qapi: add QMP output visitor

Type of Visiter class that serves as the inverse of the input visitor:
it takes a series of native C types and uses their values to construct a
corresponding QObject. The command marshaling/dispatcher functions will
use this to convert the output of QMP functions into a QObject that can
be sent over the wire.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>

Makefile.objs

@@ -375,7 +375,7 @@ libcacard-y = cac.o event.o vcard.o vreader.o vcard_emul_nss.o vcard_emul_type.o
 ######################################################################
 # qapi
 
-qapi-nested-y = qapi-visit-core.o qmp-input-visitor.o
+qapi-nested-y = qapi-visit-core.o qmp-input-visitor.o qmp-output-visitor.o
 qapi-obj-y = $(addprefix qapi/, $(qapi-nested-y))
 
 vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)

qapi/qmp-output-visitor.c

@@ -0,0 +1,239 @@
+/*
+ * 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 "qmp-output-visitor.h"
+#include "qemu-queue.h"
+#include "qemu-common.h"
+#include "qemu-objects.h"
+#include "qerror.h"
+
+typedef struct QStackEntry
+{
+    QObject *value;
+    QTAILQ_ENTRY(QStackEntry) node;
+} QStackEntry;
+
+typedef QTAILQ_HEAD(QStack, QStackEntry) QStack;
+
+struct QmpOutputVisitor
+{
+    Visitor visitor;
+    QStack stack;
+};
+
+#define qmp_output_add(qov, name, value) \
+    qmp_output_add_obj(qov, name, QOBJECT(value))
+#define qmp_output_push(qov, value) qmp_output_push_obj(qov, QOBJECT(value))
+
+static QmpOutputVisitor *to_qov(Visitor *v)
+{
+    return container_of(v, QmpOutputVisitor, visitor);
+}
+
+static void qmp_output_push_obj(QmpOutputVisitor *qov, QObject *value)
+{
+    QStackEntry *e = qemu_mallocz(sizeof(*e));
+
+    e->value = value;
+    QTAILQ_INSERT_HEAD(&qov->stack, e, node);
+}
+
+static QObject *qmp_output_pop(QmpOutputVisitor *qov)
+{
+    QStackEntry *e = QTAILQ_FIRST(&qov->stack);
+    QObject *value;
+    QTAILQ_REMOVE(&qov->stack, e, node);
+    value = e->value;
+    qemu_free(e);
+    return value;
+}
+
+static QObject *qmp_output_first(QmpOutputVisitor *qov)
+{
+    QStackEntry *e = QTAILQ_LAST(&qov->stack, QStack);
+    return e->value;
+}
+
+static QObject *qmp_output_last(QmpOutputVisitor *qov)
+{
+    QStackEntry *e = QTAILQ_FIRST(&qov->stack);
+    return e->value;
+}
+
+static void qmp_output_add_obj(QmpOutputVisitor *qov, const char *name,
+                               QObject *value)
+{
+    QObject *cur;
+
+    if (QTAILQ_EMPTY(&qov->stack)) {
+        qmp_output_push_obj(qov, value);
+        return;
+    }
+
+    cur = qmp_output_last(qov);
+
+    switch (qobject_type(cur)) {
+    case QTYPE_QDICT:
+        qdict_put_obj(qobject_to_qdict(cur), name, value);
+        break;
+    case QTYPE_QLIST:
+        qlist_append_obj(qobject_to_qlist(cur), value);
+        break;
+    default:
+        qobject_decref(qmp_output_pop(qov));
+        qmp_output_push_obj(qov, value);
+        break;
+    }
+}
+
+static void qmp_output_start_struct(Visitor *v, void **obj, const char *kind,
+                                    const char *name, 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);
+}
+
+static void qmp_output_end_struct(Visitor *v, Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_pop(qov);
+}
+
+static void qmp_output_start_list(Visitor *v, const char *name, Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    QList *list = qlist_new();
+
+    qmp_output_add(qov, name, list);
+    qmp_output_push(qov, list);
+}
+
+static GenericList *qmp_output_next_list(Visitor *v, GenericList **list,
+                                         Error **errp)
+{
+    GenericList *retval = *list;
+    *list = retval->next;
+    return retval;
+}
+
+static void qmp_output_end_list(Visitor *v, Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_pop(qov);
+}
+
+static void qmp_output_type_int(Visitor *v, int64_t *obj, const char *name,
+                                Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_add(qov, name, qint_from_int(*obj));
+}
+
+static void qmp_output_type_bool(Visitor *v, bool *obj, const char *name,
+                                 Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_add(qov, name, qbool_from_int(*obj));
+}
+
+static void qmp_output_type_str(Visitor *v, char **obj, const char *name,
+                                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, double *obj, const char *name,
+                                   Error **errp)
+{
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_add(qov, name, qfloat_from_double(*obj));
+}
+
+static void qmp_output_type_enum(Visitor *v, int *obj, const char *strings[],
+                                 const char *kind, const char *name,
+                                 Error **errp)
+{
+    int i = 0;
+    int value = *obj;
+    char *enum_str;
+
+    assert(strings);
+    while (strings[i++] != NULL);
+    if (value >= i - 1) {
+        error_set(errp, QERR_INVALID_PARAMETER, name ? name : "null");
+        return;
+    }
+
+    enum_str = (char *)strings[value];
+    qmp_output_type_str(v, &enum_str, name, errp);
+}
+
+QObject *qmp_output_get_qobject(QmpOutputVisitor *qov)
+{
+    QObject *obj = qmp_output_first(qov);
+    if (obj) {
+        qobject_incref(obj);
+    }
+    return obj;
+}
+
+Visitor *qmp_output_get_visitor(QmpOutputVisitor *v)
+{
+    return &v->visitor;
+}
+
+void qmp_output_visitor_cleanup(QmpOutputVisitor *v)
+{
+    QStackEntry *e, *tmp;
+
+    QTAILQ_FOREACH_SAFE(e, &v->stack, node, tmp) {
+        QTAILQ_REMOVE(&v->stack, e, node);
+        if (e->value) {
+            qobject_decref(e->value);
+        }
+        qemu_free(e);
+    }
+
+    qemu_free(v);
+}
+
+QmpOutputVisitor *qmp_output_visitor_new(void)
+{
+    QmpOutputVisitor *v;
+
+    v = qemu_mallocz(sizeof(*v));
+
+    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_enum = qmp_output_type_enum;
+    v->visitor.type_int = qmp_output_type_int;
+    v->visitor.type_bool = qmp_output_type_bool;
+    v->visitor.type_str = qmp_output_type_str;
+    v->visitor.type_number = qmp_output_type_number;
+
+    QTAILQ_INIT(&v->stack);
+
+    return v;
+}

qapi/qmp-output-visitor.h

@@ -0,0 +1,28 @@
+/*
+ * Output Visitor
+ *
+ * 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.
+ *
+ */
+
+#ifndef QMP_OUTPUT_VISITOR_H
+#define QMP_OUTPUT_VISITOR_H
+
+#include "qapi-visit-core.h"
+#include "qobject.h"
+
+typedef struct QmpOutputVisitor QmpOutputVisitor;
+
+QmpOutputVisitor *qmp_output_visitor_new(void);
+void qmp_output_visitor_cleanup(QmpOutputVisitor *v);
+
+QObject *qmp_output_get_qobject(QmpOutputVisitor *v);
+Visitor *qmp_output_get_visitor(QmpOutputVisitor *v);
+
+#endif