Re: [Qemu-devel] [Qemu-block] storing machine data in qcow images?

["Richard W.M. Jones" <rjones@redhat.com>]

On Tue, Jun 05, 2018 at 02:54:07PM -0500, Eric Blake wrote:
> On 06/05/2018 02:47 PM, Michael S. Tsirkin wrote:
> 
> >>>Layer 1:
> >>>    The string shall always be a JSON 'object'; i.e. of the form
> >>>     { "something": ... , "more": ... }
> >>>
> >>>    The key strings shall be non-null and non-empty and shall
> >>>    be unique.
> 
> >>
> >>I think it would be simpler if layer 0 simply provided a list of
> >>names/value pairs, where names are ascii strings, and values are
> >>binary data[1].  It would make layer 1 unnecessary, and allow (3)
> >>and (4) to happen.
> >>
> >>[1] In other words, Rich's proposal of "named blobs":
> >>https://www.mail-archive.com/qemu-block@nongnu.org/msg37856.html
> >
> >I think simple is beautiful, too. But assuming they
> >really are binary how are blobs encoded?
> >Did binary really mean UTF-8 here?

By binary I actually meant binary.  The idea is you could
store things like PNG images in them (for icons).

> Binary blobs can always be base64 encoded for representation within
> a valid JSON UTF-8 string (and we already have several QMP
> interfaces that utilize base64 encoding to pass through what is
> otherwise invalid UTF-8).  It does inflate things slightly compared
> to a format that allows a raw length coupled with raw data, but that
> is not necessarily a problem.

Of course how we represent them externally and/or while
using QMP / qemu-img to store and retrieve them is up for grabs.
Doesn't JSON allow binary to be encoded?  (Knowing how poorly
done JSON is, I wouldn't be surprised if not)

Rich.

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