mirror of
https://github.com/Icinga/icinga2.git
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90 lines
2.7 KiB
C++
90 lines
2.7 KiB
C++
/******************************************************************************
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* Icinga 2 *
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* Copyright (C) 2012-2018 Icinga Development Team (https://icinga.com/) *
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* *
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* This program is free software; you can redistribute it and/or *
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* modify it under the terms of the GNU General Public License *
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* as published by the Free Software Foundation; either version 2 *
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* of the License, or (at your option) any later version. *
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* *
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* This program 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 *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, write to the Free Software Foundation *
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. *
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******************************************************************************/
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#ifndef LAZY_INIT
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#define LAZY_INIT
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#include <atomic>
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#include <functional>
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#include <mutex>
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#include <utility>
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namespace icinga
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{
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/**
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* Lazy object initialization abstraction inspired from
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* <https://docs.microsoft.com/en-us/dotnet/api/system.lazy-1?view=netframework-4.7.2>.
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*
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* @ingroup base
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*/
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template<class T>
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class LazyInit
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{
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public:
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inline
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LazyInit(std::function<T()> initializer = []() { return T(); }) : m_Initializer(std::move(initializer))
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{
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m_Underlying.store(nullptr, std::memory_order_release);
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}
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LazyInit(const LazyInit&) = delete;
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LazyInit(LazyInit&&) = delete;
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LazyInit& operator=(const LazyInit&) = delete;
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LazyInit& operator=(LazyInit&&) = delete;
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inline
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~LazyInit()
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{
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auto ptr (m_Underlying.load(std::memory_order_acquire));
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if (ptr != nullptr) {
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delete ptr;
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}
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}
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inline
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T& Get()
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{
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auto ptr (m_Underlying.load(std::memory_order_acquire));
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if (ptr == nullptr) {
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std::unique_lock<std::mutex> lock (m_Mutex);
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ptr = m_Underlying.load(std::memory_order_acquire);
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if (ptr == nullptr) {
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ptr = new T(m_Initializer());
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m_Underlying.store(ptr, std::memory_order_release);
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}
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}
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return *ptr;
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}
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private:
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std::function<T()> m_Initializer;
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std::mutex m_Mutex;
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std::atomic<T*> m_Underlying;
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};
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}
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#endif /* LAZY_INIT */
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