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# -*- test-case-name: twisted.test.test_stateful -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
from io import BytesIO
from twisted.internet import protocol
class StatefulProtocol(protocol.Protocol):
"""A Protocol that stores state for you.
state is a pair (function, num_bytes). When num_bytes bytes of data arrives
from the network, function is called. It is expected to return the next
state or None to keep same state. Initial state is returned by
getInitialState (override it).
"""
_sful_data = None, None, 0
def makeConnection(self, transport):
protocol.Protocol.makeConnection(self, transport)
self._sful_data = self.getInitialState(), BytesIO(), 0
def getInitialState(self):
raise NotImplementedError
def dataReceived(self, data):
state, buffer, offset = self._sful_data
buffer.seek(0, 2)
buffer.write(data)
blen = buffer.tell() # how many bytes total is in the buffer
buffer.seek(offset)
while blen - offset >= state[1]:
d = buffer.read(state[1])
offset += state[1]
next = state[0](d)
if (
self.transport.disconnecting
): # XXX: argh stupid hack borrowed right from LineReceiver
return # dataReceived won't be called again, so who cares about consistent state
if next:
state = next
if offset != 0:
b = buffer.read()
buffer.seek(0)
buffer.truncate()
buffer.write(b)
offset = 0
self._sful_data = state, buffer, offset
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