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"""This module implements the TftpPacketFactory class, which can take a binary
buffer, and return the appropriate TftpPacket object to represent it, via the
parse() method."""
from __future__ import absolute_import, division, print_function, unicode_literals
from .TftpShared import *
from .TftpPacketTypes import *
class TftpPacketFactory(object):
"""This class generates TftpPacket objects. It is responsible for parsing
raw buffers off of the wire and returning objects representing them, via
the parse() method."""
def __init__(self):
self.classes = {
1: TftpPacketRRQ,
2: TftpPacketWRQ,
3: TftpPacketDAT,
4: TftpPacketACK,
5: TftpPacketERR,
6: TftpPacketOACK
}
def parse(self, buffer):
"""This method is used to parse an existing datagram into its
corresponding TftpPacket object. The buffer is the raw bytes off of
the network."""
log.debug("parsing a %d byte packet" % len(buffer))
(opcode,) = struct.unpack("!H", buffer[:2])
log.debug("opcode is %d" % opcode)
packet = self.__create(opcode)
packet.buffer = buffer
return packet.decode()
def __create(self, opcode):
"""This method returns the appropriate class object corresponding to
the passed opcode."""
tftpassert(opcode in self.classes,
"Unsupported opcode: %d" % opcode)
packet = self.classes[opcode]()
return packet
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