[python-win32] WSAAsyncSelect

[david.briant at ubs.com]

I'm looking for how to do blocking calls. If I do a blocking call into a
dll and don't release the GIL the whole of python is blocked!!!

It says in the C-API whenever you call into a C-DLL with a blocking call
you need to release the GIL i.e. the Py_BEGIN_ALLOW_THREADS macro, and
when the call returns you need to relock the GIL i.e.
Py_END_ALLOW_THREADS.

So want to know how to release and acquire the GIL from pure python
(i.e. via ctypes or win32).

By high performance I mean as high as python can offer - I don't want to
poll and select doesn't allow you to check events from the UI - so
either WSAAsyncSelect or possibly I/O completion ports. If I need more
performance then it'll be a C / C++ extension, but I'd like to get the
architecture prototyped in python first.

I have a app written in wx that needs to get and send data out of
process. All the solutions I've looked at have slow response times (due
to polling loops mainly). I have a windows message handler so I should
be able to get events from WSAAsyncSelect but I don't know how to
release and reacquire the GIL from python if I call a blocking function
in a dll.

(the select package works fine if the asynchronicity is coming from a
socket but not from a UI).

Thx

David

-----Original Message-----
From: python-win32-bounces+david.briant=ubs.com at python.org
[mailto:python-win32-bounces+david.briant=ubs.com at python.org] On Behalf
Of Tim Roberts
Sent: Fri 7-Jan-2011 18:45
To: Python-Win32 List
Subject: Re: [python-win32] WSAAsyncSelect

david.briant at ubs.com wrote:
> Does anyone know of any links where blocking I/O calls are
demonstrated
> in pure python?

Virtually all I/O calls in pure Python are blocking calls.  Did you mean
to ask about non-blocking I/O?

> I'm currently parsing the c code for _socket.pyd and reading up on
> Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS. My goal is basically
to
> produce a high performance socket that I can use with a Windows UI
> (wxpython) - so was thinking of calling ws2_32.dll but it looks like I
> might need to be a bit more careful.

Well, any time I hear "high performance," I start to wonder whether
Python is really the right choice.  How much performance do you need? 
WSAAsyncSelect is a pretty snazzy way to deal with a socket server, and
I suspect it could be adapted here without much trouble.

-- 
Tim Roberts, timr at probo.com
Providenza & Boekelheide, Inc.

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