Re: [Qemu-devel] [PATCH v3 2/5] QJSON: Add JSON writer

[Alexander Graf <agraf@suse.de>]

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On 06.01.15 16:44, Eric Blake wrote:
> On 12/26/2014 07:42 AM, Alexander Graf wrote:
>> To support programmatic JSON assembly while keeping the code that
>> generates it readable, this patch introduces a simple JSON
>> writer. It emits JSON serially into a buffer in memory.
>> 
>> The nice thing about this writer is its simplicity and low memory
>> overhead. Unlike the QMP JSON writer, this one does not need to
>> spawn QObjects for every element it wants to represent.
>> 
>> This is a prerequisite for the migration stream format
>> description generator.
>> 
>> Signed-off-by: Alexander Graf <agraf@suse.de>
>> 
>> ---
>> 
>> v2 -> v3:
>> 
>> - QOMify the QJSON object, makes for easier destruction --- 
>> include/qjson.h |  3 ++- qjson.c         | 39
>> ++++++++++++++++++++++++++++++++++++--- 2 files changed, 38
>> insertions(+), 4 deletions(-)
>> 
>> diff --git a/include/qjson.h b/include/qjson.h index
>> 8f8c145..7c54fdf 100644 --- a/include/qjson.h +++
>> b/include/qjson.h @@ -4,7 +4,7 @@ * Copyright Alexander Graf * *
>> Authors: - *  Alexander Graf <agraf@suse.de + *  Alexander Graf
>> <agraf@suse.de>
> 
> Umm, this should be squashed into 1/5.

Honestly, I think the whole patch should've gotten squashed into 1/5.
I'm not quite sure what went wrong here :).

> 
>> @@ -85,9 +88,7 @@ const char *qjson_get_str(QJSON *json)
>> 
>> QJSON *qjson_new(void) { -    QJSON *json = g_new(QJSON, 1); -
>> json->str = qstring_from_str("{ "); -    json->omit_comma =
>> true; +    QJSON *json = (QJSON *)object_new(TYPE_QJSON); return
>> json;
> 
> This undoes the dangling object that I complained about on patch
> 1; maybe there's some more squashing to do?...
> 
> 
>> +static void qjson_initfn(Object *obj) +{ +    QJSON *json =
>> (QJSON *)object_dynamic_cast(obj, TYPE_QJSON); +
>> assert(json); + +    json->str = qstring_from_str("{ "); +
>> json->omit_comma = true;
> 
> ...or is it still an incomplete object, just now in a different
> location?

The idea is that you call finish and only then receive the string. I
don't think doing that from get_str would be too much of an
improvement - it'd still be wrong if we're in the middle of assembling
an object.


Alex
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