Re: [Qemu-devel] [PATCH v5 05/18] qapi: add QMP input visitor

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On 07/12/2011 08:16 AM, Luiz Capitulino wrote:
> On Mon, 11 Jul 2011 19:05:58 -0500
> Michael Roth<mdroth@linux.vnet.ibm.com>  wrote:
>
>> On 07/07/2011 09:32 AM, Luiz Capitulino wrote:
>>> On Tue,  5 Jul 2011 08:02:32 -0500
>>> Michael Roth<mdroth@linux.vnet.ibm.com>   wrote:
>>>
>>>> A type of Visiter class that is used to walk a qobject's
>>>> structure and assign each entry to the corresponding native C type.
>>>> Command marshaling function will use this to pull out QMP command
>>>> parameters recieved over the wire and pass them as native arguments
>>>> to the corresponding C functions.
>>>>
>>>> Signed-off-by: Michael Roth<mdroth@linux.vnet.ibm.com>
>>>> ---
>>>>    Makefile.objs            |    2 +-
>>>>    qapi/qmp-input-visitor.c |  264 ++++++++++++++++++++++++++++++++++++++++++++++
>>>>    qapi/qmp-input-visitor.h |   27 +++++
>>>>    qerror.h                 |    3 +
>>>>    4 files changed, 295 insertions(+), 1 deletions(-)
>>>>    create mode 100644 qapi/qmp-input-visitor.c
>>>>    create mode 100644 qapi/qmp-input-visitor.h
>>>>
>>>> diff --git a/Makefile.objs b/Makefile.objs
>>>> index 0077014..997ecef 100644
>>>> --- a/Makefile.objs
>>>> +++ b/Makefile.objs
>>>> @@ -375,7 +375,7 @@ libcacard-y = cac.o event.o vcard.o vreader.o vcard_emul_nss.o vcard_emul_type.o
>>>>    ######################################################################
>>>>    # qapi
>>>>
>>>> -qapi-nested-y = qapi-visit-core.o
>>>> +qapi-nested-y = qapi-visit-core.o qmp-input-visitor.o
>>>>    qapi-obj-y = $(addprefix qapi/, $(qapi-nested-y))
>>>>
>>>>    vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)
>>>> diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
>>>> new file mode 100644
>>>> index 0000000..80912bb
>>>> --- /dev/null
>>>> +++ b/qapi/qmp-input-visitor.c
>>>> @@ -0,0 +1,264 @@
>>>> +/*
>>>> + * Input Visitor
>>>> + *
>>>> + * 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.
>>>> + *
>>>> + */
>>>> +
>>>> +#include "qmp-input-visitor.h"
>>>> +#include "qemu-queue.h"
>>>> +#include "qemu-common.h"
>>>> +#include "qemu-objects.h"
>>>> +#include "qerror.h"
>>>> +
>>>> +#define QIV_STACK_SIZE 1024
>>>> +
>>>> +typedef struct StackObject
>>>> +{
>>>> +    const QObject *obj;
>>>> +    const  QListEntry *entry;
>>>> +} StackObject;
>>>> +
>>>> +struct QmpInputVisitor
>>>> +{
>>>> +    Visitor visitor;
>>>> +    const QObject *obj;
>>>> +    StackObject stack[QIV_STACK_SIZE];
>>>> +    int nb_stack;
>>>> +};
>>>> +
>>>> +static QmpInputVisitor *to_qiv(Visitor *v)
>>>> +{
>>>> +    return container_of(v, QmpInputVisitor, visitor);
>>>> +}
>>>> +
>>>> +static const QObject *qmp_input_get_object(QmpInputVisitor *qiv, const char *name)
>>>> +{
>>>> +    const QObject *qobj;
>>>> +
>>>> +    if (qiv->nb_stack == 0) {
>>>> +        qobj = qiv->obj;
>>>> +    } else {
>>>> +        qobj = qiv->stack[qiv->nb_stack - 1].obj;
>>>> +    }
>>>> +
>>>> +    if (name&&   qobject_type(qobj) == QTYPE_QDICT) {
>>>> +        return qdict_get(qobject_to_qdict(qobj), name);
>>>> +    } else if (qiv->nb_stack>   0&&   qobject_type(qobj) == QTYPE_QLIST) {
>>>> +        return qlist_entry_obj(qiv->stack[qiv->nb_stack - 1].entry);
>>>> +    }
>>>> +
>>>> +    return qobj;
>>>> +}
>>>> +
>>>> +static void qmp_input_push(QmpInputVisitor *qiv, const QObject *obj, Error **errp)
>>>> +{
>>>> +    qiv->stack[qiv->nb_stack].obj = obj;
>>>> +    if (qobject_type(obj) == QTYPE_QLIST) {
>>>> +        qiv->stack[qiv->nb_stack].entry = qlist_first(qobject_to_qlist(obj));
>>>> +    }
>>>> +    qiv->nb_stack++;
>>>> +
>>>> +    if (qiv->nb_stack>= QIV_STACK_SIZE) {
>>>> +        error_set(errp, QERR_BUFFER_OVERRUN);
>>>> +        return;
>>>> +    }
>>>> +}
>>>> +
>>>> +static void qmp_input_pop(QmpInputVisitor *qiv, Error **errp)
>>>> +{
>>>> +    qiv->nb_stack--;
>>>> +    if (qiv->nb_stack<   0) {
>>>> +        error_set(errp, QERR_BUFFER_OVERRUN);
>>>> +        return;
