"""Scheduling utility methods and classes.
API Stability: Unstable
@author: U{Jp Calderone<mailto:exarkun@twistedmatrix.com>}
"""
from twisted.python.runtime import seconds
from twisted.internet import reactor
from twisted.internet import defer
class LoopingCall:
"""Call a function repeatedly.
@ivar f: The function to call.
@ivar a: A tuple of arguments to pass the function.
@ivar kw: A dictionary of keyword arguments to pass to the function.
"""
call = None
running = False
deferred = None
interval = None
count = None
starttime = None
def __init__(self, f, *a, **kw):
self.f = f
self.a = a
self.kw = kw
def start(self, interval):
"""Start running function every interval seconds.
@param interval: The number of seconds between calls. May be less than
one. Precision will depend on the underlying platform, the available
hardware, and the load on the system.
@return: A Deferred whose callback will be invoked with C{self} when
C{self.stop} is called, or whose errback will be invoked if the function
raises an exception.
"""
assert not self.running
self.running = True
d = self.deferred = defer.Deferred()
self.starttime = seconds()
self.count = 0
self.interval = interval
self._loop()
return d
def stop(self):
"""Stop running function."""
assert self.running
self.running = False
if self.call is not None:
self.call.cancel()
self.call = None
d, self.deferred = self.deferred, None
d.callback(self)
def _loop(self):
self.call = None
try:
self.f(*self.a, **self.kw)
except:
d, self.deferred = self.deferred, None
d.errback()
return
fromNow = self.starttime - seconds()
while self.running:
self.count += 1
fromStart = self.count * self.interval
delay = fromNow + fromStart
if delay > 0:
self.call = reactor.callLater(delay, self._loop)
return