Adding upstream version 4:7.4.7.upstream/4%7.4.7upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 203 insertions, 0 deletions

diff --git a/include/salhelper/singletonref.hxx b/include/salhelper/singletonref.hxx
new file mode 100644
index 000000000..191e585c1
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+++ b/include/salhelper/singletonref.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 .
+ */
+
+/*
+ * This file is part of LibreOffice published API.
+ */
+
+#ifndef INCLUDED_SALHELPER_SINGLETONREF_HXX
+#define INCLUDED_SALHELPER_SINGLETONREF_HXX
+
+#include "sal/config.h"
+
+#include <cstddef>
+
+#include "osl/mutex.hxx"
+#include "rtl/instance.hxx"
+#include "osl/diagnose.h"
+#include "osl/getglobalmutex.hxx"
+
+
+namespace salhelper{
+
+
+/** @short  template for implementing singleton classes.
+
+            Such classes can be instantiated every time they
+            are needed. But the internal wrapped object will
+            be created one times only. Of course it's used
+            resources are referenced one times only too.
+            This template hold it alive till the last
+            reference is gone. Further all operations
+            on this reference are threadsafe. Only
+            calls directly to the internal object (which modify
+            its state) must be made threadsafe by the object itself
+            or from outside.
+
+    @attention  To prevent the code against race conditions, it's not
+                allowed to start operations inside the ctor
+                of the internal wrapped object - especially operations
+                which needs a reference to the same singleton too.
+
+                The only chance to suppress such strange constellations
+                is a lazy-init mechanism.
+
+                <ul>
+                    <li>a) The singleton class can provide a special init()
+                           method, which must be called as first after creation.</li>
+                    <li>b) The singleton class can call a special impl_init()
+                           method implicit for every called interface method.</li>
+                </ul>
+
+                Note further that this singleton pattern can work only, if
+                all user of such singleton are located inside the same library!
+                Because static values can't be exported - e.g. from windows libraries.
+ */
+template< class SingletonClass >
+class SingletonRef
+{
+
+    // member
+
+    private:
+
+        /** @short  pointer to the internal wrapped singleton. */
+        static SingletonClass* m_pInstance;
+
+        /** @short  ref count, which regulate creation and removing of m_pInstance. */
+        static sal_Int32 m_nRef;
+
+
+    // interface
+
+    public:
+
+
+        /** @short  standard ctor.
+
+                    The internal wrapped object is created only,
+                    if its ref count was 0. Otherwise this method
+                    does nothing ... except increasing of the internal
+                    ref count!
+         */
+        SingletonRef()
+        {
+            // GLOBAL SAFE ->
+            ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
+
+            // must be increased before(!) the check is done.
+            // Otherwise this check can fail inside the same thread ...
+            ++m_nRef;
+            if (m_nRef == 1)
+                m_pInstance = new SingletonClass();
+
+            OSL_ENSURE(m_nRef>0 && m_pInstance, "Race? Ref count of singleton >0, but instance is NULL!");
+            // <- GLOBAL SAFE
+        }
+
+
+        /** @short  standard dtor.
+
+                    The internal wrapped object is removed only,
+                    if its ref count will be 0. Otherwise this method
+                    does nothing ... except decreasing of the internal
+                    ref count!
+         */
+        ~SingletonRef()
+        {
+            // GLOBAL SAFE ->
+            ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
+
+            // must be decreased before(!) the check is done.
+            // Otherwise this check can fail inside the same thread ...
+            --m_nRef;
+            if (m_nRef == 0)
+            {
+                delete m_pInstance;
+                m_pInstance = NULL;
+            }
+            // <- GLOBAL SAFE
+        }
+
+#if defined LIBO_INTERNAL_ONLY
+        SingletonRef & operator =(SingletonRef const &) = default;
+#endif
+
+        /** @short  Allows rSingle->someBodyOp().
+         */
+        SingletonClass* operator->() const
+        {
+            // GLOBAL SAFE ->
+            ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
+            return m_pInstance;
+            // <- GLOBAL SAFE
+        }
+
+
+        /** @short  Allows (*rSingle).someBodyOp().
+         */
+        SingletonClass& operator*() const
+        {
+            // GLOBAL SAFE ->
+            ::osl::MutexGuard aLock(SingletonRef::ownStaticLock());
+            return *m_pInstance;
+            // <- GLOBAL SAFE
+        }
+
+
+    // helper
+
+    private:
+        SingletonRef(SingletonRef &) SAL_DELETED_FUNCTION;
+
+        /** @short  creates an own mutex for guarding static contents.
+
+                    The global mutex the osl library is used one times
+                    only to create an own static mutex, which can be used
+                    next time to guard own static member operations.
+         */
+        struct SingletonLockInit
+        {
+            ::osl::Mutex* operator()()
+            {
+                static ::osl::Mutex aInstance;
+                return &aInstance;
+            }
+        };
+
+        ::osl::Mutex& ownStaticLock() const
+        {
+            return *rtl_Instance< ::osl::Mutex,
+                                  SingletonLockInit,
+                                  ::osl::MutexGuard,
+                                  ::osl::GetGlobalMutex >::create(SingletonLockInit(), ::osl::GetGlobalMutex());
+        }
+};
+
+template< class SingletonClass >
+SingletonClass* SingletonRef< SingletonClass >::m_pInstance = NULL;
+
+template< class SingletonClass >
+sal_Int32 SingletonRef< SingletonClass >::m_nRef = 0;
+
+} // namespace salhelper
+
+#endif // INCLUDED_SALHELPER_SINGLETONREF_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */