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utils.py
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utils.py
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"""
Filename : utils.py
Summary : define utilities
Author : HyunJun KIM (2019204054)
"""
import random
import time
LOSS_PROB = 0.1
class Timer:
"""
Timer class to implement timeout
"""
def __init__(self, d):
self._ongoing = False
self._curr_time = 0
self._duration = d
def start(self): # timer start
if not self._ongoing and self._curr_time == 0:
self._curr_time = time.time()
self._ongoing = True
def isOngoing(self): # check timer is working
return self._ongoing
def reset(self): # reset timer
if self._ongoing:
self._ongoing = False
if self._curr_time:
self._curr_time = 0
def chk_timeout(self): # check current packet timeout
if not self.isOngoing():
return False
else:
return time.time() - self._curr_time >= self._duration
def send(packet, sock, addr):
"""
send function implemented
:param packet: packet to send
:param sock: python socket object
:param addr: (Address, Port)tuple
:return sent successfully
"""
if random.random() > LOSS_PROB: # if not loss
sock.sendto(packet, addr)
return True
elif packet == b'\xff\xff\xff\xff': # if received packet is packet(-1)
sock.sendto(packet, addr)
return True
else: # if loss, don't send
return False
def recv(sock): # packet receiver
pack, addr = sock.recvfrom(1024)
return pack, addr
def make_packet(sequence): # packet maker
bytes = sequence.to_bytes(4, byteorder='little', signed=True)
return bytes
def extract_packet(packet): # packet extractor
seq_num = int.from_bytes(packet[0:4], byteorder='little',signed=True)
return seq_num