3b098d5697
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>
116 lines
3.7 KiB
C
116 lines
3.7 KiB
C
/*
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* Core Definitions for QAPI Visitor implementations
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*
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* Copyright (C) 2012-2016 Red Hat, Inc.
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*
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* Author: Paolo Bonizni <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#ifndef QAPI_VISITOR_IMPL_H
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#define QAPI_VISITOR_IMPL_H
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#include "qapi/visitor.h"
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/*
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* This file describes the callback interface for implementing a QAPI
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* visitor. For the client interface, see visitor.h. When
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* implementing the callbacks, it is easiest to declare a struct with
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* 'Visitor visitor;' as the first member. A callback's contract
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* matches the corresponding public functions' contract unless stated
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* otherwise. In the comments below, some callbacks are marked "must
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* be set for $TYPE visits to work"; if a visitor implementation omits
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* that callback, it should also document that it is only useful for a
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* subset of QAPI.
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*/
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/*
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* There are three classes of visitors; setting the class determines
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* how QAPI enums are visited, as well as what additional restrictions
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* can be asserted.
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*/
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typedef enum VisitorType {
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VISITOR_INPUT,
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VISITOR_OUTPUT,
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VISITOR_DEALLOC,
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} VisitorType;
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struct Visitor
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{
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/* Must be set to visit structs */
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void (*start_struct)(Visitor *v, const char *name, void **obj,
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size_t size, Error **errp);
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/* Optional; intended for input visitors */
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void (*check_struct)(Visitor *v, Error **errp);
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/* Must be set to visit structs */
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void (*end_struct)(Visitor *v, void **obj);
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/* Must be set; implementations may require @list to be non-null,
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* but must document it. */
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void (*start_list)(Visitor *v, const char *name, GenericList **list,
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size_t size, Error **errp);
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/* Must be set */
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GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
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/* Must be set */
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void (*end_list)(Visitor *v, void **list);
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/* Must be set by input and dealloc visitors to visit alternates;
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* optional for output visitors. */
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void (*start_alternate)(Visitor *v, const char *name,
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GenericAlternate **obj, size_t size,
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bool promote_int, Error **errp);
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/* Optional, needed for dealloc visitor */
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void (*end_alternate)(Visitor *v, void **obj);
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/* Must be set */
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void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
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Error **errp);
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/* Must be set */
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void (*type_uint64)(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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/* Optional; fallback is type_uint64() */
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void (*type_size)(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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/* Must be set */
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void (*type_bool)(Visitor *v, const char *name, bool *obj, Error **errp);
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/* Must be set */
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void (*type_str)(Visitor *v, const char *name, char **obj, Error **errp);
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/* Must be set to visit numbers */
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void (*type_number)(Visitor *v, const char *name, double *obj,
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Error **errp);
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/* Must be set to visit arbitrary QTypes */
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void (*type_any)(Visitor *v, const char *name, QObject **obj,
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Error **errp);
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/* Must be set to visit explicit null values. */
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void (*type_null)(Visitor *v, const char *name, Error **errp);
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/* Must be set for input visitors, optional otherwise. The core
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* takes care of the return type in the public interface. */
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void (*optional)(Visitor *v, const char *name, bool *present);
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/* Must be set */
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VisitorType type;
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/* Must be set for output visitors, optional otherwise. */
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void (*complete)(Visitor *v, void *opaque);
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/* Must be set */
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void (*free)(Visitor *v);
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};
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#endif
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