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 --- qapi/qmp-output-visitor.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) (limited to 'qapi/qmp-output-visitor.c') diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c index 3d12623cf9..0452056d42 100644 --- a/qapi/qmp-output-visitor.c +++ b/qapi/qmp-output-visitor.c @@ -33,6 +33,7 @@ struct QmpOutputVisitor Visitor visitor; QStack stack; /* Stack of containers that haven't yet been finished */ QObject *root; /* Root of the output visit */ + QObject **result; /* User's storage location for result */ }; #define qmp_output_add(qov, name, value) \ @@ -200,18 +201,17 @@ static void qmp_output_type_null(Visitor *v, const char *name, Error **errp) /* Finish building, and return the root object. * The root object is never null. The caller becomes the object's * owner, and should use qobject_decref() when done with it. */ -QObject *qmp_output_get_qobject(QmpOutputVisitor *qov) +static void qmp_output_complete(Visitor *v, void *opaque) { + QmpOutputVisitor *qov = to_qov(v); + /* A visit must have occurred, with each start paired with end. */ assert(qov->root && QTAILQ_EMPTY(&qov->stack)); + assert(opaque == qov->result); qobject_incref(qov->root); - return qov->root; -} - -Visitor *qmp_output_get_visitor(QmpOutputVisitor *v) -{ - return &v->visitor; + *qov->result = qov->root; + qov->result = NULL; } static void qmp_output_free(Visitor *v) @@ -228,7 +228,7 @@ static void qmp_output_free(Visitor *v) g_free(qov); } -QmpOutputVisitor *qmp_output_visitor_new(void) +Visitor *qmp_output_visitor_new(QObject **result) { QmpOutputVisitor *v; @@ -247,9 +247,12 @@ QmpOutputVisitor *qmp_output_visitor_new(void) v->visitor.type_number = qmp_output_type_number; v->visitor.type_any = qmp_output_type_any; v->visitor.type_null = qmp_output_type_null; + v->visitor.complete = qmp_output_complete; v->visitor.free = qmp_output_free; QTAILQ_INIT(&v->stack); + *result = NULL; + v->result = result; - return v; + return &v->visitor; } -- cgit 1.4.1