Re: [Jython-dev] Jython buffer protocol

[Jeff A. <ja...@fa...>]

On 11/05/2016 14:38, Stefan Richthofer wrote:
> Sounds like good news! Would you put a draft e.g. on github once it is
> somehow at a sane state?
How was it Jim dignified our process ... ah yes, commit-then-review. :) 
I'll share the elements somehow to check my thinking.
>> ByteBuffer getByteBuffer(int... indices);
> I wonder what this is supposed to do; afaik ByteBuffer supports no
> multi-index logic. (Correct me if I'm wrong).
No, but PyBuffer does. The above returns a ByteBuffer where the position 
has been set corresponding to the index polynomial.
>> // Extract column c
>> ByteBuffer bb = pybuf.getNIOByteBuffer(PyBUF.FULL);
>> for (int r=0; r<x.length; r++)
>>       x[r] = bb.getFloat( pybuf.index(r,c) );
> This looks slow, because method calls are slow (compared to array-access)
> and it requires at least two calls per index.
I prefer it to x[r] = pybuf.getByteBuffer(r, c).getFloat() which has 
object construction too. If you want speed you have to do the index 
calculation by striding from pybuf.index(0,c), but then you will still 
call ByteBuffer.getFloat(int) rather than an array access. I think 
efficiency has ceased to be the main objective. Client code that uses 
array access (equivalently, Pointer) will break when it encounters your 
ByteBuffer-based objects, so we should make access via the ByteBuffer 
convenient.
>> I'm following the deprecation route at the moment, but bearing in mind
>> Jim's view that breaking change is acceptable by virtue of low adoption,
> I wonder if there is any evidence how low adoption currently is at all.
> Are there any publicly known projects using this?
I abbreviated Jim's argument here. Few and sophisticated enough to adapt 
was his view. I can't find any public projects using our PyBuffer. To 
suffer from the change, they would have to be projects that use Pointer, 
not just PyBuffer.

Jeff