Re: [PATCH] qcow2: Explicit mention of padding bytes

[Max Reitz]

On 27.02.20 15:45, Eric Blake wrote:
> Although we already covered the need for padding bytes with our
> changes in commit 3ae3fcfa, commit 66fcbca5 just added one byte and
> relied on the earlier text for implicitly covering 7 padding bytes.
> For consistency with other parts of the header,

Those other places are about table entries where there is padding to the
next entry of the table, though.  In addition, for those other places
it’s the only mention that they are padded.

For the header, there is a whole own section describing the padding, so
I don’t quite see the point.

> it does not hurt to be
> explicit that this version of the header is using padding bytes, and
> if we later add other extension fields, we can rework the allocation
> of those padding bytes to match those additions.
> 
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  docs/interop/qcow2.txt | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt
> index 5597e244746e..193ac7c5c1af 100644
> --- a/docs/interop/qcow2.txt
> +++ b/docs/interop/qcow2.txt
> @@ -209,6 +209,8 @@ version 2.
>                      Available compression type values:
>                          0: zlib <https://www.zlib.net/>
> 
> +          105 - m:  Zero padding to round up the header size to the next
> +                    multiple of 8.

And if we really want this, I think it might as well be specific, i.e.
“105 - 112”.  We would have to adjust it every time we add a new field
anyway.

Max

>  === Header padding ===
>

signature.asc
Description: OpenPGP digital signature