: m_ptr		(other.m_ptr)
	, m_state	(other.m_state)
{
	acquire();
}

/*--------------------------------------------------------------------*//*!
 * \brief Initialize shared pointer from another SharedPtr.
 * \param other Pointer to be shared.
 *
 * Y* must be convertible to T*.
 *//*--------------------------------------------------------------------*/
template<typename T>
template<typename Y>
inline SharedPtr<T>::SharedPtr (const SharedPtr<Y>& other)
	: m_ptr		(other.m_ptr)
	, m_state	(other.m_state)
{
	acquire();
}

/*--------------------------------------------------------------------*//*!
 * \brief Initialize shared pointer from weak reference.
 * \param other Pointer to be shared.
 *
 * Y* must be convertible to T*.
 *//*--------------------------------------------------------------------*/
template<typename T>
template<typename Y>
inline SharedPtr<T>::SharedPtr (const WeakPtr<Y>& other)
	: m_ptr		(DE_NULL)
	, m_state	(DE_NULL)
{
	acquireFromWeak(other);
}

template<typename T>
inline SharedPtr<T>::~SharedPtr (void)
{
	release();
}

/*--------------------------------------------------------------------*//*!
 * \brief Assign from other shared pointer.
 * \param other Pointer to be shared.
 * \return Reference to this SharedPtr.
 *
 * Reference to current pointer is released and reference to new pointer is
 * acquired.
 *
 * Y* must be convertible to T*.
 *//*--------------------------------------------------------------------*/
template<typename T>
template<typename Y>
inline SharedPtr<T>& SharedPtr<T>::operator= (const SharedPtr<Y>& other)
{
	if (m_state == other.m_state)
		return *this;

	// Release current reference.
	release();

	// Copy from other and acquire reference.
	m_ptr	= other.m_ptr;
	m_state	= other.m_state;

	acquire();

	return *this;
}

/*--------------------------------------------------------------------*//*!
 * \brief Assign from other shared pointer.
 * \param other Pointer to be shared.
 * \return Reference to this SharedPtr.
 *
 * Reference to current pointer is released and reference to new pointer is
 * acquired.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline SharedPtr<T>& SharedPtr<T>::operator= (const SharedPtr<T>& other)
{
	if (m_state == other.m_state)
		return *this;

	// Release current reference.
	release();

	// Copy from other and acquire reference.
	m_ptr	= other.m_ptr;
	m_state	= other.m_state;

	acquire();

	return *this;
}

/*--------------------------------------------------------------------*//*!
 * \brief Assign from weak pointer.
 * \param other Weak reference.
 * \return Reference to this SharedPtr.
 *
 * Tries to acquire reference to WeakPtr, releases current reference and
 * holds reference to new pointer.
 *
 * If WeakPtr can't be acquired, throws DeadReferenceException and doesn't
 * release the current reference.
 *
 * If WeakPtr references same pointer as SharedPtr this call will always
 * succeed.
 *
 * Y* must be convertible to T*.
 *//*--------------------------------------------------------------------*/
template<typename T>
template<typename Y>
inline SharedPtr<T>& SharedPtr<T>::operator= (const WeakPtr<Y>& other)
{
	if (m_state == other.m_state)
		return *this;

	{
		SharedPtr<T> sharedOther(other);
		*this = other;
	}

	return *this;
}

/*--------------------------------------------------------------------*//*!
 * \brief Type conversion operator.
 *
 * T* must be convertible to Y*.
 *//*--------------------------------------------------------------------*/
template<class T>
template<typename Y>
inline SharedPtr<T>::operator SharedPtr<Y> (void) const
{
	return SharedPtr<Y>(*this);
}

/*--------------------------------------------------------------------*//*!
 * \brief Compare pointers.
 * \param a A
 * \param b B
 * \return true if A and B point to same object, false otherwise.
 *//*--------------------------------------------------------------------*/
template<class T, class U>
inline bool operator== (const SharedPtr<T>& a, const SharedPtr<U>& b) throw()
{
	return a.get() == b.get();
}

/*--------------------------------------------------------------------*//*!
 * \brief Compare pointers.
 * \param a A
 * \param b B
 * \return true if A and B point to different objects, false otherwise.
 *//*--------------------------------------------------------------------*/
template<class T, class U>
inline bool operator!= (const SharedPtr<T>& a, const SharedPtr<U>& b) throw()
{
	return a.get() != b.get();
}

/** Swap pointer contents. */
template<typename T>
inline void SharedPtr<T>::swap (SharedPtr<T>& other)
{
	using std::swap;
	swap(m_ptr,		other.m_ptr);
	swap(m_state,	other.m_state);
}

