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/**
* @file llsafehandle.h
* @brief Reference-counted object where Object() is valid, not NULL.
*
* $LicenseInfo:firstyear=2002&license=viewergpl$
*
* Copyright (c) 2002-2009, Linden Research, Inc.
*
* Second Life Viewer Source Code
* The source code in this file ("Source Code") is provided by Linden Lab
* to you under the terms of the GNU General Public License, version 2.0
* ("GPL"), unless you have obtained a separate licensing agreement
* ("Other License"), formally executed by you and Linden Lab. Terms of
* the GPL can be found in doc/GPL-license.txt in this distribution, or
* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
*
* There are special exceptions to the terms and conditions of the GPL as
* it is applied to this Source Code. View the full text of the exception
* in the file doc/FLOSS-exception.txt in this software distribution, or
* online at
* http://secondlifegrid.net/programs/open_source/licensing/flossexception
*
* By copying, modifying or distributing this software, you acknowledge
* that you have read and understood your obligations described above,
* and agree to abide by those obligations.
*
* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
* COMPLETENESS OR PERFORMANCE.
* $/LicenseInfo$
*/
#ifndef LLSAFEHANDLE_H
#define LLSAFEHANDLE_H
#include "llerror.h" // *TODO: consider eliminating this
// Expands LLPointer to return a pointer to a special instance of class Type instead of NULL.
// This is useful in instances where operations on NULL pointers are semantically safe and/or
// when error checking occurs at a different granularity or in a different part of the code
// than when referencing an object via a LLSafeHandle.
template <class Type>
class LLSafeHandle
{
public:
LLSafeHandle() :
mPointer(NULL)
{
}
LLSafeHandle(Type* ptr) :
mPointer(NULL)
{
assign(ptr);
}
LLSafeHandle(const LLSafeHandle<Type>& ptr) :
mPointer(NULL)
{
assign(ptr.mPointer);
}
// support conversion up the type hierarchy. See Item 45 in Effective C++, 3rd Ed.
template<typename Subclass>
LLSafeHandle(const LLSafeHandle<Subclass>& ptr) :
mPointer(NULL)
{
assign(ptr.get());
}
~LLSafeHandle()
{
unref();
}
const Type* operator->() const { return nonNull(mPointer); }
Type* operator->() { return nonNull(mPointer); }
Type* get() const { return mPointer; }
// we disallow these operations as they expose our null objects to direct manipulation
// and bypass the reference counting semantics
//const Type& operator*() const { return *nonNull(mPointer); }
//Type& operator*() { return *nonNull(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; }
operator const Type*() const { return mPointer; }
bool operator !=(Type* ptr) const { return (mPointer != ptr); }
bool operator ==(Type* ptr) const { return (mPointer == ptr); }
bool operator ==(const LLSafeHandle<Type>& ptr) const { return (mPointer == ptr.mPointer); }
bool operator < (const LLSafeHandle<Type>& ptr) const { return (mPointer < ptr.mPointer); }
bool operator > (const LLSafeHandle<Type>& ptr) const { return (mPointer > ptr.mPointer); }
LLSafeHandle<Type>& operator =(Type* ptr)
{
assign(ptr);
return *this;
}
LLSafeHandle<Type>& operator =(const LLSafeHandle<Type>& ptr)
{
assign(ptr.mPointer);
return *this;
}
// support assignment up the type hierarchy. See Item 45 in Effective C++, 3rd Ed.
template<typename Subclass>
LLSafeHandle<Type>& operator =(const LLSafeHandle<Subclass>& ptr)
{
assign(ptr.get());
return *this;
}
public:
typedef Type* (*NullFunc)();
static const NullFunc sNullFunc;
protected:
void ref()
{
if (mPointer)
{
mPointer->ref();
}
}
void unref()
{
if (mPointer)
{
Type *tempp = mPointer;
mPointer = NULL;
tempp->unref();
if (mPointer != NULL)
{
llwarns << "Unreference did assignment to non-NULL because of destructor" << llendl;
unref();
}
}
}
void assign(Type* ptr)
{
if( mPointer != ptr )
{
unref();
mPointer = ptr;
ref();
}
}
static Type* nonNull(Type* ptr)
{
return ptr == NULL ? sNullFunc() : ptr;
}
protected:
Type* mPointer;
};
#endif
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