Re: [PATCH] delaying dd allocation

[Ondrej Oprala]

On 04/10/2013 10:03 PM, Pádraig Brady wrote:
> On 01/23/2013 10:48 AM, Ondrej Oprala wrote:
> > +  /* Delay buffer allocation if possible.  */
> > +  if ((skip_records > OFF_T_MAX / input_blocksize)
> > +      || 0 > skip_via_lseek (input_file, STDIN_FILENO, 0, SEEK_CUR))
> > +    alloc_ibuf ();
> >   
> > -  /* Write a sentinel to the slop after the buffer,
> > -     to allow efficient checking for NUL blocks.  */
> > -  assert (sizeof (uintptr_t) <= OUTPUT_BLOCK_SLOP);
> > -  memset (obuf + output_blocksize, 1, sizeof (uintptr_t));
> > +  if ((seek_records > OFF_T_MAX / output_blocksize)
> > +      || 0 > skip_via_lseek (output_file, STDOUT_FILENO, 0, SEEK_CUR))
> > +    alloc_obuf ();
> This doesn't look right.
> skip_via_lseek() doesn't support lseek(..., 0, SEEK_CUR)
> and may always warn for tape devices?
> Also does skip bytes need to be considered?
> Also you don't always need to allocate both buffers.
>
> How about avoiding new conditions altogether and just
> alloc_[io]buf() before they're needed
> (i.e. closer to the read() as I suggested originally).
>
> Also I adjusted the memory limits in the test,
> to reduce the chances of false positives,
> and bolstered the test cases to cater for the
> new allocation calls within skip().
>
> I'll push the attached soon.
>
> thanks,
> Pádraig.
Thanks for looking at this,
the changes seem great.

thanks,
Ondrej