Re: Better MI memory commands

Vladimir Prus
2010-07-09T18:54:18Z

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?