89 lines
2.3 KiB
C++
89 lines
2.3 KiB
C++
/**
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* @file lllazyvalue.h
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* @brief generic functor/value abstraction for lazy evaluation of a value
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* parsing construction parameters from xml and LLSD
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*
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* $LicenseInfo:firstyear=2008&license=viewergpl$
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*
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* Copyright (c) 2008-2009, Linden Research, Inc.
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*
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* Second Life Viewer Source Code
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* The source code in this file ("Source Code") is provided by Linden Lab
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* to you under the terms of the GNU General Public License, version 2.0
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* ("GPL"), unless you have obtained a separate licensing agreement
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* ("Other License"), formally executed by you and Linden Lab. Terms of
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* the GPL can be found in doc/GPL-license.txt in this distribution, or
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* online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
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*
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* There are special exceptions to the terms and conditions of the GPL as
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* it is applied to this Source Code. View the full text of the exception
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* in the file doc/FLOSS-exception.txt in this software distribution, or
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* online at
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* http://secondlifegrid.net/programs/open_source/licensing/flossexception
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*
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* By copying, modifying or distributing this software, you acknowledge
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* that you have read and understood your obligations described above,
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* and agree to abide by those obligations.
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*
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* ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
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* WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
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* COMPLETENESS OR PERFORMANCE.
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* $/LicenseInfo$
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*/
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#ifndef LL_LAZY_VALUE_H
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#define LL_LAZY_VALUE_H
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#include <boost/function.hpp>
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// Holds on to a value of type T *or* calls a functor to generate a value of type T
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template<typename T>
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class LLLazyValue
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{
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public:
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typedef typename boost::add_reference<typename boost::add_const<T>::type>::type T_const_ref;
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typedef typename boost::function<T_const_ref (void)> function_type;
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public:
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LLLazyValue(const function_type& value)
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: mValueGetter(value)
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{}
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LLLazyValue(T_const_ref value)
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: mValue(value)
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{}
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LLLazyValue()
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: mValue()
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{}
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void set(const LLLazyValue& val)
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{
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mValueGetter = val.mValueGetter;
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}
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void set(T_const_ref val)
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{
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mValue = val;
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mValueGetter = NULL;
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}
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T_const_ref get() const
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{
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if (!mValueGetter.empty())
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{
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return mValueGetter();
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}
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return mValue;
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}
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bool isUsingFunction() const
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{
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return mValueGetter != NULL;
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}
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private:
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function_type mValueGetter;
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T mValue;
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};
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#endif // LL_LAZY_VALUE_H
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