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# Copyright (C) 2006 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program 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
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""The 'medium' layer for the smart servers and clients.
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"Medium" here is the noun meaning "a means of transmission", not the adjective
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for "the quality between big and small."
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Media carry the bytes of the requests somehow (e.g. via TCP, wrapped in HTTP, or
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over SSH), and pass them to and from the protocol logic. See the overview in
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bzrlib/transport/smart/__init__.py.
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from bzrlib.lazy_import import lazy_import
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lazy_import(globals(), """
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from bzrlib.smart import protocol
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from bzrlib.transport import ssh
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# We must not read any more than 64k at a time so we don't risk "no buffer
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# space available" errors on some platforms. Windows in particular is likely
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# to give error 10053 or 10055 if we read more than 64k from a socket.
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_MAX_READ_SIZE = 64 * 1024
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def _get_protocol_factory_for_bytes(bytes):
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"""Determine the right protocol factory for 'bytes'.
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This will return an appropriate protocol factory depending on the version
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of the protocol being used, as determined by inspecting the given bytes.
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The bytes should have at least one newline byte (i.e. be a whole line),
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otherwise it's possible that a request will be incorrectly identified as
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Typical use would be::
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factory, unused_bytes = _get_protocol_factory_for_bytes(bytes)
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server_protocol = factory(transport, write_func, root_client_path)
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server_protocol.accept_bytes(unused_bytes)
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:param bytes: a str of bytes of the start of the request.
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:returns: 2-tuple of (protocol_factory, unused_bytes). protocol_factory is
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a callable that takes three args: transport, write_func,
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root_client_path. unused_bytes are any bytes that were not part of a
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protocol version marker.
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if bytes.startswith(protocol.MESSAGE_VERSION_THREE):
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protocol_factory = protocol.build_server_protocol_three
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bytes = bytes[len(protocol.MESSAGE_VERSION_THREE):]
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elif bytes.startswith(protocol.REQUEST_VERSION_TWO):
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protocol_factory = protocol.SmartServerRequestProtocolTwo
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bytes = bytes[len(protocol.REQUEST_VERSION_TWO):]
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protocol_factory = protocol.SmartServerRequestProtocolOne
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return protocol_factory, bytes
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def _get_line(read_bytes_func):
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"""Read bytes using read_bytes_func until a newline byte.
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This isn't particularly efficient, so should only be used when the
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expected size of the line is quite short.
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:returns: a tuple of two strs: (line, excess)
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while newline_pos == -1:
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new_bytes = read_bytes_func(1)
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# Ran out of bytes before receiving a complete line.
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newline_pos = bytes.find('\n')
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line = bytes[:newline_pos+1]
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excess = bytes[newline_pos+1:]
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class SmartMedium(object):
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"""Base class for smart protocol media, both client- and server-side."""
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self._push_back_buffer = None
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def _push_back(self, bytes):
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"""Return unused bytes to the medium, because they belong to the next
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This sets the _push_back_buffer to the given bytes.
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if self._push_back_buffer is not None:
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raise AssertionError(
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"_push_back called when self._push_back_buffer is %r"
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% (self._push_back_buffer,))
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self._push_back_buffer = bytes
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def _get_push_back_buffer(self):
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if self._push_back_buffer == '':
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raise AssertionError(
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'%s._push_back_buffer should never be the empty string, '
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'which can be confused with EOF' % (self,))
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bytes = self._push_back_buffer
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self._push_back_buffer = None
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def read_bytes(self, desired_count):
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"""Read some bytes from this medium.
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:returns: some bytes, possibly more or less than the number requested
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in 'desired_count' depending on the medium.
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if self._push_back_buffer is not None:
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return self._get_push_back_buffer()
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bytes_to_read = min(desired_count, _MAX_READ_SIZE)
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return self._read_bytes(bytes_to_read)
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def _read_bytes(self, count):
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raise NotImplementedError(self._read_bytes)
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"""Read bytes from this request's response until a newline byte.
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This isn't particularly efficient, so should only be used when the
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expected size of the line is quite short.
