83 lines
2.2 KiB
C++
83 lines
2.2 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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* $LicenseInfo:firstyear=2008&license=viewerlgpl$
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* Second Life Viewer Source Code
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* Copyright (C) 2010, Linden Research, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation;
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* version 2.1 of the License only.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
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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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