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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:06:44 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:06:44 +0000
commited5640d8b587fbcfed7dd7967f3de04b37a76f26 (patch)
tree7a5f7c6c9d02226d7471cb3cc8fbbf631b415303 /include/comphelper/doublecheckedinit.hxx
parentInitial commit. (diff)
downloadlibreoffice-ed5640d8b587fbcfed7dd7967f3de04b37a76f26.tar.xz
libreoffice-ed5640d8b587fbcfed7dd7967f3de04b37a76f26.zip
Adding upstream version 4:7.4.7.upstream/4%7.4.7upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'include/comphelper/doublecheckedinit.hxx')
-rw-r--r--include/comphelper/doublecheckedinit.hxx64
1 files changed, 64 insertions, 0 deletions
diff --git a/include/comphelper/doublecheckedinit.hxx b/include/comphelper/doublecheckedinit.hxx
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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: */