[RFC PATCH 01/12] qapi: Add visit_next_struct_member()

[Kevin Wolf <kwolf@redhat.com>]

This adds a way to generically deal with an unknown set of members in
input visitors by just getting the name of the next unvisited member.
QOM object creation code will use it to have generic code that calls
property setters which then in turn have the more specific knowledge how
to visit the respective member.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 include/qapi/visitor-impl.h  |  3 +++
 include/qapi/visitor.h       |  2 ++
 qapi/qapi-visit-core.c       |  6 ++++++
 qapi/qobject-input-visitor.c | 16 ++++++++++++++++
 qapi/trace-events            |  1 +
 5 files changed, 28 insertions(+)

diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 2badec5ba4..af66a850ed 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -57,6 +57,9 @@ struct Visitor
     /* Must be set to visit structs */
     void (*end_struct)(Visitor *v, void **obj);
 
+    /* Must be set for input visitors to visit structs */
+    const char *(*next_struct_member)(Visitor *v);
+
     /* Must be set; implementations may require @list to be non-null,
      * but must document it. */
     bool (*start_list)(Visitor *v, const char *name, GenericList **list,
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index d53a84c9ba..5a1a28f9ad 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -326,6 +326,8 @@ bool visit_check_struct(Visitor *v, Error **errp);
  */
 void visit_end_struct(Visitor *v, void **obj);
 
+/* TODO */
+const char *visit_next_struct_member(Visitor *v);
 
 /*** Visiting lists ***/
 
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 6c13510a2b..82fb63e459 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -70,6 +70,12 @@ void visit_end_struct(Visitor *v, void **obj)
     v->end_struct(v, obj);
 }
 
+const char *visit_next_struct_member(Visitor *v)
+{
+    trace_visit_next_struct_member(v);
+    return v->next_struct_member(v);
+}
+
 bool visit_start_list(Visitor *v, const char *name, GenericList **list,
                       size_t size, Error **errp)
 {
diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c
index f0b4c7ca9d..a409b841af 100644
--- a/qapi/qobject-input-visitor.c
+++ b/qapi/qobject-input-visitor.c
@@ -310,6 +310,21 @@ static void qobject_input_end_struct(Visitor *v, void **obj)
     qobject_input_pop(v, obj);
 }
 
+static const char *qobject_input_next_struct_member(Visitor *v)
+{
+    QObjectInputVisitor *qiv = to_qiv(v);
+    StackObject *tos = QSLIST_FIRST(&qiv->stack);
+    GHashTableIter iter;
+    const char *key;
+
+    assert(qobject_type(tos->obj) == QTYPE_QDICT && tos->h);
+    g_hash_table_iter_init(&iter, tos->h);
+    if (g_hash_table_iter_next(&iter, (void **)&key, NULL)) {
+        return key;
+    }
+    return false;
+}
+
 
 static bool qobject_input_start_list(Visitor *v, const char *name,
                                      GenericList **list, size_t size,
@@ -700,6 +715,7 @@ static QObjectInputVisitor *qobject_input_visitor_base_new(QObject *obj)
     v->visitor.start_struct = qobject_input_start_struct;
     v->visitor.check_struct = qobject_input_check_struct;
     v->visitor.end_struct = qobject_input_end_struct;
+    v->visitor.next_struct_member = qobject_input_next_struct_member;
     v->visitor.start_list = qobject_input_start_list;
     v->visitor.next_list = qobject_input_next_list;
     v->visitor.check_list = qobject_input_check_list;
diff --git a/qapi/trace-events b/qapi/trace-events
index ab108c4f0e..2d91bb6ae3 100644
--- a/qapi/trace-events
+++ b/qapi/trace-events
@@ -7,6 +7,7 @@ visit_complete(void *v, void *opaque) "v=%p opaque=%p"
 visit_start_struct(void *v, const char *name, void *obj, size_t size) "v=%p name=%s obj=%p size=%zu"
 visit_check_struct(void *v) "v=%p"
 visit_end_struct(void *v, void *obj) "v=%p obj=%p"
+visit_next_struct_member(void *v) "v=%p"
 
 visit_start_list(void *v, const char *name, void *obj, size_t size) "v=%p name=%s obj=%p size=%zu"
 visit_next_list(void *v, void *tail, size_t size) "v=%p tail=%p size=%zu"
-- 
2.31.1