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:returns: a string of bytes ending in a newline (byte 0x0A).
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line, excess = _get_line(self.read_bytes)
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self._push_back(excess)
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class SmartServerStreamMedium(SmartMedium):
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"""Handles smart commands coming over a stream.
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The stream may be a pipe connected to sshd, or a tcp socket, or an
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in-process fifo for testing.
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One instance is created for each connected client; it can serve multiple
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requests in the lifetime of the connection.
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The server passes requests through to an underlying backing transport,
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which will typically be a LocalTransport looking at the server's filesystem.
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:ivar _push_back_buffer: a str of bytes that have been read from the stream
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but not used yet, or None if there are no buffered bytes. Subclasses
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should make sure to exhaust this buffer before reading more bytes from
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the stream. See also the _push_back method.
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def __init__(self, backing_transport, root_client_path='/'):
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"""Construct new server.
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:param backing_transport: Transport for the directory served.
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# backing_transport could be passed to serve instead of __init__
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self.backing_transport = backing_transport
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self.root_client_path = root_client_path
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self.finished = False
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SmartMedium.__init__(self)
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"""Serve requests until the client disconnects."""
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# Keep a reference to stderr because the sys module's globals get set to
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# None during interpreter shutdown.
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from sys import stderr
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while not self.finished:
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server_protocol = self._build_protocol()
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self._serve_one_request(server_protocol)
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stderr.write("%s terminating on exception %s\n" % (self, e))
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def _build_protocol(self):
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"""Identifies the version of the incoming request, and returns an
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a protocol object that can interpret it.
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If more bytes than the version prefix of the request are read, they will
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be fed into the protocol before it is returned.
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:returns: a SmartServerRequestProtocol.
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bytes = self._get_line()
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protocol_factory, unused_bytes = _get_protocol_factory_for_bytes(bytes)
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protocol = protocol_factory(
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self.backing_transport, self._write_out, self.root_client_path)
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protocol.accept_bytes(unused_bytes)
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def _serve_one_request(self, protocol):
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"""Read one request from input, process, send back a response.
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:param protocol: a SmartServerRequestProtocol.
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self._serve_one_request_unguarded(protocol)
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except KeyboardInterrupt:
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self.terminate_due_to_error()
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def terminate_due_to_error(self):
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"""Called when an unhandled exception from the protocol occurs."""
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raise NotImplementedError(self.terminate_due_to_error)
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def _read_bytes(self, desired_count):
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"""Get some bytes from the medium.
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:param desired_count: number of bytes we want to read.
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raise NotImplementedError(self._read_bytes)
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class SmartServerSocketStreamMedium(SmartServerStreamMedium):
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def __init__(self, sock, backing_transport, root_client_path='/'):
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:param sock: the socket the server will read from. It will be put
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SmartServerStreamMedium.__init__(
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self, backing_transport, root_client_path=root_client_path)
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sock.setblocking(True)
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def _serve_one_request_unguarded(self, protocol):
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while protocol.next_read_size():
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# We can safely try to read large chunks. If there is less data
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# than _MAX_READ_SIZE ready, the socket wil just return a short
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# read immediately rather than block.
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bytes = self.read_bytes(_MAX_READ_SIZE)
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protocol.accept_bytes(bytes)
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self._push_back(protocol.unused_data)
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def _read_bytes(self, desired_count):
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# We ignore the desired_count because on sockets it's more efficient to
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# read large chunks (of _MAX_READ_SIZE bytes) at a time.
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return self.socket.recv(_MAX_READ_SIZE)
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def terminate_due_to_error(self):
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# TODO: This should log to a server log file, but no such thing
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# exists yet. Andrew Bennetts 2006-09-29.
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def _write_out(self, bytes):
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osutils.send_all(self.socket, bytes)
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class SmartServerPipeStreamMedium(SmartServerStreamMedium):
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def __init__(self, in_file, out_file, backing_transport):
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"""Construct new server.
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:param in_file: Python file from which requests can be read.
