Parse binary data into structures using structures

parse_binary_structures.py

#!/usr/bin/env python3

# https://github.com/malinoff/structures - not actively developed
import structures
from structures import Repeat, Struct, Bytes, Integer, Contextual, RepeatExactly, BitFields, Const, Computed

class Test(Struct):
    const_val = Const(b'AB')
    bit_fields = BitFields('b1: 4, b2: 3, b3: 1')
    variable_array_length = Integer(1)
    computed_variable = Computed(lambda x: x["variable_array_length"] * 100)
    variable_array = structures.If(
        lambda x: True, Contextual(RepeatExactly, lambda x:(Integer(1), x['variable_array_length'])))
    # Without 'If'
    # variable_array = structures.Contextual(RepeatExactly, lambda x:(Integer(1), x['variable_array_length']))
    fixed_array = RepeatExactly(Integer(2, byteorder='big', signed=False), 2)
    
data1 = b'AB\xAA\x01\xAB\x01\x02\x03\x04'
data2 = b'AB\xAA\x02\xAB\xCD\x05\x06\x07\x08'

print(Test().parse(data1)) 
# {'const_val': b'AB', 'bit_fields': {'b1': 10, 'b2': 5, 'b3': 0}, 'variable_array_length': 1, computed_variable': 100, 'variable_array': [171], 'fixed_array': [258, 772]}
print(Test().parse(data2))
# {'const_val': b'AB', 'bit_fields': {'b1': 10, 'b2': 5, 'b3': 0}, 'variable_array_length': 2, computed_variable': 100, 'variable_array': [171, 205], 'fixed_array': [1286, 1800]}