qom: add generic string parsing/printing

Add generic property accessors that take a string and parse it
appropriately for the property type.  All the magic here is done
by the new string-based visitors.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/object.h

@@ -729,6 +729,30 @@ int64_t object_property_get_int(Object *obj, const char *name,
 void object_property_set(Object *obj, struct Visitor *v, const char *name,
                          struct Error **errp);
 
+/**
+ * object_property_parse:
+ * @obj: the object
+ * @string: the string that will be used to parse the property value.
+ * @name: the name of the property
+ * @errp: returns an error if this function fails
+ *
+ * Parses a string and writes the result into a property of an object.
+ */
+void object_property_parse(Object *obj, const char *string,
+                           const char *name, struct Error **errp);
+
+/**
+ * object_property_print:
+ * @obj: the object
+ * @name: the name of the property
+ * @errp: returns an error if this function fails
+ *
+ * Returns a string representation of the value of the property.  The
+ * caller shall free the string.
+ */
+char *object_property_print(Object *obj, const char *name,
+                            struct Error **errp);
+
 /**
  * object_property_get_type:
  * @obj: the object

qom/object.c

@@ -13,6 +13,8 @@
 #include "qemu/object.h"
 #include "qemu-common.h"
 #include "qapi/qapi-visit-core.h"
+#include "qapi/string-input-visitor.h"
+#include "qapi/string-output-visitor.h"
 
 /* TODO: replace QObject with a simpler visitor to avoid a dependency
  * of the QOM core on QObject?  */
@@ -782,6 +784,29 @@ int64_t object_property_get_int(Object *obj, const char *name,
     return retval;
 }
 
+void object_property_parse(Object *obj, const char *string,
+                           const char *name, Error **errp)
+{
+    StringInputVisitor *mi;
+    mi = string_input_visitor_new(string);
+    object_property_set(obj, string_input_get_visitor(mi), name, errp);
+
+    string_input_visitor_cleanup(mi);
+}
+
+char *object_property_print(Object *obj, const char *name,
+                            Error **errp)
+{
+    StringOutputVisitor *mo;
+    char *string;
+
+    mo = string_output_visitor_new();
+    object_property_get(obj, string_output_get_visitor(mo), name, NULL);
+    string = string_output_get_string(mo);
+    string_output_visitor_cleanup(mo);
+    return string;
+}
+
 const char *object_property_get_type(Object *obj, const char *name, Error **errp)
 {
     ObjectProperty *prop = object_property_find(obj, name);