Barrier.h

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#ifndef HYPERTABLE_BARRIER_H
#define HYPERTABLE_BARRIER_H

#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>

#include "Mutex.h"

namespace Hypertable {

  class Barrier {
  public:

    Barrier() : m_hold(false), m_counter(0) {
    }

    void enter() {
      ScopedLock lock(m_mutex);
      while (m_hold)
        m_unblocked_cond.wait(lock);
      m_counter++;
    }

    void exit() {
      ScopedLock lock(m_mutex);
      m_counter--;
      if (m_hold && m_counter == 0)
        m_quiesced_cond.notify_one();
    }

    void put_up() {
      ScopedLock lock(m_mutex);
      m_hold = true;
      while (m_counter > 0)
        m_quiesced_cond.wait(lock);
    }

    void take_down() {
      ScopedLock lock(m_mutex);
      m_hold = false;
      m_unblocked_cond.notify_all();
    }

    class ScopedActivator {
    public:
      ScopedActivator(Barrier &barrier) : m_barrier(barrier) {
        m_barrier.put_up();
      }
      ~ScopedActivator() {
        m_barrier.take_down();
      }
    private:
      Barrier &m_barrier;
    };

  private:
    Mutex            m_mutex;
    boost::condition m_unblocked_cond;
    boost::condition m_quiesced_cond;
    bool             m_hold;
    uint32_t         m_counter;

  };

}

#endif // HYPERTABLE_BARRIER_H