3020fb15fe
For further reuse in more source files. Change-Id: I2fcbb98a81725e14d6d433f62622d2c48d146de1 Reviewed-on: https://gerrit.libreoffice.org/55763 Tested-by: Jenkins Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
64 lines
2.3 KiB
C++
64 lines
2.3 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* This file incorporates work covered by the following license notice:
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright
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* ownership. The ASF licenses this file to you under the Apache
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* License, Version 2.0 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.apache.org/licenses/LICENSE-2.0 .
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*/
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#ifndef INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
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#define INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
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#include <osl/getglobalmutex.hxx>
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#include <atomic>
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// HACK: <atomic> includes <stdbool.h>, which in some Clang versions does '#define bool bool',
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// which confuses clang plugins.
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#undef bool
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#include <functional>
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namespace comphelper
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{
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/**
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* Thread-safe singleton creation.
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*
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* It is normally sufficient to create singletons using static variables in a function.
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* This function is only for use cases that have a more complex lifetime of the object,
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* such as when the object may require specific cleanup or may be created more times
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* (e.g. when there is a "singleton" per each instance of another object).
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*/
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template <typename Type, typename Function = std::function<Type*()>,
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typename Guard = osl::MutexGuard, typename GuardCtor = osl::GetGlobalMutex>
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static inline Type* doubleCheckedInit(std::atomic<Type*>& pointer, Function function,
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GuardCtor guardCtor = osl::GetGlobalMutex())
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{
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Type* p = pointer.load(std::memory_order_acquire);
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if (!p)
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{
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Guard guard(guardCtor());
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p = pointer.load(std::memory_order_relaxed);
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if (!p)
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{
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p = function();
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pointer.store(p, std::memory_order_release);
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}
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}
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return p;
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}
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} // namespace
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#endif // INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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