A simple but effective Queue structure in C for School projects.

queue.c

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

#include "queue.h"


Queue *queue_new(Queue *q, size_t size, bool (*equals)(const void*, const void*))
{
	if (size <= 0) return NULL;
	q->data     = malloc((size+1)* sizeof(*q->data), false);
	q->front = q->rear = 0;
	q->equals = equals;
	return q;
}
void queue_destroy(Queue *q)
{
	if (q == NULL) return;
	free(q->data);     q->data = NULL;
}

bool queue_contains(Queue *q, Object key)
{
	if (q->equals == NULL) {
		fprintf(stderr, "%s: equals callback undefined\n", __func__);
		return false;
	}

	for (int idx = q->front; idx < q->rear; idx++) {
		if (q->equals(q->data[idx], key)) {
			return true;
		}
	}
	return false;
}

void queue_push(Queue *q, Object key)
{
	if (queue_contains(q, key)) { return; }
	q->data[q->rear++] = key;
}

Object queue_pop(Queue *q)
{
	return q->data[q->front++];
}

int queue_size(Queue *q) { return q->rear - q->front; }
bool queue_is_empty(Queue *q) { return q->front == q->rear; }

void queue_reset(Queue *q)
{
	q->front = q->rear = 0;
}

queue.h

#ifndef _QUEUE_H_
#define _QUEUE_H_

typedef unsigned char bool;
#define true  1
#define false 0

typedef void* Object;

typedef struct _queue {
	int front, rear;
	void* *data;      /* data[idx] = obj */
	bool (*equals)(const void*, const void*);
} Queue;

Queue *queue_new(Queue *q, size_t size, bool (*equals)(const void*, const void*));
void   queue_destroy(Queue *q);
bool   queue_contains(Queue *q, Object key);
void   queue_push(Queue *q, Object key);
Object queue_pop(Queue *q);
int    queue_size(Queue *q);
bool   queue_is_empty(Queue *q);
void   queue_reset(Queue *q);
void   queue_sort(Queue *q);

#endif