onoff_switch.h

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/***************************************************************************
 * include/stxxl/bits/common/onoff_switch.h
 *
 * Kind of binary semaphore: initially OFF, then multiple waiters can attach
 * to the switch, which get notified one-by-one when switched ON.
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2002 Roman Dementiev <[email protected]>
 * Copyright (C) 2013 Timo Bingmann <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#ifndef STXXL_COMMON_ONOFF_SWITCH_HEADER
#define STXXL_COMMON_ONOFF_SWITCH_HEADER

#include <stxxl/bits/config.h>

#include <stxxl/bits/noncopyable.h>
#include <stxxl/bits/common/mutex.h>
#include <stxxl/bits/common/condition_variable.h>


STXXL_BEGIN_NAMESPACE

class onoff_switch : private noncopyable
{
 //! mutex for condition variable
 mutex m_mutex;

 //! condition variable
 condition_variable m_cond;

 //! the switch's state
 bool m_on;

public:
 //! construct switch
 onoff_switch(bool flag = false)
 : m_on(flag)
 { }
 //! turn switch ON and notify one waiter
 void on()
 {
 scoped_mutex_lock lock(m_mutex);
 m_on = true;
 lock.unlock();
 m_cond.notify_one();
 }
 //! turn switch OFF and notify one waiter
 void off()
 {
 scoped_mutex_lock lock(m_mutex);
 m_on = false;
 lock.unlock();
 m_cond.notify_one();
 }
 //! wait for switch to turn ON
 void wait_for_on()
 {
 scoped_mutex_lock lock(m_mutex);
 if (!m_on)
 m_cond.wait(lock);
 }
 //! wait for switch to turn OFF
 void wait_for_off()
 {
 scoped_mutex_lock lock(m_mutex);
 if (m_on)
 m_cond.wait(lock);
 }
 //! return true if switch is ON
 bool is_on()
 {
 scoped_mutex_lock lock(m_mutex);
 return m_on;
 }
};

STXXL_END_NAMESPACE

#endif // !STXXL_COMMON_ONOFF_SWITCH_HEADER