jiter

Fast iterable JSON parser.

Documentation is available at docs.rs/jiter.

jiter has three interfaces:

• [JsonValue] an enum representing JSON data
• [Jiter] an iterator over JSON data
• [python_parse] which parses a JSON string into a Python object

JsonValue Example

See [the JsonValue docs][JsonValue] for more details.

use jiter::JsonValue;

fn main() {
    let json_data = r#"
        {
            "name": "John Doe",
            "age": 43,
            "phones": [
                "+44 1234567",
                "+44 2345678"
            ]
        }"#;
    let json_value = JsonValue::parse(json_data.as_bytes(), true).unwrap();
    println!("{:#?}", json_value);
}

returns:

Object(
    {
        "name": Str("John Doe"),
        "age": Int(43),
        "phones": Array(
            [
                Str("+44 1234567"),
                Str("+44 2345678"),
            ],
        ),
    },
)

Jiter Example

To use [Jiter], you need to know what schema you're expecting:

use jiter::{Jiter, NumberInt, Peek};

fn main() {
    let json_data = r#"
        {
            "name": "John Doe",
            "age": 43,
            "phones": [
                "+44 1234567",
                "+44 2345678"
            ]
        }"#;
    let mut jiter = Jiter::new(json_data.as_bytes(), true);
    assert_eq!(jiter.next_object().unwrap(), Some("name"));
    assert_eq!(jiter.next_str().unwrap(), "John Doe");
    assert_eq!(jiter.next_key().unwrap(), Some("age"));
    assert_eq!(jiter.next_int().unwrap(), NumberInt::Int(43));
    assert_eq!(jiter.next_key().unwrap(), Some("phones"));
    assert_eq!(jiter.next_array().unwrap(), Some(Peek::String));
    // we know the next value is a string as we just asserted so
    assert_eq!(jiter.known_str().unwrap(), "+44 1234567");
    assert_eq!(jiter.array_step().unwrap(), Some(Peek::String));
    // same again
    assert_eq!(jiter.known_str().unwrap(), "+44 2345678");
    // next we'll get `None` from `array_step` as the array is finished
    assert_eq!(jiter.array_step().unwrap(), None);
    // and `None` from `next_key` as the object is finished
    assert_eq!(jiter.next_key().unwrap(), None);
    // and we check there's nothing else in the input
    jiter.finish().unwrap();
}

Benchmarks

There are lies, damned lies and benchmarks.

In particular, serde-json benchmarks use serde_json::Value which is significantly slower than deserializing to a string.

For more details, see the benchmarks.

running 48 tests
test big_jiter_iter                    ... bench:   3,662,616 ns/iter (+/- 88,878)
test big_jiter_value                   ... bench:   6,998,605 ns/iter (+/- 292,383)
test big_serde_value                   ... bench:  29,793,191 ns/iter (+/- 576,173)
test bigints_array_jiter_iter          ... bench:      11,836 ns/iter (+/- 414)
test bigints_array_jiter_value         ... bench:      28,979 ns/iter (+/- 938)
test bigints_array_serde_value         ... bench:     129,797 ns/iter (+/- 5,096)
test floats_array_jiter_iter           ... bench:      19,302 ns/iter (+/- 631)
test floats_array_jiter_value          ... bench:      31,083 ns/iter (+/- 921)
test floats_array_serde_value          ... bench:     208,932 ns/iter (+/- 6,167)
test lazy_map_lookup_1_10              ... bench:         615 ns/iter (+/- 15)
test lazy_map_lookup_2_20              ... bench:       1,776 ns/iter (+/- 36)
test lazy_map_lookup_3_50              ... bench:       4,291 ns/iter (+/- 77)
test massive_ints_array_jiter_iter     ... bench:      62,244 ns/iter (+/- 1,616)
test massive_ints_array_jiter_value    ... bench:      82,889 ns/iter (+/- 1,916)
test massive_ints_array_serde_value    ... bench:     498,650 ns/iter (+/- 47,759)
test medium_response_jiter_iter        ... bench:           0 ns/iter (+/- 0)
test medium_response_jiter_value       ... bench:       3,521 ns/iter (+/- 101)
test medium_response_jiter_value_owned ... bench:       6,088 ns/iter (+/- 180)
test medium_response_serde_value       ... bench:       9,383 ns/iter (+/- 342)
test pass1_jiter_iter                  ... bench:           0 ns/iter (+/- 0)
test pass1_jiter_value                 ... bench:       3,048 ns/iter (+/- 79)
test pass1_serde_value                 ... bench:       6,588 ns/iter (+/- 232)
test pass2_jiter_iter                  ... bench:         384 ns/iter (+/- 9)
test pass2_jiter_value                 ... bench:       1,259 ns/iter (+/- 44)
test pass2_serde_value                 ... bench:       1,237 ns/iter (+/- 38)
test sentence_jiter_iter               ... bench:         283 ns/iter (+/- 10)
test sentence_jiter_value              ... bench:         357 ns/iter (+/- 15)
test sentence_serde_value              ... bench:         428 ns/iter (+/- 9)
test short_numbers_jiter_iter          ... bench:           0 ns/iter (+/- 0)
test short_numbers_jiter_value         ... bench:      18,085 ns/iter (+/- 613)
test short_numbers_serde_value         ... bench:      87,253 ns/iter (+/- 1,506)
test string_array_jiter_iter           ... bench:         615 ns/iter (+/- 18)
test string_array_jiter_value          ... bench:       1,410 ns/iter (+/- 44)
test string_array_jiter_value_owned    ... bench:       2,863 ns/iter (+/- 151)
test string_array_serde_value          ... bench:       3,467 ns/iter (+/- 60)
test true_array_jiter_iter             ... bench:         299 ns/iter (+/- 8)
test true_array_jiter_value            ... bench:         995 ns/iter (+/- 29)
test true_array_serde_value            ... bench:       1,207 ns/iter (+/- 36)
test true_object_jiter_iter            ... bench:       2,482 ns/iter (+/- 84)
test true_object_jiter_value           ... bench:       2,058 ns/iter (+/- 45)
test true_object_serde_value           ... bench:       7,991 ns/iter (+/- 370)
test unicode_jiter_iter                ... bench:         315 ns/iter (+/- 7)
test unicode_jiter_value               ... bench:         389 ns/iter (+/- 6)
test unicode_serde_value               ... bench:         445 ns/iter (+/- 6)
test x100_jiter_iter                   ... bench:          12 ns/iter (+/- 0)
test x100_jiter_value                  ... bench:          20 ns/iter (+/- 1)
test x100_serde_iter                   ... bench:          72 ns/iter (+/- 3)
test x100_serde_value                  ... bench:          83 ns/iter (+/- 3)