include/unotools/weakref.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
  13  *   with this work for additional information regarding copyright
  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 /*
  21  * This file is part of LibreOffice published API.
  22  */
  23 #pragma once
  24
  25 #include <sal/config.h>
  26
  27 #include <com/sun/star/uno/Reference.hxx>
  28 #include <com/sun/star/uno/XInterface.hpp>
  29 #include <cppuhelper/weakref.hxx>
  30 #include <cppuhelper/weak.hxx>
  31 #include <rtl/ref.hxx>
  32
  33 namespace unotools
  34 {
  35 /** The WeakReference<> holds a weak reference to an object.
  36
  37     That object must implement the css::uno::XWeak interface.
  38
  39     The WeakReference itself is *not* thread safe, just as
  40     Reference itself isn't, but the implementation of the listeners etc.
  41     behind it *is* thread-safe, so multiple threads can have their own
  42     WeakReferences to the same XWeak object.
  43
  44     @tparam interface_type Must be a C++ implementation class type, not a UNO interface type.  (See
  45     the C++20 requires-clause on the get member.  That clause is not put on the class as a whole to
  46     avoid overly tight requirements on when interface_type needs to be complete.)
  47 */
  48 template <class interface_type>
  49 class SAL_WARN_UNUSED WeakReference : public css::uno::WeakReferenceHelper
  50 {
  51 public:
  52     /** Default ctor.  Creates an empty weak reference.
  53     */
  54     WeakReference()
  55         : WeakReferenceHelper()
  56     {
  57     }
  58
  59     /** Copy ctor.  Initialize this reference with a hard reference.
  60
  61         @param rRef another hard ref
  62     */
  63     WeakReference(const rtl::Reference<interface_type>& rRef)
  64         : WeakReferenceHelper(css::uno::Reference<css::uno::XWeak>(rRef))
  65     {
  66     }
  67
  68     /** Copy ctor.  Initialize this reference with a hard reference.
  69
  70         @param rRef another hard ref
  71     */
  72     WeakReference(interface_type& rRef)
  73         : WeakReferenceHelper(&rRef)
  74     {
  75     }
  76
  77     /** Copy ctor.  Initialize this reference with a hard reference.
  78
  79         @param rRef another hard ref
  80     */
  81     WeakReference(interface_type* pRef)
  82         : WeakReferenceHelper(
  83               css::uno::Reference<css::uno::XWeak>(static_cast<cppu::OWeakObject*>(pRef)))
  84     {
  85     }
  86
  87     /** Releases this reference and takes over hard reference xInt.
  88         If the implementation behind xInt does not support XWeak
  89         or XInt is null, then this reference is null.
  90
  91         @param xInt another hard reference
  92     */
  93     WeakReference& operator=(const rtl::Reference<interface_type>& xInt)
  94     {
  95         WeakReferenceHelper::operator=(xInt);
  96         return *this;
  97     }
  98
  99     WeakReference& operator=(rtl::Reference<interface_type>&& xInt)
 100     {
 101         WeakReferenceHelper::operator=(std::move(xInt));
 102         return *this;
 103     }
 104
 105     WeakReference& operator=(interface_type* pInt)
 106     {
 107         WeakReferenceHelper::operator=(
 108             css::uno::Reference<css::uno::XWeak>(static_cast<::cppu::OWeakObject*>(pInt)));
 109         return *this;
 110     }
 111
 112     /**  Gets a hard reference to the object.
 113
 114          @return hard reference or null, if the weakly referenced interface has gone
 115     */
 116     rtl::Reference<interface_type> SAL_CALL get() const
 117 #if !(defined __clang__ && __clang_major__ <= 15)
 118         requires(!cppu::detail::isUnoInterfaceType<interface_type>)
 119 #endif
 120     {
 121         css::uno::Reference<css::uno::XInterface> xInterface = WeakReferenceHelper::get();
 122         // If XInterface is an ambiguous base of interface_type, we have to use dynamic_cast,
 123         // otherwise we can use the faster static_cast.
 124         if constexpr (std::is_convertible_v<interface_type*, css::uno::XInterface*>)
 125             return static_cast<interface_type*>(xInterface.get());
 126         else
 127             return dynamic_cast<interface_type*>(xInterface.get());
 128     }
 129
 130     /**  Gets a hard reference to the object.
 131
 132          @return hard reference or null, if the weakly referenced interface has gone
 133     */
 134     operator ::rtl::Reference<interface_type>() const { return get(); }
 135 };
 136 }
 137
 138 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */