ftp.disi.unige.it/2015-02-11.ftp.disi.unige.it.tar/ftp.disi.unige.it/pub/.person/CataniaB/teach-act/esempi/Comp-Sep/queue.c

C/C++ Source or Header | 1997-04-22 | 720b | 46 lines

#include <stdio.h>
#include "queue.h"

char is_empty_queue(queue *p) { return(p->head->next == p->tail); }

list lmakecell(void) { return (list) malloc (sizeof (struct qcell));}

void empty_queue(queue *p)
{
    p->head = lmakecell();
    p->tail = lmakecell();
    p->head->next=p->tail;
}

void destroy(queue *p)
{
    free(p->tail);
    free(p->head);
}

void enqueue(generic el,queue *p)
{
  list q;

  p->tail->el=el;
  q =lmakecell();
  p->tail->next=q;
  p->tail=q;
}

generic dequeue (queue *p)
{
  list q;
  generic e;
  if (!is_empty_queue(p))
    {
      q=p->head->next;
      e = q->el;
      p->head->next=q->next;
      free(q);
      return (e);
    }
  return NULL;
 }