232 lines
7.9 KiB
Python
232 lines
7.9 KiB
Python
"""Convert between frames and higher-level AMQP methods"""
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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 __future__ import absolute_import
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from collections import defaultdict, deque
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from struct import pack, unpack
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from .basic_message import Message
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from .exceptions import AMQPError, UnexpectedFrame
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from .five import range, string
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from .serialization import AMQPReader
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__all__ = ['MethodReader']
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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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"""Helper class to build up a multi-frame method."""
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def __init__(self, method_sig, args, channel):
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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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parts = self.body_parts
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self.body_received += len(payload)
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if self.body_received == self.body_size:
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if parts:
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parts.append(payload)
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self.msg.body = bytes().join(parts)
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else:
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self.msg.body = payload
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self.complete = True
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else:
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parts.append(payload)
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class MethodReader(object):
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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 :exc:`ConnectionError` 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, ChannelError)`` 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 = deque()
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self.running = False
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self.partial_messages = {}
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self.heartbeats = 0
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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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# not an actual byte count, just incremented whenever we receive
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self.bytes_recv = 0
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self._quick_put = self.queue.append
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self._quick_get = self.queue.popleft
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def _next_method(self):
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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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queue = self.queue
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put = self._quick_put
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read_frame = self.source.read_frame
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while not queue:
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try:
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frame_type, channel, payload = read_frame()
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except Exception as exc:
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#
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# Connection was closed? Framing Error?
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#
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put(exc)
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break
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self.bytes_recv += 1
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if frame_type not in (self.expected_types[channel], 8):
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put((
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channel,
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UnexpectedFrame(
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'Received frame {0} while expecting type: {1}'.format(
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frame_type, self.expected_types[channel]))))
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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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elif frame_type == 8:
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self._process_heartbeat(channel, payload)
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def _process_heartbeat(self, channel, payload):
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self.heartbeats += 1
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def _process_method_frame(self, channel, payload):
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"""Process Method frames"""
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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(
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method_sig, args, channel,
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)
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self.expected_types[channel] = 2
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else:
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self._quick_put((channel, method_sig, args, None))
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def _process_content_header(self, channel, payload):
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"""Process Content Header frames"""
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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._quick_put((channel, partial.method_sig,
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partial.args, partial.msg))
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self.partial_messages.pop(channel, None)
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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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"""Process Content Body frames"""
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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._quick_put((channel, partial.method_sig,
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partial.args, partial.msg))
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self.partial_messages.pop(channel, None)
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self.expected_types[channel] = 1
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def read_method(self):
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"""Read a method from the peer."""
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self._next_method()
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m = self._quick_get()
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if isinstance(m, Exception):
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raise m
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if isinstance(m, tuple) and isinstance(m[1], AMQPError):
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raise m[1]
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return m
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class MethodWriter(object):
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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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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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self.bytes_sent = 0
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def write_method(self, channel, method_sig, args, content=None):
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write_frame = self.dest.write_frame
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payload = pack('>HH', method_sig[0], method_sig[1]) + args
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if content:
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# do this early, so we can raise an exception if there's a
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# problem with the content properties, before sending the
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# first frame
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body = content.body
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if isinstance(body, string):
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coding = content.properties.get('content_encoding', None)
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if coding is None:
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coding = content.properties['content_encoding'] = 'UTF-8'
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body = body.encode(coding)
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properties = content._serialize_properties()
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write_frame(1, channel, payload)
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if content:
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payload = pack('>HHQ', method_sig[0], 0, len(body)) + properties
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write_frame(2, channel, payload)
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chunk_size = self.frame_max - 8
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for i in range(0, len(body), chunk_size):
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write_frame(3, channel, body[i:i + chunk_size])
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self.bytes_sent += 1
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