193 lines
6.8 KiB
Python
193 lines
6.8 KiB
Python
from collections import deque
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from time import monotonic
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from types import FunctionType
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import math
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from .errors import QueueEmpty, QueueFull, StackEmpty, StackFull
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class TTLQueue:
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"""A FIFO data structure with per-item time to live (TTL)
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All items will have a default time to live, after that has
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expired (on the next mutating operation a.k.a put or get)
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expired elements will be popped out automatically.
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It is also possible to set a different TTL for every item and to
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define the maximum queue size
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Note: This queue is NOT thread safe and must be properly locked
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when used with multiple threads
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:param qsize: The max size of the queue, defaults to 0 (no limit)
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:type qsize: int, optional
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:param ttl: The TTL for every item in the queue, defaults to 0 (no TTL)
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:type ttl: int, optional
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:param timer: The timer function that the queue will use to
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keep track of elapsed time. Defaults to time.monotonic(), but can
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be customized. Any function that yields an incremental value
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on each subsequent call is acceptable, but its return values
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should not be repeated during runtime to avoid nonsense results
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:type timer: class: FunctionType, optional
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"""
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def __init__(self, qsize: int = 0, ttl: int = 0, timer: FunctionType = monotonic):
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"""Object constructor"""
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self.qsize = qsize if qsize else math.inf # Infinite size
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self.ttl = ttl
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self.timer = timer
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self._queue = deque()
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def expire(self, when: int):
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"""Pops expired element out of the queue if their TTL has
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expired by when units of time (usually seconds)
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:param when: The expiry date to check items against. Items' whose
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insertion date, according to self.timer, is less or equal
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than this number will be automatically deleted
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:type when: int
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"""
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i = 0
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n = len(self._queue)
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while i < n:
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try:
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date, element = self._queue[i]
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except IndexError:
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break
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if date <= when:
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del self._queue[i]
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i += 1
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def put(self, element, ttl: int = 0):
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"""Puts an item onto the queue
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:param element: The element to put in the queue
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:type element: object
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:param ttl: If you want to override the default ttl
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of the class for a specific element, you can specify
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that, defaults to 0 (use the default TTL)
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:param ttl: int, optional
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:raises QueueFull: If the queue is full
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"""
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ttl = ttl if ttl else self.ttl
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self.expire(self.timer())
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if len(self._queue) < self.qsize:
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self._queue.append((self.timer() + ttl, element))
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else:
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raise QueueFull("The queue is full!")
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def get(self):
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"""Gets an item from the queue, raising QueueEmpty if the
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queue is empty
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"""
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self.expire(self.timer())
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if not self._queue:
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raise QueueEmpty("The queue is empty!")
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return self._queue.popleft()[1]
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def __repr__(self):
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"""Implements repr(self)"""
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string = "TTLQueue({list}, qsize={qsize}, ttl={ttl}, timer={timer})"
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values = [t[1] for t in self._queue]
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return string.format(list=values, qsize=self.qsize, ttl=self.ttl, timer=self.timer)
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def __iter__(self):
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"""Implements iter(self)"""
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for _, element in self._queue:
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yield element
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class TTLStack:
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"""A stack-like (LIFO) data structure with per-item time to live (TTL)
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All items will have a default time to live, after that has
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expired (on the next mutating operation a.k.a push or pop)
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expired elements will be popped out automatically.
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It is also possible to set a different TTL for every item and to
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define the maximum stack
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Note: This stack is NOT thread safe and must be properly locked
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when used with multiple threads
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:param size: The max size of the stack, defaults to 0 (no limit)
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:type size: int, optional
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:param ttl: The TTL for every item in the stack, defaults to 0 (no TTL)
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:type ttl: int, optional
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:param timer: The timer function that the stack will use to
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keep track of elapsed time. Defaults to time.monotonic(), but can
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be customized. Any function that yields an incremental value
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on each subsequent call is acceptable, but its return values
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should not be repeated during runtime to avoid nonsense results
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:type timer: class: FunctionType, optional
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"""
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def __init__(self, size: int = 0, ttl: int = 0, timer: FunctionType = monotonic):
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"""Object constructor"""
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self.timer = timer
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self.ttl = ttl
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self.size = size if size else math.inf
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self._stack = deque()
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def push(self, element, ttl: int = 0):
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"""Pushes an item onto the stack
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:param element: The element to push
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:type element: object
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:param ttl: If you want to override the default ttl
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of the class for a specific element, you can specify
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that, defaults to 0 (use the default TTL)
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:param ttl: int, optional
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:raises StackFull: If the stack is full
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"""
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ttl = ttl if ttl else self.ttl
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self.expire(self.timer())
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if len(self._stack) < self.size:
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self._stack.appendleft((self.timer() + ttl, element))
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else:
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raise StackFull("The stack is full!")
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def pop(self):
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"""Pops an item from the stack, raising StackEmpty if the
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stack is empty
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:raises StackEmpty: If the stack is empty
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"""
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self.expire(self.timer())
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if not self._stack:
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raise StackEmpty("The stack is empty!")
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return self._stack.popleft()[1]
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def __repr__(self):
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"""Implements repr(self)"""
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string = "TTLStack({list}, size={qsize}, ttl={ttl}, timer={timer})"
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values = [t[1] for t in self._stack]
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return string.format(list=values, qsize=self.size, ttl=self.ttl, timer=self.timer)
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def expire(self, when: int):
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"""Pops expired element out of the stack if their TTL has
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expired by when units of time (usually seconds)
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:param when: The expiry date to check items against. Items' whose
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insertion date, according to self.timer, is less or equal
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than this number will be automatically deleted
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:type when: int
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"""
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i = 0
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n = len(self._stack)
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while i < n:
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try:
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date, element = self._stack[i]
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except IndexError:
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break
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if date <= when:
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del self._stack[i]
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i += 1
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