llpointer.h

/** 
 * @file llpointer.h
 * @brief A reference-counted pointer for objects derived from LLRefCount
 *
 * $LicenseInfo:firstyear=2002&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 * 
 * 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;
 * version 2.1 of the License only.
 * 
 * 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 for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */
#ifndef LLPOINTER_H
#define LLPOINTER_H

#include "llerror.h"	// *TODO: consider eliminating this
#include "llmutex.h"

//----------------------------------------------------------------------------
// RefCount objects should generally only be accessed by way of LLPointer<>'s
// NOTE: LLPointer<LLFoo> x = new LLFoo(); MAY NOT BE THREAD SAFE
//   if LLFoo::LLFoo() does anything like put itself in an update queue.
//   The queue may get accessed before it gets assigned to x.
// The correct implementation is:
//   LLPointer<LLFoo> x = new LLFoo; // constructor does not do anything interesting
//   x->instantiate(); // does stuff like place x into an update queue

// see llthread.h for LLThreadSafeRefCount

//----------------------------------------------------------------------------

// Note: relies on Type having ref() and unref() methods
template <class Type> class LLPointer
{
public:

	LLPointer() : 
		mPointer(NULL)
	{
	}

	LLPointer(Type* ptr) : 
		mPointer(ptr)
	{
		ref();
	}

	LLPointer(const LLPointer<Type>& ptr) : 
		mPointer(ptr.mPointer)
	{
		ref();
	}

	// support conversion up the type hierarchy.  See Item 45 in Effective C++, 3rd Ed.
	template<typename Subclass>
	LLPointer(const LLPointer<Subclass>& ptr) : 
		mPointer(ptr.get())
	{
		ref();
	}

	~LLPointer()								
	{
		unref();
	}

	Type*	get() const							{ return mPointer; }
	const Type*	operator->() const				{ return mPointer; }
	Type*	operator->()						{ return mPointer; }
	const Type&	operator*() const				{ return *mPointer; }
	Type&	operator*()							{ return *mPointer; }

	operator BOOL()  const						{ return (mPointer != NULL); }
	operator bool()  const						{ return (mPointer != NULL); }
	bool operator!() const						{ return (mPointer == NULL); }
	bool isNull() const							{ return (mPointer == NULL); }
	bool notNull() const						{ return (mPointer != NULL); }

	operator Type*()       const				{ return mPointer; }
	bool operator !=(Type* ptr) const           { return (mPointer != ptr); 	}
	bool operator ==(Type* ptr) const           { return (mPointer == ptr); 	}
	bool operator ==(const LLPointer<Type>& ptr) const           { return (mPointer == ptr.mPointer); 	}
	bool operator < (const LLPointer<Type>& ptr) const           { return (mPointer < ptr.mPointer); 	}
	bool operator > (const LLPointer<Type>& ptr) const           { return (mPointer > ptr.mPointer); 	}

	LLPointer<Type>& operator =(Type* ptr)                   
	{ 
		assign(ptr);
		return *this; 
	}

	LLPointer<Type>& operator =(const LLPointer<Type>& ptr)  
	{ 
		assign(ptr);
		return *this; 
	}

	// support assignment up the type hierarchy. See Item 45 in Effective C++, 3rd Ed.
	template<typename Subclass>
	LLPointer<Type>& operator =(const LLPointer<Subclass>& ptr)  
	{ 
		assign(ptr.get());
		return *this; 
	}
	
	// Just exchange the pointers, which will not change the reference counts.
	static void swap(LLPointer<Type>& a, LLPointer<Type>& b)
	{
		Type* temp = a.mPointer;
		a.mPointer = b.mPointer;
		b.mPointer = temp;
	}

protected:
#ifdef LL_LIBRARY_INCLUDE
	void ref();                             
	void unref();
#else
	void ref()                             
	{ 
		if (mPointer)
		{
			mPointer->ref();
		}
	}

	void unref()
	{
		if (mPointer)
		{
			Type *temp = mPointer;
			mPointer = NULL;
			temp->unref();
			if (mPointer != NULL)
			{
				LL_WARNS() << "Unreference did assignment to non-NULL because of destructor" << LL_ENDL;
				unref();
			}
		}
	}
#endif // LL_LIBRARY_INCLUDE

	void assign(const LLPointer<Type>& ptr)
	{
		if (mPointer != ptr.mPointer)
		{
			unref();
			mPointer = ptr.mPointer;
			ref();
		}
	}

protected:
	Type*	mPointer;
};

template <class Type> class LLConstPointer
{
public:
	LLConstPointer() : 
		mPointer(NULL)
	{
	}

