/* * File: queue.c * ------------- * This file implements the queue.h abstraction using an array. */#include <stdio.h>#include "genlib.h"#include "queue.h"/* * Constants: * ---------- * MaxQueueSize -- Maximum number of elements in the queue */#define MaxQueueSize 10/* * Type: queueCDT * -------------- * This type provides the concrete counterpart to the queueADT. * The representation used here consists of an array coupled * with an integer indicating the effective size.  This * representation means that Dequeue must shift the existing * elements in the queue. */struct queueCDT {    void *array[MaxQueueSize];    int len;};/* Exported entries *//* * Function: NewQueue * ------------------ * This function allocates and initializes the storage for a * new queue. */queueADT NewQueue(void){    queueADT queue;    queue = New(queueADT);    queue->len = 0;    return (queue);}/* * Function: FreeQueue * ------------------- * This function frees the queue storage. */void FreeQueue(queueADT queue){    FreeBlock(queue);}/* * Function: Enqueue * ----------------- * This function adds a new element to the queue. */void Enqueue(queueADT queue, void *obj){    if (queue->len == MaxQueueSize) {        Error("Enqueue called on a full queue");    }    queue->array[queue->len++] = obj;}/* * Function: Dequeue * ----------------- * This function removes and returns the data value at the * head of the queue. */void *Dequeue(queueADT queue){    void *result;    int i;    if (queue->len == 0) Error("Dequeue of empty queue");    result = queue->array[0];    for (i = 1; i < queue->len; i++) {        queue->array[i - 1] = queue->array[i];    }    queue->len--;    return (result);}/* * Function: QueueLength * --------------------- * This function returns the number of elements in the queue. */int QueueLength(queueADT queue){    return (queue->len);}