C_lib/linked_lists/queue.c

/*
* C_lib Copyright (C) 2021 Wael Karram.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

/* This file contains the function implementations for queues. */
/* Include guards + includes. */
#ifndef QUEUE_C
#define QUEUE_C
#include "queue.h"
#endif /* QUEUE_C */
/* Include dependencies from linked list. */
#ifndef SINGLE_LINKED_LIST_H
#include "single_linked_list.h"
#endif

/* Function implementations. */

/* This function initializes a new empty queue. */
/* Will return a pointer to the queue on success, otherwise will return NULL. */
static inline queue_t *initialize_queue() {
	/* Variables. */
	queue_t *result;

	/* Attempt to allocate. */
	result = (queue_t*) malloc(sizeof(queue_t));

	/* Check if the allocation failed. */
	if (!result)
		return NULL;

	/* Allocate the internal list struct. */
	result->list = (linked_list_t*) malloc(sizeof(linked_list_t));

	/* Check if the allocation failed. */
	if (!(result->list)) {
		free(result);
		return NULL;
	}

	/* Initialize the internal fields. */
	result->tail = NULL;
	result->list->head = NULL;
	result->list->length = 0;

	/* Return the result. */
	return result;
}

/* This function enqueues a node. */
/* This function attempts to enqueue a given node into the given queue. */
static inline void enqueue(queue_t *queue, node_t *node) {
	/* Input sanity check. */
	assert(queue && (queue->list) && node && (((queue->list->head) && (queue->tail)) || (!(queue->list->head) && !(queue->tail))));

	/* Delegate. */
	prepend_node_single_linked_list(queue->list, node);
	/* Check if to update the tail. */
	if (!(queue->tail) || queue->list->length == 1)
		queue->tail = node;
}

/* This function allocates and enqueues a node. */
/* This function attempts to create a node then enqueue it into the given queue, on success will return SUCCESS_CODE_QUEUE_C, otherwise will return FAILURE_CODE_QUEUE_C. */
static inline int enqueue_data(queue_t *queue, void *data) {
	/* Variables. */
	node_t *node;

	/* Input sanity check. */
	assert(queue && (queue->list) && (((queue->list->head) && (queue->tail)) || (!(queue->list->head) && !(queue->tail))));

	/* Attempt to allocate the node. */
	node = (node_t*) malloc(sizeof(node));
	if (!node)
		return FAILURE_CODE_QUEUE_C;

	/* Add the data to the node. */
	node->data = data;

	/* Attempt to enqueue the node. */
	enqueue(queue, node);
	return SUCCESS_CODE_QUEUE_C;
}

/* This function dequeues a node. */
/* This function attempts to dequeue a node from the given queue, on success will return a pointer to the dequeued node - otherwise returns NULL. */
static inline node_t *dequeue(queue_t *queue) {
	/* Variables. */
	node_t *result, *replacement, *tmp;
	int i;

	/* Input sanity check. */
	assert(queue && (queue->list) && (((queue->list->head) && (queue->tail)) || (!(queue->list->head) && !(queue->tail))));

	/* Attempt to dequeue the node. */
	/* Check if the length is zero. */
	if (!(queue->list->length) || !(queue->tail))
		return NULL;
	if (queue->list->length == 1) {
		/* A queue that is of length 1. */
		result = queue->list->head;
		queue->list->head = NULL;
		queue->tail = NULL;
	} else {
		/* This is the general case, move the tail and unlink. */
		/* Set the result to be the tail. */
		result = queue->tail;
		/* Attempt to find the new tail. */
		tmp = queue->list->head;
		while (tmp->next != result)
			tmp = tmp->next;
		/* Unlink and set the new tail. */
		tmp->next = NULL;
		queue->tail = tmp;
	}
	/* Decrease the length. */
	(queue->list->length)--;

	/* Return the node. */
	return result;
}

/* This function frees all the nodes of the given queue and the queue itself (setting it to NULL). */
/* Note that it doesn't touch the data stored within the queue's nodes, might exhibit undefined behavior when the internal state of the queue isn't coherent. */
static inline void clear_queue(queue_t **queue) {
	/* Sanity check. */
	assert(queue && (*queue) && ((*queue)->list));

	/* Delegate to implementation (linked list). */
	clear_list_single_linked_list(&((*queue)->list));

	/* Successfully cleared the internal structure, just free the queue struct and set the pointer to NULL. */
	free(*queue);
	*queue = NULL;
}

/* This function frees all the nodes of the given queue and the queue itself (setting it to NULL).*/
/* Might exhibit undefined behavior on inconsistent internal state of the queue. */
/* If free_function is NULL, then it the standard library's free() call is used. */
static inline void clear_queue_data(queue_t **queue, void (*free_func)(const void*)) {
	/* Sanity check. */
	assert(queue && (*queue));

	/* Delegate to implementation (linked list). */
	clear_list_data_single_linked_list(&((*queue)->list), free_func);

	/* Successfully cleared the internal structure, just free the queue struct and set the pointer to NULL. */
	free(*queue);
	*queue = NULL;
}

/* This function deletes all the nodes of the given queue, but doesn't touch the queue struct itself or the stored data. */
static inline void clear_queue_nodes(queue_t *queue) {
	/* Sanity check. */
	assert(queue && (queue->list));

	/* Check if there is anything to remove. */
	if (!(queue->list->length) || !(queue->list->head))
		return;

	/* Delegate to implementation in linked list. */
	clear_list_nodes_single_linked_list(queue->list);
	queue->tail = NULL;
}

/* This function deletes all the nodes of the given queue, but doesn't touch the queue struct itself or the stored data. */
static inline void clear_queue_nodes_data(queue_t *queue, void (*free_function)(const void*)) {
	/* Sanity check. */
	assert(queue && (queue->list));

	/* Check if there is anything to remove. */
	if (!(queue->list->length) || !(queue->list->head))
		return;

	/* Delegate to implementation in linked list. */
	clear_list_nodes_data_single_linked_list(queue->list, free_function);
	queue->tail = NULL;
}

/* This function serializes the queue. */
/* Note that it'll return NULL on allocation failure or invalid input. */
/* Note that the array has to be allocated by the caller. */
/* The array setting function is used to set the values at an index, takes the pointer to the array, index and value to put. */
void *serialize_queue(queue_t *queue, void (*array_setting_function)(void*, size_t, void*), void *array) {
	/* Delegate. */
	return (!queue) ? NULL : serialize_linked_list(queue->list, array_setting_function, array);
}