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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 .
*/
#pragma once
#include <mutex>
#include <osl/conditn.hxx>
namespace framework{
/*-************************************************************************************************************
@short implement a gate to block multiple threads at the same time or unblock all
@descr A gate can be used as a negative-condition! You can open a "door" - wait() will not block ...
or you can close it - wait() blocks till open() is called again.
Then all currently waiting threads are running immediately - but new ones are blocked!
@attention To prevent us against wrong using, the default ctor, copy ctor and the =operator are marked private!
@devstatus ready to use
*//*-*************************************************************************************************************/
class Gate
{
// public methods
public:
/*-****************************************************************************************************
@short ctor
@descr These initialize the object right as an open gate.
*//*-*****************************************************************************************************/
Gate()
: m_bClosed ( false )
{
open();
}
/*-****************************************************************************************************
@short dtor
@descr Is user forget it - we open the gate ...
blocked threads can running ... but I don't know
if it's right - we are destroyed yet!?
*//*-*****************************************************************************************************/
~Gate()
{
open();
}
/*-****************************************************************************************************
@short copy-ctor
@descr Forbid copy construction
*//*-*****************************************************************************************************/
Gate(const Gate&) = delete;
/*-****************************************************************************************************
@short copy-assignment
@descr Forbid copy assigning
*//*-*****************************************************************************************************/
Gate& operator=(const Gate&) = delete;
/*-****************************************************************************************************
@short open the gate
@descr A wait() call will not block then.
@seealso method close()
*//*-*****************************************************************************************************/
void open()
{
// We must safe access to our internal member!
std::unique_lock aLock( m_aAccessLock );
// Set condition -> wait don't block any longer -> gate is open
m_aPassage.set();
// Check if operation was successful!
// Check returns false if condition isn't set => m_bClosed will be true then => we must return false; opening failed
m_bClosed = !m_aPassage.check();
}
/*-****************************************************************************************************
@short close the gate
@descr A wait() call will block then.
@seealso method open()
*//*-*****************************************************************************************************/
void close()
{
// We must safe access to our internal member!
std::unique_lock aLock( m_aAccessLock );
// Reset condition -> wait blocks now -> gate is closed
m_aPassage.reset();
// Check if operation was successful!
// Check returns false if condition was reset => m_bClosed will be true then => we can return true; closing ok
m_bClosed = !m_aPassage.check();
}
/*-****************************************************************************************************
@short must be called to pass the gate
@descr If gate "open" => wait() will not block.
If gate "closed" => wait() will block till somewhere open it again.
@seealso method wait()
@seealso method open()
*//*-*****************************************************************************************************/
void wait()
{
// We must safe access to our internal member!
std::unique_lock aLock( m_aAccessLock );
// If gate not closed - caller can pass it.
if( m_bClosed )
{
// Then we must release used access lock -
// because next call will block...
// and if we hold the access lock nobody else can use this object without a deadlock!
aLock.unlock();
// Wait for opening gate...
m_aPassage.wait();
}
}
// private member
private:
std::mutex m_aAccessLock;
::osl::Condition m_aPassage;
bool m_bClosed;
}; // class Gate
} // namespace framework
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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