How to pack and unpack using ctypes (Structure <-> str)
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)
Their send is the (more-or-less) equivalent of pack, and 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 x into y. Of course, you'll probably have a variable as the second argument, rather than a literal packing of x.
Have a look at this link on binary i/o in python:
http://www.dabeaz.com/blog/2009/08/python-binary-io-handling.html
Based on this you can simply write the following to read from a buffer (not just files):
g = open("foo","rb")q = Example()g.readinto(q)To write is simply:
g.write(q)The same for using sockets:
s.send(q)and
s.recv_into(q)I did some testing with pack/unpack and ctypes and this approach is the fastest except for writing straight in C