Re: [Qemu-devel] [PATCH v2][ 11/21] qapi: add QMP output visiter

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri,  3 Jun 2011 17:33:09 -0500
Michael Roth <mdroth@linux.vnet.ibm.com> wrote:

> Type of Visiter class that serves as the inverse of the input visiter:
> it takes a series of native C types and uses their values to construct a
> corresponding QObject. The command marshaling/dispatcher functions will
> use this to convert the output of QMP functions into a QObject that can
> be sent over the wire.
> 
> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  qapi/qmp-output-visiter.c |  180 +++++++++++++++++++++++++++++++++++++++++++++
>  qapi/qmp-output-visiter.h |   27 +++++++
>  2 files changed, 207 insertions(+), 0 deletions(-)
>  create mode 100644 qapi/qmp-output-visiter.c
>  create mode 100644 qapi/qmp-output-visiter.h
> 
> diff --git a/qapi/qmp-output-visiter.c b/qapi/qmp-output-visiter.c
> new file mode 100644
> index 0000000..4a7cb36
> --- /dev/null
> +++ b/qapi/qmp-output-visiter.c
> @@ -0,0 +1,180 @@
> +#include "qmp-output-visiter.h"
> +#include "qemu-queue.h"
> +#include "qemu-common.h"
> +#include "qemu-objects.h"
> +
> +typedef struct QStackEntry
> +{
> +    QObject *value;
> +    QTAILQ_ENTRY(QStackEntry) node;
> +} QStackEntry;
> +
> +typedef QTAILQ_HEAD(QStack, QStackEntry) QStack;
> +
> +struct QmpOutputVisiter
> +{
> +    Visiter visiter;
> +    QStack stack;
> +};
> +
> +#define qmp_output_add(qov, name, value) qmp_output_add_obj(qov, name, QOBJECT(value))
> +#define qmp_output_push(qov, value) qmp_output_push_obj(qov, QOBJECT(value))
> +
> +static QmpOutputVisiter *to_qov(Visiter *v)
> +{
> +    return container_of(v, QmpOutputVisiter, visiter);
> +}
> +
> +static void qmp_output_push_obj(QmpOutputVisiter *qov, QObject *value)
> +{
> +    QStackEntry *e = qemu_mallocz(sizeof(*e));
> +
> +    e->value = value;
> +    QTAILQ_INSERT_HEAD(&qov->stack, e, node);
> +}
> +
> +static QObject *qmp_output_pop(QmpOutputVisiter *qov)
> +{
> +    QStackEntry *e = QTAILQ_FIRST(&qov->stack);
> +    QObject *value;
> +    QTAILQ_REMOVE(&qov->stack, e, node);
> +    value = e->value;
> +    qemu_free(e);
> +    return value;
> +}
> +
> +static QObject *qmp_output_first(QmpOutputVisiter *qov)
> +{
> +    QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
> +    return e->value;
> +}
> +
> +static QObject *qmp_output_last(QmpOutputVisiter *qov)
> +{
> +    QStackEntry *e = QTAILQ_FIRST(&qov->stack);
> +    return e->value;
> +}
> +
> +static void qmp_output_add_obj(QmpOutputVisiter *qov, const char *name, QObject *value)
> +{
> +    QObject *cur;
> +
> +    if (QTAILQ_EMPTY(&qov->stack)) {
> +        qmp_output_push_obj(qov, value);
> +        return;
> +    }
> +
> +    cur = qmp_output_last(qov);
> +
> +    switch (qobject_type(cur)) {
> +    case QTYPE_QDICT:
> +        qdict_put_obj(qobject_to_qdict(cur), name, value);
> +        break;
> +    case QTYPE_QLIST:
> +        qlist_append_obj(qobject_to_qlist(cur), value);
> +        break;
> +    default:
> +        qobject_decref(qmp_output_pop(qov));

I'm not sure I understand when we should discard an item like this,
shouldn't this be an assert()?

