p2pool/util/variable.py

   1 import itertools
   2
   3 from twisted.internet import defer, reactor
   4 from twisted.python import failure, log
   5
   6 class Event(object):
   7     def __init__(self):
   8         self.observers = {}
   9         self.id_generator = itertools.count()
  10         self._once = None
  11
  12     def watch(self, func):
  13         id = self.id_generator.next()
  14         self.observers[id] = func
  15         return id
  16     def unwatch(self, id):
  17         self.observers.pop(id)
  18
  19     @property
  20     def once(self):
  21         res = self._once
  22         if res is None:
  23             res = self._once = Event()
  24         return res
  25
  26     def happened(self, *event):
  27         for id, func in sorted(self.observers.iteritems()):
  28             try:
  29                 func(*event)
  30             except:
  31                 log.err(None, "Error while processing Event callbacks:")
  32
  33         if self._once is not None:
  34             self._once.happened(*event)
  35             self._once = None
  36
  37     def get_deferred(self, timeout=None):
  38         once = self.once
  39         df = defer.Deferred()
  40         id1 = once.watch(lambda *event: df.callback(event))
  41         if timeout is not None:
  42             def do_timeout():
  43                 df.errback(failure.Failure(defer.TimeoutError('in Event.get_deferred')))
  44                 once.unwatch(id1)
  45                 once.unwatch(x)
  46             delay = reactor.callLater(timeout, do_timeout)
  47             x = once.watch(lambda *event: delay.cancel())
  48         return df
  49
  50 class Variable(object):
  51     def __init__(self, value):
  52         self.value = value
  53         self.changed = Event()
  54
  55     def set(self, value):
  56         if value == self.value:
  57             return
  58
  59         self.value = value
  60         self.changed.happened(value)
  61
  62     def get_not_none(self):
  63         if self.value is not None:
  64             return defer.succeed(self.value)
  65         else:
  66             df = defer.Deferred()
  67             self.changed.once.watch(df.callback)
  68             return df