Queue
QueueSimple lightweight queue implementation using data size registration and singly linked lists as the underlying type
/*
Author: Jared Thomas
Date: Tuesday, August 2, 2022
Type-generic queue using singly linked lists
*/
#include <stdlib.h>
#include <stdio.h>
typedef struct Node {
void * data;
struct Node * next;
} Node;
typedef struct Queue {
Node * head;
size_t data_size;
} Queue;
typedef struct Person {
char const * name;
unsigned short int age;
char const * occupation;
} Person;
Queue *create_queue();
void register_new_size(Queue *, size_t data_size);
void enqueue(Queue *, void *data);
void *front(Queue *);
int length(Queue *);
int is_empty(Queue *);
void dequeue(Queue *);
Queue *copy_queue(Queue *);
void print(Queue *);
void destroy_queue(Queue *);
int is_empty(Queue *b)
{
if(b->head == NULL) { return 1; }
return 0;
}
Queue *create_queue()
{
Queue *new_queue = (Queue *)malloc(sizeof(Queue));
new_queue->head = NULL;
return new_queue;
}
void destroy_queue(Queue *b)
{
while(!is_empty(b)) {
dequeue(b);
}
free(b);
}
void enqueue(Queue *b, void *data)
{
Node *new_node = (Node *)malloc(sizeof(Node));
new_node->data = malloc(b->data_size);
memcpy(new_node->data, data, b->data_size);
new_node->next = NULL;
if(is_empty(b)) {
b->head = new_node;
return;
}
Node *n = b->head;
while(n->next != NULL) {
n = n->next;
}
n->next = new_node;
}
void *front(Queue *b)
{
return (b->head)->data;
}
int length(Queue *b)
{
Queue *copy = create_queue();
register_new_size(copy, b->data_size);
int count = 0;
while(!is_empty(b)) {
enqueue(copy, front(b));
dequeue(b);
count++;
}
while(!is_empty(copy)) {
enqueue(b, front(copy));
dequeue(copy);
}
destroy_queue(copy);
return count;
}
void dequeue(Queue *b)
{
Node *upcoming = b->head->next;
free(b->head);
b->head = NULL;
if(upcoming != NULL) {
b->head = upcoming;
}
}
Queue *copy_queue(Queue *b)
{
Queue *copy = create_queue();
register_new_size(copy, b->data_size);
int count = length(b);
while(count > 0) {
void *d = front(b);
enqueue(copy, d);
dequeue(b);
enqueue(b, d);
count--;
}
return copy;
}
void print(Queue *b)
{
if(is_empty(b)) {
printf("[empty]\n");
return;
}
Queue *copy = copy_queue(b);
printf("[");
while(!is_empty(copy)) {
struct Person *d = (struct Person *)front(copy);
printf("%s, ", d->name);
dequeue(copy);
}
printf("]");
printf("\n");
destroy_queue(copy);
}
void register_new_size(Queue *b, size_t data_size)
{
b->data_size = data_size;
}
int main(void)
{
Queue *queue = create_queue();
Person chase = { "Chase", 49, "Banker" };
Person evan = { "Evan", 34, "Doctor" };
Person susie = { "Susie", 43, "Teacher" };
register_new_size(queue, sizeof(Person));
enqueue(queue, &chase);
enqueue(queue, &evan);
enqueue(queue, &susie);
print(queue);
dequeue(queue);
print(queue);
dequeue(queue);
print(queue);
dequeue(queue);
print(queue);
destroy_queue(queue);
return 0;
}
```
