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OU4/queue.h

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+#ifndef __QUEUE_H
+#define __QUEUE_H
+
+#include <stdbool.h>
+#include "util.h"
+
+/*
+ * Declaration of a generic queue for the "Datastructures and
+ * algorithms" courses at the Department of Computing Science, Umea
+ * University. The queue stores void pointers, so it can be used to
+ * store all types of values. After use, the function queue_kill must
+ * be called to de-allocate the dynamic memory used by the queue
+ * itself. The de-allocation of any dynamic memory allocated for the
+ * element values is the responsibility of the user of the queue,
+ * unless a kill_function is registered in queue_empty.
+ *
+ * Authors: Niclas Borlin (niclas@cs.umu.se)
+ *          Adam Dahlgren Lindstrom (dali@cs.umu.se)
+ *
+ * Based on earlier code by: Johan Eliasson (johane@cs.umu.se).
+ *
+ * Version information:
+ *   v1.0  2018-01-28: First public version.
+ *   v1.1  2024-05-10: Added/updated print_internal to enhance encapsulation.
+ */
+
+// ==========PUBLIC DATA TYPES============
+
+// Queue type.
+typedef struct queue queue;
+
+// ==========DATA STRUCTURE INTERFACE==========
+
+/**
+ * queue_empty() - Create an empty queue.
+ * @kill_func: A pointer to a function (or NULL) to be called to
+ *             de-allocate memory on remove/kill.
+ *
+ * Returns: A pointer to the new queue.
+ */
+queue *queue_empty(kill_function kill_func);
+
+/**
+ * queue_is_empty() - Check if a queue is empty.
+ * @q: Queue to check.
+ *
+ * Returns: True if queue is empty, otherwise false.
+ */
+bool queue_is_empty(const queue *q);
+
+/**
+ * queue_enqueue() - Put a value at the end of the queue.
+ * @q: Queue to manipulate.
+ * @v: Value (pointer) to be put in the queue.
+ *
+ * Returns: The modified queue.
+ */
+queue *queue_enqueue(queue *q, void *v);
+
+/**
+ * queue_dequeue() - Remove the element at the front of a queue.
+ * @q: Queue to manipulate.
+ *
+ * NOTE: Undefined for an empty queue.
+ *
+ * Returns: The modified queue.
+ */
+queue *queue_dequeue(queue *q);
+
+/**
+ * queue_front() - Inspect the value at the front of the queue.
+ * @q: Queue to inspect.
+ *
+ * Returns: The value at the top of the queue.
+ *          NOTE: The return value is undefined for an empty queue.
+ */
+void *queue_front(const queue *q);
+
+/**
+ * queue_kill() - Destroy a given queue.
+ * @q: Queue to destroy.
+ *
+ * Return all dynamic memory used by the queue and its elements. If a
+ * kill_func was registered at queue creation, also calls it for each
+ * element to kill any user-allocated memory occupied by the element values.
+ *
+ * Returns: Nothing.
+ */
+void queue_kill(queue *q);
+
+/**
+ * queue_print() - Iterate over the queue elements and print their values.
+ * @q: Queue to inspect.
+ * @print_func: Function called for each element.
+ *
+ * Iterates over the queue and calls print_func with the value stored
+ * in each element.
+ *
+ * Returns: Nothing.
+ */
+void queue_print(const queue *q, inspect_callback print_func);
+
+/**
+ * queue_print_internal() - Print the internal structure of the queue in dot format.
+ * @q: Queue to inspect.
+ * @print_func: Function called for each element value.
+ * @desc: String with a description/state of the queue, or NULL for no description.
+ * @indent_level: Indentation level, 0 for outermost
+ *
+ * Iterates over the queue and outputs dot code that shows the internal
+ * structure of the queue.  The dot code can be visualized by
+ * Graphviz.
+ *
+ * On linux system, the output can be parsed by the dot program, e.g.
+ *
+ *   <queue_program> | dot -Tsvg > /tmp/dot.svg; firefox /tmp/dot.svg
+ *
+ * where <queue_program> is the name of the executable
+ *
+ * The output may also be possible to visualize online on
+ * https://dreampuf.github.io/GraphvizOnline/ or google "graphviz
+ * online".
+ *
+ * For documention of the dot language, see graphviz.org.
+ *
+ * Returns: Nothing.
+ */
+void queue_print_internal(const queue *q, inspect_callback print_func, const char *desc,
+                          int indent_level);
+
+#endif