Populating an array member of a ctypes structure

ctypes_struct_array.py

#!/usr/bin/env python3
import sys
from ctypes import *

assert sys.version_info >= (3,5)

class Struct(LittleEndianStructure):
    _fields_ = [
        ('a',       c_uint32),
        ('b',       c_uint32),
        ('c',       c_uint32),
        ('buffer',  c_uint8 * 32),
    ]

    def getbytes(self):
        return bytes(self)

def main():
    s = Struct(
        a = 0x11111111,
        b = 0x22222222,
        c = 0x33333333,
    )

    # Option 1: read into
    with open(__file__, 'rb') as f:
        n = f.readinto(s.buffer)
        print("Read {} bytes into buffer".format(n))
    print(s.getbytes().hex())

    # Option 2: assignment
    # Annoying that you can't easily get the type of the 'buffer' field
    # (https://stackoverflow.com/a/6061483/119527)
    data = b'\x77' * 32
    artype = c_uint8 * 32
    s.buffer = artype(*data)
    print(s.getbytes().hex())

    # Option 3: memmove()
    data = b'\x66' * 32
    memmove(s.buffer, data, len(data))
    print(s.getbytes().hex())

if __name__ == '__main__':
    main()