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:param out_file: Python file to write responses.
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:param backing_transport: Transport for the directory served.
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SmartServerStreamMedium.__init__(self, backing_transport)
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if sys.platform == 'win32':
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# force binary mode for files
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for f in (in_file, out_file):
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fileno = getattr(f, 'fileno', None)
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msvcrt.setmode(fileno(), os.O_BINARY)
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def _serve_one_request_unguarded(self, protocol):
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# We need to be careful not to read past the end of the current
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# request, or else the read from the pipe will block, so we use
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# protocol.next_read_size().
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bytes_to_read = protocol.next_read_size()
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if bytes_to_read == 0:
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# Finished serving this request.
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bytes = self.read_bytes(bytes_to_read)
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# Connection has been closed.
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protocol.accept_bytes(bytes)
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def _read_bytes(self, desired_count):
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return self._in.read(desired_count)
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def terminate_due_to_error(self):
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# TODO: This should log to a server log file, but no such thing
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# exists yet. Andrew Bennetts 2006-09-29.
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def _write_out(self, bytes):
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self._out.write(bytes)
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class SmartClientMediumRequest(object):
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"""A request on a SmartClientMedium.
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Each request allows bytes to be provided to it via accept_bytes, and then
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the response bytes to be read via read_bytes.
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request.accept_bytes('123')
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request.finished_writing()
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result = request.read_bytes(3)
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request.finished_reading()
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It is up to the individual SmartClientMedium whether multiple concurrent
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requests can exist. See SmartClientMedium.get_request to obtain instances
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of SmartClientMediumRequest, and the concrete Medium you are using for
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details on concurrency and pipelining.
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def __init__(self, medium):
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"""Construct a SmartClientMediumRequest for the medium medium."""
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self._medium = medium
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# we track state by constants - we may want to use the same
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# pattern as BodyReader if it gets more complex.
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# valid states are: "writing", "reading", "done"
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self._state = "writing"
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def accept_bytes(self, bytes):
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"""Accept bytes for inclusion in this request.
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This method may not be be called after finished_writing() has been
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called. It depends upon the Medium whether or not the bytes will be
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immediately transmitted. Message based Mediums will tend to buffer the
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bytes until finished_writing() is called.
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:param bytes: A bytestring.
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if self._state != "writing":
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raise errors.WritingCompleted(self)
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self._accept_bytes(bytes)
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def _accept_bytes(self, bytes):
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"""Helper for accept_bytes.
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Accept_bytes checks the state of the request to determing if bytes
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should be accepted. After that it hands off to _accept_bytes to do the
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raise NotImplementedError(self._accept_bytes)
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def finished_reading(self):
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"""Inform the request that all desired data has been read.
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This will remove the request from the pipeline for its medium (if the
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medium supports pipelining) and any further calls to methods on the
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request will raise ReadingCompleted.
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if self._state == "writing":
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raise errors.WritingNotComplete(self)
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if self._state != "reading":
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raise errors.ReadingCompleted(self)
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self._finished_reading()
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def _finished_reading(self):
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"""Helper for finished_reading.
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finished_reading checks the state of the request to determine if
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finished_reading is allowed, and if it is hands off to _finished_reading
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to perform the action.
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raise NotImplementedError(self._finished_reading)
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def finished_writing(self):
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"""Finish the writing phase of this request.
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This will flush all pending data for this request along the medium.
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After calling finished_writing, you may not call accept_bytes anymore.
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if self._state != "writing":
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raise errors.WritingCompleted(self)
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self._state = "reading"
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self._finished_writing()
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def _finished_writing(self):
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"""Helper for finished_writing.
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finished_writing checks the state of the request to determine if
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finished_writing is allowed, and if it is hands off to _finished_writing
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to perform the action.
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raise NotImplementedError(self._finished_writing)
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def read_bytes(self, count):
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"""Read bytes from this requests response.
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This method will block and wait for count bytes to be read. It may not
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be invoked until finished_writing() has been called - this is to ensure
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a message-based approach to requests, for compatibility with message
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based mediums like HTTP.
