A Python Implementation Of the Fixed-Size Queue
"""
A homogeneous fixed-size queue.
"""
from array import array
class FixedsizeQueue(object):
"""
A fixed size queue is a homogeneous FIFO queue that can't grow.
"""
def __init__(self, max_size, typecode='i'):
self.size = 0
self.head = 0
self.tail = 0
self.typecode = typecode
self.max = max_size
self._data = None
return
@property
def data(self):
"""
:return: an array of size self.max, type self.typecode
"""
if self._data is None:
self._data = array(self.typecode, [0 for i in range(self.max)])
return self._data
def enqueue(self, item):
"""
:param:
- `item`: the item to add to the queue
:return: True if added, False if full
"""
if self.size == self.max:
return False
self.data[self.tail] = item
self.size += 1
self.tail += 1
if self.tail == self.max:
self.tail = 0
return True
def dequeue(self):
"""
:return: oldest item or None
"""
if self.size == 0:
return
item = self.data[self.head]
self.size -= 1
self.head += 1
if self.head == self.max:
self.head = 0
return item
def reset(self):
"""
:postcondition: head, tail and size reset to 0
"""
self.size = 0
self.tail = 0
self.head = 0
return
def empty(self):
"""
:return: True if the queue is empty.
"""
return self.size == 0
def full(self):
"""
:return: True if the queue is full.
"""
return self.size == self.max
# end class FixedsizeQueue
