include/stxxl/bits/io/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 <dementiev@mpi-sb.mpg.de>
 *  Copyright (C) 2008, 2009 Andreas Beckmann <beckmann@cs.uni-frankfurt.de>
 *  Copyright (C) 2009 Johannes Singler <singler@ira.uka.de>
 *
 *  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> _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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