[Python-3000] Revised PEP for buffer protocol

[Josiah Carlson]

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.

 - Josiah