From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NZPjf-0002ug-1F for qemu-devel@nongnu.org; Mon, 25 Jan 2010 09:16:11 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NZPja-0002qb-0a for qemu-devel@nongnu.org; Mon, 25 Jan 2010 09:16:10 -0500 Received: from [199.232.76.173] (port=53266 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NZPjZ-0002qO-N3 for qemu-devel@nongnu.org; Mon, 25 Jan 2010 09:16:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52752) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NZPjY-0005lx-Jr for qemu-devel@nongnu.org; Mon, 25 Jan 2010 09:16:05 -0500 From: Markus Armbruster Subject: Re: [Qemu-devel] [PATCH 08/11] QMP: Asynchronous messages enable/disable support References: <1264108180-3666-1-git-send-email-lcapitulino@redhat.com> <1264108180-3666-9-git-send-email-lcapitulino@redhat.com> <4B59E8DF.5020001@codemonkey.ws> <4B5C2251.7050509@redhat.com> <20100124110725.GA5668@shareable.org> <4B5C68D6.6090502@codemonkey.ws> <20100124183514.GA14840@shareable.org> <20100125094916.5d493493@doriath> Date: Mon, 25 Jan 2010 15:15:59 +0100 In-Reply-To: <20100125094916.5d493493@doriath> (Luiz Capitulino's message of "Mon, 25 Jan 2010 09:49:16 -0200") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: qemu-devel@nongnu.org, Avi Kivity Luiz Capitulino writes: > On Sun, 24 Jan 2010 18:35:14 +0000 > Jamie Lokier 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. JSON requires control characters in strings to be escaped. RFC 4627 section 2.5: A string begins and ends with quotation marks. All Unicode characters may be placed within the quotation marks except for the characters that must be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F). > In practice it doesn't, afaik. If it doesn't, then it's not proper JSON, is it?