Re: Better MI memory commands

[Vladimir Prus <vladimir at codesourcery dot com>]

On Wednesday 07 July 2010 20:29:55 Daniel Jacobowitz wrote:

> > -           if (xfer == 0)
> > -             return xfered;
> > -           if (xfer < 0)
> > -             {
> > -               remaining = half;               
> > -             }
> > -           else
> > -             {
> > -               /* We have successfully read the first half.  So, the
> > -                  error must be in the second half.  Adjust start and
> > -                  remaining to point at the second half.  */
> > -               xfered += xfer;
> > -               start += xfer;
> > -               remaining -= xfer;
> > -             }
> > -           half = remaining/2;
> > +           xfree (buffer);
> > +           xfered += to_read;
> >           }
> 
> Why do we skip to_read bytes if we succeed at reading zero bytes?
> For that matter, what does a return value of zero mean?  It seems like
> this would mean the same as -1.

I am not really sure. Per documentation of target_read:

   Return the number of bytes actually transfered, or -1 if the
   transfer is not supported or otherwise fails.  Return of a positive
   value less than LEN indicates that no further transfer is possible.

So, value of 0 seems to mean 'there are no more bytes that that, honest', 
and that we probably don't need to try further. Documentation for
to_xfer_partial seem to give such meaning to return of 0. On the
other hand, it's not clear what return value of <LEN might mean,
and whether we should try to read remaining chunk. What would you suggest?

Thanks,

-- 
Vladimir Prus
CodeSourcery
vladimir@codesourcery.com
(650) 331-3385 x722