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receiver.py
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"""
This module contains various functions related to the receiver
"""
from utils import get_bin, list2int, int2list
class Receiver():
"""
This class forms the basic structure of the receiver object
"""
def __init__(self, num_messages):
"""
It intializes the receiver's state as empty (no message has been received)
Parameters
----------
num_messages : `int`
Number of messages the receiver is expected to receive
"""
self.received_messages_list = [False] * num_messages
self.messages_list = [[]] * num_messages
self.received_packet_list = [False] * num_messages
def update_packet_reception(self, packet_number, received):
"""
Updates the reception of the `packet_number` packet in the receiver's
memory
Parameters
----------
packet_number : `int`
The packet number whose is reception state is being stored
received : `bool`
whether the packet was received or not
"""
self.received_packet_list[packet_number] = received
def receive_packet(self, packet_header, packet, size):
"""
Receive a packet and split it into its constituent symbols
Parameters
----------
packet_header : `list` or `int`
stores information about the constituent symbols whether coded or not and with
what symbols
packet : `list`
actual contents of the packet
size : `int`
Number of symbols in the packet
"""
for packet_number, message in zip(packet_header, packet):
if type(packet_number) is list:
self.decode(packet_number, message)
else:
self.messages_list[packet_number] = message
self.received_messages_list[packet_number] = True
def decode(self, coding_list, coded_message):
"""
Decodes a coded symbol
Parameters
----------
coding_list : `list`
List of symbols which has been coded together
coded_message : `list`
The actual message
"""
ans = 0
for idx in coding_list:
ans += self.received_messages_list[idx]
if ans == len(coding_list):
# print('All packets are already present')
pass
elif ans < len(coding_list) - 1:
# print('Decoding cannot be done as more than one messages are missing')
pass
else:
coded_message = list2int(coded_message)
for idx in coding_list:
if self.received_messages_list[idx]:
coded_message = coded_message ^ list2int(self.messages_list[idx])
else:
decoded_idx = idx
self.messages_list[decoded_idx] = int2list(coded_message, 8)
self.received_messages_list[decoded_idx] = True
def send_feedback(self, packet_number, delay_tolerance):
"""
Generate feedback for the sender
Parameters
----------
packet_number : `int`
The current packet number received
delay_tolerance : `int`
The delay tolerance
Returns
-------
`list`
The feedback for the sender
"""
# Interval of interest starting position
lower = max(0, packet_number - delay_tolerance + 1)
try:
index = packet_number - self.received_messages_list.index(False, lower, packet_number+1)
num_unreceived = (packet_number + 1 - lower) - sum(self.received_messages_list[lower:packet_number+1])
except ValueError as _:
index = 0
num_unreceived = 0
feedback = str(int(self.received_messages_list[packet_number])) + get_bin(index, 8) + get_bin(num_unreceived, 8)
return feedback