extended_queue.cpp

飞机场模拟系统

#include  "Extended_queue.h"

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


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


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

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


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

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


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

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


int Extended_queue::size() const
/*
Post:   Return the number of entries in the Extended_Extended_queue.
*/
{
   return count;
}