Unpacking Nested C Structs In Python

I am trying to unpack a C struct that is handed to my Python program in binary form and includes another nested struct. The relevant part of the C header looks like this: typedef s

Solution 1:

1. You Struct format does not match with C structure. (final H should be 6H)
2. struct.unpack(6h, ..) does return 6 fields. (not one with 6 elements)

So your code should looks like ..

s = struct.Struct('= B B H H 6h 6h 6h 6H')
fields = s.unpack(packet_data)
seq, _type, flags, upTimestamp = fields[:4]
x = fields[4:10]
y = fields[10:16]
z = fields[16:22]
lowTimestamp = fields[22:]

Solution 2:

You can try construct http://construct.readthedocs.io/en/latest/

import construct as cstruct
def mps_packet_header(name):
    return cstruct.Struct(
        name,
        cstruct.UNInt8('seq'),
        cstruct.UNInt8('type'),
        cstruct.UNInt16('flags'),
        cstruct.UNInt16('upTimestamp'),
    )

mps_acc_packet_t = cstruct.Struct(
    'mps_acc_packet_t',
    mps_packet_header('header')
    cstruct.Array(6, cstruct.NInt16('x')),
    cstruct.Array(6, cstruct.NInt16('y')),
    cstruct.Array(6, cstruct.NInt16('z')),
    cstruct.Array(6, cstruct.UNInt16('lowTimestamp')),
)

accpacket_t = mps_acc_packet_t
...
...
packet_data = ....
packet = accpacket_t.parse(packet_data)
print(packet)
print(packet.header)
print(packet.x, packet.y, packet.z)