On Sun, 24 Jan 2010 18:35:14 +0000 Jamie Lokier <ja...@shareable.org> wrote:
> Anthony Liguori wrote: > > >I'd like to be able to connect and be sure not to receive any async > > >messages, from simple scripts with simple output parsing. > > > > You can't have simple output parsing with QMP. You need a full JSON > > stack. The simplest script would be a python script that uses the > > builtin json support. Having async messages means that you'll have to > > loop on recv in order make sure that the response is a command response > > vs. an async message. It's just a few lines more of code so I have a > > hard time believing it's really a problem. > > > > But what you probably want is a python QMP library and that would mean > > you wouldn't need the few more lines of code. > > You're right. To be honest, parsing JSON can be done in a single Perl > regexp; a "full JSON stack" isn't much. > > On that note, it'd be good if the end of a QMP message is framed with > something that can't appear inside the JSON value, without having to > parse the JSON incrementally on each partial read(). There are plenty > of short character sequences to choose from that can't appear. Some > JSON parsers expect a whole well-formed expression or throw a parse > error - it's what people do over HTTP after all. So you wait until > you think you've read a whole one, then pass it to the JSON parser. The Monitor sends a CRLF sequence at the end of each line and I have maintained that behaivor for QMP, but it's hard to _guarantee_ that this sequence won't appear inside a json-string. In practice it doesn't, afaik.
