144 lines
4.0 KiB
Python
144 lines
4.0 KiB
Python
# Copyright (C) 2010 Aldo Cortesi
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import Queue, threading
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should_exit = False
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class DummyReply:
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"""
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A reply object that does nothing. Useful when we need an object to seem
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like it has a channel, and during testing.
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"""
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def __init__(self):
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self.acked = False
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def __call__(self, msg=False):
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self.acked = True
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class Reply:
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"""
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Messages sent through a channel are decorated with a "reply" attribute.
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This object is used to respond to the message through the return
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channel.
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"""
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def __init__(self, obj):
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self.obj = obj
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self.q = Queue.Queue()
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self.acked = False
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def __call__(self, msg=None):
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if not self.acked:
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self.acked = True
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if msg is None:
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self.q.put(self.obj)
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else:
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self.q.put(msg)
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class Channel:
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def __init__(self, q):
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self.q = q
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def ask(self, m):
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"""
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Decorate a message with a reply attribute, and send it to the
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master. then wait for a response.
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"""
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m.reply = Reply(m)
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self.q.put(m)
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while not should_exit:
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try:
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# The timeout is here so we can handle a should_exit event.
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g = m.reply.q.get(timeout=0.5)
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except Queue.Empty: # pragma: nocover
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continue
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return g
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def tell(self, m):
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"""
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Decorate a message with a dummy reply attribute, send it to the
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master, then return immediately.
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"""
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m.reply = DummyReply()
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self.q.put(m)
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class Slave(threading.Thread):
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"""
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Slaves get a channel end-point through which they can send messages to
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the master.
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"""
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def __init__(self, channel, server):
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self.channel, self.server = channel, server
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self.server.set_channel(channel)
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threading.Thread.__init__(self)
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def run(self):
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self.server.serve_forever()
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class Master:
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"""
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Masters get and respond to messages from slaves.
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"""
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def __init__(self, server):
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"""
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server may be None if no server is needed.
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"""
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self.server = server
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self.masterq = Queue.Queue()
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def tick(self, q):
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changed = False
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try:
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# This endless loop runs until the 'Queue.Empty'
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# exception is thrown. If more than one request is in
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# the queue, this speeds up every request by 0.1 seconds,
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# because get_input(..) function is not blocking.
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while True:
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# Small timeout to prevent pegging the CPU
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msg = q.get(timeout=0.01)
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self.handle(msg)
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changed = True
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except Queue.Empty:
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pass
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return changed
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def run(self):
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global should_exit
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should_exit = False
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self.server.start_slave(Slave, Channel(self.masterq))
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while not should_exit:
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self.tick(self.masterq)
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self.shutdown()
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def handle(self, msg):
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c = "handle_" + msg.__class__.__name__.lower()
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m = getattr(self, c, None)
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if m:
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m(msg)
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else:
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msg.reply()
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def shutdown(self):
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global should_exit
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if not should_exit:
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should_exit = True
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if self.server:
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self.server.shutdown()
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