[Python-3000] Revised PEP for buffer protocol
ncoghlan at gmail.com
Wed Mar 21 10:47:19 CET 2007
Josiah Carlson wrote:
> Nick Coghlan <ncoghlan at gmail.com> wrote:
>> Josiah Carlson wrote:
>>> "Travis E. Oliphant" <oliphant.travis at ieee.org> wrote:
>>>> The buffer interface should allow discontiguous memory areas to
>>>> share standard striding information. However, consumers that do
>>>> not want to deal with strided memory should also be able to
>>>> request a contiguous segment easily.
>>> I don't believe this is necessary. While the point of the buffer
>>> interface is to offer direct access to memory regions of an object or
>>> structure, being able to ask "can I get a contiguous segment" isn't
>>> really reasonable. The response is either going to be "yes, that's how I
>>> represent it anyways" or "no, that's not how I represent the data". But
>>> this bit of meta information is easily acquired by *getting* the buffer
>>> and checking the stride.
>> I think the point is for there to be something in the standard library
>> or Python core that makes it easy for a consumer to *copy* the data to a
>> contiguous memory segment in the event the consumer can't directly
>> handle non-contiguous data (e.g. a C API function that takes the source
>> object, a pointer to the destination memory block, and an optional slice
>> object defining a subsection of the memory block to be retrieved)
> But that still isn't a use-case for the "I want a contiguous view". The
> consumer needs to construct a memory region, copy the non-contiguous
> data, then pass it on somewhere else. The object offering the original
> view shouldn't need to offer anything special to make it happen.
It's a use case that any C API updates associated with this PEP need to
handle though. It's along the lines of a type supporting 3 different
abstract C API functions just by providing a tp_index slot.
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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