Re: [Qemu-devel] [PATCH 08/11] qjson: Simplify by using json-output-visitor

[Eric Blake <eblake@redhat.com>]

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On 12/11/2015 04:10 AM, Paolo Bonzini wrote:
> 
> 
> On 11/12/2015 00:53, Eric Blake wrote:
>> Instead of rolling our own limited JSON outputter, we can just
>> wrap the more full-featured JSON output Visitor.
>>
>> This slightly changes the output (different spacing), but the
>> result is still equivalent JSON contents.
>>
>> Signed-off-by: Eric Blake <eblake@redhat.com>
>> ---
>>  qjson.c | 61 ++++++++++++++++++++++---------------------------------------
>>  1 file changed, 22 insertions(+), 39 deletions(-)
> 
> I didn't find out which tree your patches apply to, but this:
> 

>      if (vmdesc) {
> -        json_prop_int(vmdesc, "size", size);
> -        json_start_array(vmdesc, "fields");
> -        json_start_object(vmdesc, NULL);
> -        json_prop_str(vmdesc, "name", "data");
> -        json_prop_int(vmdesc, "size", size);
> -        json_prop_str(vmdesc, "type", "buffer");
> -        json_end_object(vmdesc);
> -        json_end_array(vmdesc);
> +        visit_type_int(vmdesc, size, "size", &error_abort);

visit_type_int() takes 'int64_t*', not 'int'.  In places, that means I'd
have to add a temporary variable to cover the fact that the input is not
the right type for writing '&size'

> @@ -1068,9 +1070,11 @@ void qemu_savevm_state_complete_precopy(QEMUFile *f, bool iterable_only)
>          return;
>      }
>  
> -    vmdesc = qjson_new();
> -    json_prop_int(vmdesc, "page_size", TARGET_PAGE_SIZE);
> -    json_start_array(vmdesc, "devices");
> +    vmdesc_jov = json_output_visitor_new();
> +    vmdesc = json_output_get_visitor(vmdesc_jov);
> +    visit_start_struct(vmdesc, NULL, 0, NULL, &error_abort);
> +    visit_type_int(vmdesc, TARGET_PAGE_SIZE, "page_size", &error_abort);

...or even cover the case where it is a constant whose address does not
even exist.

> 
> compiles and is pretty much a 1:1 translation from the qjson.c API to the
> visitor API (using this patch as a guide).  Feel free to include it and
> remove qjson.c.  Alternatively, you can leave out this patch and I'll test
> and submit the transition.

So the patch to avoid qjson.c is not quite 1:1. Still, I'll go ahead and
complete the patch for my v2, to see if you still like it.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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