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Date: Fri, 14 May 2010 13:15:52 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 3/8] Add QBuffer
References: <cover.1273843151.git.jan.kiszka@siemens.com>
	<6e14cbfe3764b46d9bd6d2db61d41fd9c85dd54e.1273843151.git.jan.kiszka@siemens.com>
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Juan Quintela <quintela@redhat.com>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>, Avi Kivity <avi@redhat.com>

On 05/14/2010 08:20 AM, Jan Kiszka wrote:
> diff --git a/qjson.c b/qjson.c
> index 483c667..4d1c21a 100644
> --- a/qjson.c
> +++ b/qjson.c
> @@ -19,7 +19,9 @@
>   #include "qlist.h"
>   #include "qbool.h"
>   #include "qfloat.h"
> +#include "qbuffer.h"
>   #include "qdict.h"
> +#include "base64.h"
>
>   typedef struct JSONParsingState
>   {
> @@ -235,6 +237,20 @@ static void to_json(const QObject *obj, QString *str)
>           }
>           break;
>       }
> +    case QTYPE_QBUFFER: {
> +        QBuffer *val = qobject_to_qbuffer(obj);
> +        size_t data_size = qbuffer_get_size(val);
> +        size_t str_len = ((data_size + 2) / 3) * 4;
> +        char *buffer = qemu_malloc(str_len + 3);
> +
> +        buffer[0] = '"';
> +        base64_encode(qbuffer_get_data(val), data_size, buffer + 1);
> +        buffer[str_len + 1] = '"';
> +        buffer[str_len + 2] = 0;
> +        qstring_append(str, buffer);
> +        qemu_free(buffer);
> +        break;
> +    }
>    

Instead of encoding just as a string, it would be a good idea to encode 
it as something like:

{'__class__': 'base64', 'data': ...}

We've discussed using hidden properties to describe special things like 
abstract classes and since we already have this namespace reserved, I 
think it's a good time to use it.

The advantage is that in a dynamic language like Python, the parser can 
convert base64 to binary strings automatically without having to 
understand the QMP protocol.

Regards,

Anthony Liguori

>       case QTYPE_QERROR:
>           /* XXX: should QError be emitted? */
>       case QTYPE_NONE:
> diff --git a/qobject.h b/qobject.h
> index 07de211..45c4fa0 100644
> --- a/qobject.h
> +++ b/qobject.h
> @@ -44,6 +44,7 @@ typedef enum {
>       QTYPE_QFLOAT,
>       QTYPE_QBOOL,
>       QTYPE_QERROR,
> +    QTYPE_QBUFFER,
>   } qtype_code;
>
>   struct QObject;
>