/** Swap operator for SharedPtr's. */
template<typename T>
inline void swap (SharedPtr<T>& a, SharedPtr<T>& b)
{
	a.swap(b);
}

/*--------------------------------------------------------------------*//*!
 * \brief Set pointer to null.
 *
 * clear() removes current reference and sets pointer to null value.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline void SharedPtr<T>::clear (void)
{
	release();
	m_ptr	= DE_NULL;
	m_state	= DE_NULL;
}

template<typename T>
inline void SharedPtr<T>::acquireFromWeak (const WeakPtr<T>& weakRef)
{
	DE_ASSERT(!m_ptr && !m_state);

	SharedPtrStateBase* state = weakRef.m_state;

	if (!state)
		return; // Empty reference.

	{
		deInt32 oldCount, newCount;

		// Do atomic compare and increment.
		do
		{
			oldCount = state->strongRefCount;
			if (oldCount == 0)
				throw DeadReferenceException();
			newCount = oldCount+1;
		} while (deAtomicCompareExchange32((deUint32 volatile*)&state->strongRefCount, (deUint32)oldCount, (deUint32)newCount) != (deUint32)oldCount);

		deAtomicIncrement32(&state->weakRefCount);
	}

	m_ptr	= weakRef.m_ptr;
	m_state	= state;
}

template<typename T>
inline void SharedPtr<T>::acquire (void)
{
	if (m_state)
	{
		deAtomicIncrement32(&m_state->strongRefCount);
		deAtomicIncrement32(&m_state->weakRefCount);
	}
}

template<typename T>
inline void SharedPtr<T>::release (void)
{
	if (m_state)
	{
		if (deAtomicDecrement32(&m_state->strongRefCount) == 0)
		{
			m_ptr = DE_NULL;
			m_state->deletePtr();
		}

		if (deAtomicDecrement32(&m_state->weakRefCount) == 0)
		{
			delete m_state;
			m_state = DE_NULL;
		}
	}
}

// WeakPtr template implementation.

/*--------------------------------------------------------------------*//*!
 * \brief Construct empty weak pointer.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline WeakPtr<T>::WeakPtr (void)
	: m_ptr		(DE_NULL)
	, m_state	(DE_NULL)
{
}

/*--------------------------------------------------------------------*//*!
 * \brief Construct weak pointer from other weak reference.
 * \param other Weak reference.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline WeakPtr<T>::WeakPtr (const WeakPtr<T>& other)
	: m_ptr		(other.m_ptr)
	, m_state	(other.m_state)
{
	acquire();
}

/*--------------------------------------------------------------------*//*!
 * \brief Construct weak pointer from shared pointer.
 * \param other Shared pointer.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline WeakPtr<T>::WeakPtr (const SharedPtr<T>& other)
	: m_ptr		(other.m_ptr)
	, m_state	(other.m_state)
{
	acquire();
}

template<typename T>
inline WeakPtr<T>::~WeakPtr (void)
{
	release();
}

/*--------------------------------------------------------------------*//*!
 * \brief Assign from another weak pointer.
 * \param other Weak reference.
 * \return Reference to this WeakPtr.
 *
 * The current weak reference is removed first and then a new weak reference
 * to the object pointed by other is taken.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline WeakPtr<T>& WeakPtr<T>::operator= (const WeakPtr<T>& other)
{
	if (this == &other)
		return *this;

	release();

	m_ptr	= other.m_ptr;
	m_state	= other.m_state;

	acquire();

	return *this;
}

/*--------------------------------------------------------------------*//*!
 * \brief Assign from shared pointer.
 * \param other Shared pointer.
 * \return Reference to this WeakPtr.
 *
 * The current weak reference is removed first and then a new weak reference
 * to the object pointed by other is taken.
 *//*--------------------------------------------------------------------*/
template<typename T>
inline WeakPtr<T>& WeakPtr<T>::operator= (const SharedPtr<T>& other)
{
	release();

	m_ptr	= other.m_ptr;
	m_state	= other.m_state;

	acquire();

	return *this;
}

template<typename T>
inline void WeakPtr<T>::acquire (void)
{
	if (m_state)
		deAtomicIncrement32(&m_state->weakRefCount);
}

template<typename T>
inline void WeakPtr<T>::release (void)
{
	if (m_state)
	{
		if (deAtomicDecrement32(&m_state->weakRefCount) == 0)
		{
			delete m_state;
			m_state	= DE_NULL;
			m_ptr	= DE_NULL;
		}
	}
}

} // de

#endif // _DESHAREDPTR_HPP