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