1 # Copyright (c) 2010 Google Inc. All rights reserved.

     2 #

     3 # Redistribution and use in source and binary forms, with or without

     4 # modification, are permitted provided that the following conditions are

     5 # met:

     6 #

     7 #     * Redistributions of source code must retain the above copyright

     8 # notice, this list of conditions and the following disclaimer.

     9 #     * Redistributions in binary form must reproduce the above

    10 # copyright notice, this list of conditions and the following disclaimer

    11 # in the documentation and/or other materials provided with the

    12 # distribution.

    13 #     * Neither the name of Google Inc. nor the names of its

    14 # contributors may be used to endorse or promote products derived from

    15 # this software without specific prior written permission.

    16 #

    17 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

    18 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

    19 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

    20 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

    21 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

    22 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

    23 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

    24 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

    25 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

    26 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

    27 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    28 

    29 

    30 class MessagePumpDelegate(object):

    31     def schedule(self, interval, callback):

    32         raise NotImplementedError, "subclasses must implement"

    33 

    34     def message_available(self, message):

    35         raise NotImplementedError, "subclasses must implement"

    36 

    37     def final_message_delivered(self):

    38         raise NotImplementedError, "subclasses must implement"

    39 

    40 

    41 class MessagePump(object):

    42     interval = 10 # seconds

    43 

    44     def __init__(self, delegate, message_queue):

    45         self._delegate = delegate

    46         self._message_queue = message_queue

    47         self._schedule()

    48 

    49     def _schedule(self):

    50         self._delegate.schedule(self.interval, self._callback)

    51 

    52     def _callback(self):

    53         (messages, is_running) = self._message_queue.take_all()

    54         for message in messages:

    55             self._delegate.message_available(message)

    56         if not is_running:

    57             self._delegate.final_message_delivered()

    58             return

    59         self._schedule()