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.h b/json-glib/json-debug.h
index 20f22c6..695917f 100644
--- a/json-glib/json-debug.h
+++ b/json-glib/json-debug.h
@@ -7,7 +7,8 @@ G_BEGIN_DECLS
 
 typedef enum {
   JSON_DEBUG_PARSER  = 1 << 0,
-  JSON_DEBUG_GOBJECT = 1 << 1
+  JSON_DEBUG_GOBJECT = 1 << 1,
+  JSON_DEBUG_PATH    = 1 << 2
 } JsonDebugFlags;
 
 #ifdef JSON_ENABLE_DEBUG