245 lines
7.1 KiB
Python
245 lines
7.1 KiB
Python
"""
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Convert between frames and higher-level AMQP methods
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"""
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# Copyright (C) 2007-2008 Barry Pederson <bp@barryp.org>
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library 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 GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
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from Queue import Empty, Queue
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from struct import pack, unpack
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try:
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from collections import defaultdict
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except:
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class defaultdict(dict):
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"""
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Mini-implementation of collections.defaultdict that
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appears in Python 2.5 and up.
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"""
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def __init__(self, default_factory):
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dict.__init__(self)
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self.default_factory = default_factory
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def __getitem__(self, key):
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try:
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return dict.__getitem__(self, key)
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except KeyError:
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result = self.default_factory()
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dict.__setitem__(self, key, result)
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return result
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from basic_message import Message
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from exceptions import *
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from serialization import AMQPReader
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__all__ = [
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'MethodReader',
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]
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#
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# MethodReader needs to know which methods are supposed
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# to be followed by content headers and bodies.
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#
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_CONTENT_METHODS = [
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(60, 50), # Basic.return
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(60, 60), # Basic.deliver
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(60, 71), # Basic.get_ok
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]
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class _PartialMessage(object):
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"""
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Helper class to build up a multi-frame method.
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"""
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def __init__(self, method_sig, args):
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self.method_sig = method_sig
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self.args = args
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self.msg = Message()
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self.body_parts = []
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self.body_received = 0
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self.body_size = None
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self.complete = False
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def add_header(self, payload):
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class_id, weight, self.body_size = unpack('>HHQ', payload[:12])
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self.msg._load_properties(payload[12:])
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self.complete = (self.body_size == 0)
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def add_payload(self, payload):
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self.body_parts.append(payload)
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self.body_received += len(payload)
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if self.body_received == self.body_size:
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self.msg.body = ''.join(self.body_parts)
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self.complete = True
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class MethodReader(object):
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"""
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Helper class to receive frames from the broker, combine them if
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necessary with content-headers and content-bodies into complete methods.
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Normally a method is represented as a tuple containing
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(channel, method_sig, args, content).
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In the case of a framing error, an AMQPConnectionException is placed
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in the queue.
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In the case of unexpected frames, a tuple made up of
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(channel, AMQPChannelException) is placed in the queue.
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"""
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def __init__(self, source):
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self.source = source
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self.queue = Queue()
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self.running = False
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self.partial_messages = {}
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# For each channel, which type is expected next
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self.expected_types = defaultdict(lambda:1)
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def _next_method(self):
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"""
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Read the next method from the source, once one complete method has
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been assembled it is placed in the internal queue.
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"""
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while self.queue.empty():
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try:
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frame_type, channel, payload = self.source.read_frame()
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except Exception, e:
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#
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# Connection was closed? Framing Error?
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#
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self.queue.put(e)
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break
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if self.expected_types[channel] != frame_type:
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self.queue.put((
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channel,
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Exception('Received frame type %s while expecting type: %s' %
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(frame_type, self.expected_types[channel])
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)
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))
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elif frame_type == 1:
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self._process_method_frame(channel, payload)
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elif frame_type == 2:
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self._process_content_header(channel, payload)
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elif frame_type == 3:
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self._process_content_body(channel, payload)
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def _process_method_frame(self, channel, payload):
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"""
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Process Method frames
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"""
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method_sig = unpack('>HH', payload[:4])
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args = AMQPReader(payload[4:])
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if method_sig in _CONTENT_METHODS:
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#
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# Save what we've got so far and wait for the content-header
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#
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self.partial_messages[channel] = _PartialMessage(method_sig, args)
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self.expected_types[channel] = 2
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else:
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self.queue.put((channel, method_sig, args, None))
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def _process_content_header(self, channel, payload):
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"""
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Process Content Header frames
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"""
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partial = self.partial_messages[channel]
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partial.add_header(payload)
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if partial.complete:
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#
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# a bodyless message, we're done
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#
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self.queue.put((channel, partial.method_sig, partial.args, partial.msg))
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del self.partial_messages[channel]
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self.expected_types[channel] = 1
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else:
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#
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# wait for the content-body
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#
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self.expected_types[channel] = 3
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def _process_content_body(self, channel, payload):
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"""
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Process Content Body frames
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"""
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partial = self.partial_messages[channel]
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partial.add_payload(payload)
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if partial.complete:
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#
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# Stick the message in the queue and go back to
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# waiting for method frames
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#
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self.queue.put((channel, partial.method_sig, partial.args, partial.msg))
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del self.partial_messages[channel]
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self.expected_types[channel] = 1
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def read_method(self):
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"""
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Read a method from the peer.
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"""
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self._next_method()
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m = self.queue.get()
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if isinstance(m, Exception):
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raise m
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return m
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class MethodWriter(object):
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"""
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Convert AMQP methods into AMQP frames and send them out
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to the peer.
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"""
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def __init__(self, dest, frame_max):
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self.dest = dest
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self.frame_max = frame_max
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def write_method(self, channel, method_sig, args, content=None):
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payload = pack('>HH', method_sig[0], method_sig[1]) + args
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self.dest.write_frame(1, channel, payload)
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if content:
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body = content.body
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payload = pack('>HHQ', method_sig[0], 0, len(body)) + \
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content._serialize_properties()
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self.dest.write_frame(2, channel, payload)
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while body:
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payload, body = body[:self.frame_max - 8], body[self.frame_max -8:]
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self.dest.write_frame(3, channel, payload)
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