#ifndef _Semaphore_h_
#define _Semaphore_h_

#include <pthread.h>

class Semaphore{
public:
  Semaphore(int initial) { 
    val = initial; 
    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&condition, NULL);
  }
  
  ~Semaphore(){
    pthread_mutex_destroy(&mutex);
    pthread_cond_destroy(&condition);
  }
  
  void wait(){
    pthread_mutex_lock(&mutex);
    while (val == 0)
      pthread_cond_wait(&condition, &mutex);
      
    --val;
      
    pthread_mutex_unlock(&mutex);
  }
  
  void signal(){
    pthread_mutex_lock(&mutex);
    ++val;
    if (val == 1) pthread_cond_signal(&condition);
    
    pthread_mutex_unlock(&mutex);
  }
  
protected:
  int val;
  
  pthread_mutex_t mutex;
  pthread_cond_t condition;

};

#endif // _Semaphore_h_