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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.
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