[libvirt] [PATCH] json: add stream parser

[Dmitry Guryanov]

On 130314 10:53:59, Daniel P. Berrange wrote:
> On Thu, Mar 14, 2013 at 12:55:15PM +0400, Dmitry Guryanov wrote:
> > Add function virJSONValueFromStream, which reads data from
> > a stream and passes it to json parser. When end of the object
> > is reached, it returns this object.
> > To avoid reading from the stream by single bytes it reads to
> > a buffer (in a structure virJSONStreamParserState), which should
> > be passed to a consequent call of this function. So if the end
> > of one object and the beginning of the next object have been
> > read by a single system call - virJSONValueFromStream handle
> > it correctly.
> > 
> > example of usage:
> > 
> > virJSONValuePtr v;
> > virJSONStreamParserState state;
> > 
> > memset(&state, 0, sizeof(state));
> > 
> > while (1) {
> >     v = virJSONValueFromStream(mon->fd, &state);
> >     if (v == (void *)-1)
> >         /* error */
> >         break;
> > 
> >     if (v == NULL)
> >         /* file descriptor has been closed */
> >         break;
> > 
> >     /* handle object 'v' */
> > }
> > 
> > I need such function for the parallels driver. It caches info
> > about domains and needs some mechanism to update this cache.
> > There is a "prlsrvctl monitor" command which waits for events
> > forever and prints info about events to stdout in json format.
> > So parallels driver could start separate thread which will
> > read from prlsrvctl's stdout and update cache accordingly.
> > 
> > There is the same task in qemu_monitor_json, but each json object
> > is printed in a separate line there. It's not possible in my case,
> > because some fields could have line endings.
> 
> Even QEMU could output multi-line JSON if you set the 'pretty' flag,
> so this would be useful for QEMU driver too at some point.
> 
> > 
> > Signed-off-by: Dmitry Guryanov <dguryanov at parallels.com>
> > ---
> >  src/util/virjson.c |  110 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  src/util/virjson.h |    8 ++++
> >  2 files changed, 118 insertions(+), 0 deletions(-)
> 
> Since this is reasonably complex code can you also add
> some more test cases to the tests/jsontest.c  file to
> cover this functionality.
> 

Yes, I'll send test in a separate patch.

> Daniel
> -- 
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-- 
Dmitry Guryanov