subclassing with new fields

[waszil]

Hi! This is a great project! I have been playing with it, and I cannot accomplish the following thing: I would need to define some protocol packets, each having the same header, but different fields. I did something like this:

class Header(protlib.CStruct):
    id = protlib.CUChar(default=0)
    timestamp = protlib.CUInt(default=0x44332211)

class SomePacket(protlib.CStruct):
    header = Header(id=1).get_type()
    some_payload_data = protlib.CUChar(default=0)
    other_payload_data = protlib.CChar(default=-1)

p = SomePacket(header=Header())

print(p)
print(' '.join('%.2X' % b for b in p.serialize()))

that gives

SomePacket(header=Header(id=0, timestamp=1144201745), some_payload_data=0, other_payload_data=-1)
00 44 33 22 11 00 FF

so the id is not set properly. I can do the following, which works, but it is not so nice:

class SomePacket(protlib.CStruct):
    header = Header.get_type()
    some_payload_data = protlib.CUChar(default=0)
    other_payload_data = protlib.CChar(default=-1)

p = SomePacket(header=Header(id=1))

it gives the expected bytestream:

SomePacket(header=Header(id=1, timestamp=1144201745), some_payload_data=0, other_payload_data=-1)
01 44 33 22 11 00 FF

I wonder, if it would be possible to define the packet like this, without having to specify

class SomePacket(protlib.CStruct):
    header = Header(id=1)
    some_payload_data = protlib.CUChar(default=0)
    other_payload_data = protlib.CChar(default=-1)

p = SomePacket()

Thanks, and again, nice job!

[knl]

Hi @waszil I had the similar issue. Wondering if this could help you:

class Header(protlib.CStruct):
    id = protlib.CUChar(default=0)
    timestamp = protlib.CUInt(default=0x44332211)

class SomePacket(protlib.CStruct):
    header = Header().get_type(default=Header(id=1))
    some_payload_data = protlib.CUChar(default=0)
    other_payload_data = protlib.CChar(default=-1)

p = SomePacket()

print(p)
print(' '.join('%.2X' % b for b in p.serialize()))

which yields

01 44 33 22 11 00 FF