On Tue, 11/24 13:45, Markus Armbruster wrote:
> Paolo Bonzini <pbonz...@redhat.com> writes:
>
> > On 24/11/2015 06:22, Fam Zheng wrote:
> >> case OFORMAT_JSON:
> >> - printf("%s{ \"start\": %"PRId64", \"length\": %"PRId64",
> >> \"depth\": %d,"
> >> - " \"zero\": %s, \"data\": %s",
> >> - (e->start == 0 ? "[" : ",\n"),
> >> - e->start, e->length, e->depth,
> >> - (e->flags & BDRV_BLOCK_ZERO) ? "true" : "false",
> >> - (e->flags & BDRV_BLOCK_DATA) ? "true" : "false");
> >> + if (e->start == 0) {
> >> + printf("[");
> >> + } else {
> >> + printf(",");
> >> + }
> >> +
> >> + dict = qdict_new();
> >> + qdict_put(dict, "start", qint_from_int(e->start));
> >> + qdict_put(dict, "length", qint_from_int(e->length));
> >> + qdict_put(dict, "depth", qint_from_int(e->depth));
> >> + qdict_put(dict, "zero", qbool_from_bool(e->flags &
> >> BDRV_BLOCK_ZERO));
> >> + qdict_put(dict, "data", qbool_from_bool(e->flags &
> >> BDRV_BLOCK_DATA));
> >> if (e->flags & BDRV_BLOCK_OFFSET_VALID) {
> >> - printf(", \"offset\": %"PRId64"", e->offset);
> >> + qdict_put(dict, "offset", qint_from_int(e->offset));
> >> }
> >> - putchar('}');
> >> + str = qobject_to_json(QOBJECT(dict));
> >> + printf("%s\n", qstring_get_str(str));
> >
> > I think it's better if you use QAPI for this. You can make MapEntry a
> > QAPI struct and generate the QObject through a QMP visitor.
> >
> > The reason is that we could add JSON visitors that let us parse or
> > produce JSON without going through the expensive QObject creation. Even
> > though that is far away, the least explicit QObject manipulation we
> > have, the better.
>
> I concur.
>
> Manual messing with QDict is of course fine when a higher-level
> interface doesn't fit. But here, we serialize a struct to JSON, and
> that's something QAPI is meant to do. Having to define a QAPI type may
> be a bit of a bother, but once that's done, the "serialize this struct
> to JSON" code becomes less tedious. qemu-img.c already has a few
> examples; search for qmp_output_visitor_new().
Can we do streaming with QAPI? The size of "MapEntry array" can be huge.
Fam
