fifo.h

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// Larbin
// Sebastien Ailleret
// 09-11-99 -> 20-01-00

/* standard fifo in RAM */

#ifndef FIFO_H
#define FIFO_H

#define std_size 100

#include <pthread.h>

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

 public:
  /* Specific constructor */
  Fifo (uint size = std_size);

  /* Destructor */
  virtual ~Fifo ();

  /* Reduce the size of tab if necessary */
  void reduce ();

  /* 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>
Fifo<T>::Fifo (uint size = std_size) {
  tab = new T*[size];
  this->size = size;
  in = 0;
  out = 0;
  pthread_mutex_init (&lock, NULL);
  pthread_cond_init (&nonEmpty, NULL);
}

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

template <class T>
void Fifo<T>::reduce () {
  if (size > std_size && ((in + size - out) % size)*3 < size) {
	// if the tab is too big, reduce it
	T **tmp = new T*[size/2];
	uint i;
	for (i=0; ((out+i) % size) != in; i++) {
	  tmp[i] = tab[(out+i) % size];
	}
	out = 0;
	in = i;
	size /= 2;
	delete [] tab;
	tab = tmp;
  }
}

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

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

template <class T>
void Fifo<T>::put (T *obj) {
  pthread_mutex_lock(&lock);
  tab[in] = obj;
  if (in == out) {
    pthread_cond_broadcast(&nonEmpty);
  }
  in = (in + 1) % size;
  if (in == out) {
    T **tmp;
    tmp = new T*[2*size];
    for (uint i=out; i<size; i++) {
      tmp[i] = tab[i];
    }
    for (uint i=0; i<in; i++) {
      tmp[i+size] = tab[i];
    }
    in += size;
    size *= 2;
    delete [] tab;
    tab = tmp;
  }
  pthread_mutex_unlock(&lock);
}

template <class T>
void Fifo<T>::putForce (T *obj) {
  put(obj);
}

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

#endif // FIFO_H