From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59784) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQIZm-0006Pb-Pt for qemu-devel@nongnu.org; Tue, 05 Jun 2018 16:29:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQIZl-0006sk-Rm for qemu-devel@nongnu.org; Tue, 05 Jun 2018 16:29:06 -0400 Date: Tue, 5 Jun 2018 23:28:55 +0300 From: "Michael S. Tsirkin" Message-ID: <20180605231419-mutt-send-email-mst@kernel.org> References: <20180528212054.GH2209@redhat.com> <20180528212510.GC4660@redhat.com> <20180529064415.GA4756@localhost.localdomain> <2b3eef00-f326-c1e6-0e4b-b7602646eec4@redhat.com> <20180605092159.GA2544@work-vm> <20180605190324.GA11372@localhost.localdomain> <20180605223934-mutt-send-email-mst@kernel.org> <20180605195855.GC1455@redhat.com> <6f6ecbb5-3175-44d0-5922-b13ac163f006@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6f6ecbb5-3175-44d0-5922-b13ac163f006@redhat.com> Subject: Re: [Qemu-devel] [Qemu-block] storing machine data in qcow images? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: "Richard W.M. Jones" , Eduardo Habkost , Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, stefanha@redhat.com, Max Reitz , "Dr. David Alan Gilbert" On Tue, Jun 05, 2018 at 03:09:17PM -0500, Eric Blake wrote: > 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. But there isn't a way to figure out that a string is base64, which means each application needs to know whether it's a string or a binary. How about specifying the encoding in the value? string value: [A-Za-z][^=\0]=S[^\0]* base64 value: [A-Za-z][^=\0]=B[A-Za-z0-9+/]* or the key: S[A-Za-z][^=\0]=[^\0]* base64 value: B[A-Za-z][^=\0]=[A-Za-z0-9+/]* ? -- MST