#===============================================================
# --- (Un)Pack msg length and msg itself ---
#===============================================================
from struct import * 
import asyncio, socket 

def send_msg(sock, msg):
    # Prefix each message with a 4-byte length (network byte order)
    msg = struct.pack('>I', len(msg)) + msg
    sock.sendall(msg)

def send_msg_async(writer, msg):
    # Prefix each message with a 4-byte length (network byte order)
    msg = struct.pack('>I', len(msg)) + msg 
    writer.write(msg) 
    #sock.sendall(msg)

def recv_msg(reader):
    # Read message length and unpack it into an integer
    raw_msglen = reader.read(255) 
    if not raw_msglen:
        return None
    msglen = unpack('>I', raw_msglen)[0]
    # Read the message data
    return recvall(reader)

def recvall(reader, n):
    # Helper function to recv n bytes or return None if EOF is hit
    data = bytearray()
    while len(data) < n:
        packet = reader.read(n - len(data))
        if not packet:
            return None
        data.extend(packet)
    return data