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if self._state == "writing":
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raise errors.WritingNotComplete(self)
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if self._state != "reading":
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raise errors.ReadingCompleted(self)
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return self._read_bytes(count)
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def _read_bytes(self, count):
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"""Helper for SmartClientMediumRequest.read_bytes.
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read_bytes checks the state of the request to determing if bytes
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should be read. After that it hands off to _read_bytes to do the
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By default this forwards to self._medium.read_bytes because we are
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operating on the medium's stream.
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return self._medium.read_bytes(count)
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line = self._read_line()
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if not line.endswith('\n'):
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# end of file encountered reading from server
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raise errors.ConnectionReset(
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"please check connectivity and permissions",
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"(and try -Dhpss if further diagnosis is required)")
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def _read_line(self):
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"""Helper for SmartClientMediumRequest.read_line.
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By default this forwards to self._medium._get_line because we are
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operating on the medium's stream.
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return self._medium._get_line()
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class SmartClientMedium(SmartMedium):
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"""Smart client is a medium for sending smart protocol requests over."""
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def __init__(self, base):
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super(SmartClientMedium, self).__init__()
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self._protocol_version_error = None
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self._protocol_version = None
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self._done_hello = False
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# Be optimistic: we assume the remote end can accept new remote
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# requests until we get an error saying otherwise.
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# _remote_version_is_before tracks the bzr version the remote side
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# can be based on what we've seen so far.
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self._remote_version_is_before = None
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def _is_remote_before(self, version_tuple):
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"""Is it possible the remote side supports RPCs for a given version?
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needed_version = (1, 2)
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if medium._is_remote_before(needed_version):
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fallback_to_pre_1_2_rpc()
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except UnknownSmartMethod:
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medium._remember_remote_is_before(needed_version)
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fallback_to_pre_1_2_rpc()
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:seealso: _remember_remote_is_before
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if self._remote_version_is_before is None:
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# So far, the remote side seems to support everything
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return version_tuple >= self._remote_version_is_before
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def _remember_remote_is_before(self, version_tuple):
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"""Tell this medium that the remote side is older the given version.
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:seealso: _is_remote_before
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if (self._remote_version_is_before is not None and
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version_tuple > self._remote_version_is_before):
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raise AssertionError(
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"_remember_remote_is_before(%r) called, but "
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"_remember_remote_is_before(%r) was called previously."
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% (version_tuple, self._remote_version_is_before))
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self._remote_version_is_before = version_tuple
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def protocol_version(self):
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"""Find out if 'hello' smart request works."""
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if self._protocol_version_error is not None:
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raise self._protocol_version_error
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if not self._done_hello:
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medium_request = self.get_request()
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# Send a 'hello' request in protocol version one, for maximum
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# backwards compatibility.
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client_protocol = protocol.SmartClientRequestProtocolOne(medium_request)
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client_protocol.query_version()
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self._done_hello = True
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except errors.SmartProtocolError, e:
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# Cache the error, just like we would cache a successful
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self._protocol_version_error = e
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def should_probe(self):
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"""Should RemoteBzrDirFormat.probe_transport send a smart request on
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Some transports are unambiguously smart-only; there's no need to check
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if the transport is able to carry smart requests, because that's all
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it is for. In those cases, this method should return False.
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But some HTTP transports can sometimes fail to carry smart requests,
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but still be usuable for accessing remote bzrdirs via plain file
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accesses. So for those transports, their media should return True here
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so that RemoteBzrDirFormat can determine if it is appropriate for that
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def disconnect(self):
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"""If this medium maintains a persistent connection, close it.
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The default implementation does nothing.
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def remote_path_from_transport(self, transport):
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"""Convert transport into a path suitable for using in a request.
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Note that the resulting remote path doesn't encode the host name or
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anything but path, so it is only safe to use it in requests sent over
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the medium from the matching transport.
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medium_base = urlutils.join(self.base, '/')
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rel_url = urlutils.relative_url(medium_base, transport.base)
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return urllib.unquote(rel_url)
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class SmartClientStreamMedium(SmartClientMedium):
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"""Stream based medium common class.
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SmartClientStreamMediums operate on a stream. All subclasses use a common
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SmartClientStreamMediumRequest for their requests, and should implement
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_accept_bytes and _read_bytes to allow the request objects to send and
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def __init__(self, base):
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SmartClientMedium.__init__(self, base)
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self._current_request = None
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def accept_bytes(self, bytes):
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self._accept_bytes(bytes)
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"""The SmartClientStreamMedium knows how to close the stream when it is
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"""Flush the output stream.
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This method is used by the SmartClientStreamMediumRequest to ensure that
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all data for a request is sent, to avoid long timeouts or deadlocks.
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raise NotImplementedError(self._flush)
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def get_request(self):
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"""See SmartClientMedium.get_request().
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SmartClientStreamMedium always returns a SmartClientStreamMediumRequest
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return SmartClientStreamMediumRequest(self)
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class SmartSimplePipesClientMedium(SmartClientStreamMedium):
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"""A client medium using simple pipes.
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This client does not manage the pipes: it assumes they will always be open.
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def __init__(self, readable_pipe, writeable_pipe, base):
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SmartClientStreamMedium.__init__(self, base)
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self._readable_pipe = readable_pipe
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self._writeable_pipe = writeable_pipe
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def _accept_bytes(self, bytes):
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"""See SmartClientStreamMedium.accept_bytes."""
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self._writeable_pipe.write(bytes)
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"""See SmartClientStreamMedium._flush()."""
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self._writeable_pipe.flush()
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def _read_bytes(self, count):
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"""See SmartClientStreamMedium._read_bytes."""
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return self._readable_pipe.read(count)
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class SmartSSHClientMedium(SmartClientStreamMedium):
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"""A client medium using SSH."""
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def __init__(self, host, port=None, username=None, password=None,
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base=None, vendor=None, bzr_remote_path=None):
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"""Creates a client that will connect on the first use.
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:param vendor: An optional override for the ssh vendor to use. See
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bzrlib.transport.ssh for details on ssh vendors.
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SmartClientStreamMedium.__init__(self, base)
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self._connected = False
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self._password = password
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self._username = username
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self._read_from = None
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self._ssh_connection = None
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self._vendor = vendor
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self._write_to = None
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self._bzr_remote_path = bzr_remote_path
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if self._bzr_remote_path is None:
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symbol_versioning.warn(
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'bzr_remote_path is required as of bzr 0.92',
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DeprecationWarning, stacklevel=2)
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self._bzr_remote_path = os.environ.get('BZR_REMOTE_PATH', 'bzr')
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def _accept_bytes(self, bytes):
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"""See SmartClientStreamMedium.accept_bytes."""
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self._ensure_connection()
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self._write_to.write(bytes)
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def disconnect(self):
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"""See SmartClientMedium.disconnect()."""
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if not self._connected:
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self._read_from.close()
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self._write_to.close()
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self._ssh_connection.close()
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self._connected = False
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def _ensure_connection(self):
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"""Connect this medium if not already connected."""
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if self._vendor is None:
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vendor = ssh._get_ssh_vendor()
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vendor = self._vendor
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self._ssh_connection = vendor.connect_ssh(self._username,
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self._password, self._host, self._port,
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command=[self._bzr_remote_path, 'serve', '--inet',
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'--directory=/', '--allow-writes'])
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self._read_from, self._write_to = \
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self._ssh_connection.get_filelike_channels()
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self._connected = True
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"""See SmartClientStreamMedium._flush()."""
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self._write_to.flush()
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def _read_bytes(self, count):
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"""See SmartClientStreamMedium.read_bytes."""
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if not self._connected:
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raise errors.MediumNotConnected(self)
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bytes_to_read = min(count, _MAX_READ_SIZE)
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return self._read_from.read(bytes_to_read)
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# Port 4155 is the default port for bzr://, registered with IANA.
