request_with_waiters.cpp

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/***************************************************************************
 * lib/io/request_with_waiters.cpp
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2002 Roman Dementiev <[email protected]>
 * Copyright (C) 2008 Andreas Beckmann <[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)
 **************************************************************************/

#include <stxxl/bits/common/mutex.h>
#include <stxxl/bits/common/onoff_switch.h>
#include <stxxl/bits/io/request_with_waiters.h>
#include <stxxl/bits/parallel.h>

#include <algorithm>
#include <functional>


STXXL_BEGIN_NAMESPACE

bool request_with_waiters::add_waiter(onoff_switch* sw)
{
 // this lock needs to be obtained before poll(), otherwise a race
 // condition might occur: the state might change and notify_waiters()
 // could be called between poll() and insert() resulting in waiter sw
 // never being notified
 scoped_mutex_lock lock(waiters_mutex);

 if (poll()) // request already finished
 {
 return true;
 }

 waiters.insert(sw);

 return false;
}

void request_with_waiters::delete_waiter(onoff_switch* sw)
{
 scoped_mutex_lock lock(waiters_mutex);
 waiters.erase(sw);
}

void request_with_waiters::notify_waiters()
{
 scoped_mutex_lock lock(waiters_mutex);
 std::for_each(waiters.begin(),
 waiters.end(),
 std::mem_fun(&onoff_switch::on)
 _STXXL_FORCE_SEQUENTIAL);
}

/*
int request_with_waiters::nwaiters()
{
 scoped_mutex_lock lock(waiters_mutex);
 return waiters.size();
}
*/

STXXL_END_NAMESPACE
// vim: et:ts=4:sw=4