>>>> +    }
>>>> +}
>>>> +
>>>> +static void qmp_input_start_struct(Visitor *v, void **obj, const char *kind, const char *name, size_t size, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QDICT) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "QDict");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    qmp_input_push(qiv, qobj, errp);
>>>> +    if (error_is_set(errp)) {
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    if (obj) {
>>>> +        *obj = qemu_mallocz(size);
>>>> +    }
>>>> +}
>>>> +
>>>> +static void qmp_input_end_struct(Visitor *v, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +
>>>> +    qmp_input_pop(qiv, errp);
>>>> +}
>>>> +
>>>> +static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QLIST) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "list");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    qmp_input_push(qiv, qobj, errp);
>>>> +}
>>>> +
>>>> +static GenericList *qmp_input_next_list(Visitor *v, GenericList **list, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    GenericList *entry;
>>>> +    StackObject *so =&qiv->stack[qiv->nb_stack - 1];
>>>> +
>>>> +    if (so->entry == NULL) {
>>>> +        return NULL;
>>>> +    }
>>>> +
>>>> +    entry = qemu_mallocz(sizeof(*entry));
>>>> +    if (*list) {
>>>> +        so->entry = qlist_next(so->entry);
>>>> +        if (so->entry == NULL) {
>>>> +            qemu_free(entry);
>>>> +            return NULL;
>>>> +        }
>>>> +        (*list)->next = entry;
>>>> +    }
>>>> +    *list = entry;
>>>> +
>>>> +
>>>> +    return entry;
>>>> +}
>>>> +
>>>> +static void qmp_input_end_list(Visitor *v, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +
>>>> +    qmp_input_pop(qiv, errp);
>>>> +}
>>>> +
>>>> +static void qmp_input_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QINT) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "integer");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    *obj = qint_get_int(qobject_to_qint(qobj));
>>>> +}
>>>> +
>>>> +static void qmp_input_type_bool(Visitor *v, bool *obj, const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QBOOL) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "boolean");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    *obj = qbool_get_int(qobject_to_qbool(qobj));
>>>> +}
>>>> +
>>>> +static void qmp_input_type_str(Visitor *v, char **obj, const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QSTRING) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "string");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    *obj = qemu_strdup(qstring_get_str(qobject_to_qstring(qobj)));
>>>> +}
>>>> +
>>>> +static void qmp_input_type_number(Visitor *v, double *obj, const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj || qobject_type(qobj) != QTYPE_QFLOAT) {
>>>> +        error_set(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null", "double");
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    *obj = qfloat_get_double(qobject_to_qfloat(qobj));
>>>> +}
>>>> +
>>>> +static void qmp_input_type_enum(Visitor *v, int *obj, const char *kind, const char *name, Error **errp)
>>>> +{
>>>> +    int64_t value;
>>>> +    qmp_input_type_int(v,&value, name, errp);
>>>> +    *obj = value;
>>>> +}
>>>> +
>>>> +static void qmp_input_start_optional(Visitor *v, bool *present,
>>>> +                                     const char *name, Error **errp)
>>>> +{
>>>> +    QmpInputVisitor *qiv = to_qiv(v);
>>>> +    const QObject *qobj = qmp_input_get_object(qiv, name);
>>>> +
>>>> +    if (!qobj) {
>>>> +        *present = false;
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    *present = true;
>>>> +}
>>>> +
>>>> +static void qmp_input_end_optional(Visitor *v, Error **errp)
>>>> +{
>>>> +}
>>>> +
>>>> +Visitor *qmp_input_get_visitor(QmpInputVisitor *v)
>>>> +{
>>>> +    return&v->visitor;
>>>> +}
>>>> +
>>>> +void qmp_input_visitor_cleanup(QmpInputVisitor *v)
>>>> +{
>>>
>>> We talked about doing a qobject_incref(v->obj) in qmp_input_visitor_new() and
>>> decrefing here.
