Skip to content

go-faster/jx

Folders and files

NameName
Last commit message
Last commit date

Latest commit

85fb610 · Nov 5, 2021
Nov 5, 2021
Oct 29, 2021
Oct 28, 2021
Oct 28, 2021
Oct 31, 2021
Nov 5, 2021
Nov 30, 2016
Oct 28, 2021
Nov 5, 2021
Nov 4, 2021
Nov 2, 2021
Oct 31, 2021
Oct 28, 2021
Nov 4, 2021
Nov 3, 2021
Nov 2, 2021
Nov 3, 2021
Oct 31, 2021
Nov 5, 2021
Nov 4, 2021
Nov 3, 2021
Nov 2, 2021
Nov 5, 2021
Nov 5, 2021
Nov 3, 2021
Nov 3, 2021
Nov 5, 2021
Nov 5, 2021
Nov 3, 2021
Oct 30, 2021
Oct 30, 2021
Oct 31, 2021
Nov 3, 2021
Nov 3, 2021
Nov 2, 2021
Nov 2, 2021
Oct 31, 2021
Oct 31, 2021
Oct 31, 2021
Oct 30, 2021
Nov 5, 2021
Nov 2, 2021
Nov 2, 2021
Oct 31, 2021
Nov 5, 2021
Oct 31, 2021
Nov 5, 2021
Nov 2, 2021
Nov 4, 2021
Oct 28, 2021
Nov 5, 2021
Nov 5, 2021
Oct 28, 2021
Nov 5, 2021
Nov 3, 2021
Oct 30, 2021
Nov 5, 2021
Oct 31, 2021
Oct 31, 2021
Nov 5, 2021
Nov 5, 2021
Oct 31, 2021
Oct 31, 2021
Oct 31, 2021

Repository files navigation

jx Go Reference codecov

Package jx implements encoding and decoding of json [RFC 7159]. Lightweight fork of jsoniter.

go get github.com/ogen-go/jx

Features

  • Directly encode and decode json values
  • No reflect or interface{}
  • Pools and direct buffer access for less (or none) allocations
  • Multi-pass decoding
  • Validation

See usage for examples. Mostly suitable for fast low-level json manipulation with high control. Used in ogen project for json (un)marshaling code generation based on json and OpenAPI schemas.

Why

Most of jsoniter issues are caused by necessity to be drop-in replacement for standard encoding/json. Removing such constrains greatly simplified implementation and reduced scope, allowing to focus on json stream processing.

  • Reduced scope
    • No reflection
    • No encoding/json adapter
    • 4x less code (8.5K to 2K SLOC)
  • Fuzzing, improved test coverage
  • Drastically refactored and simplified
    • Explicit error returns
    • No Config or API

Usage

Decode

Use jx.Decoder. Zero value is valid, but constructors are available for convenience:

To reuse decoders and their buffers, use jx.GetDecoder and jx.PutDecoder alongside with reset functions:

Decoder is reset on PutDecoder.

d := jx.DecodeStr(`{"values":[4,8,15,16,23,42]}`)

// Save all integers from "values" array to slice.
var values []int

// Iterate over each object field.
if err := d.Obj(func(d *jx.Decoder, key string) error {
    switch key {
    case "values":
        // Iterate over each array element.
        return d.Arr(func(d *jx.Decoder) error {
            v, err := d.Int()
            if err != nil {
                return err
            }
            values = append(values, v)
            return nil
        })
    default:
        // Skip unknown fields if any.
        return d.Skip()
    }
}); err != nil {
    panic(err)
}

fmt.Println(values)
// Output: [4 8 15 16 23 42]

Encode

Use jx.Encoder. Zero value is valid, reuse with jx.GetEncoder, jx.PutEncoder and jx.Encoder.Reset(). Encoder is reset on PutEncoder.

var e jx.Encoder
e.ObjStart()         // {
e.ObjField("values") // "values":
e.ArrStart()         // [
for i, v := range []int{4, 8, 15, 16, 23, 42} {
    if i != 0 {
        e.More() // ,
    }
    e.Int(v)
}
e.ArrEnd() // ]
e.ObjEnd() // }
fmt.Println(e)
fmt.Println("Buffer len:", len(e.Bytes()))
// Output: {"values":[4,8,15,16,23,42]}
// Buffer len: 28

Raw

Use jx.Decoder.Raw to read raw json values, similar to json.RawMessage.

d := jx.DecodeStr(`{"foo": [1, 2, 3]}`)

var raw jx.Raw
if err := d.Obj(func(d *jx.Decoder, key string) error {
    v, err := d.Raw()
    if err != nil {
        return err
    }
    raw = v
    return nil
}); err != nil {
    panic(err)
}

fmt.Println(raw.Type(), raw)
// Output:
// array [1, 2, 3]

Number

Use jx.Decoder.Num to read numbers, similar to json.Number. Also supports number strings, like "12345", which is common compatible way to represent uint64.

d := jx.DecodeStr(`{"foo": "10531.0"}`)

var n jx.Num
if err := d.Obj(func(d *jx.Decoder, key string) error {
    v, err := d.Num()
    if err != nil {
        return err
    }
    n = v
    return nil
}); err != nil {
    panic(err)
}

fmt.Println(n)
fmt.Println("positive:", n.Positive())

// Can decode floats with zero fractional part as integers:
v, err := n.Int64()
if err != nil {
    panic(err)
}
fmt.Println("int64:", v)
// Output:
// "10531.0"
// positive: true
// int64: 10531

Validate

Check that byte slice is valid json with jx.Valid:

fmt.Println(jx.Valid([]byte(`{"field": "value"}`))) // true
fmt.Println(jx.Valid([]byte(`"Hello, world!"`)))    // true
fmt.Println(jx.Valid([]byte(`["foo"}`)))            // false

Capture

The jx.Decoder.Capture method allows to unread everything is read in callback. Useful for multi-pass parsing:

d := jx.DecodeStr(`["foo", "bar", "baz"]`)
var elems int
// NB: Currently Capture does not support io.Reader, only buffers.
if err := d.Capture(func(d *jx.Decoder) error {
	// Everything decoded in this callback will be rolled back.
	return d.Arr(func(d *jx.Decoder) error {
		elems++
		return d.Skip()
	})
}); err != nil {
	panic(err)
}
// Decoder is rolled back to state before "Capture" call.
fmt.Println("Read", elems, "elements on first pass")
fmt.Println("Next element is", d.Next(), "again")

// Output:
// Read 3 elements on first pass
// Next element is array again

ObjBytes

The Decoder.ObjBytes method tries not to allocate memory for keys, reusing existing buffer.

d := DecodeStr(`{"id":1,"randomNumber":10}`)
d.ObjBytes(func(d *Decoder, key []byte) error {
    switch string(key) {
    case "id":
    case "randomNumber":
    }
    return d.Skip()
})

Roadmap

  • Support Raw decoding
  • Rework json.Number
  • Rework Any
  • Support Raw for io.Reader
  • Support Capture for io.Reader
  • Decide what to do with base64

Non-goals

  • Code generation for decoding or encoding
  • Replacement for encoding/json
  • Reflection or interface{} based encoding or decoding
  • Support for json path or similar

This package should be kept as simple as possible and be used as low-level foundation for high-level projects like code generator.

License

MIT, same as jsoniter