Line data    Source code

       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             : #include "unotools/readwritemutexguard.hxx"
      21             : #include <tools/debug.hxx>
      22             : 
      23             : namespace utl {
      24             : 
      25           0 : ReadWriteGuard::ReadWriteGuard( ReadWriteMutex& rMutexP,
      26             :             sal_Int32 nRequestMode )
      27           0 :         : rMutex( rMutexP )
      28             : {
      29             :     // don't do anything until a pending write completed (or another
      30             :     // ReadWriteGuard leaves the ctor phase)
      31           0 :     ::osl::MutexGuard aGuard( rMutex.pWriteMutex );
      32           0 :     nMode = nRequestMode;
      33           0 :     if ( nMode & ReadWriteGuardMode::nWrite )
      34             :     {
      35           0 :         rMutex.pWriteMutex->acquire();
      36             :         // wait for any read to complete
      37             : // TODO: set up a waiting thread instead of a loop
      38           0 :         bool bWait = true;
      39           0 :         do
      40             :         {
      41           0 :             rMutex.pMutex->acquire();
      42           0 :             bWait = (rMutex.nReadCount != 0);
      43           0 :             if ( nMode & ReadWriteGuardMode::nCriticalChange )
      44           0 :                 bWait |= (rMutex.nBlockCriticalCount != 0);
      45           0 :             rMutex.pMutex->release();
      46             :         } while ( bWait );
      47             :     }
      48           0 :     else if ( nMode & ReadWriteGuardMode::nBlockCritical )
      49             :     {
      50           0 :         rMutex.pMutex->acquire();
      51           0 :         ++rMutex.nBlockCriticalCount;
      52           0 :         rMutex.pMutex->release();
      53             :     }
      54             :     else
      55             :     {
      56           0 :         rMutex.pMutex->acquire();
      57           0 :         ++rMutex.nReadCount;
      58           0 :         rMutex.pMutex->release();
      59           0 :     }
      60           0 : }
      61             : 
      62           0 : ReadWriteGuard::~ReadWriteGuard()
      63             : {
      64           0 :     if ( nMode & ReadWriteGuardMode::nWrite )
      65           0 :         rMutex.pWriteMutex->release();
      66           0 :     else if ( nMode & ReadWriteGuardMode::nBlockCritical )
      67             :     {
      68           0 :         rMutex.pMutex->acquire();
      69           0 :         --rMutex.nBlockCriticalCount;
      70           0 :         rMutex.pMutex->release();
      71             :     }
      72             :     else
      73             :     {
      74           0 :         rMutex.pMutex->acquire();
      75           0 :         --rMutex.nReadCount;
      76           0 :         rMutex.pMutex->release();
      77             :     }
      78           0 : }
      79             : 
      80           0 : void ReadWriteGuard::changeReadToWrite()
      81             : {
      82           0 :     bool bOk = !(nMode & (ReadWriteGuardMode::nWrite | ReadWriteGuardMode::nBlockCritical));
      83             :     DBG_ASSERT( bOk, "ReadWriteGuard::changeReadToWrite: can't" );
      84           0 :     if ( bOk )
      85             :     {
      86             :         // MUST release read before acquiring write mutex or dead lock would
      87             :         // occur if there was a write in another thread waiting for this read
      88             :         // to complete.
      89           0 :         rMutex.pMutex->acquire();
      90           0 :         --rMutex.nReadCount;
      91           0 :         rMutex.pMutex->release();
      92             : 
      93           0 :         rMutex.pWriteMutex->acquire();
      94           0 :         nMode |= ReadWriteGuardMode::nWrite;
      95             :         // wait for any other read to complete
      96             : // TODO: set up a waiting thread instead of a loop
      97           0 :         bool bWait = true;
      98           0 :         do
      99             :         {
     100           0 :             rMutex.pMutex->acquire();
     101           0 :             bWait = (rMutex.nReadCount != 0);
     102           0 :             rMutex.pMutex->release();
     103             :         } while ( bWait );
     104             :     }
     105           0 : }
     106             : 
     107             : }   // namespace utl
     108             : 
     109             : /* vim:set shiftwidth=4 softtabstop=4 expandtab: */