-The Server and Message classes are the two that clients interact
-with..
-
-This module is compatible with Python 2.1.
-
-Author: Robb Shecter
-"""
-
-#---------------------------------------------------------------------------
-
-class Publisher:
- """
- The publish/subscribe server. This class is a Singleton.
- """
- def __init__(self):
- self.topicDict = {}
- self.functionDict = {}
- self.subscribeAllList = []
- self.messageCount = 0
- self.deliveryCount = 0
-
-
- #
- # Public API
- #
-
- def subscribe(self, topic, listener):
- """
- Add the given subscription to the list. This will
- add an entry recording the fact that the listener wants
- to get messages for (at least) the given topic. This
- method may be called multiple times for one listener,
- registering it with many topics. It can also be invoked
- many times for a particular topic, each time with a
- different listener.
-
- listener: expected to be either a method or function that
- takes zero or one parameters. (Not counting 'self' in the
- case of methods. If it accepts a parameter, it will be given
- a reference to a Message object.
-
- topic: will be converted to a tuple if it isn't one.
- It's a pattern matches any topic that it's a sublist
- of. For example, this pattern:
-
- ('sports',)
-
- would match these:
-
- ('sports',)
- ('sports', 'baseball')
- ('sports', 'baseball', 'highscores')
-
- but not these:
-
- ()
- ('news')
- (12345)
- """
- if not callable(listener):
- raise TypeError('The P/S listener, '+`listener`+', is not callable.')
- aTopic = Topic(topic)
-
- # Determine now (at registration time) how many parameters
- # the listener expects, and get a reference to a function which
- # calls it correctly at message-send time.
- callableVersion = self.__makeCallable(listener)
-
- # Add this tuple to a list which is in a dict keyed by
- # the topic's first element.
- self.__addTopicToCorrectList(aTopic, listener, callableVersion)
-
- # Add to a dict in order to speed-up unsubscribing.
- self.__addFunctionLookup(listener, aTopic)
-
-
- def unsubscribe(self, listener):
- """
- Remove the given listener from the registry,
- for all topics that it's associated with.
- """
- if not callable(listener):
- raise TypeError('The P/S listener, '+`listener`+', is not callable.')
- topicList = self.getAssociatedTopics(listener)
- for aTopic in topicList:
- subscriberList = self.__getTopicList(aTopic)
- listToKeep = []
- for subscriber in subscriberList:
- if subscriber[0] != listener:
- listToKeep.append(subscriber)
- self.__setTopicList(aTopic, listToKeep)
- self.__delFunctionLookup(listener)
-
-
- def getAssociatedTopics(self, listener):
- """
- Return a list of topics the given listener is
- registered with.
- """
- return self.functionDict.get(listener, [])
-
-
- def sendMessage(self, topic, data=None):
- """
- Relay a message to registered listeners.
- """
- aTopic = Topic(topic)
- message = Message(aTopic.items, data)
- topicList = self.__getTopicList(aTopic)
-
- # Send to the matching topics
- for subscriber in topicList:
- if subscriber[1].matches(aTopic):
- subscriber[2](message)
-
- # Send to any listeners registered for ALL
- for subscriber in self.subscribeAllList:
- subscriber[2](message)
-
-
- #
- # Private methods
- #
-
- def __makeCallable(self, function):
- """
- Return a function that is what the server
- will actually call.
-
- This is a time optimization: this removes a test
- for the number of parameters from the inner loop
- of sendMessage().
- """
- parameters = self.__parameterCount(function)
- if parameters == 0:
- # Return a function that calls the listener
- # with no arguments.
- return lambda m, f=function: f()
- elif parameters == 1:
- # Return a function that calls the listener
- # with one argument (which will be the message).
- return lambda m, f=function: f(m)
- else:
- raise TypeError('The publish/subscribe listener, '+`function`+', has wrong parameter count')
-
-
- def __parameterCount(self, callableObject):
- """
- Return the effective number of parameters required
- by the callable object. In other words, the 'self'
- parameter of methods is not counted.
- """
- try:
- # Try to handle this like a method
- return callableObject.im_func.func_code.co_argcount - 1
- except AttributeError:
- pass
-
- try:
- # Try to handle this like a function
- return callableObject.func_code.co_argcount
- except AttributeError:
- raise 'Cannot determine if this is a method or function: '+str(callableObject)
-
- def __addFunctionLookup(self, aFunction, aTopic):
- try:
- aList = self.functionDict[aFunction]
- except KeyError:
- aList = []
- self.functionDict[aFunction] = aList
- aList.append(aTopic)
-
-
- def __delFunctionLookup(self, aFunction):
- try:
- del self.functionDict[aFunction]
- except KeyError:
- print 'Warning: listener not found. Logic error in PublishSubscribe?', aFunction
-
-
- def __addTopicToCorrectList(self, topic, listener, callableVersion):
- if len(topic.items) == 0:
- self.subscribeAllList.append((listener, topic, callableVersion))
- else:
- self.__getTopicList(topic).append((listener, topic, callableVersion))
-
-
- def __getTopicList(self, aTopic):
- """
- Return the correct sublist of subscribers based on the
- given topic.
