Add qemuMonitorJSONGetObjectProperty() method for QMP qom-get command

Add a new qemuMonitorJSONGetObjectProperty() method to support invocation
of the 'qom-get' JSON monitor command with a provided path, property, and
expected data type return. The qemuMonitorJSONObjectProperty is similar to
virTypedParameter; however, a future patch will extend it a bit to include
a void pointer to balloon driver statistic data.

NOTE: The ObjectProperty structures and API are added only for the
      purpose of the qemumonitorjsontest

The provided test will execute a qom-get on "/machine/i440fx" which will
return a property "realized".

src/qemu/qemu_monitor_json.c

@@ -4605,6 +4605,92 @@ void qemuMonitorJSONListPathFree(qemuMonitorJSONListPathPtr paths)
     VIR_FREE(paths);
 }
 
+
+int qemuMonitorJSONGetObjectProperty(qemuMonitorPtr mon,
+                                     const char *path,
+                                     const char *property,
+                                     qemuMonitorJSONObjectPropertyPtr prop)
+{
+    int ret;
+    virJSONValuePtr cmd;
+    virJSONValuePtr reply = NULL;
+    virJSONValuePtr data;
+    const char *tmp;
+
+    if (!(cmd = qemuMonitorJSONMakeCommand("qom-get",
+                                           "s:path", path,
+                                           "s:property", property,
+                                           NULL)))
+        return -1;
+
+    ret = qemuMonitorJSONCommand(mon, cmd, &reply);
+
+    if (ret == 0)
+        ret = qemuMonitorJSONCheckError(cmd, reply);
+
+    if (ret < 0)
+        goto cleanup;
+
+    ret = -1;
+
+    if (!(data = virJSONValueObjectGet(reply, "return"))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("qom-get reply was missing return data"));
+        goto cleanup;
+    }
+
+    switch ((qemuMonitorJSONObjectPropertyType) prop->type) {
+    /* Simple cases of boolean, int, long, uint, ulong, double, and string
+     * will receive return value as part of {"return": xxx} statement
+     */
+    case QEMU_MONITOR_OBJECT_PROPERTY_BOOLEAN:
+        ret = virJSONValueGetBoolean(data, &prop->val.b);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_INT:
+        ret = virJSONValueGetNumberInt(data, &prop->val.iv);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_LONG:
+        ret = virJSONValueGetNumberLong(data, &prop->val.l);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_UINT:
+        ret = virJSONValueGetNumberUint(data, &prop->val.ui);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_ULONG:
+        ret = virJSONValueGetNumberUlong(data, &prop->val.ul);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_DOUBLE:
+        ret = virJSONValueGetNumberDouble(data, &prop->val.d);
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_STRING:
+        tmp = virJSONValueGetString(data);
+        if (tmp && VIR_STRDUP(prop->val.str, tmp) < 0)
+            goto cleanup;
+        if (tmp)
+            ret = 0;
+        break;
+    case QEMU_MONITOR_OBJECT_PROPERTY_LAST:
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("qom-get invalid object property type %d"),
+                       prop->type);
+        goto cleanup;
+        break;
+    }
+
+    if (ret == -1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("qom-get reply was missing return data"));
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    virJSONValueFree(cmd);
+    virJSONValueFree(reply);
+
+    return ret;
+}
+
+
 int qemuMonitorJSONGetObjectProps(qemuMonitorPtr mon,
                                   const char *type,
                                   char ***props)

src/qemu/qemu_monitor_json.h

@@ -349,6 +349,41 @@ int qemuMonitorJSONGetObjectListPaths(qemuMonitorPtr mon,
 
 void qemuMonitorJSONListPathFree(qemuMonitorJSONListPathPtr paths);
 
+/* ObjectProperty structures and API are public only for qemumonitorjsontest */
+/* Flags for the 'type' field in _qemuMonitorJSONObjectProperty */
+typedef enum {
+    QEMU_MONITOR_OBJECT_PROPERTY_BOOLEAN=1,
+    QEMU_MONITOR_OBJECT_PROPERTY_INT,
+    QEMU_MONITOR_OBJECT_PROPERTY_LONG,
+    QEMU_MONITOR_OBJECT_PROPERTY_UINT,
+    QEMU_MONITOR_OBJECT_PROPERTY_ULONG,
+    QEMU_MONITOR_OBJECT_PROPERTY_DOUBLE,
+    QEMU_MONITOR_OBJECT_PROPERTY_STRING,
+
+    QEMU_MONITOR_OBJECT_PROPERTY_LAST
+} qemuMonitorJSONObjectPropertyType;
+
+typedef struct _qemuMonitorJSONObjectProperty qemuMonitorJSONObjectProperty;
+typedef qemuMonitorJSONObjectProperty *qemuMonitorJSONObjectPropertyPtr;
+struct _qemuMonitorJSONObjectProperty {
+    int type;    /* qemuMonitorJSONObjectPropertyType */
+    union {
+        bool b;
+        int iv;
+        long long l;
+        unsigned int ui;
+        unsigned long long ul;
+        double d;
+        char *str;
+    } val;
+};
+
+int qemuMonitorJSONGetObjectProperty(qemuMonitorPtr mon,
+                                     const char *path,
+                                     const char *property,
+                                     qemuMonitorJSONObjectPropertyPtr prop)
+    ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3) ATTRIBUTE_NONNULL(4);
+
 int qemuMonitorJSONGetObjectProps(qemuMonitorPtr mon,
                                   const char *type,
                                   char ***props)

tests/qemumonitorjsontest.c

@@ -777,6 +777,53 @@ cleanup:
 }
 
 
+/*
+ * This test will use a path to /machine/i440fx which should exist in order
+ * to ensure that the qom-get property fetch works properly. The following
+ * is the execution and expected return:
+ *
+ *
+ *  { "execute": "qom-get","arguments": \
+ *      { "path": "/machine/i440fx","property": "realized"}}
+ *   {"return": true}
+ */
+static int
+testQemuMonitorJSONGetObjectProperty(const void *data)
+{
+    const virDomainXMLOptionPtr xmlopt = (virDomainXMLOptionPtr)data;
+    qemuMonitorTestPtr test = qemuMonitorTestNew(true, xmlopt);
+    int ret = -1;
+    qemuMonitorJSONObjectProperty prop;
+
+    if (!test)
+        return -1;
+
+    if (qemuMonitorTestAddItem(test, "qom-get",
+                               "{ \"return\": true }") < 0)
+        goto cleanup;
+
+    /* Present with path and property */
+    memset(&prop, 0, sizeof(qemuMonitorJSONObjectProperty));
+    prop.type = QEMU_MONITOR_OBJECT_PROPERTY_BOOLEAN;
+    if (qemuMonitorJSONGetObjectProperty(qemuMonitorTestGetMonitor(test),
+                                         "/machine/i440fx",
+                                         "realized",
+                                         &prop) < 0)
+        goto cleanup;
+
+    if (!prop.val.b) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       "expected true, but false returned");
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    qemuMonitorTestFree(test);
+    return ret;
+}
+
+
 static int
 mymain(void)
 {
@@ -808,6 +855,7 @@ mymain(void)
     DO_TEST(AttachChardev);
     DO_TEST(DetachChardev);
     DO_TEST(GetListPaths);
+    DO_TEST(GetObjectProperty);
 
     virObjectUnref(xmlopt);