request_queue_impl_qwqr.h

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/***************************************************************************
 * include/stxxl/bits/io/request_queue_impl_qwqr.h
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2002 Roman Dementiev <[email protected]>
 * Copyright (C) 2008, 2009 Andreas Beckmann <[email protected]>
 * Copyright (C) 2009 Johannes Singler <[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_IO_REQUEST_QUEUE_IMPL_QWQR_HEADER
#define STXXL_IO_REQUEST_QUEUE_IMPL_QWQR_HEADER

#include <list>

#include <stxxl/bits/io/request_queue_impl_worker.h>
#include <stxxl/bits/common/mutex.h>


STXXL_BEGIN_NAMESPACE

//! \addtogroup iolayer
//! \{

class request_queue_impl_qwqr : public request_queue_impl_worker
{
private:
 typedef request_queue_impl_qwqr self;
 typedef std::list<request_ptr> queue_type;

 mutex write_mutex;
 mutex read_mutex;
 queue_type write_queue;
 queue_type read_queue;

 state<thread_state> m_thread_state;
 thread_type thread;
 semaphore sem;

 static const priority_op _priority_op = WRITE;

 static void * worker(void* arg);

public:
 // \param n max number of requests simultaneously submitted to disk
 request_queue_impl_qwqr(int n = 1);

 // in a multi-threaded setup this does not work as intended
 // also there were race conditions possible
 // and actually an old value was never restored once a new one was set ...
 // so just disable it and all it's nice implications
 void set_priority_op(priority_op op)
 {
 //_priority_op = op;
 STXXL_UNUSED(op);
 }
 void add_request(request_ptr& req);
 bool cancel_request(request_ptr& req);
 ~request_queue_impl_qwqr();
};

//! \}

STXXL_END_NAMESPACE

#endif // !STXXL_IO_REQUEST_QUEUE_IMPL_QWQR_HEADER
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