qapi: Make more of qobject_to()

This patch reworks some places which use either qobject_type() checks
plus qobject_to(), where the latter alone is sufficient, or NULL checks
plus qobject_type() checks where we can simply do a qobject_to() != NULL
check.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-6-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to() parameter ordering]
Signed-off-by: Eric Blake <eblake@redhat.com>

qapi/qobject-input-visitor.c

@@ -339,7 +339,7 @@ static GenericList *qobject_input_next_list(Visitor *v, GenericList *tail,
     QObjectInputVisitor *qiv = to_qiv(v);
     StackObject *tos = QSLIST_FIRST(&qiv->stack);
 
-    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
+    assert(tos && qobject_to(QList, tos->obj));
 
     if (!tos->entry) {
         return NULL;
@@ -353,7 +353,7 @@ static void qobject_input_check_list(Visitor *v, Error **errp)
     QObjectInputVisitor *qiv = to_qiv(v);
     StackObject *tos = QSLIST_FIRST(&qiv->stack);
 
-    assert(tos && tos->obj && qobject_type(tos->obj) == QTYPE_QLIST);
+    assert(tos && qobject_to(QList, tos->obj));
 
     if (tos->entry) {
         error_setg(errp, "Only %u list elements expected in %s",

qobject/json-parser.c

@@ -276,7 +276,8 @@ static void parser_context_free(JSONParserContext *ctxt)
  */
 static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
 {
-    QObject *key = NULL, *value;
+    QObject *value;
+    QString *key = NULL;
     JSONToken *peek, *token;
 
     peek = parser_context_peek_token(ctxt);
@@ -285,8 +286,8 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
         goto out;
     }
 
-    key = parse_value(ctxt, ap);
-    if (!key || qobject_type(key) != QTYPE_QSTRING) {
+    key = qobject_to(QString, parse_value(ctxt, ap));
+    if (!key) {
         parse_error(ctxt, peek, "key is not a string in object");
         goto out;
     }
@@ -308,14 +309,14 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
         goto out;
     }
 
-    qdict_put_obj(dict, qstring_get_str(qobject_to(QString, key)), value);
+    qdict_put_obj(dict, qstring_get_str(key), value);
 
-    qobject_decref(key);
+    QDECREF(key);
 
     return 0;
 
 out:
-    qobject_decref(key);
+    QDECREF(key);
 
     return -1;
 }

qobject/qdict.c

@@ -882,18 +882,20 @@ QObject *qdict_crumple(const QDict *src, Error **errp)
 
         child = qdict_get(two_level, prefix);
         if (suffix) {
-            if (child) {
-                if (qobject_type(child) != QTYPE_QDICT) {
+            QDict *child_dict = qobject_to(QDict, child);
+            if (!child_dict) {
+                if (child) {
                     error_setg(errp, "Key %s prefix is already set as a scalar",
                                prefix);
                     goto error;
                 }
-            } else {
-                child = QOBJECT(qdict_new());
-                qdict_put_obj(two_level, prefix, child);
+
+                child_dict = qdict_new();
+                qdict_put_obj(two_level, prefix, QOBJECT(child_dict));
             }
+
             qobject_incref(ent->value);
-            qdict_put_obj(qobject_to(QDict, child), suffix, ent->value);
+            qdict_put_obj(child_dict, suffix, ent->value);
         } else {
             if (child) {
                 error_setg(errp, "Key %s prefix is already set as a dict",
@@ -913,9 +915,9 @@ QObject *qdict_crumple(const QDict *src, Error **errp)
     multi_level = qdict_new();
     for (ent = qdict_first(two_level); ent != NULL;
          ent = qdict_next(two_level, ent)) {
-
-        if (qobject_type(ent->value) == QTYPE_QDICT) {
-            child = qdict_crumple(qobject_to(QDict, ent->value), errp);
+        QDict *dict = qobject_to(QDict, ent->value);
+        if (dict) {
+            child = qdict_crumple(dict, errp);
             if (!child) {
                 goto error;
             }