/home/tdf/lode/jenkins/workspace/lo_tb_master_linux_dbg/include/o3tl/lazy_update.hxx

Update output object lazily.

Update output object lazily This template collects data in input type, and updates the output type with the given update functor, but only if the output is requested. Useful if updating is expensive, or input changes frequently, but output is only comparatively seldom used.

LazyUpdate<InType,OutType,decltype(F)> myValue(F);
*myValue = newInput;
myValue->updateInput( this, that, those );

output( *myValue );
        

or

output( myValue.getOutValue() );
        

if the compiler does not recognize the const context.

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
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 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
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 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
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#ifndef INCLUDED_O3TL_LAZY_UPDATE_HXX
#define INCLUDED_O3TL_LAZY_UPDATE_HXX
 
#include <utility>
 
namespace o3tl
{
    template<typename In, typename Out, typename Func> class LazyUpdate {
    public:
        LazyUpdate(Func func): func_(std::move(func)), input_(), dirty_(true) {}
 
        In const & getInValue() const { return input_; }
 
        Out const & getOutValue() const { return update(); }
 
        In & operator *() {
            dirty_ = true;
            return input_;
        }
 
        In * operator ->() {
            dirty_ = true;
            return &input_;
        }
 
        Out const & operator *() const { return update();  }
 
        Out const * operator ->() const { return &update(); }
 
    private:
        Out const & update() const {
            if (dirty_) {
                output_ = func_(input_);
                dirty_ = false;
            }
            return output_;
        }
 
        Func const func_;
        In input_;
        mutable Out output_;
        mutable bool dirty_;
    };
}
 
#endif
 
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