dbaccess/source/sdbtools/inc/connectiondependent.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.
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   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 #pragma once
  21
  22 #include <com/sun/star/sdbc/XConnection.hpp>
  23 #include <com/sun/star/lang/DisposedException.hpp>
  24 #include <com/sun/star/uno/XComponentContext.hpp>
  25
  26 #include <cppuhelper/weakref.hxx>
  27 #include <osl/mutex.hxx>
  28 #include <utility>
  29
  30 namespace sdbtools
  31 {
  32
  33     // ConnectionDependentComponent
  34     class ConnectionDependentComponent
  35     {
  36     private:
  37         mutable ::osl::Mutex    m_aMutex;
  38         css::uno::WeakReference< css::sdbc::XConnection >
  39                                 m_aConnection;
  40         css::uno::Reference< css::uno::XComponentContext >
  41                                 m_aContext;
  42
  43         /** a hard reference to the connection we're working for
  44
  45             This member is only valid as long as a EntryGuard is on the stack.
  46             The guard will, in its constructor, set the member, and reset it in its destructor.
  47             This ensures that the connection is only held hard when it's needed, and weak otherwise.
  48         */
  49         css::uno::Reference< css::sdbc::XConnection >
  50                                 m_xConnection;
  51
  52     protected:
  53         ::osl::Mutex&   getMutex() const { return m_aMutex; }
  54
  55         const css::uno::Reference< css::uno::XComponentContext >&
  56                         getContext() const { return m_aContext; }
  57
  58     protected:
  59         class EntryGuard;
  60
  61     protected:
  62         explicit ConnectionDependentComponent( css::uno::Reference< css::uno::XComponentContext > _xContext )
  63             :m_aContext(std::move( _xContext ))
  64         {
  65         }
  66
  67         /** sets the connection we depend on.
  68
  69             To be called exactly once.
  70
  71             @param  _rxConnection
  72                 the connection to set
  73         */
  74         void    setWeakConnection( const css::uno::Reference< css::sdbc::XConnection >& _rxConnection )
  75         {
  76             m_aConnection = _rxConnection;
  77         }
  78
  79         const css::uno::Reference< css::sdbc::XConnection >&
  80                 getConnection() const { return m_xConnection; }
  81
  82     public:
  83     struct GuardAccess;
  84     friend struct GuardAccess;
  85         /** helper for granting exclusive access to various other methods
  86         */
  87         struct GuardAccess { friend class EntryGuard; private: GuardAccess() { } };
  88
  89         ::osl::Mutex&   getMutex( GuardAccess ) const { return m_aMutex; }
  90
  91         bool acquireConnection( GuardAccess )
  92         {
  93             m_xConnection.set(m_aConnection);
  94             return m_xConnection.is();
  95         }
  96         void releaseConnection( GuardAccess )
  97         {
  98             m_xConnection.clear();
  99         }
 100     };
 101
 102     // ConnectionDependentComponent::EntryGuard
 103     /** a class for guarding methods of a connection-dependent component
 104
 105         This class serves multiple purposes:
 106         <ul><li>It ensures multi-threading safety by guarding the component's mutex
 107                 as long as it lives.</li>
 108             <li>It ensures that the component's connection is alive. The constructor
 109                 throws a DisposedException if no hard reference to the connection can
 110                 be obtained.</li>
 111         </ul>
 112     */
 113     class ConnectionDependentComponent::EntryGuard
 114     {
 115     private:
 116         ::osl::MutexGuard               m_aMutexGuard;
 117         ConnectionDependentComponent&   m_rComponent;
 118
 119     public:
 120         explicit EntryGuard( ConnectionDependentComponent& _rComponent )
 121             :m_aMutexGuard( _rComponent.getMutex( ConnectionDependentComponent::GuardAccess() ) )
 122             ,m_rComponent( _rComponent )
 123         {
 124             if ( !m_rComponent.acquireConnection( ConnectionDependentComponent::GuardAccess() ) )
 125                 throw css::lang::DisposedException();
 126         }
 127
 128         ~EntryGuard()
 129         {
 130             m_rComponent.releaseConnection( ConnectionDependentComponent::GuardAccess() );
 131         }
 132     };
 133
 134 } // namespace sdbtools
 135
 136 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */