path: root/rdiff-backup/src/connection.py

execfile("rdiff.py")
import types, os, tempfile, cPickle, shutil, traceback

#######################################################################
#
# connection - Code that deals with remote execution
#

class ConnectionError(Exception): pass
class ConnectionReadError(ConnectionError): pass

class ConnectionQuit(Exception): pass


class Connection:
	"""Connection class - represent remote execution

	The idea is that, if c is an instance of this class, c.foo will
	return the object on the remote side.  For functions, c.foo will
	return a function that, when called, executes foo on the remote
	side, sending over the arguments and sending back the result.

	"""
	def __repr__(self): return self.__str__()


class LocalConnection(Connection):
	"""Local connection

	This is a dummy connection class, so that LC.foo just evaluates to
	foo using global scope.

	"""
	def __init__(self):
		"""This prevents two instances of LocalConnection"""
		assert not Globals.local_connection
		self.conn_number = 0 # changed by SetConnections for server

	def __getattr__(self, name):
		try: return globals()[name]
		except KeyError:
			builtins = globals()["__builtins__"]
			try:
				if type(builtins) is types.ModuleType:
					return builtins.__dict__[name]
				else: return builtins[name]
			except KeyError: raise NameError, name

	def __setattr__(self, name, value):
		globals()[name] = value

	def __delattr__(self, name):
		del globals()[name]

	def __str__(self): return "LocalConnection"

	def reval(self, function_string, *args):
		return apply(eval(function_string), args)

	def quit(self): pass

Globals.local_connection = LocalConnection()
Globals.connections.append(Globals.local_connection)
# Following changed by server in SetConnections
Globals.connection_dict[0] = Globals.local_connection


class ConnectionRequest:
	"""Simple wrapper around a PipeConnection request"""
	def __init__(self, function_string, num_args):
		self.function_string = function_string
		self.num_args = num_args

	def __str__(self):
		return "ConnectionRequest: %s with %d arguments" % \
			   (self.function_string, self.num_args)


class LowLevelPipeConnection(Connection):
	"""Routines for just sending objects from one side of pipe to another

	Each thing sent down the pipe is paired with a request number,
	currently limited to be between 0 and 255.  The size of each thing
	should be less than 2^56.

	Each thing also has a type, indicated by one of the following
	characters:

	o - generic object
	i - iterator/generator of RORPs
	f - file object
	b - string
	q - quit signal
	t - TempFile
	R - RPath
	r - RORPath only
	c - PipeConnection object

	"""
	def __init__(self, inpipe, outpipe):
		"""inpipe is a file-type open for reading, outpipe for writing"""
		self.inpipe = inpipe
		self.outpipe = outpipe

	def __str__(self):
		"""Return string version

		This is actually an important function, because otherwise
		requests to represent this object would result in "__str__"
		being executed on the other side of the connection.

		"""
		return "LowLevelPipeConnection"

	def _put(self, obj, req_num):
		"""Put an object into the pipe (will send raw if string)"""
		Log.conn("sending", obj, req_num)
		if type(obj) is types.StringType: self._putbuf(obj, req_num)
		elif isinstance(obj, Connection): self._putconn(obj, req_num)
		elif isinstance(obj, TempFile): self._puttempfile(obj, req_num)
		elif isinstance(obj, RPath): self._putrpath(obj, req_num)
		elif isinstance(obj, RORPath): self._putrorpath(obj, req_num)
		elif ((hasattr(obj, "read") or hasattr(obj, "write"))
			  and hasattr(obj, "close")): self._putfile(obj, req_num)
		elif hasattr(obj, "next"): self._putiter(obj, req_num)
		else: self._putobj(obj, req_num)

	def _putobj(self, obj, req_num):
		"""Send a generic python obj down the outpipe"""
		self._write("o", cPickle.dumps(obj, 1), req_num)

	def _putbuf(self, buf, req_num):
		"""Send buffer buf down the outpipe"""
		self._write("b", buf, req_num)

	def _putfile(self, fp, req_num):
		"""Send a file to the client using virtual files"""
		self._write("f", str(VirtualFile.new(fp)), req_num)

	def _putiter(self, iterator, req_num):
		"""Put an iterator through the pipe"""
		self._write("i", str(VirtualFile.new(RORPIter.ToFile(iterator))),
					req_num)

	def _puttempfile(self, tempfile, req_num):
		"""Put a tempfile into pipe.  See _putrpath"""
		tf_repr = (tempfile.conn.conn_number, tempfile.base,
				   tempfile.index, tempfile.data)
		self._write("t", cPickle.dumps(tf_repr, 1), req_num)

	def _putrpath(self, rpath, req_num):
		"""Put an rpath into the pipe

		The rpath's connection will be encoded as its conn_number.  It
		and the other information is put in a tuple.

		"""
		rpath_repr = (rpath.conn.conn_number, rpath.base,
					  rpath.index, rpath.data)
		self._write("R", cPickle.dumps(rpath_repr, 1), req_num)

	def _putrorpath(self, rorpath, req_num):
		"""Put an rorpath into the pipe

		This is only necessary because if there is a .file attached,
		it must be excluded from the pickling

		"""
		rorpath_repr = (rorpath.index, rorpath.data)
		self._write("r", cPickle.dumps(rorpath_repr, 1), req_num)

	def _putconn(self, pipeconn, req_num):
		"""Put a connection into the pipe

		A pipe connection is represented just as the integer (in
		string form) of its connection number it is *connected to*.

		"""
		self._write("c", str(pipeconn.conn_number), req_num)

	def _putquit(self):
		"""Send a string that takes down server"""
		self._write("q", "", 255)

	def _write(self, headerchar, data, req_num):
		"""Write header and then data to the pipe"""
		self.outpipe.write(headerchar + chr(req_num) + self._l2s(len(data)))
		self.outpipe.write(data)
		self.outpipe.flush()

	def _read(self, length):
		"""Read length bytes from inpipe, returning result"""
		return self.inpipe.read(length)

	def _s2l(self, s):
		"""Convert string to long int"""
		assert len(s) == 7
		l = 0L
		for i in range(7): l = l*256 + ord(s[i])
		return l

	def _l2s(self, l):
		"""Convert long int to string"""
		s = ""
		for i in range(7):
			l, remainder = divmod(l, 256)
			s = chr(remainder) + s
		assert remainder == 0
		return s

	def _get(self):
		"""Read an object from the pipe and return (req_num, value)"""
		header_string = self.inpipe.read(9)
		if not len(header_string) == 9:
			raise ConnectionReadError("Truncated header string (problem "
									  "probably originated remotely)")
		try:
			format_string, req_num, length = (header_string[0],
											  ord(header_string[1]),
											  self._s2l(header_string[2:]))
		except IndexError: raise ConnectionError()
		if format_string == "o": result = cPickle.loads(self._read(length))
		elif format_string == "b": result = self._read(length)
		elif format_string == "f":
			result = VirtualFile(self, int(self._read(length)))
		elif format_string == "i":
			result = RORPIter.FromFile(BufferedRead(
				VirtualFile(self, int(self._read(length)))))
		elif format_string == "t":
			result = self._gettempfile(self._read(length))
		elif format_string == "r":
			result = self._getrorpath(self._read(length))
		elif format_string == "R": result = self._getrpath(self._read(length))
		elif format_string == "c":
			result = Globals.connection_dict[int(self._read(length))]
		else:
			assert format_string == "q", header_string
			raise ConnectionQuit("Received quit signal")
		Log.conn("received", result, req_num)
		return (req_num, result)

	def _getrorpath(self, raw_rorpath_buf):
		"""Reconstruct RORPath object from raw data"""
		index, data = cPickle.loads(raw_rorpath_buf)
		return RORPath(index, data)

	def _gettempfile(self, raw_tf_buf):
		"""Return TempFile object indicated by raw_tf_buf"""
		conn_number, base, index, data = cPickle.loads(raw_tf_buf)
		return TempFile(Globals.connection_dict[conn_number],
						base, index, data)

	def _getrpath(self, raw_rpath_buf):
		"""Return RPath object indicated by raw_rpath_buf"""
		conn_number, base, index, data = cPickle.loads(raw_rpath_buf)
		return RPath(Globals.connection_dict[conn_number], base, index, data)

	def _close(self):
		"""Close the pipes associated with the connection"""
		self.outpipe.close()
		self.inpipe.close()


class PipeConnection(LowLevelPipeConnection):
	"""Provide server and client functions for a Pipe Connection

	Both sides act as modules that allows for remote execution.  For
	instance, self.conn.pow(2,8) will execute the operation on the
	server side.

	The only difference between the client and server is that the
	client makes the first request, and the server listens first.

	"""
	def __init__(self, inpipe, outpipe, conn_number = 0):
		"""Init PipeConnection

		conn_number should be a unique (to the session) integer to
		identify the connection.  For instance, all connections to the
		client have conn_number 0.  Other connections can use this
		number to route commands to the correct process.

		"""
		LowLevelPipeConnection.__init__(self, inpipe, outpipe)
		self.conn_number = conn_number
		self.unused_request_numbers = {}
		for i in range(256): self.unused_request_numbers[i] = None

	def __str__(self): return "PipeConnection %d" % self.conn_number

	def get_response(self, desired_req_num):
		"""Read from pipe, responding to requests until req_num.

		Sometimes after a request is sent, the other side will make
		another request before responding to the original one.  In
		that case, respond to the request.  But return once the right
		response is given.

		"""
		while 1:
			try: req_num, object = self._get()
			except ConnectionQuit:
				self._put("quitting", self.get_new_req_num())
				return
			if req_num == desired_req_num: return object
			else:
				assert isinstance(object, ConnectionRequest)
				self.answer_request(object, req_num)

	def answer_request(self, request, req_num):
		"""Put the object requested by request down the pipe"""
		del self.unused_request_numbers[req_num]
		argument_list = []
		for i in range(request.num_args):
			arg_req_num, arg = self._get()
			assert arg_req_num == req_num
			argument_list.append(arg)
		try: result = apply(eval(request.function_string), argument_list)
		except: result = self.extract_exception()
		self._put(result, req_num)
		self.unused_request_numbers[req_num] = None

	def extract_exception(self):
		"""Return active exception"""
		Log("Sending back exception: \n" +
			"".join(traceback.format_tb(sys.exc_info()[2])), 2)
		return sys.exc_info()[1]

	def Server(self):
		"""Start server's read eval return loop"""
		Globals.server = 1
		Globals.connections.append(self)
		Log("Starting server", 6)
		self.get_response(-1)

	def reval(self, function_string, *args):
		"""Execute command on remote side

		The first argument should be a string that evaluates to a
		function, like "pow", and the remaining are arguments to that
		function.

		"""
		req_num = self.get_new_req_num()
		self._put(ConnectionRequest(function_string, len(args)), req_num)
		for arg in args: self._put(arg, req_num)
		result = self.get_response(req_num)
		self.unused_request_numbers[req_num] = None
		if isinstance(result, Exception): raise result
		else: return result

	def get_new_req_num(self):
		"""Allot a new request number and return it"""
		if not self.unused_request_numbers:
			raise ConnectionError("Exhaused possible connection numbers")
		req_num = self.unused_request_numbers.keys()[0]
		del self.unused_request_numbers[req_num]
		return req_num

	def quit(self):
		"""Close the associated pipes and tell server side to quit"""
		assert not Globals.server
		self._putquit()
		self._get()
		self._close()

	def __getattr__(self, name):
		"""Intercept attributes to allow for . invocation"""
		return EmulateCallable(self, name)


class RedirectedConnection(Connection):
	"""Represent a connection more than one move away

	For instance, suppose things are connected like this: S1---C---S2.
	If Server1 wants something done by Server2, it will have to go
	through the Client.  So on S1's side, S2 will be represented by a
	RedirectedConnection.

	"""
	def __init__(self, conn_number, routing_number = 0):
		"""RedirectedConnection initializer

		Returns a RedirectedConnection object for the given
		conn_number, where commands are routed through the connection
		with the given routing_number.  0 is the client, so the
		default shouldn't have to be changed.

		"""
		self.conn_number = conn_number
		self.routing_number = routing_number
		self.routing_conn = Globals.connection_dict[routing_number]

	def __str__(self):
		return "RedirectedConnection %d,%d" % (self.conn_number,
											   self.routing_number)

	def __getattr__(self, name):
		return EmulateCallable(self.routing_conn,
		   "Globals.get_dict_val('connection_dict', %d).%s"
							   % (self.conn_number, name))


class EmulateCallable:
	"""This is used by PipeConnection in calls like conn.os.chmod(foo)"""
	def __init__(self, connection, name):
		self.connection = connection
		self.name = name
	def __call__(self, *args):
		return apply(self.connection.reval, (self.name,) + args)
	def __getattr__(self, attr_name):
		return EmulateCallable(self.connection,
							   "%s.%s" % (self.name, attr_name))


class VirtualFile:
	"""When the client asks for a file over the connection, it gets this

	The returned instance then forwards requests over the connection.
	The class's dictionary is used by the server to associate each
	with a unique file number.

	"""
	#### The following are used by the server
	vfiles = {}
	counter = 0

	def getbyid(cls, id):
		return cls.vfiles[id]
	getbyid = classmethod(getbyid)

	def readfromid(cls, id, length):
		return cls.vfiles[id].read(length)
	readfromid = classmethod(readfromid)

	def readlinefromid(cls, id):
		return cls.vfiles[id].readline()
	readlinefromid = classmethod(readlinefromid)

	def writetoid(cls, id, buffer):
		return cls.vfiles[id].write(buffer)
	writetoid = classmethod(writetoid)

	def closebyid(cls, id):
		fp = cls.vfiles[id]
		del cls.vfiles[id]
		return fp.close()
	closebyid = classmethod(closebyid)

	def new(cls, fileobj):
		"""Associate a new VirtualFile with a read fileobject, return id"""
		count = cls.counter
		cls.vfiles[count] = fileobj
		cls.counter = count + 1
		return count
	new = classmethod(new)


	#### And these are used by the client
	def __init__(self, connection, id):
		self.connection = connection
		self.id = id

	def read(self, length = -1):
		return self.connection.VirtualFile.readfromid(self.id, length)

	def readline(self):
		return self.connection.VirtualFile.readlinefromid(self.id)

	def write(self, buf):
		return self.connection.VirtualFile.writetoid(self.id, buf)

	def close(self):
		return self.connection.VirtualFile.closebyid(self.id)