constantsizedfifo.h

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// Larbin
// Sebastien Ailleret
// 15-04-00 -> 15-04-00

/* this fifo will not grow
 */

#ifndef CONSTANTFIFO_H
#define CONSTANTFIFO_H

#include <assert.h>
#include <pthread.h>

#include "xutils/GenericFifo.h"

template <class T>
class ConstantSizedFifo : public GenericFifo<T> {
 protected:
  uint size;
  T **tab;
  pthread_mutex_t lock;
  pthread_cond_t nonEmpty;

 public:
  /* Specific constructor */
  ConstantSizedFifo (uint size);

  /* Destructor */
  virtual ~ConstantSizedFifo ();

  /* get the first object */
  virtual T *get ();

  /* get the first object (non totally blocking)
   * return NULL if there is none
   */
  virtual T *tryGet ();

  /* add an object in the fifo */
  virtual void put (T *obj);

  /* add an object in the fifo
   * never block !!!
   */
  virtual void putForce (T *obj);

  /* how many itmes are there inside ? */
  virtual int getLength ();
};

template <class T>
ConstantSizedFifo<T>::ConstantSizedFifo (uint size) {
  this->size = size+1;
  tab = new T*[this->size];
  in = 0;
  out = 0;
  pthread_mutex_init (&lock, NULL);
  pthread_cond_init (&nonEmpty, NULL);
}

template <class T>
ConstantSizedFifo<T>::~ConstantSizedFifo () {
  delete [] tab;
  pthread_mutex_destroy (&lock);
  pthread_cond_destroy (&nonEmpty);
}

template <class T>
T *ConstantSizedFifo<T>::get () {
  T *tmp;
  pthread_mutex_lock(&lock);
  while (in == out) {
    pthread_cond_wait(&nonEmpty, &lock);
  }
  tmp = tab[out];
  out = (out + 1) % size;
  pthread_mutex_unlock(&lock);
  return tmp;
}

template <class T>
T *ConstantSizedFifo<T>::tryGet () {
  T *tmp = NULL;
  pthread_mutex_lock(&lock);
  if (in != out) {
	// The stack is not empty
	tmp = tab[out];
	out = (out + 1) % size;
  }
  pthread_mutex_unlock(&lock);
  return tmp;
}

template <class T>
void ConstantSizedFifo<T>::put (T *obj) {
  pthread_mutex_lock(&lock);
  tab[in] = obj;
  if (in == out) {
    pthread_cond_broadcast(&nonEmpty);
  }
  in = (in + 1) % size;
  assert (in != out);
  pthread_mutex_unlock(&lock);
}

template <class T>
void ConstantSizedFifo<T>::putForce (T *obj) {
  pthread_mutex_lock(&lock);
  tab[in] = obj;
  if (in == out) {
    pthread_cond_broadcast(&nonEmpty);
  }
  in = (in + 1) % size;
  assert(in != out);
  pthread_mutex_unlock(&lock);
}

template <class T>
int ConstantSizedFifo<T>::getLength () {
  int tmp;
  pthread_mutex_lock(&lock);
  tmp = (in + size - out) % size;
  pthread_mutex_unlock(&lock);
  return tmp;
}

#endif // CONSTANTFIFO_H