queue.cc

/****************************************************
 * File Name: queue.cc
 * Author: Robert Kruse and Alexander Ryba
 *         from "Data Structures and Program Design in C++"
 * Course: CSCI 132
 * Purpose: Implementation of Queue class
 *****************************************************/

#include "queue.h"

Queue::Queue() 
  /*
Post: The Queue is initialized to be empty.
  */
{
  count = 0;
  rear = maxqueue - 1;
  front = 0;
} // default constructor


bool Queue::empty() const
  /*
Post: Return true if the Queue is empty, otherwise return false.
  */
{
  return count == 0;
} //empty


Error_code Queue::append(const Queue_entry &item)
  /*
Post: item is added to the rear of the Queue. If the Queue is full
return an Error_code of overflow and leave the Queue unchanged.
  */

{
  if (count >= maxqueue) return overflow;
  count++;
  rear = ((rear + 1) == maxqueue) ? 0 : (rear + 1);
  entry[rear] = item;
  return success;
} //append


Error_code Queue::serve()
  /*
Post: The front of the Queue is removed. If the Queue
is empty return an Error_code of underflow.
  */

{
  if (count <= 0) return underflow;
  count--;
  front = ((front + 1) == maxqueue) ? 0 : (front + 1);
  return success;
} //serve


Error_code Queue::retrieve(Queue_entry &item) const
  /*
Post: The front of the Queue retrieved to the output
      parameter item. If the Queue is empty return an Error_code of underflow.
  */

{
  if (count <= 0) return underflow;
  item = entry[front];
  return success;
} //retrieve