qapi: Add new visit_complete() function
Making each output visitor provide its own output collection
function was the only remaining reason for exposing visitor
sub-types to the rest of the code base. Add a polymorphic
visit_complete() function which is a no-op for input visitors,
and which populates an opaque pointer for output visitors. For
maximum type-safety, also add a parameter to the output visitor
constructors with a type-correct version of the output pointer,
and assert that the two uses match.
This approach was considered superior to either passing the
output parameter only during construction (action at a distance
during visit_free() feels awkward) or only during visit_complete()
(defeating type safety makes it easier to use incorrectly).
Most callers were function-local, and therefore a mechanical
conversion; the testsuite was a bit trickier, but the previous
cleanup patch minimized the churn here.
The visit_complete() function may be called at most once; doing
so lets us use transfer semantics rather than duplication or
ref-count semantics to get the just-built output back to the
caller, even though it means our behavior is not idempotent.
Generated code is simplified as follows for events:
|@@ -26,7 +26,7 @@ void qapi_event_send_acpi_device_ost(ACP
| QDict *qmp;
| Error *err = NULL;
| QMPEventFuncEmit emit;
|- QmpOutputVisitor *qov;
|+ QObject *obj;
| Visitor *v;
| q_obj_ACPI_DEVICE_OST_arg param = {
| info
|@@ -39,8 +39,7 @@ void qapi_event_send_acpi_device_ost(ACP
|
| qmp = qmp_event_build_dict("ACPI_DEVICE_OST");
|
|- qov = qmp_output_visitor_new();
|- v = qmp_output_get_visitor(qov);
|+ v = qmp_output_visitor_new(&obj);
|
| visit_start_struct(v, "ACPI_DEVICE_OST", NULL, 0, &err);
| if (err) {
|@@ -55,7 +54,8 @@ void qapi_event_send_acpi_device_ost(ACP
| goto out;
| }
|
|- qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
|+ visit_complete(v, &obj);
|+ qdict_put_obj(qmp, "data", obj);
| emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err);
and for commands:
| {
| Error *err = NULL;
|- QmpOutputVisitor *qov = qmp_output_visitor_new();
| Visitor *v;
|
|- v = qmp_output_get_visitor(qov);
|+ v = qmp_output_visitor_new(ret_out);
| visit_type_AddfdInfo(v, "unused", &ret_in, &err);
|- if (err) {
|- goto out;
|+ if (!err) {
|+ visit_complete(v, ret_out);
| }
|- *ret_out = qmp_output_get_qobject(qov);
|-
|-out:
| error_propagate(errp, err);
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/qom/object.c b/qom/object.c
index 2407b66..8166b7d 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1221,7 +1221,6 @@
const char *typename, Error **errp)
{
Error *err = NULL;
- StringOutputVisitor *sov;
Visitor *v;
char *str;
int ret;
@@ -1241,15 +1240,14 @@
enumprop = prop->opaque;
- sov = string_output_visitor_new(false);
- v = string_output_get_visitor(sov);
+ v = string_output_visitor_new(false, &str);
object_property_get(obj, v, name, &err);
if (err) {
error_propagate(errp, err);
visit_free(v);
return 0;
}
- str = string_output_get_string(sov);
+ visit_complete(v, &str);
visit_free(v);
v = string_input_visitor_new(str);
visit_type_enum(v, name, &ret, enumprop->strings, errp);
@@ -1264,25 +1262,23 @@
uint16List **list, Error **errp)
{
Error *err = NULL;
- StringOutputVisitor *ov;
Visitor *v;
char *str;
- ov = string_output_visitor_new(false);
- object_property_get(obj, string_output_get_visitor(ov),
- name, &err);
+ v = string_output_visitor_new(false, &str);
+ object_property_get(obj, v, name, &err);
if (err) {
error_propagate(errp, err);
goto out;
}
- str = string_output_get_string(ov);
+ visit_complete(v, &str);
+ visit_free(v);
v = string_input_visitor_new(str);
visit_type_uint16List(v, NULL, list, errp);
g_free(str);
- visit_free(v);
out:
- visit_free(string_output_get_visitor(ov));
+ visit_free(v);
}
void object_property_parse(Object *obj, const char *string,
@@ -1296,21 +1292,21 @@
char *object_property_print(Object *obj, const char *name, bool human,
Error **errp)
{
- StringOutputVisitor *sov;
+ Visitor *v;
char *string = NULL;
Error *local_err = NULL;
- sov = string_output_visitor_new(human);
- object_property_get(obj, string_output_get_visitor(sov), name, &local_err);
+ v = string_output_visitor_new(human, &string);
+ object_property_get(obj, v, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto out;
}
- string = string_output_get_string(sov);
+ visit_complete(v, &string);
out:
- visit_free(string_output_get_visitor(sov));
+ visit_free(v);
return string;
}