spinlock.h

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/*
 *  Copyright (C) 2004 Bregmasoft
 * 
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2 of the License, or (at your option) any later
 * version.
 * 
 * This program 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
 * Place, Suite 330, Boston, MA 02111-1307 USA
 */
#ifndef ZYGOMA_SPINLOCK_H_ 
#define ZYGOMA_SPINLOCK_H_ 

#include <atomic.h>

namespace Zygoma
{
  class SpinLockMutex
  {
    friend class SpinLock;

  public:
    SpinLockMutex();

    ~SpinLockMutex();

  private:
    void acquire();
    void release();

  protected:
    /* @{ */
    static const AtomicWord SPIN_LOCK_AVAILABLE   = 0;

    static const AtomicWord SPIN_LOCK_UNAVAILABLE = ~SPIN_LOCK_AVAILABLE;
    /* @} */

  private:
    AtomicWord m_key;
  };

  inline void
  SpinLockMutex::acquire()
  {
    register AtomicWord lock = SPIN_LOCK_UNAVAILABLE;
    do
    {
      lock = atomicExchange(&m_key, lock);
    } while (lock != SPIN_LOCK_AVAILABLE);
  }

  inline void
  SpinLockMutex::release()
  {
      atomicExchange(&m_key, SPIN_LOCK_AVAILABLE);
  }

  class SpinLock
  {
  public:
    SpinLock(SpinLockMutex& mutex)
    : m_mutex(mutex)
    { m_mutex.acquire(); }

    ~SpinLock()
    { m_mutex.release(); }

  protected:
    SpinLock(const SpinLock&);            /* unimplemented */
    SpinLock& operator=(const SpinLock&); /* unimplemented */

  protected:
    SpinLockMutex& m_mutex;
  };
} // namespace Zygoma

#endif // ZYGOMA_SPINLOCK_H_ 

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