ThreadQueue.h

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/*                                              -*- mode:C++ -*-
  ThreadQueue.h Thread-Safe byte buffer
  Copyright (C) 2014 The Regents of the University of New Mexico.  All rights reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  USA
*/

#ifndef QUE_H
#define QUE_H

#include "itype.h"
#include "Mutex.h"
#include "Logger.h"

#define THREADQUEUE_MAX_BYTES (2048)   // How big does this actually need to be?

namespace MFM
{
  class ThreadQueue
  {
  private:

    Mutex m_mutex;

    struct MoreInputIsAvailable : public Mutex::Predicate
    {
      ThreadQueue & m_threadQueue;
      MoreInputIsAvailable(ThreadQueue & tq) : Predicate(tq.m_mutex), m_threadQueue(tq) { }

      virtual bool EvaluatePrecondition()
      {
        bool ret = m_threadQueue.m_heldBytes == 0;
        if (!ret)
        {
          LOG.Error("MoreInputIsAvailable precondition failed: m_heldBytes = %d",
                    m_threadQueue.m_heldBytes);
        }
        return ret;
      }

      virtual bool EvaluatePredicate()
      {
        return m_threadQueue.m_heldBytes > 0;
      }
    } m_moreInputIsAvailable;

    u8 m_queueData[THREADQUEUE_MAX_BYTES];

    u32 m_writeHead;

    u32 m_readHead;

    u32 m_heldBytes;

    u32 UnsafeRead(u8* bytes, u32 length);

  public:

    ThreadQueue();

    ~ThreadQueue();

    void Write(u8* bytes, u32 length);

    void ReadBlocking(u8* bytes, u32 length);

    u32 Read(u8* bytes, u32 length);

    void PeekRead(u8* toBuffer, u32 index, u32 length);

    u32 BytesAvailable() ;

    void Flush();

  };
}

#endif /* QUE_H */