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# Copyright (C) 2008 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
import collections
from cStringIO import StringIO
from bzrlib import (
debug,
errors,
)
from bzrlib.trace import mutter
class MessageHandler(object):
"""Base class for handling messages received via the smart protocol.
As parts of a message are received, the corresponding PART_received method
will be called.
"""
def __init__(self):
self.headers = None
def headers_received(self, headers):
"""Called when message headers are received.
This default implementation just stores them in self.headers.
"""
self.headers = headers
def byte_part_received(self, byte):
"""Called when a 'byte' part is received.
Note that a 'byte' part is a message part consisting of exactly one
byte.
"""
raise NotImplementedError(self.byte_received)
def bytes_part_received(self, bytes):
"""Called when a 'bytes' part is received.
A 'bytes' message part can contain any number of bytes. It should not
be confused with a 'byte' part, which is always a single byte.
"""
raise NotImplementedError(self.bytes_received)
def structure_part_received(self, structure):
"""Called when a 'structure' part is received.
:param structure: some structured data, which will be some combination
of list, dict, int, and str objects.
"""
raise NotImplementedError(self.bytes_received)
def protocol_error(self, exception):
"""Called when there is a protocol decoding error.
The default implementation just re-raises the exception.
"""
raise
def end_received(self):
"""Called when the end of the message is received."""
# No-op by default.
pass
class ConventionalRequestHandler(MessageHandler):
"""A message handler for "conventional" requests.
"Conventional" is used in the sense described in
doc/developers/network-protocol.txt: a simple message with arguments and an
optional body.
Possible states:
* args: expecting args
* body: expecting body (terminated by receiving a post-body status)
* error: expecting post-body error
* end: expecting end of message
* nothing: finished
"""
def __init__(self, request_handler, responder):
MessageHandler.__init__(self)
self.request_handler = request_handler
self.responder = responder
self.expecting = 'args'
self._should_finish_body = False
self._response_sent = False
def protocol_error(self, exception):
if self.responder.response_sent:
# We can only send one response to a request, no matter how many
# errors happen while processing it.
return
self.responder.send_error(exception)
def byte_part_received(self, byte):
if self.expecting == 'body':
if byte == 'S':
# Success. Nothing more to come except the end of message.
self.expecting = 'end'
elif byte == 'E':
# Error. Expect an error structure.
self.expecting = 'error'
else:
raise errors.SmartProtocolError(
'Non-success status byte in request body: %r' % (byte,))
else:
raise errors.SmartProtocolError(
'Unexpected message part: byte(%r)' % (byte,))
def structure_part_received(self, structure):
if self.expecting == 'args':
self._args_received(structure)
elif self.expecting == 'error':
self._error_received(structure)
else:
raise errors.SmartProtocolError(
'Unexpected message part: structure(%r)' % (structure,))
def _args_received(self, args):
self.expecting = 'body'
self.request_handler.args_received(args)
if self.request_handler.finished_reading:
self._response_sent = True
self.responder.send_response(self.request_handler.response)
self.expecting = 'end'
def _error_received(self, error_args):
self.expecting = 'end'
self.request_handler.post_body_error_received(error_args)
def bytes_part_received(self, bytes):
if self.expecting == 'body':
self._should_finish_body = True
self.request_handler.accept_body(bytes)
else:
raise errors.SmartProtocolError(
'Unexpected message part: bytes(%r)' % (bytes,))
def end_received(self):
if self.expecting not in ['body', 'end']:
raise errors.SmartProtocolError(
'End of message received prematurely (while expecting %s)'
% (self.expecting,))
self.expecting = 'nothing'
self.request_handler.end_received()
if not self.request_handler.finished_reading:
raise errors.SmartProtocolError(
"Complete conventional request was received, but request "
"handler has not finished reading.")
if not self._response_sent:
self.responder.send_response(self.request_handler.response)
class ResponseHandler(object):
"""Abstract base class for an object that handles a smart response."""
def read_response_tuple(self, expect_body=False):
"""Reads and returns the response tuple for the current request.
:keyword expect_body: a boolean indicating if a body is expected in the
response. Some protocol versions needs this information to know
when a response is finished. If False, read_body_bytes should
*not* be called afterwards. Defaults to False.
:returns: tuple of response arguments.
"""
raise NotImplementedError(self.read_response_tuple)
def read_body_bytes(self, count=-1):
"""Read and return some bytes from the body.
:param count: if specified, read up to this many bytes. By default,
reads the entire body.
:returns: str of bytes from the response body.
"""
raise NotImplementedError(self.read_body_bytes)
def read_streamed_body(self):
"""Returns an iterable that reads and returns a series of body chunks.
"""
raise NotImplementedError(self.read_streamed_body)
def cancel_read_body(self):
"""Stop expecting a body for this response.
If expect_body was passed to read_response_tuple, this cancels that
expectation (and thus finishes reading the response, allowing a new
request to be issued). This is useful if a response turns out to be an
error rather than a normal result with a body.