	LLConstPointer(const Type* ptr) : 
		mPointer(ptr)
	{
		ref();
	}

	LLConstPointer(const LLConstPointer<Type>& ptr) : 
		mPointer(ptr.mPointer)
	{
		ref();
	}

	// support conversion up the type hierarchy.  See Item 45 in Effective C++, 3rd Ed.
	template<typename Subclass>
	LLConstPointer(const LLConstPointer<Subclass>& ptr) : 
		mPointer(ptr.get())
	{
		ref();
	}

	~LLConstPointer()
	{
		unref();
	}

	const Type*	get() const						{ return mPointer; }
	const Type*	operator->() const				{ return mPointer; }
	const Type&	operator*() const				{ return *mPointer; }

	operator BOOL()  const						{ return (mPointer != NULL); }
	operator bool()  const						{ return (mPointer != NULL); }
	bool operator!() const						{ return (mPointer == NULL); }
	bool isNull() const							{ return (mPointer == NULL); }
	bool notNull() const						{ return (mPointer != NULL); }

	operator const Type*()       const			{ return mPointer; }
	bool operator !=(const Type* ptr) const     { return (mPointer != ptr); 	}
	bool operator ==(const Type* ptr) const     { return (mPointer == ptr); 	}
	bool operator ==(const LLConstPointer<Type>& ptr) const           { return (mPointer == ptr.mPointer); 	}
	bool operator < (const LLConstPointer<Type>& ptr) const           { return (mPointer < ptr.mPointer); 	}
	bool operator > (const LLConstPointer<Type>& ptr) const           { return (mPointer > ptr.mPointer); 	}

	LLConstPointer<Type>& operator =(const Type* ptr)                   
	{
		if( mPointer != ptr )
		{
			unref(); 
			mPointer = ptr; 
			ref();
		}

		return *this; 
	}

	LLConstPointer<Type>& operator =(const LLConstPointer<Type>& ptr)  
	{ 
		if( mPointer != ptr.mPointer )
		{
			unref(); 
			mPointer = ptr.mPointer;
			ref();
		}
		return *this; 
	}

	// support assignment up the type hierarchy. See Item 45 in Effective C++, 3rd Ed.
	template<typename Subclass>
	LLConstPointer<Type>& operator =(const LLConstPointer<Subclass>& ptr)  
	{ 
		if( mPointer != ptr.get() )
		{
			unref(); 
			mPointer = ptr.get();
			ref();
		}
		return *this; 
	}
	
	// Just exchange the pointers, which will not change the reference counts.
	static void swap(LLConstPointer<Type>& a, LLConstPointer<Type>& b)
	{
		const Type* temp = a.mPointer;
		a.mPointer = b.mPointer;
		b.mPointer = temp;
	}

protected:
#ifdef LL_LIBRARY_INCLUDE
	void ref();                             
	void unref();
#else // LL_LIBRARY_INCLUDE
	void ref()                             
	{ 
		if (mPointer)
		{
			mPointer->ref();
		}
	}

	void unref()
	{
		if (mPointer)
		{
			const Type *temp = mPointer;
			mPointer = NULL;
			temp->unref();
			if (mPointer != NULL)
			{
				LL_WARNS() << "Unreference did assignment to non-NULL because of destructor" << LL_ENDL;
				unref();
			}
		}
	}
#endif // LL_LIBRARY_INCLUDE
protected:
	const Type*	mPointer;
};

template<typename Type>
class LLCopyOnWritePointer : public LLPointer<Type>
{
public:
	typedef LLCopyOnWritePointer<Type> self_t;
    typedef LLPointer<Type> pointer_t;
    
	LLCopyOnWritePointer() 
	:	mStayUnique(false)
	{}

	LLCopyOnWritePointer(Type* ptr) 
	:	LLPointer<Type>(ptr),
		mStayUnique(false)
	{}

	LLCopyOnWritePointer(LLPointer<Type>& ptr)
	:	LLPointer<Type>(ptr),
		mStayUnique(false)
	{
		if (ptr.mForceUnique)
		{
			makeUnique();
		}
	}

	Type* write()
	{
		makeUnique();
		return pointer_t::mPointer;
	}

	void makeUnique()
	{
		if (pointer_t::notNull() && pointer_t::mPointer->getNumRefs() > 1)
		{
			*(pointer_t* )(this) = new Type(*pointer_t::mPointer);
		}
	}

	const Type*	operator->() const	{ return pointer_t::mPointer; }
	const Type&	operator*() const	{ return *pointer_t::mPointer; }

	void setStayUnique(bool stay) { makeUnique(); mStayUnique = stay; }
private:
	bool mStayUnique;
};

#endif