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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 .
*/
#ifndef INCLUDED_FRAMEWORK_INC_THREADHELP_WRITEGUARD_HXX
#define INCLUDED_FRAMEWORK_INC_THREADHELP_WRITEGUARD_HXX
#include <threadhelp/inoncopyable.h>
#include <threadhelp/irwlock.h>
namespace framework{
/*-************************************************************************************************************//**
@short implement a guard to set write locks
@descr This guard should be used to set a lock for reading AND writing object internal member.
We never need a own mutex to safe our internal member access - because
a guard is used as function-local member only. There exist no multithreaded access to it really ...
@attention a) To prevent us against wrong using, the default ctor, copy ctor and the =operator are maked private!
b) Use interface "IRWLock" of set LockHelper only - because we must support a finer granularity of locking.
Interface "IMutex" should be used by easier guard implementations ... like "ResetableGuard"!
@implements -
@base INonCopyable
@devstatus ready to use
*//*-*************************************************************************************************************/
class WriteGuard : private INonCopyable
{
//-------------------------------------------------------------------------------------------------------------
// public methods
//-------------------------------------------------------------------------------------------------------------
public:
/*-****************************************************************************************************//**
@short ctor
@descr These ctors initialize the guard with a reference to used lock member of object to protect.
Null isn't allowed as value!
@seealso -
@param "pLock" ,reference to used lock member of object to protect
@param "rLock" ,reference to used lock member of object to protect
@return -
@onerror -
*//*-*****************************************************************************************************/
inline WriteGuard( IRWLock* pLock )
: m_pLock ( pLock )
, m_eMode ( E_NOLOCK )
{
lock();
}
//*********************************************************************************************************
inline WriteGuard( IRWLock& rLock )
: m_pLock ( &rLock )
, m_eMode ( E_NOLOCK )
{
lock();
}
/*-****************************************************************************************************//**
@short dtor
@descr We unlock the used lock member automaticly if user forget it.
@seealso -
@param -
@return -
@onerror -
*//*-*****************************************************************************************************/
inline ~WriteGuard()
{
unlock();
}
/*-****************************************************************************************************//**
@short set write lock
@descr Call this method to set the write lock. The call will block till all current threads are synchronized!
@seealso method unlock()
@param -
@return -
@onerror -
*//*-*****************************************************************************************************/
inline void lock()
{
switch( m_eMode )
{
case E_NOLOCK : {
// Acquire write access and set return state.
// Mode is set later if it was successful!
m_pLock->acquireWriteAccess();
m_eMode = E_WRITELOCK;
}
break;
case E_READLOCK : {
// User has downgrade to read access before!
// We must release it before we can set a new write access!
m_pLock->releaseReadAccess();
m_pLock->acquireWriteAccess();
m_eMode = E_WRITELOCK;
}
break;
default: break; // nothing to do
}
}
/*-****************************************************************************************************//**
@short unset write lock
@descr Call this method to unlock the rw-lock temp.!
Normaly we do it at dtor automaticly for you ...
@seealso method lock()
@param -
@return -
@onerror -
*//*-*****************************************************************************************************/
inline void unlock()
{
switch( m_eMode )
{
case E_READLOCK : {
// User has downgraded to a read lock before!
// => There isn't really a write lock ...
m_pLock->releaseReadAccess();
m_eMode = E_NOLOCK;
}
break;
case E_WRITELOCK : {
m_pLock->releaseWriteAccess();
m_eMode = E_NOLOCK;
}
break;
default: break; // nothing to do
}
}
/*-****************************************************************************************************//**
@short downgrade write access to read access without new blocking!
@descr If this write lock is set you can change it to a "read lock".
An "upgrade" is the same like new calling "lock()"!
@seealso -
@param -
@return -
@onerror -
*//*-*****************************************************************************************************/
inline void downgrade()
{
if( m_eMode == E_WRITELOCK )
{
m_pLock->downgradeWriteAccess();
m_eMode = E_READLOCK;
}
}
/*-****************************************************************************************************//**
@short return internal states
@descr For user they dont know what they are doing ...
@seealso -
@param -
@return Current set lock mode.
@onerror No error should occur.
*//*-*****************************************************************************************************/
inline ELockMode getMode() const
{
return m_eMode;
}
//-------------------------------------------------------------------------------------------------------------
// private methods
//-------------------------------------------------------------------------------------------------------------
private:
/*-****************************************************************************************************//**
@short disable using of these functions!
@descr It's not allowed to use this methods. Different problem can occur otherwise.
Thats why we disable it by make it private.
@seealso other ctor
@param -
@return -
@onerror -
*//*-*****************************************************************************************************/
WriteGuard();
//-------------------------------------------------------------------------------------------------------------
// private member
//-------------------------------------------------------------------------------------------------------------
private:
IRWLock* m_pLock ; /// reference to lock-member of protected object
ELockMode m_eMode ; /// protection against multiple lock calls without unlock and difference between supported lock modi
}; // class WriteGuard
} // namespace framework
#endif // INCLUDED_FRAMEWORK_INC_THREADHELP_WRITEGUARD_HXX
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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