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# -*- test-case-name: foolscap.test.test_eventual -*-
from twisted.internet import reactor, defer
from twisted.python import log
class _SimpleCallQueue(object):
# XXX TODO: merge epsilon.cooperator in, and make this more complete.
def __init__(self):
self._events = []
self._flushObservers = []
self._timer = None
def append(self, cb, args, kwargs):
self._events.append((cb, args, kwargs))
if not self._timer:
self._timer = reactor.callLater(0, self._turn)
def _turn(self):
self._timer = None
# flush all the messages that are currently in the queue. If anything
# gets added to the queue while we're doing this, those events will
# be put off until the next turn.
events, self._events = self._events, []
for cb, args, kwargs in events:
try:
cb(*args, **kwargs)
except:
log.err()
if not self._events:
observers, self._flushObservers = self._flushObservers, []
for o in observers:
o.callback(None)
def flush(self):
"""Return a Deferred that will fire (with None) when the call queue
is completely empty."""
if not self._events:
return defer.succeed(None)
d = defer.Deferred()
self._flushObservers.append(d)
return d
_theSimpleQueue = _SimpleCallQueue()
def eventually(cb, *args, **kwargs):
"""This is the eventual-send operation, used as a plan-coordination
primitive. The callable will be invoked (with args and kwargs) in a later
reactor turn. Doing 'eventually(a); eventually(b)' guarantees that a will
be called before b.
Any exceptions that occur in the callable will be logged with log.err().
If you really want to ignore them, be sure to provide a callable that
catches those exceptions.
This function returns None. If you care to know when the callable was
run, be sure to provide a callable that notifies somebody.
"""
_theSimpleQueue.append(cb, args, kwargs)
def fireEventually(value=None):
"""This returns a Deferred which will fire in a later reactor turn, after
the current call stack has been completed, and after all other deferreds
previously scheduled with callEventually().
"""
d = defer.Deferred()
eventually(d.callback, value)
return d
def flushEventualQueue(_ignored=None):
"""This returns a Deferred which fires when the eventual-send queue is
finally empty. This is useful to wait upon as the last step of a Trial
test method.
"""
return _theSimpleQueue.flush()
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