This might be a silly question but I couldn't find a good answer in the docs or anywhere.
If I use struct to define a binary structure, the struct has 2 symmetrical methods for serialization and deserialization (pack and unpack) but it seems ctypes doesn't have a straightforward way to do this. Here's my solution, which feels wrong:
from ctypes import *
_fields_ = [
buf = string_at(byref(ctype_instance), sizeof(ctype_instance))
def Unpack(ctype, buf):
cstring = create_string_buffer(buf)
ctype_instance = cast(pointer(cstring), POINTER(ctype)).contents
if __name__ == "__main__":
e = Example(12, 13)
buf = Pack(e)
e2 = Unpack(Example, buf)
assert(e.index == e2.index)
assert(e.counter == e2.counter)
# note: for some reason e == e2 is False...
The PythonInfo wiki has a solution for this.
FAQ: How do I copy bytes to Python from a ctypes.Structure?
def send(self): return buffer(self)[:]
FAQ: How do I copy bytes to a ctypes.Structure from Python?
def receiveSome(self, bytes): fit = min(len(bytes), ctypes.sizeof(self)) ctypes.memmove(ctypes.addressof(self), bytes, fit)
send is the (more-or-less) equivalent of
receiveSome is sort of a
pack_into. If you have a "safe" situation where you're unpacking into a struct of the same type as the original, you can one-line it like
memmove(addressof(y), buffer(x)[:], sizeof(y)) to copy
y. Of course, you'll probably have a variable as the second argument, rather than a literal packing of