diff options
Diffstat (limited to 'collaboration/dispatch/dispatcher.py')
| -rw-r--r-- | collaboration/dispatch/dispatcher.py | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/collaboration/dispatch/dispatcher.py b/collaboration/dispatch/dispatcher.py new file mode 100644 index 0000000..45c32fe --- /dev/null +++ b/collaboration/dispatch/dispatcher.py @@ -0,0 +1,191 @@ +import weakref +import saferef + +WEAKREF_TYPES = (weakref.ReferenceType, saferef.BoundMethodWeakref) + + +def _make_id(target): + if hasattr(target, 'im_func'): + return (id(target.im_self), id(target.im_func)) + return id(target) + + +class Signal(object): + """Base class for all signals + + Internal attributes: + receivers -- { receriverkey (id) : weakref(receiver) } + """ + + def __init__(self, providing_args=None): + """providing_args -- A list of the arguments this signal can pass along + in a send() call. + """ + self.receivers = [] + if providing_args is None: + providing_args = [] + self.providing_args = set(providing_args) + + def connect(self, receiver, sender=None, weak=True, dispatch_uid=None): + """Connect receiver to sender for signal + + receiver -- a function or an instance method which is to + receive signals. Receivers must be + hashable objects. + + if weak is True, then receiver must be weak-referencable + (more precisely saferef.safeRef() must be able to create + a reference to the receiver). + + Receivers must be able to accept keyword arguments. + + If receivers have a dispatch_uid attribute, the receiver will + not be added if another receiver already exists with that + dispatch_uid. + + sender -- the sender to which the receiver should respond + Must either be of type Signal, or None to receive events + from any sender. + + weak -- whether to use weak references to the receiver + By default, the module will attempt to use weak + references to the receiver objects. If this parameter + is false, then strong references will be used. + + dispatch_uid -- an identifier used to uniquely identify a particular + instance of a receiver. This will usually be a string, though it + may be anything hashable. + + returns None + """ + if dispatch_uid: + lookup_key = (dispatch_uid, _make_id(sender)) + else: + lookup_key = (_make_id(receiver), _make_id(sender)) + + if weak: + receiver = saferef.safeRef(receiver, + onDelete=self._remove_receiver) + + for r_key, _ in self.receivers: + if r_key == lookup_key: + break + else: + self.receivers.append((lookup_key, receiver)) + + def disconnect(self, receiver=None, sender=None, weak=True, + dispatch_uid=None): + """Disconnect receiver from sender for signal + + receiver -- the registered receiver to disconnect. May be none if + dispatch_uid is specified. + sender -- the registered sender to disconnect + weak -- the weakref state to disconnect + dispatch_uid -- the unique identifier of the receiver to disconnect + + disconnect reverses the process of connect. + + If weak references are used, disconnect need not be called. + The receiver will be remove from dispatch automatically. + + returns None + """ + + if dispatch_uid: + lookup_key = (dispatch_uid, _make_id(sender)) + else: + lookup_key = (_make_id(receiver), _make_id(sender)) + + for idx, (r_key, _) in enumerate(self.receivers): + if r_key == lookup_key: + del self.receivers[idx] + + def send(self, sender, **named): + """Send signal from sender to all connected receivers. + + sender -- the sender of the signal + Either a specific object or None. + + named -- named arguments which will be passed to receivers. + + Returns a list of tuple pairs [(receiver, response), ... ]. + + If any receiver raises an error, the error propagates back + through send, terminating the dispatch loop, so it is quite + possible to not have all receivers called if a raises an + error. + """ + + responses = [] + if not self.receivers: + return responses + + for receiver in self._live_receivers(_make_id(sender)): + response = receiver(signal=self, sender=sender, **named) + responses.append((receiver, response)) + return responses + + def send_robust(self, sender, **named): + """Send signal from sender to all connected receivers catching errors + + sender -- the sender of the signal + Can be any python object (normally one registered with + a connect if you actually want something to occur). + + named -- named arguments which will be passed to receivers. + These arguments must be a subset of the argument names + defined in providing_args. + + Return a list of tuple pairs [(receiver, response), ... ], + may raise DispatcherKeyError + + if any receiver raises an error (specifically any subclass of + Exception), the error instance is returned as the result for that + receiver. + """ + + responses = [] + if not self.receivers: + return responses + + # Call each receiver with whatever arguments it can accept. + # Return a list of tuple pairs [(receiver, response), ... ]. + for receiver in self._live_receivers(_make_id(sender)): + try: + response = receiver(signal=self, sender=sender, **named) + except Exception, err: + responses.append((receiver, err)) + else: + responses.append((receiver, response)) + return responses + + def _live_receivers(self, senderkey): + """Filter sequence of receivers to get resolved, live receivers + + This checks for weak references + and resolves them, then returning only live + receivers. + """ + none_senderkey = _make_id(None) + + for (receiverkey_, r_senderkey), receiver in self.receivers: + if r_senderkey == none_senderkey or r_senderkey == senderkey: + if isinstance(receiver, WEAKREF_TYPES): + # Dereference the weak reference. + receiver = receiver() + if receiver is not None: + yield receiver + else: + yield receiver + + def _remove_receiver(self, receiver): + """Remove dead receivers from connections.""" + + to_remove = [] + for key, connected_receiver in self.receivers: + if connected_receiver == receiver: + to_remove.append(key) + for key in to_remove: + for idx, (r_key, _) in enumerate(self.receivers): + if r_key == key: + del self.receivers[idx] |