Re: [Qemu-devel] [PATCH v16 11/24] qmp-input: Refactor when list is advanced

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> In the QMP input visitor, visiting a list traverses two objects:
> the QAPI GenericList of the caller (which gets advanced in
> visit_next_list() regardless of this patch), and the QList input
> that we are converting to QAPI.  For consistency with QDict
> visits, we want to consume elements from the input QList during
> the visit_type_FOO() for the list element; that is, we want ALL
> the code for consuming an input to live in qmp_input_get_object(),
> rather than having it split according to whether we are visiting
> a dict or a list.  Making qmp_input_get_object() the common point
> of consumption will make it easier for a later patch to refactor
> visit_start_list() to cover the GenericList * head of a QAPI list,
> and in turn will get rid of the 'first' flag (which lived in
> qmp_input_next_list() pre-patch, and is hoisted to StackObject
> by this patch).
>
> This patch is therefore shifting the post-condition use of
> 'entry' from:
>
>         start_list next_list type_ELT ... next_list type_ELT next_list 
> end_list
>  visit                       1st elt                last elt
>  entry  NULL       1st elt   1st elt      last elt  last elt NULL      gone

You added a line "visit", but the introduction still only mentions
'entry'.  Mildly confusing.  If you have an idea on how to improve it, I
can touch it up on commit.

>
> where type_ELT() returns (entry ? entry : 1st elt) and next_list() steps
> entry
>
> to this usage:
>
>         start_list next_list type_ELT ... next_list type_ELT next_list 
> end_list
>  visit                       1st elt                last elt
>  entry  1st elt    1nd elt   2nd elt      last elt  NULL     NULL      gone
>
> where type_ELT() steps entry and returns the old entry, and next_list()
> leaves entry alone.
>
> Signed-off-by: Eric Blake <address@hidden>

Patch looks good.