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"""
Read/Write AMQP frames over network transports.
2009-01-14 Barry Pederson <bp@barryp.org>
"""
# Copyright (C) 2009 Barry Pederson <bp@barryp.org>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
import socket
#
# See if Python 2.6+ SSL support is available
#
try:
import ssl
HAVE_PY26_SSL = True
except:
HAVE_PY26_SSL = False
from struct import pack, unpack
AMQP_PORT = 5672
# Yes, Advanced Message Queuing Protocol Protocol is redundant
AMQP_PROTOCOL_HEADER = 'AMQP\x01\x01\x09\x01'
class _AbstractTransport(object):
"""
Common superclass for TCP and SSL transports
"""
def __init__(self, host, connect_timeout):
if ':' in host:
host, port = host.split(':', 1)
port = int(port)
else:
port = AMQP_PORT
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.settimeout(connect_timeout)
try:
self.sock.connect((host, port))
except socket.error:
self.sock.close()
raise
self.sock.settimeout(None)
self._setup_transport()
self._write(AMQP_PROTOCOL_HEADER)
def __del__(self):
self.close()
def _read(self, n):
"""
Read exactly n bytes from the peer
"""
raise NotImplementedError('Must be overriden in subclass')
def _setup_transport(self):
"""
Do any additional initialization of the class (used
by the subclasses).
"""
pass
def _write(self, s):
"""
Completely write a string to the peer.
"""
raise NotImplementedError('Must be overriden in subclass')
def close(self):
if self.sock is not None:
self.sock.close()
self.sock = None
def read_frame(self):
"""
Read an AMQP frame.
"""
frame_type, channel, size = unpack('>BHI', self._read(7))
payload = self._read(size)
ch = self._read(1)
if ch == '\xce':
return frame_type, channel, payload
else:
raise Exception('Framing Error, received 0x%02x while expecting 0xce' % ord(ch))
def write_frame(self, frame_type, channel, payload):
"""
Write out an AMQP frame.
"""
size = len(payload)
self._write(pack('>BHI%dsB' % size,
frame_type, channel, size, payload, 0xce))
class SSLTransport(_AbstractTransport):
"""
Transport that works over SSL
"""
def _setup_transport(self):
"""
Wrap the socket in an SSL object, either the
new Python 2.6 version, or the older Python 2.5 and
lower version.
"""
if HAVE_PY26_SSL:
self.sslobj = ssl.wrap_socket(self.sock)
self.sslobj.do_handshake()
else:
self.sslobj = socket.ssl(self.sock)
def _read(self, n):
"""
It seems that SSL Objects read() method may not supply as much
as you're asking for, at least with extremely large messages.
somewhere > 16K - found this in the test_channel.py test_large
unittest.
"""
result = self.sslobj.read(n)
while len(result) < n:
s = self.sslobj.read(n - len(result))
if not s:
raise IOError('Socket closed')
result += s
return result
def _write(self, s):
"""
Write a string out to the SSL socket fully.
"""
while s:
n = self.sslobj.write(s)
if not n:
raise IOError('Socket closed')
s = s[n:]
class TCPTransport(_AbstractTransport):
"""
Transport that deals directly with TCP socket.
"""
def _setup_transport(self):
"""
Setup to _write() directly to the socket, and
do our own buffered reads.
"""
self._write = self.sock.sendall
self._read_buffer = ''
def _read(self, n):
"""
Read exactly n bytes from the socket
"""
while len(self._read_buffer) < n:
s = self.sock.recv(65536)
if not s:
raise IOError('Socket closed')
self._read_buffer += s
result = self._read_buffer[:n]
self._read_buffer = self._read_buffer[n:]
return result
def create_transport(host, connect_timeout, ssl=False):
"""
Given a few parameters from the Connection constructor,
select and create a subclass of _AbstractTransport.
"""
if ssl:
return SSLTransport(host, connect_timeout)
else:
return TCPTransport(host, connect_timeout)
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