[Python-Dev] Omit Py_buffer struct from Stable ABI for Python 3.2? (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Wed Jan 5 15:24:29 CET 2011

On Wed, 5 Jan 2011 14:03:41 +0000 Mark Dickinson <dickinsm at gmail.com> wrote:

On Wed, Jan 5, 2011 at 1:13 PM, Antoine Pitrou <solipsis at pitrou.net> wrote: > On Wed, 5 Jan 2011 12:55:55 +0000 > Mark Dickinson <dickinsm at gmail.com> wrote: >> The need for obj is a little ugly:  as far as I can tell, it's >> meaningless for a 3rd-party object that wants to export buffers---it's >> only really used by the memoryview object and by internal Python >> types. > > I don't think it's ugly. It's the only way to know which object exported > a Pybuffer. Otherwise you have to track the information separately, > which is quite a bit uglier (especially when in conjunction with > PyArgParseTuple and friends).

Maybe I'm misunderstanding. What's the responsibility of a buffer export w.r.t. the obj field---i.e., what should 3rd party code be filling that obj field with in a call to getbuffer?

It would let PyBuffer_FillInfo() do the job. If it doesn't want to, it must put itself in that field, and increment its reference count.

It looks to me as though it's really the memoryview object that needs this information;

No, anyone wanting to release a buffer without keeping separate track of the original object needs it. As I said, this also applies to users of PyArg_ParseTuple and friends ("s*", "y*" etc. format codes).

Isn't that what the 'base' field in PyMemoryViewObject in PEP 3118 was supposed to be for?

Perhaps, but practice (implementing "s*" etc.) suggested it was useful in other cases. That field ('base') is removed in 3.2.

Regards

Antoine.

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