[Python-3000] Google Sprint Ideas

Alexander Belopolsky alexander.belopolsky at gmail.com
Mon Aug 21 06:43:53 CEST 2006

On Aug 21, 2006, at 12:01 AM, Martin v. Löwis wrote:

> Alexander Belopolsky schrieb:
>> For Py3k, I would like to suggest a buffer protocol modelled
>> after iovec structure that is used by the readv system call.
>> On many systems readv is more efficient than repeated calls
>> to read and I think Py3k will benefit from a direct access to
>> that feature.
> -1

What is this -1 for:

a) buffer protocol in Py3k?
b) multisegment buffer protocol?
c) readinto that supports multisegment buffers?

Note that in 2.x buffer protocol is multisegment, but readinto
only supports single-segment buffers.

> It's difficult to use, and I question that there is any
> benefit.

I often deal with the system (kx.com) that represents matrices as
nested lists (1d lists of floats are contiguous).  My matrices are
stored on disk as C-style 2d arrays.  If fileinto would support
multisegment buffers, I would be able to update in-memory data
from files on disk just with a call to it.  Currently I have to do it in
a loop.

> I believe readv is there primarily for symmetry with
> writev and hasn't any sensible uses on its own. writev is
> there so you can add additional headers/trailers around data
> blocks you received from higher layers. I even doubt that
> exposing writev in Python would make a measurable performance
> difference.

I did not suggest to expose anything in Python.  AFAIK, the buffer  
is a C API only. 

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