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, 2 insertions, 1 deletions

diff --git a/json-glib/json-debug.c b/json-glib/json-debug.c
index dd725c4..c0dc2e9 100644
--- a/json-glib/json-debug.c
+++ b/json-glib/json-debug.c
@@ -10,7 +10,8 @@ static gboolean     json_debug_flags_set = FALSE;
 #ifdef JSON_ENABLE_DEBUG
 static const GDebugKey json_debug_keys[] = {
   { "parser", JSON_DEBUG_PARSER },
-  { "gobject", JSON_DEBUG_GOBJECT }
+  { "gobject", JSON_DEBUG_GOBJECT },
+  { "path", JSON_DEBUG_PATH }
 };
 #endif /* JSON_ENABLE_DEBUG */