unicorn/qemu/qapi/qmp-output-visitor.c
Eric Blake 85af4b2030
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);

Backports commit 3b098d56979d2f7fd707c5be85555d114353a28d from qemu
2018-02-25 01:20:03 -05:00

259 lines
7.3 KiB
C

/*
* Core Definitions for QAPI/QMP Command Registry
*
* Copyright IBM, Corp. 2011
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp-output-visitor.h"
#include "qapi/visitor-impl.h"
#include "qemu/queue.h"
#include "qemu-common.h"
#include "qapi/qmp/types.h"
#include "qapi/qmp/qerror.h"
typedef struct QStackEntry
{
QObject *value;
void *qapi; /* sanity check that caller uses same pointer */
QTAILQ_ENTRY(QStackEntry) node;
} QStackEntry;
typedef QTAILQ_HEAD(QStack, QStackEntry) QStack;
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) \
qmp_output_add_obj(qov, name, QOBJECT(value))
#define qmp_output_push(qov, value, qapi) \
qmp_output_push_obj(qov, QOBJECT(value), qapi)
static QmpOutputVisitor *to_qov(Visitor *v)
{
return container_of(v, QmpOutputVisitor, visitor);
}
/* Push @value onto the stack of current QObjects being built */
static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value,
void *qapi)
{
QStackEntry *e = g_malloc0(sizeof(*e));
assert(qov->root);
assert(value);
e->value = value;
e->qapi = qapi;
QTAILQ_INSERT_HEAD(&qov->stack, e, node);
}
/* Pop a value off the stack of QObjects being built, and return it. */
static QObject *qmp_output_pop(QmpOutputVisitor *qov, void *qapi)
{
QStackEntry *e = QTAILQ_FIRST(&qov->stack);
QObject *value;
assert(e);
assert(e->qapi == qapi);
QTAILQ_REMOVE(&qov->stack, e, node);
value = e->value;
assert(value);
g_free(e);
return value;
}
/* Add @value to the current QObject being built.
* If the stack is visiting a dictionary or list, @value is now owned
* by that container. Otherwise, @value is now the root. */
static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name,
QObject *value)
{
QStackEntry *e = QTAILQ_FIRST(&qov->stack);
QObject *cur = e ? e->value : NULL;
if (!cur) {
/* Don't allow reuse of visitor on more than one root */
assert(!qov->root);
qov->root = value;
} else {
switch (qobject_type(cur)) {
case QTYPE_QDICT:
assert(name);
qdict_put_obj(qobject_to_qdict(cur), name, value);
break;
case QTYPE_QLIST:
assert(!name);
qlist_append_obj(qobject_to_qlist(cur), value);
break;
default:
g_assert_not_reached();
}
}
}
static void qmp_output_start_struct(Visitor *v, const char *name, void **obj,
size_t unused, Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
QDict *dict = qdict_new();
qmp_output_add(qov, name, dict);
qmp_output_push(qov, dict, obj);
}
static void qmp_output_end_struct(Visitor *v, void **obj)
{
QmpOutputVisitor *qov = to_qov(v);
QObject *value = qmp_output_pop(qov, obj);
assert(qobject_type(value) == QTYPE_QDICT);
}
static void qmp_output_start_list(Visitor *v, const char *name,
GenericList **listp, size_t size,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
QList *list = qlist_new();
qmp_output_add(qov, name, list);
qmp_output_push(qov, list, listp);
}
static GenericList *qmp_output_next_list(Visitor *v, GenericList *tail,
size_t size)
{
return tail->next;
}
static void qmp_output_end_list(Visitor *v, void **obj)
{
QmpOutputVisitor *qov = to_qov(v);
QObject *value = qmp_output_pop(qov, obj);
assert(qobject_type(value) == QTYPE_QLIST);
}
static void qmp_output_type_int64(Visitor *v, const char *name, int64_t *obj,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_add(qov, name, qint_from_int(*obj));
}
static void qmp_output_type_uint64(Visitor *v, const char *name, uint64_t *obj,
Error **errp)
{
/* FIXME: QMP outputs values larger than INT64_MAX as negative */
QmpOutputVisitor *qov = to_qov(v);
qmp_output_add(qov, name, qint_from_int(*obj));
}
static void qmp_output_type_bool(Visitor *v, const char *name, bool *obj,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_add(qov, name, qbool_from_bool(*obj));
}
static void qmp_output_type_str(Visitor *v, const char *name, char **obj,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
if (*obj) {
qmp_output_add(qov, name, qstring_from_str(*obj));
} else {
qmp_output_add(qov, name, qstring_from_str(""));
}
}
static void qmp_output_type_number(Visitor *v, const char *name, double *obj,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_add(qov, name, qfloat_from_double(*obj));
}
static void qmp_output_type_any(Visitor *v, const char *name, QObject **obj,
Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qobject_incref(*obj);
qmp_output_add_obj(qov, name, *obj);
}
static void qmp_output_type_null(Visitor *v, const char *name, Error **errp)
{
QmpOutputVisitor *qov = to_qov(v);
qmp_output_add_obj(qov, name, qnull());
}
/* 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. */
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);
*qov->result = qov->root;
qov->result = NULL;
}
static void qmp_output_free(Visitor *v)
{
QmpOutputVisitor *qov = to_qov(v);
QStackEntry *e, *tmp;
QTAILQ_FOREACH_SAFE(e, &qov->stack, node, tmp) {
QTAILQ_REMOVE(&qov->stack, e, node);
g_free(e);
}
qobject_decref(qov->root);
g_free(qov);
}
Visitor *qmp_output_visitor_new(QObject **result)
{
QmpOutputVisitor *v;
v = g_malloc0(sizeof(*v));
v->visitor.type = VISITOR_OUTPUT;
v->visitor.start_struct = qmp_output_start_struct;
v->visitor.end_struct = qmp_output_end_struct;
v->visitor.start_list = qmp_output_start_list;
v->visitor.next_list = qmp_output_next_list;
v->visitor.end_list = qmp_output_end_list;
v->visitor.type_int64 = qmp_output_type_int64;
v->visitor.type_uint64 = qmp_output_type_uint64;
v->visitor.type_bool = qmp_output_type_bool;
v->visitor.type_str = qmp_output_type_str;
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->visitor;
}