232 lines
9.9 KiB
C++
232 lines
9.9 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* This file incorporates work covered by the following license notice:
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright
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* ownership. The ASF licenses this file to you under the Apache
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* License, Version 2.0 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.apache.org/licenses/LICENSE-2.0 .
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*/
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#ifndef INCLUDED_FRAMEWORK_INC_THREADHELP_WRITEGUARD_HXX
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#define INCLUDED_FRAMEWORK_INC_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 really ...
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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 really 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 occur.
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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 occur 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 // INCLUDED_FRAMEWORK_INC_THREADHELP_WRITEGUARD_HXX
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/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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