- """
- try:
- elementZero = aTopic.items[0]
- except IndexError:
- return self.subscribeAllList
-
- try:
- subList = self.topicDict[elementZero]
- except KeyError:
- subList = []
- self.topicDict[elementZero] = subList
- return subList
-
-
- def __setTopicList(self, aTopic, aSubscriberList):
- try:
- self.topicDict[aTopic.items[0]] = aSubscriberList
- except IndexError:
- self.subscribeAllList = aSubscriberList
-
-
- def __call__(self):
- return self
-
-
-# Create an instance with the same name as the class, effectivly
-# hiding the class object so it can't be instantiated any more. From
-# this point forward any calls to Publisher() will invoke the __call__
-# of this instance which just returns itself.
-#
-# The only flaw with this approach is that you can't derive a new
-# class from Publisher without jumping through hoops. If this ever
-# becomes an issue then a new Singleton implementaion will need to be
-# employed.
-Publisher = Publisher()
-
-
-#---------------------------------------------------------------------------
-
-class Message:
- """
- A simple container object for the two components of
- a message; the topic and the data.
- """
- def __init__(self, topic, data):
- self.topic = topic
- self.data = data
-
- def __str__(self):
- return '[Topic: '+`self.topic`+', Data: '+`self.data`+']'
-
-
-#---------------------------------------------------------------------------
-
-class Topic:
- """
- A class that represents a publish/subscribe topic.
- Currently, it's only used internally in the framework; the
- API expects and returns plain old tuples.
-
- It currently exists mostly as a place to keep the matches()
- function. This function, though, could also correctly be
- seen as an attribute of the P/S server. Getting rid of this
- class would also mean one fewer object instantiation per
- message send.
- """
-
- listType = type([])
- tupleType = type(())
-
- def __init__(self, items):
- # Make sure we have a tuple.
- if type(items) == self.__class__.listType:
- items = tuple(items)
- elif type(items) != self.__class__.tupleType:
- items = (items,)
- self.items = items
- self.length = len(items)
-
-
- def matches(self, aTopic):
- """
- Consider myself to be a topic pattern,
- and return True if I match the given specific
- topic. For example,
- a = ('sports')
- b = ('sports','baseball')
- a.matches(b) --> 1
- b.matches(a) --> 0
- """
- # The question this method answers is equivalent to;
- # is my list a sublist of aTopic's? So, my algorithm
- # is: 1) make a copy of the aTopic list which is
- # truncated to the pattern's length. 2) Test for
- # equality.
- #
- # This algorithm may be somewhat memory-intensive,
- # because it creates a temporary list on each
- # call to match. A possible to-do would be to
- # re-write this with a hand-coded loop.
- return (self.items == aTopic.items[:self.length])
-
-
- def __repr__(self):
- import string
- return '<Topic>' + string.join(map(repr, self.items), ', ') + '</Topic>'
-
-
- def __eq__(self, aTopic):
- """
- Return True if I equal the given topic. We're considered
- equal if our tuples are equal.
- """
- if type(self) != type(aTopic):
- return 0
- else:
- return self.items == aTopic.items
-
-
- def __ne__(self, aTopic):
- """
- Return False if I equal the given topic.
- """
- return not self == aTopic
-
-
-#---------------------------------------------------------------------------
-
-
-#
-# Code for a simple command-line test
-#
-if __name__ == '__main__':
-
- class SimpleListener:
- def __init__(self, number):
- self.number = number
- def notify(self, message):
- print '#'+str(self.number)+' got the message:', message
-
- # Build a list of ten listeners.
- lList = []
- for x in range(10):
- lList.append(SimpleListener(x))
-
- server = Publisher()
-
- # Everyone's interested in politics...
- for x in lList:
- Publisher().subscribe(topic='politics', listener=x.notify) # also tests singleton
-
- # But only the first four are interested in trivia.
- for x in lList[:4]:
- server.subscribe(topic='trivia', listener=x.notify)
-
- # This one subscribes to everything.
- everythingListener = SimpleListener(999)
- server.subscribe(topic=(), listener=everythingListener.notify)
-
- # Now send out two messages, testing topic matching.
- server.sendMessage(topic='trivia', data='What is the capitol of Oregon?')
- server.sendMessage(topic=('politics','germany'), data='The Greens have picked up another seat in the Bundestag.')
-
-#---------------------------------------------------------------------------
projects / wxWidgets.git / blobdiff