Low level I/O: because I could

[eryk sun]

On Wed, May 10, 2017 at 10:30 PM, Rob Gaddi
<rgaddi at highlandtechnology.invalid> wrote:
> Sorry, but I'm just too proud of this.
>
> Given that you have:
>
>   class RegisterLayout(ctypes.Structure):
>     ...yadayadayada...
>
> You can then:
>
>   fh = os.open('/dev/devicethingy', os.O_RDWR)
>   mm = mmap.mmap(fh, ctypes.sizeof(RegisterLayout))
>   registers = RegisterLayout.from_buffer(mm)
>
> And it just works.  Behaves exactly the same way memory-mapping that struct
> in C would.  Sure the accesses take dict lookups, and that definitely slows
> you down a bit.  If you REALLY really needed that speed you'd be writing C.
> But it works.

To clarify, the dict lookup here is to bind the CField data descriptor
from the class dict. It isn't using the instance dict.