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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 .
*/
#include <unotools/readwritemutexguard.hxx>
#include <tools/debug.hxx>
namespace utl {
ReadWriteGuard::ReadWriteGuard( ReadWriteMutex& rMutexP,
ReadWriteGuardMode nRequestMode )
: rMutex( rMutexP )
{
// don't do anything until a pending write completed (or another
// ReadWriteGuard leaves the ctor phase)
::osl::MutexGuard aGuard( rMutex.maWriteMutex );
nMode = nRequestMode;
if ( nMode & ReadWriteGuardMode::Write )
{
rMutex.maWriteMutex.acquire();
// wait for any read to complete
// TODO: set up a waiting thread instead of a loop
bool bWait = true;
do
{
rMutex.maMutex.acquire();
bWait = (rMutex.nReadCount != 0);
if ( nMode & ReadWriteGuardMode::CriticalChange )
bWait |= (rMutex.nBlockCriticalCount != 0);
rMutex.maMutex.release();
} while ( bWait );
}
else if ( nMode & ReadWriteGuardMode::BlockCritical )
{
rMutex.maMutex.acquire();
++rMutex.nBlockCriticalCount;
rMutex.maMutex.release();
}
else
{
rMutex.maMutex.acquire();
++rMutex.nReadCount;
rMutex.maMutex.release();
}
}
ReadWriteGuard::~ReadWriteGuard()
{
if ( nMode & ReadWriteGuardMode::Write )
rMutex.maWriteMutex.release();
else if ( nMode & ReadWriteGuardMode::BlockCritical )
{
rMutex.maMutex.acquire();
--rMutex.nBlockCriticalCount;
rMutex.maMutex.release();
}
else
{
rMutex.maMutex.acquire();
--rMutex.nReadCount;
rMutex.maMutex.release();
}
}
void ReadWriteGuard::changeReadToWrite()
{
bool bOk = !(nMode & (ReadWriteGuardMode::Write | ReadWriteGuardMode::BlockCritical));
DBG_ASSERT( bOk, "ReadWriteGuard::changeReadToWrite: can't" );
if ( bOk )
{
// MUST release read before acquiring write mutex or dead lock would
// occur if there was a write in another thread waiting for this read
// to complete.
rMutex.maMutex.acquire();
--rMutex.nReadCount;
rMutex.maMutex.release();
rMutex.maWriteMutex.acquire();
nMode |= ReadWriteGuardMode::Write;
// wait for any other read to complete
// TODO: set up a waiting thread instead of a loop
bool bWait = true;
do
{
rMutex.maMutex.acquire();
bWait = (rMutex.nReadCount != 0);
rMutex.maMutex.release();
} while ( bWait );
}
}
} // namespace utl
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