nop-json

This is full-featured modern JSON implementation according to ECMA-404 standard.

This crate allows deserialization of JSON io::Read stream into primitive types (bool, i32, etc.), String and any other types that implement special trait called TryFromJson, which can be implemented automatically through #[derive(TryFromJson)] for your structs and enums.

And serialization back to JSON through DebugToJson trait, that acts like Debug, allowing to print your objects with println!() and such.

It allows to read whitespece-separated JSON values from stream in sequence. It also allows to pipe blob strings to a writer.

This implementation avoids unnecessary memory allocations and temporary object creations.

Documentation

Installation

In Cargo.toml of your project add:

[dependencies]
nop-json = "1.0"

Change log

Public API changed in version 1.0.0 over 0.0.4. Now Reader::new() accepts Iterator<u8>, because it works faster. See Reader::new() for how to use io::Read.

Examples

Deserializing simple values

use nop_json::Reader;

let mut reader = Reader::new(r#" true  100.5  "Hello"  [true, false] "#.as_bytes());

let the_true: bool = reader.read().unwrap();
let the_hundred_point_five: f32 = reader.read().unwrap();
let the_hello: String = reader.read().unwrap();
let the_array: Vec<bool> = reader.read().unwrap();

assert_eq!(the_true, true);
assert_eq!(the_hundred_point_five, 100.5);
assert_eq!(the_hello, "Hello");
assert_eq!(the_array, vec![true, false]);

First need to create a Reader object giving it something that implements std::io::Read. In example above i use &[u8].

Then call reader.read() to read each value from stream to some variable that implements TryFromJson. This crate has implementation of TryFromJson for many primitive types, Vec, HashMap, and more.

Deserializing any JSON values

use nop_json::{Reader, Value};
use std::convert::TryInto;

let mut reader = Reader::new(r#" true  100.5  "Hello"  [true, false] "#.as_bytes());

let the_true: Value = reader.read().unwrap();
let the_hundred_point_five: Value = reader.read().unwrap();
let the_hello: Value = reader.read().unwrap();
let the_array: Value = reader.read().unwrap();

assert_eq!(the_true, Value::Bool(true));
let the_hundred_point_five: f32 = the_hundred_point_five.try_into().unwrap();
assert_eq!(the_hundred_point_five, 100.5f32);
assert_eq!(the_hello, Value::String("Hello".to_string()));
assert_eq!(the_array, Value::Array(vec![Value::Bool(true), Value::Bool(false)]));

We have generic Value type that can hold any JSON node.

Deserializing/serializing objects

use nop_json::{Reader, TryFromJson, DebugToJson};

#[derive(TryFromJson, DebugToJson, PartialEq)]
struct Point {x: i32, y: i32}

#[derive(TryFromJson, DebugToJson, PartialEq)]
enum Geometry
{	#[json(point)] Point(Point),
	#[json(cx, cy, r)] Circle(i32, i32, i32),
	Nothing,
}

let mut reader = Reader::new(r#" {"point": {"x": 0, "y": 0}} "#.as_bytes());
let obj: Geometry = reader.read().unwrap();
println!("Serialized back to JSON: {:?}", obj);

See TryFromJson, DebugToJson.

Serializing scalar values

You can println!() word "true" or "false" to serialize a boolean. Also numbers can be printed as println!() does by default. The format is JSON-compatible. To serialize a &str, you can use escape function.

Alternatively you can create a Value object, and serialize it.

Skipping a value from stream

To skip current value without storing it (and allocating memory), read it to the () type.

use nop_json::Reader;

let mut reader = Reader::new(r#" true  100.5  "Hello"  [true, false] "#.as_bytes());

let _: () = reader.read().unwrap();
let _: () = reader.read().unwrap();
let _: () = reader.read().unwrap();
let _: () = reader.read().unwrap();

Reading binary data

See read_blob.

License: MIT

nop-json 1.0.1