Add GObject serialization support for JSON-GLib

This commit adds json-gobject.h and json_serialize_gobject() to
JSON-GLib, to serialize a GObject instance into a JSON data stream.

1 files changed, 169 insertions, 0 deletions

diff --git a/json-glib/json-gobject.c b/json-glib/json-gobject.c
new file mode 100644
index 0000000..ee652aa
--- /dev/null
+++ b/json-glib/json-gobject.c
@@ -0,0 +1,169 @@
+/* json-gobject.h - JSON GObject integration
+ * 
+ * This file is part of JSON-GLib
+ * Copyright (C) 2007  OpenedHand Ltd.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * Author:
+ *   Emmanuele Bassi  <ebassi@openedhand.com>
+ */
+
+/**
+ * SECTION:json-gobject
+ * @short_description: Serialize and deserialize GObjects
+ *
+ * JSON-GLib provides API for serializing and deserializing #GObject<!-- -->s
+ * to and from JSON data streams.
+ *
+ * The simplest form to serialize a #GObject class is calling the
+ * json_serialize_gobject() function on a #GObject instance: every
+ * property using a fundamental type (or a type that can be coherced
+ * into a fundamental type) will be converted into a JSON type.
+ */
+
+#include "config.h"
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "json-gobject.h"
+#include "json-parser.h"
+#include "json-generator.h"
+
+static JsonNode *
+json_serialize_pspec (GObject    *gobject,
+                      GParamSpec *pspec)
+{
+  JsonNode *retval = NULL;
+  GValue real_value = { 0, };
+  GValue value = { 0, };
+
+  g_value_init (&real_value, G_PARAM_SPEC_VALUE_TYPE (pspec));
+  g_object_get_property (gobject, pspec->name, &real_value);
+  
+  if (!G_TYPE_FUNDAMENTAL (G_VALUE_TYPE (&real_value)))
+    {
+      g_warning ("Complex types are not supported.");
+      return NULL;
+    }
+
+  switch (G_VALUE_TYPE (&real_value))
+    {
+    case G_TYPE_INT:
+    case G_TYPE_BOOLEAN:
+    case G_TYPE_FLOAT:
+      /* JSON native types */
+      retval = json_node_new (JSON_NODE_VALUE);
+      g_value_init (&value, G_VALUE_TYPE (&real_value));
+      g_value_copy (&real_value, &value);
+      json_node_set_value (retval, &value);
+      g_value_unset (&value);
+      break;
+
+    case G_TYPE_STRING:
+      /* strings might be NULL */
+      if (!g_value_get_string (&real_value))
+        retval = json_node_new (JSON_NODE_NULL);
+      else
+        {
+          retval = json_node_new (JSON_NODE_VALUE);
+          g_value_init (&value, G_TYPE_STRING);
+          g_value_set_string (&value, g_value_get_string (&real_value));
+          json_node_set_value (retval, &value);
+          g_value_unset (&value);
+        }
+      break;
+
+    case G_TYPE_UINT:
+    case G_TYPE_LONG:
+    case G_TYPE_ULONG:
+    case G_TYPE_CHAR:
+    case G_TYPE_UCHAR:
+    case G_TYPE_ENUM:
+    case G_TYPE_FLAGS:
+      /* these should fit into an int */
+      retval = json_node_new (JSON_NODE_VALUE);
+      g_value_init (&value, G_TYPE_INT);
+      g_value_copy (&real_value, &value);
+      json_node_set_value (retval, &value);
+      g_value_unset (&value);
+      break;
+
+    case G_TYPE_NONE:
+      retval = json_node_new (JSON_NODE_NULL);
+      break;
+
+    default:
+      g_warning ("Unsupported type `%s'",
+                 g_type_name (G_VALUE_TYPE (&real_value)));
+      break;
+    }
+
+  g_value_unset (&real_value);
+
+  return retval;
+}
+
+/**
+ * json_serialize_gobject:
+ * @gobject: a #GObject
+ * @length: return value for the length of the buffer, or %NULL
+ *
+ * Serializes a #GObject into a JSON data stream.
+ *
+ * Return value: a JSON data stream representing the passed #GObject
+ */
+gchar *
+json_serialize_gobject (GObject *gobject,
+                        gsize   *length)
+{
+  JsonGenerator *gen;
+  JsonNode *root;
+  JsonObject *object;
+  GParamSpec **pspecs;
+  guint n_pspecs, i;
+  gchar *data;
+
+  g_return_val_if_fail (G_IS_OBJECT (gobject), NULL);
+
+  object = json_object_new ();
+
+  root = json_node_new (JSON_NODE_OBJECT);
+  json_node_take_object (root, object);
+
+  pspecs = g_object_class_list_properties (G_OBJECT_GET_CLASS (gobject),
+                                           &n_pspecs);
+
+  for (i = 0; i < n_pspecs; i++)
+    {
+      GParamSpec *pspec = pspecs[i];
+      JsonNode *value;
+
+      /* read only what we can */
+      if (!(pspec->flags & G_PARAM_READABLE))
+        continue;
+
+      value = json_serialize_pspec (gobject, pspec);
+      if (value)
+        json_object_add_member (object, pspec->name, value);
+    }
+
+  g_free (pspecs);
+
+  gen = json_generator_new ();
+  json_generator_set_root (gen, root);
+  g_object_set (gen, "pretty", TRUE, NULL);
+  data = json_generator_to_data (gen, length);
+  g_object_unref (gen);
+
+  return data;
+}