Re: [Qemu-devel] [PATCH] let qemu-img info genereate json output

[Anthony Liguori <aliguori@us.ibm.com>]

Wenchao Xia <xiawenc@linux.vnet.ibm.com> writes:

>   This patch would add option -j in qemu-img info command, which
> would generate json output in stdout.

This is a great idea.

>
> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
> ---
>  qemu-img.c |  306 +++++++++++++++++++++++++++++++++++++++++++++++++++--------
>  1 files changed, 264 insertions(+), 42 deletions(-)
>
> diff --git a/qemu-img.c b/qemu-img.c
> index 80cfb9b..a514c17 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -33,6 +33,9 @@
>  #include <windows.h>
>  #endif
>  
> +#include "qint.h"
> +#include "qjson.h"
> +
>  typedef struct img_cmd_t {
>      const char *name;
>      int (*handler)(int argc, char **argv);
> @@ -84,6 +87,7 @@ static void help(void)
>             "  '-p' show progress of command (only certain commands)\n"
>             "  '-S' indicates the consecutive number of bytes that must contain only zeros\n"
>             "       for qemu-img to create a sparse image during conversion\n"
> +           "  '-j' try get json output, which would be in stdout,
> only valid in info command\n"

I think an --format=json option would be a bit more extensible and
better matches what most tools are doing these days.

>             "\n"
>             "Parameters to check subcommand:\n"
>             "  '-r' tries to repair any inconsistencies that are found during the check.\n"
> @@ -1102,21 +1106,210 @@ static void dump_snapshots(BlockDriverState *bs)
>      g_free(sn_tab);
>  }
>  
> +/* string must be allocated on heap */
> +struct img_infos {

CodingStyle

> +    char *filename;
> +    char *fmt;
> +    uint64_t total_sectors;
> +    int64_t allocated_size;
> +    int32 enc_flag;
> +    BlockDriverInfo *bdi;
> +    char *backing_filename;
> +    char *backing_filename_full;
> +    QEMUSnapshotInfo *sn_tab;
> +    int nb_sns;
> +};
> +
> +static void img_infos_init(struct img_infos *pinfo)
> +{
> +    memset(pinfo, 0, sizeof(struct img_infos));
> +}
> +
> +#define TRY_FREE(p) { \
> +    if ((p) != NULL) { \
> +        g_free((p)); \
> +        (p) = NULL; \
> +    } \
> +}
> +static void img_infos_uninit(struct img_infos *pinfo)
> +{
> +    TRY_FREE(pinfo->filename);
> +    TRY_FREE(pinfo->fmt);
> +    TRY_FREE(pinfo->bdi);
> +    TRY_FREE(pinfo->backing_filename);
> +    TRY_FREE(pinfo->backing_filename_full);
> +    TRY_FREE(pinfo->sn_tab);
> +}
> +
> +static void snapshot_info_to_list(QList *qlist, QEMUSnapshotInfo *sn)
> +{
> +    char buf[128];
> +    QInt *qint;
> +    QString *qstr;
> +    QDict *qdic = qdict_new();
> +
> +    qstr = qstring_from_str(sn->id_str);
> +    qdict_put_obj(qdic, "id", QOBJECT(qstr));
> +    qstr = qstring_from_str(sn->name);
> +    qdict_put_obj(qdic, "name", QOBJECT(qstr));
> +
> +    snprintf(buf, sizeof(buf), "%ld", sn->vm_state_size);
> +    qstr = qstring_from_str(buf);
> +    qdict_put_obj(qdic, "vm_state_size", QOBJECT(qstr));
> +
> +    qint = qint_from_int(sn->date_sec);
> +    qdict_put_obj(qdic, "date_sec", QOBJECT(qint));
> +    qint = qint_from_int(sn->date_nsec);
> +    qdict_put_obj(qdic, "date_nsec", QOBJECT(qint));
> +    snprintf(buf, sizeof(buf), "%ld", sn->vm_clock_nsec);
> +    qstr = qstring_from_str(buf);
> +    qdict_put_obj(qdic, "vm_clock_nsec", QOBJECT(qstr));
> +    qlist_append(qlist, qdic);
> +}

No need to open code all of this.  Just describe the output as a type in
qapi-schema.json.  Then you can just #include "qapi-visit.h", then call
visit_type_ImageInfo passing in a QMPOutputVisitor.

You can then pass the QObject to the json code to pretty print it.

Regards,

Anthony Liguori