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/hmp.c b/hmp.c
index 559cad1..0cf5baa 100644
--- a/hmp.c
+++ b/hmp.c
@@ -1983,15 +1983,14 @@
Error *err = NULL;
MemdevList *memdev_list = qmp_query_memdev(&err);
MemdevList *m = memdev_list;
- StringOutputVisitor *ov;
+ Visitor *v;
char *str;
int i = 0;
while (m) {
- ov = string_output_visitor_new(false);
- visit_type_uint16List(string_output_get_visitor(ov), NULL,
- &m->value->host_nodes, NULL);
+ v = string_output_visitor_new(false, &str);
+ visit_type_uint16List(v, NULL, &m->value->host_nodes, NULL);
monitor_printf(mon, "memory backend: %d\n", i);
monitor_printf(mon, " size: %" PRId64 "\n", m->value->size);
monitor_printf(mon, " merge: %s\n",
@@ -2002,11 +2001,11 @@
m->value->prealloc ? "true" : "false");
monitor_printf(mon, " policy: %s\n",
HostMemPolicy_lookup[m->value->policy]);
- str = string_output_get_string(ov);
+ visit_complete(v, &str);
monitor_printf(mon, " host nodes: %s\n", str);
g_free(str);
- visit_free(string_output_get_visitor(ov));
+ visit_free(v);
m = m->next;
i++;
}