From 3b098d56979d2f7fd707c5be85555d114353a28d Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 9 Jun 2016 10:48:43 -0600 Subject: 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 Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster Signed-off-by: Markus Armbruster --- blockdev.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'blockdev.c') diff --git a/blockdev.c b/blockdev.c index c05aaa6ea6..0f8065c4a5 100644 --- a/blockdev.c +++ b/blockdev.c @@ -3950,10 +3950,10 @@ out: void qmp_blockdev_add(BlockdevOptions *options, Error **errp) { - QmpOutputVisitor *ov = qmp_output_visitor_new(); BlockDriverState *bs; BlockBackend *blk = NULL; QObject *obj; + Visitor *v = qmp_output_visitor_new(&obj); QDict *qdict; Error *local_err = NULL; @@ -3972,14 +3972,13 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp) } } - visit_type_BlockdevOptions(qmp_output_get_visitor(ov), NULL, &options, - &local_err); + visit_type_BlockdevOptions(v, NULL, &options, &local_err); if (local_err) { error_propagate(errp, local_err); goto fail; } - obj = qmp_output_get_qobject(ov); + visit_complete(v, &obj); qdict = qobject_to_qdict(obj); qdict_flatten(qdict); @@ -4020,7 +4019,7 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp) } fail: - visit_free(qmp_output_get_visitor(ov)); + visit_free(v); } void qmp_x_blockdev_del(bool has_id, const char *id, -- cgit 1.4.1