Re: [PATCH v2 3/6] qapi: Simplify full_name_nth() in qobject-input-visitor

[Markus Armbruster <armbru@redhat.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> Instead of counting how many elements from the top of the stack we need
> to ignore until we find the thing we're interested in, we can just
> directly pass the StackObject pointer because all callers already know
> it.
>
> We only need a different way now to tell if we want to know the name of
> something contained in the given StackObject or of the StackObject
> itself. Passing name = NULL is the obvious way to request the latter.

Is the last sentence still accurate?

> This simplifies the interface and makes it easier to use in cases where
> we have the StackObject, but don't know how many steps down the stack it
> is.

No such case exists, but the next patch adds one.  Correct?

> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  qapi/qobject-input-visitor.c | 43 ++++++++++++++++++++----------------
>  1 file changed, 24 insertions(+), 19 deletions(-)
>
> diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
> index aa95cd49bd..dd04ef0027 100644
> --- a/qapi/qobject-input-visitor.c
> +++ b/qapi/qobject-input-visitor.c
> @@ -108,20 +108,20 @@ static QObjectInputVisitor *to_qiv(Visitor *v)
>  }
>  
>  /*
> - * Find the full name of something @qiv is currently visiting.
> - * @qiv is visiting something named @name in the stack of containers
> - * @qiv->stack.
> - * If @n is zero, return its full name.
> - * If @n is positive, return the full name of the @n-th container
> - * counting from the top.  The stack of containers must have at least
> - * @n elements.
> - * The returned string is valid until the next full_name_nth(@v) or
> - * destruction of @v.
> + * Find the full name of a member in @so which @qiv is currently
> + * visiting.  If the currently visited thing is an object, @name is
> + * the (local) name of the member to describe.  If it is a list, @name
> + * is ignored and the current index (so->index) is included.
> + *
> + * If @skip_member is true, find the full name of @so itself instead.
> + * @name must be NULL then.
> + *
> + * The returned string is valid until the next full_name_so(@qiv) or
> + * destruction of @qiv.
>   */
> -static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
> -                                 int n)
> +static const char *full_name_so(QObjectInputVisitor *qiv, const char *name,
> +                                bool skip_member, StackObject *so)
>  {
> -    StackObject *so;
>      char buf[32];
>  
>      if (qiv->errname) {
> @@ -130,10 +130,14 @@ static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
>          qiv->errname = g_string_new("");
>      }
>  
> -    QSLIST_FOREACH(so , &qiv->stack, node) {
> -        if (n) {
> -            n--;
> -        } else if (qobject_type(so->obj) == QTYPE_QDICT) {
> +    if (skip_member && so) {
> +        assert(name == NULL);
> +        name = so->name;
> +        so = QSLIST_NEXT(so, node);
> +    }
> +
> +    for (; so; so = QSLIST_NEXT(so, node)) {
> +        if (qobject_type(so->obj) == QTYPE_QDICT) {
>              g_string_prepend(qiv->errname, name ?: "<anonymous>");
>              g_string_prepend_c(qiv->errname, '.');
>          } else {
> @@ -144,7 +148,6 @@ static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
>          }
>          name = so->name;
>      }
> -    assert(!n);
>  
>      if (name) {
>          g_string_prepend(qiv->errname, name);
> @@ -159,7 +162,9 @@ static const char *full_name_nth(QObjectInputVisitor *qiv, const char *name,
>  
>  static const char *full_name(QObjectInputVisitor *qiv, const char *name)
>  {
> -    return full_name_nth(qiv, name, 0);
> +    StackObject *tos = QSLIST_FIRST(&qiv->stack);
> +
> +    return full_name_so(qiv, name, false, tos);
>  }
>  
>  static QObject *qobject_input_try_get_object(QObjectInputVisitor *qiv,
> @@ -503,7 +508,7 @@ static bool qobject_input_check_list(Visitor *v, Error **errp)
>  
>      if (tos->entry) {
>          error_setg(errp, "Only %u list elements expected in %s",
> -                   tos->index + 1, full_name_nth(qiv, NULL, 1));
> +                   tos->index + 1, full_name_so(qiv, NULL, true, tos));
>          return false;
>      }
>      return true;