[Python-3000] Single buffer implied in new buffer protocol?

[Travis Oliphant]

Stefan Behnel wrote:
> Travis Oliphant wrote:
>> Stefan Behnel wrote:
>>> Anyway, my point is that this part of the protocol actually implies
>>> setting a
>>> lock on the buffer *provider* rather than the buffer itself, as the
>>> buffer
>>> provider cannot distinguish between different buffers based on a NULL
>>> pointer
>> Yes, the language in the PEP could be more clear.   Obviously, if you
>> haven't provided a Py_buffer structure to fill in, then you are only
>> asking to lock the object's buffer from other access.
> 
> That's what I'm questioning below.
>

I see what you are referring to.  The protocol to lock the buffer after 
requesting and obtaining one was not well thought out.  I think the use 
case I had in mind was locking in the buffer before actually getting it.

Once you have a buffer, I see how you may want to lock the buffer after 
getting it.   For example, I could see how you may want to go from a 
non-locked read/write where you are guaranteed by the object that it 
won't move the memory but not that someone hasn't written to the memory 
area to an exclusive write-lock where no-one else can write to the area 
until you are done.

This should be clarified in the PEP.  Can you take a stab at it?

-Travis