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BZR_DEFAULT_INTERFACE = None
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BZR_DEFAULT_PORT = 4155
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class SmartTCPClientMedium(SmartClientStreamMedium):
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"""A client medium using TCP."""
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def __init__(self, host, port, base):
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"""Creates a client that will connect on the first use."""
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SmartClientStreamMedium.__init__(self, base)
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self._connected = False
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def _accept_bytes(self, bytes):
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"""See SmartClientMedium.accept_bytes."""
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self._ensure_connection()
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osutils.send_all(self._socket, bytes)
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def disconnect(self):
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"""See SmartClientMedium.disconnect()."""
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if not self._connected:
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self._connected = False
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def _ensure_connection(self):
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"""Connect this medium if not already connected."""
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if self._port is None:
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port = BZR_DEFAULT_PORT
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port = int(self._port)
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sockaddrs = socket.getaddrinfo(self._host, port, socket.AF_UNSPEC,
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socket.SOCK_STREAM, 0, 0)
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except socket.gaierror, (err_num, err_msg):
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raise errors.ConnectionError("failed to lookup %s:%d: %s" %
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(self._host, port, err_msg))
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# Initialize err in case there are no addresses returned:
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err = socket.error("no address found for %s" % self._host)
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for (family, socktype, proto, canonname, sockaddr) in sockaddrs:
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self._socket = socket.socket(family, socktype, proto)
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self._socket.setsockopt(socket.IPPROTO_TCP,
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socket.TCP_NODELAY, 1)
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self._socket.connect(sockaddr)
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except socket.error, err:
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if self._socket is not None:
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if self._socket is None:
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# socket errors either have a (string) or (errno, string) as their
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if type(err.args) is str:
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err_msg = err.args[1]
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raise errors.ConnectionError("failed to connect to %s:%d: %s" %
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(self._host, port, err_msg))
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self._connected = True
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"""See SmartClientStreamMedium._flush().
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For TCP we do no flushing. We may want to turn off TCP_NODELAY and
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add a means to do a flush, but that can be done in the future.
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def _read_bytes(self, count):
783
"""See SmartClientMedium.read_bytes."""
784
if not self._connected:
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raise errors.MediumNotConnected(self)
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# We ignore the desired_count because on sockets it's more efficient to
787
# read large chunks (of _MAX_READ_SIZE bytes) at a time.
789
return self._socket.recv(_MAX_READ_SIZE)
790
except socket.error, e:
791
if len(e.args) and e.args[0] == errno.ECONNRESET:
792
# Callers expect an empty string in that case
798
class SmartClientStreamMediumRequest(SmartClientMediumRequest):
799
"""A SmartClientMediumRequest that works with an SmartClientStreamMedium."""
801
def __init__(self, medium):
802
SmartClientMediumRequest.__init__(self, medium)
803
# check that we are safe concurrency wise. If some streams start
804
# allowing concurrent requests - i.e. via multiplexing - then this
805
# assert should be moved to SmartClientStreamMedium.get_request,
806
# and the setting/unsetting of _current_request likewise moved into
807
# that class : but its unneeded overhead for now. RBC 20060922
808
if self._medium._current_request is not None:
809
raise errors.TooManyConcurrentRequests(self._medium)
810
self._medium._current_request = self
812
def _accept_bytes(self, bytes):
813
"""See SmartClientMediumRequest._accept_bytes.
815
This forwards to self._medium._accept_bytes because we are operating
816
on the mediums stream.
818
self._medium._accept_bytes(bytes)
820
def _finished_reading(self):
821
"""See SmartClientMediumRequest._finished_reading.
823
This clears the _current_request on self._medium to allow a new
824
request to be created.
826
if self._medium._current_request is not self:
827
raise AssertionError()
828
self._medium._current_request = None
830
def _finished_writing(self):
831
"""See SmartClientMediumRequest._finished_writing.
833
This invokes self._medium._flush to ensure all bytes are transmitted.
835
self._medium._flush()
added
removed
bzrlib/smart/medium.py
