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

[Eric Blake <eblake@redhat.com>]

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?

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.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org