>>>
>>
>> I think it was either that, or just making the QObject arg to
>> qmp_input_visitor_new() const, to make it clear it was caller-freed.
>
> No, because (at least theoretically) a client could free it before walking
> the struct with the visitor functions. The rule is: if you store it, you
> have to increment its reference or get its ownership.
>
>

Makes sense. Sucks to have to remove the const for that though...would a 
temporary cast to non-const be acceptable in a case like this?

>>
>>>> +    qemu_free(v);
>>>> +}
>>>> +
>>>> +QmpInputVisitor *qmp_input_visitor_new(const QObject *obj)
>>>> +{
>>>> +    QmpInputVisitor *v;
>>>> +
>>>> +    v = qemu_mallocz(sizeof(*v));
>>>> +
>>>> +    v->visitor.start_struct = qmp_input_start_struct;
>>>> +    v->visitor.end_struct = qmp_input_end_struct;
>>>> +    v->visitor.start_list = qmp_input_start_list;
>>>> +    v->visitor.next_list = qmp_input_next_list;
>>>> +    v->visitor.end_list = qmp_input_end_list;
>>>> +    v->visitor.type_enum = qmp_input_type_enum;
>>>> +    v->visitor.type_int = qmp_input_type_int;
>>>> +    v->visitor.type_bool = qmp_input_type_bool;
>>>> +    v->visitor.type_str = qmp_input_type_str;
>>>> +    v->visitor.type_number = qmp_input_type_number;
>>>> +    v->visitor.start_optional = qmp_input_start_optional;
>>>> +    v->visitor.end_optional = qmp_input_end_optional;
>>>> +
>>>> +    v->obj = obj;
>>>> +
>>>> +    return v;
>>>> +}
>>>> diff --git a/qapi/qmp-input-visitor.h b/qapi/qmp-input-visitor.h
>>>> new file mode 100644
>>>> index 0000000..0f77916
>>>> --- /dev/null
>>>> +++ b/qapi/qmp-input-visitor.h
>>>> @@ -0,0 +1,27 @@
>>>> +/*
>>>> + * Input Visitor
>>>> + *
>>>> + * 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_INPUT_VISITOR_H
>>>> +#define QMP_INPUT_VISITOR_H
>>>> +
>>>> +#include "qapi-visit-core.h"
>>>> +#include "qobject.h"
>>>> +
>>>> +typedef struct QmpInputVisitor QmpInputVisitor;
>>>> +
>>>> +QmpInputVisitor *qmp_input_visitor_new(const QObject *obj);
>>>> +void qmp_input_visitor_cleanup(QmpInputVisitor *v);
>>>> +
>>>> +Visitor *qmp_input_get_visitor(QmpInputVisitor *v);
>>>> +
>>>> +#endif
>>>> diff --git a/qerror.h b/qerror.h
>>>> index 16c830d..9a9fa5b 100644
>>>> --- a/qerror.h
>>>> +++ b/qerror.h
>>>> @@ -124,6 +124,9 @@ QError *qobject_to_qerror(const QObject *obj);
>>>>    #define QERR_JSON_PARSE_ERROR \
>>>>        "{ 'class': 'JSONParseError', 'data': { 'message': %s } }"
>>>>
>>>> +#define QERR_BUFFER_OVERRUN \
>>>> +    "{ 'class': 'BufferOverrun', 'data': {} }"
>>>> +
>>>
>>> You also have to add an entry in qerror.c. I slightly prefer NotEnoughMemory,
>>> but BufferOverrrun is probably fine.
>>>
>>>>    #define QERR_KVM_MISSING_CAP \
>>>>        "{ 'class': 'KVMMissingCap', 'data': { 'capability': %s, 'feature': %s } }"
>>>>
>>>
>>
>