Re: [Qemu-devel] [PATCH 06/11] qobject: add QBool type

[Luiz Capitulino]

On Sat, 17 Oct 2009 08:36:06 -0500
Anthony Liguori <address@hidden> wrote:

> We currently model as json bool as an int.  This works fine on the server side
> but it means we cannot send back proper bools to the client.  Introducing a
> proper QBool type fixes that.

 As we talked earlier today, I think it would be simpler to have QTrue,
QFalse and QNull as static objects.

 We could define that static objects get reference counting disabled, I don't
see issues in doing that and we get a very simple model.

 The big patch bellow does it, only compiled tested though.

 If you don't agree with this model, we'll have to allocate QNull objects.
Actually I would suggest a destroy() method which always resets the
refcount to 1, but then it will have the concurrency problems on threaded
applications you've mentioned.

diff --git a/Makefile b/Makefile
index e78a3d0..1f985cf 100644
--- a/Makefile
+++ b/Makefile
@@ -125,7 +125,7 @@ obj-y += net.o net-queue.o
 obj-y += qemu-char.o aio.o net-checksum.o savevm.o
 obj-y += msmouse.o ps2.o
 obj-y += qdev.o qdev-properties.o
-obj-y += qint.o qstring.o qdict.o qlist.o qemu-config.o
+obj-y += qint.o qstring.o qdict.o qlist.o qmisc.o qemu-config.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
 obj-$(CONFIG_WIN32) += tap-win32.o
diff --git a/qmisc.c b/qmisc.c
new file mode 100644
index 0000000..38a87dd
--- /dev/null
+++ b/qmisc.c
@@ -0,0 +1,31 @@
+#include "qmisc.h"
+
+/*
+ * QBool
+ */
+
+static const QType qbool_type = {
+    .code = QTYPE_QBOOL,
+};
+
+const QBool QTrue = {
+     QOBJECT_INIT_STATIC(&qbool_type),
+     .value = 1
+};
+
+const QBool QFalse = {
+     QOBJECT_INIT_STATIC(&qbool_type),
+     .value = 0
+};
+
+/*
+ * QNull
+ */
+
+static const QType qnull_type = {
+    .code = QTYPE_QNULL,
+};
+
+const qnull QNull = {
+     QOBJECT_INIT_STATIC(&qnull_type),
+};
diff --git a/qmisc.h b/qmisc.h
new file mode 100644
index 0000000..dd9d5a9
--- /dev/null
+++ b/qmisc.h
@@ -0,0 +1,38 @@
+#ifndef QMISC_H
+#define QMISC_H
+
+#include "qobject.h"
+
+/*
+ * QBool
+ */
+
+typedef struct QBool {
+    QObject_HEAD;
+    int value;
+} QBool;
+
+extern const QBool QTrue;
+extern const QBool QFalse;
+
+static inline int qbool_is_true(const QBool *qbool)
+{
+    return qbool->value;
+}
+
+static inline int qbool_is_false(const QBool *qbool)
+{
+    return !qbool->value;
+}
+
+/*
+ * QNull
+ */
+
+typedef struct qnull {
+    QObject_HEAD;
+} qnull;
+
+extern const qnull QNull;
+
+#endif /* QMISC_H */
diff --git a/qobject.h b/qobject.h
index 4cc9287..81e4d94 100644
--- a/qobject.h
+++ b/qobject.h
@@ -41,6 +41,8 @@ typedef enum {
     QTYPE_QSTRING,
     QTYPE_QDICT,
     QTYPE_QLIST,
+    QTYPE_QBOOL,
+    QTYPE_QNULL,
 } qtype_code;
 
 struct QObject;
@@ -75,12 +77,15 @@ typedef struct QObject {
     obj->base.refcnt = 1;               \
     obj->base.type   = qtype_type
 
+#define QOBJECT_INIT_STATIC(qtype_type) \
+    .base.type = qtype_type
+
 /**
  * qobject_incref(): Increment QObject's reference count
  */
 static inline void qobject_incref(QObject *obj)
 {
-    if (obj)
+    if (obj && obj->type->destroy)
         obj->refcnt++;
 }
 
@@ -90,9 +95,7 @@ static inline void qobject_incref(QObject *obj)
  */
 static inline void qobject_decref(QObject *obj)
 {
-    if (obj && --obj->refcnt == 0) {
-        assert(obj->type != NULL);
-        assert(obj->type->destroy != NULL);
+    if (obj && obj->type->destroy && --obj->refcnt == 0) {
         obj->type->destroy(obj);
     }
 }