construct_tcp_packet_header_parse_and_build.py

1from construct import Struct, Int8ub, Int16ub, Bytes, Array
2
3# Define the data structure (TCP/IP-like header)
4format = Struct(
5    "signature" / Bytes(2),
6    "version" / Int8ub,
7    "type" / Int8ub,
8    "payload_length" / Int16ub,
9    "payload" / Bytes(lambda ctx: ctx.payload_length),
10)
11
12# Data to parse
13raw_data = b"\xab\xcd\x01\x02\x00\x04\xDE\xAD\xBE\xEF"
14
15# Parsing: Binary to Python Dictionary-like object
16parsed = format.parse(raw_data)
17print(f"Parsed data: {parsed}")
18print(f"Signature: {parsed.signature}")
19
20# Building: Python Dictionary to Binary
21built = format.build(dict(
22    signature=b"\xab\xcd",
23    version=1,
24    type=2,
25    payload_length=4,
26    payload=b"\xDE\xAD\xBE\xEF"
27))
28print(f"Built bytes: {built}")
29
30assert raw_data == built