unotools/source/i18n/readwritemutexguard.cxx

   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 #include <unotools/readwritemutexguard.hxx>
  21 #include <tools/debug.hxx>
  22
  23 namespace utl {
  24
  25 ReadWriteGuard::ReadWriteGuard( ReadWriteMutex& rMutexP,
  26             ReadWriteGuardMode nRequestMode )
  27         : rMutex( rMutexP )
  28 {
  29     // don't do anything until a pending write completed (or another
  30     // ReadWriteGuard leaves the ctor phase)
  31     ::osl::MutexGuard aGuard( rMutex.maWriteMutex );
  32     nMode = nRequestMode;
  33     if ( nMode & ReadWriteGuardMode::Write )
  34     {
  35         rMutex.maWriteMutex.acquire();
  36         // wait for any read to complete
  37 // TODO: set up a waiting thread instead of a loop
  38         bool bWait = true;
  39         do
  40         {
  41             rMutex.maMutex.acquire();
  42             bWait = (rMutex.nReadCount != 0);
  43             if ( nMode & ReadWriteGuardMode::CriticalChange )
  44                 bWait |= (rMutex.nBlockCriticalCount != 0);
  45             rMutex.maMutex.release();
  46         } while ( bWait );
  47     }
  48     else if ( nMode & ReadWriteGuardMode::BlockCritical )
  49     {
  50         rMutex.maMutex.acquire();
  51         ++rMutex.nBlockCriticalCount;
  52         rMutex.maMutex.release();
  53     }
  54     else
  55     {
  56         rMutex.maMutex.acquire();
  57         ++rMutex.nReadCount;
  58         rMutex.maMutex.release();
  59     }
  60 }
  61
  62 ReadWriteGuard::~ReadWriteGuard()
  63 {
  64     if ( nMode & ReadWriteGuardMode::Write )
  65         rMutex.maWriteMutex.release();
  66     else if ( nMode & ReadWriteGuardMode::BlockCritical )
  67     {
  68         rMutex.maMutex.acquire();
  69         --rMutex.nBlockCriticalCount;
  70         rMutex.maMutex.release();
  71     }
  72     else
  73     {
  74         rMutex.maMutex.acquire();
  75         --rMutex.nReadCount;
  76         rMutex.maMutex.release();
  77     }
  78 }
  79
  80 void ReadWriteGuard::changeReadToWrite()
  81 {
  82     bool bOk = !(nMode & (ReadWriteGuardMode::Write | ReadWriteGuardMode::BlockCritical));
  83     DBG_ASSERT( bOk, "ReadWriteGuard::changeReadToWrite: can't" );
  84     if ( !bOk )
  85         return;
  86
  87     // MUST release read before acquiring write mutex or dead lock would
  88     // occur if there was a write in another thread waiting for this read
  89     // to complete.
  90     rMutex.maMutex.acquire();
  91     --rMutex.nReadCount;
  92     rMutex.maMutex.release();
  93
  94     rMutex.maWriteMutex.acquire();
  95     nMode |= ReadWriteGuardMode::Write;
  96     // wait for any other read to complete
  97 // TODO: set up a waiting thread instead of a loop
  98     bool bWait = true;
  99     do
 100     {
 101         rMutex.maMutex.acquire();
 102         bWait = (rMutex.nReadCount != 0);
 103         rMutex.maMutex.release();
 104     } while ( bWait );
 105 }
 106
 107 }   // namespace utl
 108
 109 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */