240 lines
10 KiB
C++
240 lines
10 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*************************************************************************
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*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* Copyright 2000, 2010 Oracle and/or its affiliates.
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*
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* OpenOffice.org - a multi-platform office productivity suite
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*
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* This file is part of OpenOffice.org.
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*
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* OpenOffice.org is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 3
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* only, as published by the Free Software Foundation.
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*
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* OpenOffice.org is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License version 3 for more details
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* (a copy is included in the LICENSE file that accompanied this code).
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*
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* You should have received a copy of the GNU Lesser General Public License
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* version 3 along with OpenOffice.org. If not, see
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* <http://www.openoffice.org/license.html>
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* for a copy of the LGPLv3 License.
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*
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************************************************************************/
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#ifndef __FRAMEWORK_THREADHELP_WRITEGUARD_HXX_
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#define __FRAMEWORK_THREADHELP_WRITEGUARD_HXX_
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#include <threadhelp/inoncopyable.h>
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#include <threadhelp/irwlock.h>
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namespace framework{
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/*-************************************************************************************************************//**
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@short implement a guard to set write locks
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@descr This guard should be used to set a lock for reading AND writing object internal member.
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We never need a own mutex to safe our internal member access - because
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a guard is used as function-local member only. There exist no multithreaded access to it realy ...
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@attention a) To prevent us against wrong using, the default ctor, copy ctor and the =operator are maked private!
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b) Use interface "IRWLock" of set LockHelper only - because we must support a finer granularity of locking.
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Interface "IMutex" should be used by easier guard implementations ... like "ResetableGuard"!
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@implements -
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@base INonCopyable
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@devstatus ready to use
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*//*-*************************************************************************************************************/
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class WriteGuard : private INonCopyable
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{
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//-------------------------------------------------------------------------------------------------------------
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// public methods
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//-------------------------------------------------------------------------------------------------------------
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public:
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/*-****************************************************************************************************//**
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@short ctor
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@descr These ctors initialize the guard with a reference to used lock member of object to protect.
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Null isn't allowed as value!
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@seealso -
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@param "pLock" ,reference to used lock member of object to protect
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@param "rLock" ,reference to used lock member of object to protect
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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inline WriteGuard( IRWLock* pLock )
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: m_pLock ( pLock )
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, m_eMode ( E_NOLOCK )
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{
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lock();
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}
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//*********************************************************************************************************
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inline WriteGuard( IRWLock& rLock )
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: m_pLock ( &rLock )
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, m_eMode ( E_NOLOCK )
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{
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lock();
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}
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/*-****************************************************************************************************//**
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@short dtor
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@descr We unlock the used lock member automaticly if user forget it.
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@seealso -
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@param -
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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inline ~WriteGuard()
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{
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unlock();
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}
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/*-****************************************************************************************************//**
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@short set write lock
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@descr Call this method to set the write lock. The call will block till all current threads are synchronized!
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@seealso method unlock()
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@param -
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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inline void lock()
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{
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switch( m_eMode )
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{
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case E_NOLOCK : {
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// Acquire write access and set return state.
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// Mode is set later if it was successful!
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m_pLock->acquireWriteAccess();
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m_eMode = E_WRITELOCK;
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}
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break;
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case E_READLOCK : {
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// User has downgrade to read access before!
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// We must release it before we can set a new write access!
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m_pLock->releaseReadAccess();
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m_pLock->acquireWriteAccess();
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m_eMode = E_WRITELOCK;
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}
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break;
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default: break; // nothing to do
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}
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}
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/*-****************************************************************************************************//**
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@short unset write lock
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@descr Call this method to unlock the rw-lock temp.!
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Normaly we do it at dtor automaticly for you ...
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@seealso method lock()
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@param -
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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inline void unlock()
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{
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switch( m_eMode )
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{
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case E_READLOCK : {
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// User has downgraded to a read lock before!
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// => There isn't realy a write lock ...
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m_pLock->releaseReadAccess();
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m_eMode = E_NOLOCK;
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}
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break;
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case E_WRITELOCK : {
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m_pLock->releaseWriteAccess();
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m_eMode = E_NOLOCK;
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}
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break;
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default: break; // nothing to do
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}
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}
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/*-****************************************************************************************************//**
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@short downgrade write access to read access without new blocking!
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@descr If this write lock is set you can change it to a "read lock".
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An "upgrade" is the same like new calling "lock()"!
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@seealso -
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@param -
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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inline void downgrade()
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{
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if( m_eMode == E_WRITELOCK )
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{
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m_pLock->downgradeWriteAccess();
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m_eMode = E_READLOCK;
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}
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}
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/*-****************************************************************************************************//**
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@short return internal states
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@descr For user they dont know what they are doing ...
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@seealso -
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@param -
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@return Current set lock mode.
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@onerror No error should occure.
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*//*-*****************************************************************************************************/
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inline ELockMode getMode() const
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{
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return m_eMode;
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}
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//-------------------------------------------------------------------------------------------------------------
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// private methods
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//-------------------------------------------------------------------------------------------------------------
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private:
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/*-****************************************************************************************************//**
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@short disable using of these functions!
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@descr It's not allowed to use this methods. Different problem can occure otherwise.
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Thats why we disable it by make it private.
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@seealso other ctor
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@param -
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@return -
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@onerror -
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*//*-*****************************************************************************************************/
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WriteGuard();
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//-------------------------------------------------------------------------------------------------------------
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// private member
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//-------------------------------------------------------------------------------------------------------------
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private:
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IRWLock* m_pLock ; /// reference to lock-member of protected object
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ELockMode m_eMode ; /// protection against multiple lock calls without unlock and difference between supported lock modi
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}; // class WriteGuard
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} // namespace framework
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#endif // #ifndef __FRAMEWORK_THREADHELP_WRITEGUARD_HXX_
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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