simple_generic_queue.c

#include<stdio.h>
#include<stdlib.h>
#include <string.h>

typedef struct node {
   size_t len;
   void *value;
   struct node *next;
} Node ;

Node* init_node(void* value, size_t len) {
   Node* node = (Node*)  calloc(1, sizeof(Node));
   node->len = len, node->value = value, node->next = NULL;
   return node;
}

void enqueue(Node *node, void *value) {
   if(value == NULL) return;
   printf("--\n");
   node->len++;
   if(node->next == NULL)
      node->next = init_node(value, 1), printf("aaa\n");
   else
      enqueue(node->next, value);
}

void* dequeue(Node **head, size_t n) {
   void *aux = calloc(1, n);
   memcpy(aux, (*head)->value, n);

   if((*head)->next == NULL)
      free(head);
   else {
      Node* node_aux = (*head);
      *head = node_aux->next;
      free(node_aux);
   }

   return aux;
}

void show_queue(Node* head, void (*show_val)(void*)) {
   if(head->next == NULL) {
      show_val(head->value);
      return;
   } else {
      show_val(head->value);
      show_queue(head->next, show_val);
   }
}

size_t queue_len(Node* head) { return head->len ;}

void show_int(void *n) {
   if(n == NULL)
      printf("Null Pointer\n");
   else {
      int *k = (int*) n;
      printf("%d->", *k);
   }
}

int main(void) {
   int n = 5;
   int *arr = (int*) calloc(n, sizeof(int));
   for(int i = 0; i < n; i++)
      *(arr + i) = i + 1, printf("%d ", *(arr + i));
   printf("\n");
   Node* head = init_node(&arr[0], 1);

   for(int i = 1; i < n; i++)
      enqueue(head, &arr[i]);
   show_queue(head, &show_int);

   int *p = (int*) dequeue(&head, sizeof(int));
   printf("\ndequeue: %d\n", *p);
   show_queue(head, &show_int);

   p = (int*) dequeue(&head, sizeof(int));
   printf("\ndequeue: %d\n", *p);
   show_queue(head, &show_int);

   p = (int*) dequeue(&head, sizeof(int));
   printf("\ndequeue: %d\n", *p);
   show_queue(head, &show_int);


   printf("\nTamanho da fila: %zu", queue_len(head));
   return EXIT_SUCCESS;
}