class Queue:
__slots__ = 'ring_buffer', 'max_capacity'
"""constructor with intial max capacity of 10"""
def __init__(self, capacity=10):
self.ring_buffer = RingBuffer(capacity)
self.max_capacity = capacity
"""to string function uses the internal to string of ring buffer but
points to the end"""
def __str__(self):
return str(self.ring_buffer) + '<-- end '
""" enqueue function which inserts values in the queue """
def enqueue(self, value):
if value is None:
raise Exception('cannot enqueue None element in the queue')
else:
self.ring_buffer.insert_keep_old(value)
""" dequeue function which removes values from the queue using FIFO
method
raises an exception if dequeue is done on the empty queue"""
def dequeue(self):
if self.ring_buffer.size() is 0:
raise Exception('dequeue from a empty queue is not allowed')
else:
return self.ring_buffer.remove_oldest()
""" returns the current size of the stack"""
def size(self):
return self.ring_buffer.size()
""" :return the max capacity of the stack """
def capacity(self):
return self.ring_buffer.capacity()
""" only returns the value of the first element in the queue does not
removed the element from the queue
"""
def peek(self):
if self.size() < 1:
raise Exception('peek into a empty queue is not allowed')
else:
return self.ring_buffer.start_element()