"""
raise NotImplementedError(self.cancel_read_body)
class ConventionalResponseHandler(MessageHandler, ResponseHandler):
def __init__(self):
MessageHandler.__init__(self)
self.status = None
self.args = None
self._bytes_parts = collections.deque()
self._body_started = False
self._body_stream_status = None
self._body = None
self._body_error_args = None
self.finished_reading = False
def setProtoAndMediumRequest(self, protocol_decoder, medium_request):
self._protocol_decoder = protocol_decoder
self._medium_request = medium_request
def byte_part_received(self, byte):
if byte not in ['E', 'S']:
raise errors.SmartProtocolError(
'Unknown response status: %r' % (byte,))
if self._body_started:
if self._body_stream_status is not None:
raise errors.SmartProtocolError(
'Unexpected byte part received: %r' % (byte,))
self._body_stream_status = byte
else:
if self.status is not None:
raise errors.SmartProtocolError(
'Unexpected byte part received: %r' % (byte,))
self.status = byte
def bytes_part_received(self, bytes):
self._body_started = True
self._bytes_parts.append(bytes)
def structure_part_received(self, structure):
if type(structure) is not tuple:
raise errors.SmartProtocolError(
'Args structure is not a sequence: %r' % (structure,))
if not self._body_started:
if self.args is not None:
raise errors.SmartProtocolError(
'Unexpected structure received: %r (already got %r)'
% (structure, self.args))
self.args = structure
else:
if self._body_stream_status != 'E':
raise errors.SmartProtocolError(
'Unexpected structure received after body: %r'
% (structure,))
self._body_error_args = structure
def _wait_for_response_args(self):
while self.args is None and not self.finished_reading:
self._read_more()
def _wait_for_response_end(self):
while not self.finished_reading:
self._read_more()
def _read_more(self):
next_read_size = self._protocol_decoder.next_read_size()
if next_read_size == 0:
# a complete request has been read.
self.finished_reading = True
self._medium_request.finished_reading()
return
bytes = self._medium_request.read_bytes(next_read_size)
if bytes == '':
# end of file encountered reading from server
if 'hpss' in debug.debug_flags:
mutter(
'decoder state: buf[:10]=%r, state_accept=%s',
self._protocol_decoder._get_in_buffer()[:10],
self._protocol_decoder.state_accept.__name__)
raise errors.ConnectionReset(
"Unexpected end of message. "
"Please check connectivity and permissions, and report a bug "
"if problems persist.")
self._protocol_decoder.accept_bytes(bytes)
def protocol_error(self, exception):
# Whatever the error is, we're done with this request.
self.finished_reading = True
self._medium_request.finished_reading()
raise
def read_response_tuple(self, expect_body=False):
"""Read a response tuple from the wire."""
self._wait_for_response_args()
if not expect_body:
self._wait_for_response_end()
if 'hpss' in debug.debug_flags:
mutter(' result: %r', self.args)
if self.status == 'E':
self._wait_for_response_end()
_translate_error(self.args)
return tuple(self.args)
def read_body_bytes(self, count=-1):
"""Read bytes from the body, decoding into a byte stream.
We read all bytes at once to ensure we've checked the trailer for
errors, and then feed the buffer back as read_body_bytes is called.
Like the builtin file.read in Python, a count of -1 (the default) means
read the entire body.
"""
# TODO: we don't necessarily need to buffer the full request if count
# != -1. (2008/04/30, Andrew Bennetts)
if self._body is None:
self._wait_for_response_end()
body_bytes = ''.join(self._bytes_parts)
if 'hpss' in debug.debug_flags:
mutter(' %d body bytes read', len(body_bytes))
self._body = StringIO(body_bytes)
self._bytes_parts = None
return self._body.read(count)
def read_streamed_body(self):
while not self.finished_reading:
while self._bytes_parts:
bytes_part = self._bytes_parts.popleft()
if 'hpssdetail' in debug.debug_flags:
mutter(' %d byte part read', len(bytes_part))
yield bytes_part
self._read_more()
if self._body_stream_status == 'E':
_translate_error(self._body_error_args)
def cancel_read_body(self):
self._wait_for_response_end()
def _translate_error(error_tuple):
# Many exceptions need some state from the requestor to be properly
# translated (e.g. they need a branch object). So this only translates a
# few errors, and the rest are turned into a generic ErrorFromSmartServer.
error_name = error_tuple[0]
error_args = error_tuple[1:]
if error_name == 'UnknownMethod':
raise errors.UnknownSmartMethod(error_args[0])
if error_name == 'LockContention':
raise errors.LockContention('(remote lock)')
elif error_name == 'LockFailed':
raise errors.LockFailed(*error_args[:2])
elif error_name == 'FileExists':
raise errors.FileExists(error_args[0])
elif error_name == 'NoSuchFile':
raise errors.NoSuchFile(error_args[0])
else:
raise errors.ErrorFromSmartServer(error_tuple)
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