Kevin Wolf <kw...@redhat.com> writes:
> This adds functions to the Visitor interface that can be used to define
> aliases and alias scopes.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> ---
> include/qapi/visitor-impl.h | 12 ++++++++++++
> include/qapi/visitor.h | 37 +++++++++++++++++++++++++++++++++++++
> qapi/qapi-visit-core.c | 21 +++++++++++++++++++++
> 3 files changed, 70 insertions(+)
>
> diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
> index 7362c043be..e30da2599c 100644
> --- a/include/qapi/visitor-impl.h
> +++ b/include/qapi/visitor-impl.h
> @@ -113,6 +113,18 @@ struct Visitor
> The core takes care of the return type in the public interface. */
> void (*optional)(Visitor *v, const char *name, bool *present);
>
> + /*
> + * Optional; intended for input visitors. If not given, aliases are
> + * ignored.
> + */
> + void (*define_alias)(Visitor *v, const char *alias, const char **source);
> +
> + /* Must be set if define_alias is set */
> + void (*start_alias_scope)(Visitor *v);
> +
> + /* Must be set if define_alias is set */
> + void (*end_alias_scope)(Visitor *v);
> +
> /* Must be set */
> VisitorType type;
>
> diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
> index ebc19ede7f..9bdc0ee03d 100644
> --- a/include/qapi/visitor.h
> +++ b/include/qapi/visitor.h
> @@ -459,6 +459,43 @@ void visit_end_alternate(Visitor *v, void **obj);
> */
> bool visit_optional(Visitor *v, const char *name, bool *present);
>
> +/*
> + * Defines a new alias rule.
> + *
> + * If @alias is non-NULL, the member named @alias in the external
> + * representation of the current struct is defined as an alias for the
Terminology: the big comment uses "object". See also the FIXME in
visit_start_struct()'s contract.
> + * member described by @source.
> + *
> + * If @alias is NULL, all members of the struct described by @source are
> + * considered to have alias members with the same key in the current
> + * struct.
Define "the current struct". I believe it's the object being visited.
What happens if we're currently visiting something other than an object,
i.e. the root of a tree, or a list?
> + *
> + * @source is a NULL-terminated array of names that describe the path to
> + * a member, starting from the currently visited struct.
I'm afraid "describe the path to a member" is too vague. How?
I figure this is what you have in mind:
cur = the currently visited object
for s in source:
cur = the member of cur denoted by s
When @cur is indeed an object, then "the member denoted by @s" makes
sense: you must pass a name when visiting object members, and whatever
is visited with name @s is the member denoted by @s.
"Must pass a name" is documented in the big comment:
* The @name parameter of visit_type_FOO() describes the relation
* between this QAPI value and its parent container. When visiting
* the root of a tree, @name is ignored; when visiting a member of an
* object, @name is the key associated with the value; when visiting a
* member of a list, @name is NULL; and when visiting the member of an
* alternate, @name should equal the name used for visiting the
* alternate.
But what if @cur is a list? I guess that makes no sense. Say so
explicitly, please.
> + *
> + * The alias stays valid until the current alias scope ends.
> + * visit_start/end_struct() implicitly start/end an alias scope.
> + * Additionally, visit_start/end_alias_scope() can be used to explicitly
> + * create a nested alias scope.
> + */
> +void visit_define_alias(Visitor *v, const char *alias, const char **source);
> +
> +/*
> + * Begins an explicit alias scope.
> + *
> + * Alias definitions after here will only stay valid until the
> + * corresponding visit_end_alias_scope() is called.
> + */
> +void visit_start_alias_scope(Visitor *v);
> +
> +/*
> + * Ends an explicit alias scope.
> + *
> + * Alias definitions between the correspoding visit_start_alias_scope()
> + * call and here go out of scope and won't apply in later code any more.
> + */
> +void visit_end_alias_scope(Visitor *v);
> +
> /*
> * Visit an enum value.
> *
[...]
