idea for data-type (data-format) PEP

On 11/1/06, "Martin v. Löwis" <martinv.loewis.de> wrote:

> That's also an interesting issue for the datatypes PEP:
are datatype
> objects meant to be immutable?
>
That's a question for Travis, but I would think that they
would be
immutable at the Python level, but mutable at the C level. 
In Travis'
approach array size  is not stored in the datatype, so I
don't see
much need to modify datatype objects in-place. It may be
reasonable to
allow adding fields to a record, but I don't have enough
experience
with that to comment.


> This is particularly interesting for the extended
buffer protocol:
> how long can one keep the data you get from
bt_getarrayinfo?
>
I think your question is limited to shape and strides
outputs because
dataformat is a reference counted PyObject (and PEP should
specify
whether it is a borrowed reference).

And the answer is the same as for the data from
bf_getreadbuffer/bf_getwritebuffer .  AFAIK, existing buffer
protocol
does not answer this question delegating it to the extension
module
writers who provide objects exporting their buffers.


> Also, how does the memory management work for the
results?

I think it is implied that all pointers are borrowed
references.  I
could not find any discussion of memory management in the
current
buffer protocol documentation.

This is a good question.  It may be the case that the shape
or stride
information is not available as Py_intptr_t array inside the
object
that wants to export its memory buffer.  This is not
theoretical, I
have a 64-bit application that uses objects that keep their
size
information in a 32-bit int.

BTW, I think the memory management issues with the buffer
objects have
been resolved at some point.  Any lessons to learn from
that?
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