/usr/share/pyshared/application/notification.py is in python-application 1.2.8-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 | # Copyright (C) 2009-2011 AG Projects. See LICENSE for details.
#
"""Implements a notification system"""
from __future__ import with_statement
__all__ = ['Any', 'UnknownSender', 'IObserver', 'NotificationData', 'Notification', 'NotificationCenter', 'ObserverWeakrefProxy']
import weakref
from collections import deque
from threading import Lock
from zope.interface import Interface, implements
from application import log
from application.python.descriptor import ThreadLocal
from application.python.types import Singleton
## Special objects
class SpecialType(type):
def __str__(cls):
return cls.__name__
__repr__ = __str__
class Any(object):
"""Any sender or notification name"""
__metaclass__ = SpecialType
class UnknownSender(object):
"""A special sender used for anonymous notifications"""
__metaclass__ = SpecialType
del SpecialType
## Notification Observer
class IObserver(Interface):
"""Interface describing a Notification Observer"""
def handle_notification(notification):
"""Function used to handle a posted Notification"""
class ObserverWeakrefProxy(object):
"""
A proxy that allows an observer to be weakly referenced and automatically
removes any remaining registrations that the observer didn't clean itself
before its reference count dropped to zero.
"""
implements(IObserver)
observer_map = weakref.WeakKeyDictionary()
lock = Lock()
def __new__(cls, observer):
if not IObserver.providedBy(observer):
raise TypeError("observer must implement the IObserver interface")
with cls.lock:
if observer in cls.observer_map:
return cls.observer_map[observer]
instance = object.__new__(cls)
instance.observer_ref = weakref.ref(observer, instance.cleanup)
cls.observer_map[observer] = instance
return instance
def cleanup(self, ref):
# remove all observer's remaining registrations (the ones that the observer didn't remove itself)
for notification_center in NotificationCenter._instances.itervalues():
notification_center.purge_observer(self)
def handle_notification(self, notification):
observer = self.observer_ref()
if observer is not None:
observer.handle_notification(notification)
## Notification
class NotificationData(object):
"""Object containing the notification data"""
def __init__(self, **kwargs):
self.__dict__.update(kwargs)
def __repr__(self):
return '%s(%s)' % (self.__class__.__name__, ', '.join('%s=%r' % (name, value) for name, value in self.__dict__.iteritems()))
__str__ = __repr__
class Notification(object):
"""Object representing a notification"""
def __init__(self, name, sender=UnknownSender, data=NotificationData()):
if Any in (name, sender):
raise ValueError("name and/or sender must not be the special object Any")
self.name = name
self.sender = sender
self.data = data
def __repr__(self):
return '%s(%r, %r, %r)' % (self.__class__.__name__, self.name, self.sender, self.data)
__str__ = __repr__
## Notification Center
class NotificationCenter(object):
"""
A NotificationCenter allows observers to subscribe to receive notifications
identified by name and sender and will distribute the posted notifications
according to those subscriptions.
"""
__metaclass__ = Singleton
queue = ThreadLocal(deque)
def __init__(self, name='default'):
"""
Create a NotificationCenter with the specified name. Subsequent calls
with the same `name' parameter will return the same NotificationCenter
object.
"""
self.name = name
self.observers = {}
self.lock = Lock()
def add_observer(self, observer, name=Any, sender=Any):
"""
Register an observer to receive notifications identified by a name and a
sender.
If `name' is Any, the observer will receive all notifications sent by
the specified sender. If `sender' is Any, it will receive notifications
sent by all senders, rather than from only one; if `sender' is
UnknownSender, the observer will only receive anonymous notifications.
"""
if not IObserver.providedBy(observer):
raise TypeError("observer must implement the IObserver interface")
with self.lock:
self.observers.setdefault((name, sender), set()).add(observer)
def remove_observer(self, observer, name=Any, sender=Any):
"""
Remove an observer's subscription if present, else raise KeyError.
The `name' and `sender' arguments must match the ones used to
register the observer.
See discard_observer for a variant that doesn't raise KeyError if
the observer is not registered.
"""
with self.lock:
try:
observer_set = self.observers[(name, sender)]
observer_set.remove(observer)
except KeyError:
raise KeyError("observer %r not registered for %r events from %r" % (observer, name, sender))
if not observer_set:
del self.observers[(name, sender)]
def discard_observer(self, observer, name=Any, sender=Any):
"""
Remove an observer's subscription if present, else do nothing.
The `name' and `sender' arguments must match the ones used to
register the observer.
See remove_observer for a variant that raises KeyError if the
observer is not registered.
"""
with self.lock:
observer_set = self.observers.get((name, sender), None)
if observer_set is not None:
observer_set.discard(observer)
if not observer_set:
del self.observers[(name, sender)]
def purge_observer(self, observer):
"""Remove all the observer's subscriptions."""
with self.lock:
subscriptions = [(key, observer_set) for key, observer_set in self.observers.iteritems() if observer in observer_set]
for key, observer_set in subscriptions:
observer_set.remove(observer)
if not observer_set:
del self.observers[key]
def post_notification(self, name, sender=UnknownSender, data=NotificationData()):
"""
Post a notification which will be delivered to all observers whose
subscription matches the name and sender attributes of the notification.
"""
notification = Notification(name, sender, data)
queue = self.queue
queue.append(notification)
if len(queue) > 1: # This is true if we post a notification from inside a notification handler
return
empty_set = set()
while queue:
notification = queue[0]
observers = (self.observers.get((Any, Any), empty_set) |
self.observers.get((Any, notification.sender), empty_set) |
self.observers.get((notification.name, Any), empty_set) |
self.observers.get((notification.name, notification.sender), empty_set))
for observer in observers:
try:
observer.handle_notification(notification)
except:
log.error("Exception occured in observer %r while handling notification %r" % (observer, notification.name))
log.err()
queue.popleft()
|