qemu/qapi
Eric Blake 3b098d5697 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>
2016-07-06 10:52:04 +02:00
..
block-core.json qmp: add monitor command to add/remove a child 2016-05-12 15:33:23 +02:00
block.json qmp event: Refactor QUORUM_REPORT_BAD 2016-03-14 16:46:43 +01:00
common.json kvm: add support for -machine kernel_irqchip=split 2015-12-17 17:15:40 +01:00
crypto.json crypto: implement sha224, sha384, sha512 and ripemd160 hashes 2016-07-04 15:52:36 +01:00
event.json qmp event: Refactor QUORUM_REPORT_BAD 2016-03-14 16:46:43 +01:00
introspect.json qapi: Use anonymous bases in QMP flat unions 2016-03-18 10:29:26 +01:00
Makefile.objs rename parse_enum_option to qapi_enum_parse and make it public 2014-09-08 11:12:43 +01:00
opts-visitor.c opts-visitor: Favor new visit_free() function 2016-07-06 10:52:04 +02:00
qapi-dealloc-visitor.c qapi: Add new visit_free() function 2016-07-06 10:52:04 +02:00
qapi-util.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
qapi-visit-core.c qapi: Add new visit_complete() function 2016-07-06 10:52:04 +02:00
qmp-dispatch.c qapi: Improve use of qmp/types.h 2016-07-06 10:52:03 +02:00
qmp-event.c qapi: Clean up includes 2016-02-04 17:41:30 +00:00
qmp-input-visitor.c qmp-input-visitor: Favor new visit_free() function 2016-07-06 10:52:04 +02:00
qmp-output-visitor.c qapi: Add new visit_complete() function 2016-07-06 10:52:04 +02:00
qmp-registry.c all: Remove unnecessary glib.h includes 2016-06-07 18:19:24 +03:00
rocker.json qmp/hmp: add rocker device support 2015-06-12 13:42:17 +01:00
string-input-visitor.c string-input-visitor: Favor new visit_free() function 2016-07-06 10:52:04 +02:00
string-output-visitor.c qapi: Add new visit_complete() function 2016-07-06 10:52:04 +02:00
trace.json qapi: Use 'struct' instead of 'type' in schema 2015-05-05 18:39:01 +02:00