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/string-output-visitor.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) (limited to 'qapi/string-output-visitor.c') diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c index 78aab876e3..94ac8211d1 100644 --- a/qapi/string-output-visitor.c +++ b/qapi/string-output-visitor.c @@ -58,6 +58,7 @@ struct StringOutputVisitor Visitor visitor; bool human; GString *string; + char **result; ListMode list_mode; union { int64_t s; @@ -305,16 +306,13 @@ static void end_list(Visitor *v, void **obj) sov->list_mode = LM_NONE; } -char *string_output_get_string(StringOutputVisitor *sov) +static void string_output_complete(Visitor *v, void *opaque) { - char *string = g_string_free(sov->string, false); - sov->string = NULL; - return string; -} + StringOutputVisitor *sov = to_sov(v); -Visitor *string_output_get_visitor(StringOutputVisitor *sov) -{ - return &sov->visitor; + assert(opaque == sov->result); + *sov->result = g_string_free(sov->string, false); + sov->string = NULL; } static void free_range(void *range, void *dummy) @@ -335,7 +333,7 @@ static void string_output_free(Visitor *v) g_free(sov); } -StringOutputVisitor *string_output_visitor_new(bool human) +Visitor *string_output_visitor_new(bool human, char **result) { StringOutputVisitor *v; @@ -343,6 +341,9 @@ StringOutputVisitor *string_output_visitor_new(bool human) v->string = g_string_new(NULL); v->human = human; + v->result = result; + *result = NULL; + v->visitor.type = VISITOR_OUTPUT; v->visitor.type_int64 = print_type_int64; v->visitor.type_uint64 = print_type_uint64; @@ -353,7 +354,8 @@ StringOutputVisitor *string_output_visitor_new(bool human) v->visitor.start_list = start_list; v->visitor.next_list = next_list; v->visitor.end_list = end_list; + v->visitor.complete = string_output_complete; v->visitor.free = string_output_free; - return v; + return &v->visitor; } -- cgit 1.4.1