99 lines
3.5 KiB
Python
99 lines
3.5 KiB
Python
"""\
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@file channel.py
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@author Bob Ippolito
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Copyright (c) 2005-2006, Bob Ippolito
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Copyright (c) 2007, Linden Research, Inc.
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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"""
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import collections
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from eventlet import api, greenlib
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import greenlet
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__all__ = ['channel']
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class channel(object):
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"""A channel is a control flow primitive for co-routines. It is a
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"thread-like" queue for controlling flow between two (or more) co-routines.
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The state model is:
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* If one co-routine calls send(), it is unscheduled until another
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co-routine calls receive().
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* If one co-rounte calls receive(), it is unscheduled until another
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co-routine calls send().
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* Once a paired send()/receive() have been called, both co-routeines
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are rescheduled.
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This is similar to: http://stackless.com/wiki/Channels
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"""
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balance = 0
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def _tasklet_loop(self):
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deque = self.deque = collections.deque()
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hub = api.get_hub()
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switch = greenlib.switch
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direction, caller, args = switch()
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try:
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while True:
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if direction == -1:
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# waiting to receive
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if self.balance > 0:
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sender, args = deque.popleft()
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hub.schedule_call(0, switch, sender)
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hub.schedule_call(0, switch, caller, *args)
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else:
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deque.append(caller)
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else:
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# waiting to send
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if self.balance < 0:
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receiver = deque.popleft()
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hub.schedule_call(0, switch, receiver, *args)
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hub.schedule_call(0, switch, caller)
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else:
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deque.append((caller, args))
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self.balance += direction
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direction, caller, args = hub.switch()
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finally:
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deque.clear()
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del self.deque
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self.balance = 0
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def _send_tasklet(self, *args):
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try:
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t = self._tasklet
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except AttributeError:
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t = self._tasklet = greenlib.tracked_greenlet()
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greenlib.switch(t, (self._tasklet_loop,))
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if args:
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return greenlib.switch(t, (1, greenlet.getcurrent(), args))
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else:
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return greenlib.switch(t, (-1, greenlet.getcurrent(), args))
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def receive(self):
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return self._send_tasklet()
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def send(self, value):
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return self._send_tasklet(value)
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def send_exception(self, exc):
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return self._send_tasklet(None, exc)
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