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

[Eric Blake <eblake@redhat.com>]

On 06/05/2018 02:58 PM, Richard W.M. Jones wrote:
>> 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)

JSON itself does not have a binary primitive; to pass arbitrary data 
through JSON you have to first encode that data into something like 
base64 that can then be represented as a UTF-8 string.  For reference, 
look at qapi/crypto.json and the definition of QCryptoSecretFormat.

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