#ifndef BARRIER_H_
#define BARRIER_H_

#include <pthread.h>		// has pthread_ routines

// ---- Class for barrier --------------------------------------------

class barrier {

public:

  // Constructor:  n is the number of threads that will participate.
  barrier(const int n) {
    nThreads = n;
    count = 0;
    pthread_mutex_init(&barrierLock, NULL);
    pthread_cond_init(&mustWait, NULL);
  }

  // Destructor.
  ~barrier(void) {
    pthread_mutex_destroy(&barrierLock);
    pthread_cond_destroy(&mustWait);
  }

  // Function all threads should call "at the barrier".
  void wait(void) {
    // Get lock on shared variables.
    pthread_mutex_lock(&barrierLock);
    if (++count < nThreads) {
      // not all threads have arrived yet -- wait
      pthread_cond_wait(&mustWait, &barrierLock);
    }
    else {
      // all threads have arrived -- notify waiting threads
      //   and reset for next time
      pthread_cond_broadcast(&mustWait);
      count = 0;
    }
    pthread_mutex_unlock(&barrierLock);
  }

private:
  // Make copy constructor and assignment operator private
  //   so they can't be used (since it's not clear this would 
  //   make sense).
  barrier(const barrier & bb);
  barrier & operator= (const barrier & bb);
  
  // member variables
  int nThreads;			// number of threads participating
  int count;			// number that have arrived since last
				//   reset
  pthread_mutex_t barrierLock;
  pthread_cond_t mustWait;
};

#endif // BARRIER_H_