Add initial JSONPath implementation

JSONPath is a JSON query syntax similar to what XPath does for XML;
using JSONPath it's possible to address a specific node (or set of
nodes) inside a JSON document.

The JsonPath class is a simple implementation of part of the JSONPath
proposal, as formalised by Stefan Gössner here:

  http://goessner.net/articles/JsonPath/

The covered operators are:

  • root, or '$';
  • child, both using the dot-notation and the bracket notation;
  • recursive descent, or '..';
  • subscript, or '[]';
  • set, or '[,]';
  • slice, or '[start:end:step]'.

The only missing operators are the filter, or '?()' and the script,
or '()', because implementing a JavaScript interpreter inside JSON-GLib
is not one of my greatest aspirations. It should be possible, though,
to parse and evaluate simple arithmetic conditions, in the future.

The JsonPath methods are pretty straightforward: a JsonPath instance
should be created and used to compile an expression; the compilation
might result in a syntax error or not. Then, the JsonPath instance can
be used to match any JSON tree. Like the other JSONPath implementations,
JsonPath returns a JSON array of matching nodes.

A simple, one-off static method called json_path_query() is also
provided; the method wraps the JsonPath creation, the expression
compilation, and the matching, as well as disposing the JsonPath
instance once done.

For the time being, only positive testing is provided; negative testing
for the expression compilation will follow.

1 files changed, 97 insertions, 0 deletions

diff --git a/json-glib/json-path.h b/json-glib/json-path.h
new file mode 100644
index 0000000..2bae608
--- /dev/null
+++ b/json-glib/json-path.h
@@ -0,0 +1,97 @@
+/* json-path.h - JSONPath implementation
+ *
+ * This file is part of JSON-GLib
+ * Copyright © 2011  Intel Corp.
+ *
+ * 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 2.1 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author:
+ *   Emmanuele Bassi  <ebassi@linux.intel.com>
+ */
+
+#if !defined(__JSON_GLIB_INSIDE__) && !defined(JSON_COMPILATION)
+#error "Only <json-glib/json-glib.h> can be included directly."
+#endif
+
+#ifndef __JSON_PATH_H__
+#define __JSON_PATH_H__
+
+#include <json-glib/json-types.h>
+
+G_BEGIN_DECLS
+
+#define JSON_TYPE_PATH          (json_path_get_type ())
+#define JSON_PATH(obj)          (G_TYPE_CHECK_INSTANCE_CAST ((obj), JSON_TYPE_PATH, JsonPath))
+#define JSON_IS_PATH(obj)       (G_TYPE_CHECK_INSTANCE_TYPE ((obj), JSON_TYPE_PATH))
+
+/**
+ * JSON_PATH_ERROR:
+ *
+ * Error domain for #JsonPath errors
+ *
+ * Since: 0.14
+ */
+#define JSON_PATH_ERROR         (json_path_error_quark ())
+
+/**
+ * JsonPathError:
+ * @JSON_PATH_ERROR_INVALID_QUERY: Invalid query
+ *
+ * Error code enumeration for the %JSON_PATH_ERROR domain.
+ *
+ * Since: 0.14
+ */
+typedef enum {
+  JSON_PATH_ERROR_INVALID_QUERY
+} JsonPathError;
+
+/**
+ * JsonPath:
+ *
+ * The <structname>JsonPath</structname> structure is an opaque object
+ * whose members cannot be directly accessed except through the provided
+ * API.
+ *
+ * Since: 0.14
+ */
+typedef struct _JsonPath        JsonPath;
+
+/**
+ * JsonPathClass:
+ *
+ * The <structname>JsonPathClass</structname> structure is an opaque
+ * object class whose members cannot be directly accessed.
+ *
+ * Since: 0.14
+ */
+typedef struct _JsonPathClass   JsonPathClass;
+
+GType json_path_get_type (void) G_GNUC_CONST;
+GQuark json_path_error_quark (void);
+
+JsonPath *      json_path_new           (void);
+
+gboolean        json_path_compile       (JsonPath    *path,
+                                         const char  *expression,
+                                         GError     **error);
+JsonNode *      json_path_match         (JsonPath    *path,
+                                         JsonNode    *root);
+
+JsonNode *      json_path_query         (const char  *expression,
+                                         JsonNode    *root,
+                                         GError     **error);
+
+G_END_DECLS
+
+#endif /* __JSON_PATH_H__ */