82 lines
2.2 KiB
Python
82 lines
2.2 KiB
Python
"""
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Copyright 2013 Rackspace, Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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from collections import defaultdict
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from twisted.internet.defer import maybeDeferred
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__all__ = ['EventEmitter', 'EventEmitterUnhandledError']
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class EventEmitterUnhandledError(RuntimeError):
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"""
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Error caused by no subscribers to an `error` event.
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"""
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pass
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class EventEmitter(object):
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"""
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Extremely simple pubsub style things in-process.
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Styled after the Node.js EventEmitter class
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"""
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__slots__ = ['_subs']
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def __init__(self):
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self._subs = defaultdict(list)
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def emit(self, topic, *args):
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"""
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Emit an event to a specific topic with a payload.
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"""
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ds = []
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if topic == "error":
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if len(self._subs[topic]) == 0:
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raise EventEmitterUnhandledError("No Subscribers to an error event found")
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for s in self._subs[topic]:
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ds.append(maybeDeferred(s, topic, *args))
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return ds
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def on(self, topic, callback):
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"""
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Add a handler for a specific topic.
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"""
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self.emit("newListener", topic, callback)
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self._subs[topic].append(callback)
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def once(self, topic, callback):
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"""
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Execute a specific handler just once.
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"""
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def oncecb(*args):
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self.removeListener(topic, oncecb)
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callback(*args)
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self.on(topic, oncecb)
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def removeListener(self, topic, callback):
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"""
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Remove a handler from a topic.
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"""
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self._subs[topic] = filter(lambda x: x != callback, self._subs[topic])
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def removeAllListeners(self, topic):
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"""
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Remove all listeners from a specific topic.
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"""
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del self._subs[topic]
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