> +        qmp_output_push_obj(qov, value);
> +        break;
> +    }
> +}
> +
> +static void qmp_output_start_struct(Visiter *v, void **obj, const char *kind, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    QDict *dict = qdict_new();
> +
> +    qmp_output_add(qov, name, dict);

This calls qmp_output_push() if the stack is empty...

> +    qmp_output_push(qov, dict);

...then it's called again here, so the element is added twice,
is this expected?

> +}
> +
> +static void qmp_output_end_struct(Visiter *v, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_pop(qov);
> +}
> +
> +static void qmp_output_start_list(Visiter *v, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    QList *list = qlist_new();
> +
> +    qmp_output_add(qov, name, list);
> +    qmp_output_push(qov, list);
> +}
> +
> +static GenericList *qmp_output_next_list(Visiter *v, GenericList **list, Error **errp)
> +{
> +    GenericList *retval = *list;
> +    *list = retval->next;
> +    return retval;
> +}
> +
> +static void qmp_output_end_list(Visiter *v, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_pop(qov);
> +}
> +
> +static void qmp_output_type_int(Visiter *v, int64_t *obj, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_add(qov, name, qint_from_int(*obj));
> +}
> +
> +static void qmp_output_type_bool(Visiter *v, bool *obj, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_add(qov, name, qbool_from_int(*obj));
> +}
> +
> +static void qmp_output_type_str(Visiter *v, char **obj, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_add(qov, name, qstring_from_str(*obj));
> +}
> +
> +static void qmp_output_type_number(Visiter *v, double *obj, const char *name, Error **errp)
> +{
> +    QmpOutputVisiter *qov = to_qov(v);
> +    qmp_output_add(qov, name, qfloat_from_double(*obj));
> +}
> +
> +static void qmp_output_type_enum(Visiter *v, int *obj, const char *kind, const char *name, Error **errp)
> +{
> +    int64_t value = *obj;
> +    qmp_output_type_int(v, &value, name, errp);
> +}
> +
> +QObject *qmp_output_get_qobject(QmpOutputVisiter *qov)
> +{
> +    return qmp_output_first(qov);
> +}
> +
> +Visiter *qmp_output_get_visiter(QmpOutputVisiter *v)
> +{
> +    return &v->visiter;
> +}
> +
> +QmpOutputVisiter *qmp_output_visiter_new(void)
> +{
> +    QmpOutputVisiter *v;
> +
> +    v = qemu_mallocz(sizeof(*v));
> +
> +    v->visiter.start_struct = qmp_output_start_struct;
> +    v->visiter.end_struct = qmp_output_end_struct;
> +    v->visiter.start_list = qmp_output_start_list;
> +    v->visiter.next_list = qmp_output_next_list;
> +    v->visiter.end_list = qmp_output_end_list;
> +    v->visiter.type_enum = qmp_output_type_enum;
> +    v->visiter.type_int = qmp_output_type_int;
> +    v->visiter.type_bool = qmp_output_type_bool;
> +    v->visiter.type_str = qmp_output_type_str;
> +    v->visiter.type_number = qmp_output_type_number;
> +
> +    QTAILQ_INIT(&v->stack);
> +
> +    return v;
> +}
> diff --git a/qapi/qmp-output-visiter.h b/qapi/qmp-output-visiter.h
> new file mode 100644
> index 0000000..b04ab02
> --- /dev/null
> +++ b/qapi/qmp-output-visiter.h
> @@ -0,0 +1,27 @@
> +/*
> + * Output Visiter
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + *  Anthony Liguori   <aliguori@us.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
> + * See the COPYING.LIB file in the top-level directory.
> + *
> + */
> +
> +#ifndef QMP_OUTPUT_VISITER_H
> +#define QMP_OUTPUT_VISITER_H
> +
> +#include "qapi-visit-core.h"
> +#include "qobject.h"
> +
> +typedef struct QmpOutputVisiter QmpOutputVisiter;
> +
> +QmpOutputVisiter *qmp_output_visiter_new(void);
> +
> +QObject *qmp_output_get_qobject(QmpOutputVisiter *v);
> +Visiter *qmp_output_get_visiter(QmpOutputVisiter *v);
> +
> +#endif