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message.py
88 lines (63 loc) · 2.33 KB
/
message.py
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import struct
from bitstring import BitArray
from utils import get_4_bytes_in_decimal
ID_KEEPALIVE = -1
ID_CHOKE = 0
ID_UNCHOKE = 1
ID_INTERESTED = 2
ID_NOT_INTERESTED =3
ID_HAVE = 4
ID_BITFIELD = 5
ID_REQUEST = 6
ID_PIECE = 7
ID_CANCEL = 8
ID_PORT = 9
class Message(object):
def __init__(self, msg_len=0, id=None, payload=''):
self.msg_len=msg_len
self.id=id
self.payload=payload
def __str__(self):
return '%s%s%s' % (self.msg_len, self.id, self.payload,)
def parse_message(buffer):
return parse_message_helper([], buffer)
def parse_message_helper(messages, buffer):
_msg_length_size = 4
# check for message length
if len(buffer) < _msg_length_size:
return messages, buffer
msg_len = get_4_bytes_in_decimal(buffer[0:_msg_length_size])
# keep alive message
if msg_len == 0:
messages.append(Message(id=ID_KEEPALIVE))
buffer = buffer[4:]
return parse_message_helper(messages, buffer)
# check for incomplete message
if len(buffer[1:]) < msg_len:
return messages, buffer
# consume complete message
msg_body = buffer[_msg_length_size : _msg_length_size + msg_len]
id, payload = get_message_id_and_payload(msg_body)
message = Message(msg_len=msg_len, id=id, payload=payload)
messages.append(message)
# remove parsed message and continue with the rest of the buffer
buffer = buffer[_msg_length_size + msg_len:]
return parse_message_helper(messages, buffer)
def get_message_id_and_payload(msg_body):
msg_id = struct.unpack('B', msg_body[0])[0]
payload = msg_body[1:]
return msg_id, payload
def get_interested_message():
# <len=0001><id=2>
msg_len = BitArray(uint=1, length=32).bytes
id = chr(ID_INTERESTED)
return Message(msg_len=msg_len, id=id)
def get_request_piece_message(piece_index, begin, requested_length):
# <len=0013><id=6><index><begin><length>
msg_len = BitArray(uint=13, length=32).bytes
id = chr(ID_REQUEST)
index = BitArray(uint=piece_index, length=32).bytes
begin = BitArray(uint=begin, length=32).bytes # block offset
requested_length = BitArray(uint=requested_length, length=32).bytes # block offset
payload = '%s%s%s' % (index, begin, requested_length)
return Message(msg_len=msg_len, id=id, payload=payload)