#include <stdlib.h>
#include <stdio.h>
#include "smart_pointers.h"

/* Initialize a smart pointer */
void init_smart_malloc(struct smart_pointer *sm_ptr, size_t buffer_size) {
  sm_ptr->nb_ptr = 0;
  sm_ptr->buffer_size = buffer_size;
  pthread_mutex_init(&sm_ptr->mutex, NULL);
}

/* create a new active pointer */
void* new_pointer(struct smart_pointer *sm_ptr) {
  pthread_mutex_lock(&sm_ptr->mutex);
  sm_ptr->nb_ptr++;
  if(sm_ptr->nb_ptr == 1) {
    /* allocate the buffer */
    sm_ptr->ptr = malloc(sm_ptr->buffer_size);
    if(sm_ptr->ptr == NULL) {
      fprintf(stderr, "Failed to allocate %lu bytes\n", sm_ptr->buffer_size);
    }
  }
  void* res = sm_ptr->ptr;
  pthread_mutex_unlock(&sm_ptr->mutex);

  return res;
}

/* decrement the number of active pointers, and free the buffer if there are no
 * more active pointers
 */
void smart_pointer_free(struct smart_pointer *sm_ptr) {
  pthread_mutex_lock(&sm_ptr->mutex);
  sm_ptr->nb_ptr--;
  if(sm_ptr->nb_ptr == 0) {
    free(sm_ptr->ptr);
    sm_ptr->ptr = NULL;
  }
  pthread_mutex_unlock(&sm_ptr->mutex);
}