fast-json-stringify

Compile a JSON Schema into a fast JSON serializer.

build reads a Draft-7 JSON Schema once and returns a Stringify handle that turns a matching value into a JSON string. The schema is inspected at build time, so each serialize call walks a pre-compiled plan instead of the schema. Output matches JSON.stringify byte for byte for conforming input.

The output is correct JSON when the input matches the schema. A mismatched input may produce malformed JSON or an error. Treat schemas as trusted.

Installation

[dependencies]
fast-json-stringify = "0.1"

Usage

use fast_json_stringify::{build, Value};
use serde_json::json;

let schema = json!({
    "type": "object",
    "properties": {
        "name": { "type": "string" },
        "age": { "type": "integer" }
    },
    "required": ["name"]
});

let stringify = build(&schema, None).unwrap();
let input = Value::from(json!({ "name": "Ada", "age": 36 }));
assert_eq!(stringify.call(&input).unwrap(), r#"{"name":"Ada","age":36}"#);

Stringify is cheap to clone and is Send + Sync, so one compiled serializer can run on many threads:

# use fast_json_stringify::{build, Value};
# use serde_json::json;
let stringify = build(&json!({ "type": "integer" }), None).unwrap();
assert_eq!(stringify.call(&Value::from(json!(1615))).unwrap(), "1615");

Value model

Inputs use Value, a JavaScript-shaped value type. A plain serde_json::Value converts in with From. The model adds the host objects the serializer coerces:

• Value::Date(i64) holds epoch milliseconds and renders as ISO 8601, or as a calendar date or wall-clock time under format: "date" and format: "time".
• Value::BigInt(i128) serializes as an arbitrary-precision integer.
• Value::Regex(String) serializes as its source pattern under a string schema.
• Value::Custom(Box<Value>) carries a value already passed through a toJSON hook.

Supported keywords

Serialization honors type (single or array), properties, required, additionalProperties, patternProperties, items (schema or tuple), additionalItems, oneOf, anyOf, allOf, if/then/else, $ref, $id, definitions, const, default, nullable, and format (date-time/date/time/unsafe). Other validation keywords such as enum, minLength, and maximum drive type inference or are ignored.

anyOf, oneOf, and if/then/else pick a branch by validating the value at serialize time, then serialize through the matching schema.

Options

Options controls rounding for non-integer numbers under type: "integer", external schemas for $ref resolution, and the large-array threshold and mechanism. The defaults are trunc rounding, a 20000 threshold, and the element-by-element mechanism.

License

Licensed under the MIT license.