Actson

Actson is a reactive JSON parser (sometimes referred to as non-blocking or asynchronous). It is event-based and can be used in asynchronous code (for example in combination with Tokio).

Why another JSON parser?

• Non-blocking. Other JSON parsers use blocking I/O. If you want to develop a reactive application you should use non-blocking I/O (see the Reactive Manifesto).
• Big Data. Most parsers read the full JSON text into memory to map it to a struct, for example. Actson can handle arbitrarily large JSON text. It is event-based and can be used for streaming.
• GeoRocket. Actson was primarily developed for the GeoJSON support support in GeoRocket, a high-performance reactive data store for geospatial files.

Usage

```rust use actson::{JsonParser, JsonEvent}; use actson::feeder::{DefaultJsonFeeder, JsonFeeder};

let json = r#"{"name": "Elvis"}"#.as_bytes();

let mut feeder = DefaultJsonFeeder::new(); let mut parser = JsonParser::new(); let mut i: usize = 0; loop { // feed as many bytes as possible to the parser let mut event = parser.nextevent(&mut feeder); while matches!(event, JsonEvent::NeedMoreInput) { i += feeder.feedbytes(&json[i..]); if i == json.len() { feeder.done(); } event = parser.next_event(&mut feeder); }

// do something useful with `event`

if matches!(event, JsonEvent::Error) {
   // do proper error handling here!
   panic!("Error while parsing JSON");
}

if matches!(event, JsonEvent::Eof) {
    break;
}

} ```

Other languages

Besides this implementation in Rust here, there is a Java implementation.

Acknowledgments

The event-based parser code and the JSON files used for testing are largely based on the file JSON_checker.c and the JSON test suite from JSON.org originally released under this license (basically MIT license).

License

Actson is released under the MIT license. See the LICENSE file for more information.