encgen

encgen-go

Streamable JSON encoder generator

Features

• Automatic encoder generation from Go structs
• Fluent API ensuring correct encoding order
• Efficient batch streaming for slice fields (tagged with enc:"batch")
• Supports nested structs and custom types

Installation

go install github.com/dsnidr/encgen-go/cmd/encgen@v0.1.0

Usage

1. Define a struct

Mark any fields you want to stream in batches with enc:"batch".

type Parcel struct {
	ID       string   `json:"id"`
	Name     string   `json:"name"`
	Items    []*Item  `json:"items" enc:"batch"`
	Metadata []string `json:"metadata" enc:"batch"`
	Tags     []*Tag   `json:"tags"`
}

type Item struct {
	SKU    string  `json:"sku"`
	Name   string  `json:"name"`
	Weight float64 `json:"weight"` // in kgs
}

type Tag struct {
	ID   string `json:"id"`
	Name string `json:"name"`
}

2. Run the generator

Run go generate where your struct is defined.

You can do this manually:

encgen --name <struct name>

or using go generate:

//go:generate go run github.com/dsnidr/encgen-go/cmd/encgen --name Parcel
type Parcel struct {
  ...
}

3. Use the generated encoder

buf := bytes.NewBuffer(nil)

itemsEnc := NewParcelEncoder(buf).
  Start().
  ID("test").
  Name("name").
  StartItems()

// your batching logic would go here
itemsEnc.AddItems(
  &Item{ID: "item1", Name: "test item 1", Weight: 592.0},
  &Item{ID: "item2", Name: "test item 2", Weight: 182.15},
  &Item{ID: "item3", Name: "test item 3", Weight: 23717.85})

itemsEnc.AddItems(
  &Item{ID: "item4", Name: "test item 4", Weight: 10.0})
...

err := itemsEnc.FinishItems().
  StartMetadata().
  AddMetadata("one", "two", "three").
  AddMetadata("four", "five").
  FinishMetadata().
  Tags([]*Tag{
    {ID: "tag1", Name: "Home Improvement"},
	  {ID: "tag2", Name: "Digital Goods"},
  }).
  Finish()

if err != nil {
  panic(err)
}

fmt.Println("OUTPUT")
fmt.Println(buf.String())

// OUTPUT
// {"id":"test","name":"name","items":[{"sku":"item1","name":"test item 1","weight":592},{"sku":"item2","name":"test item 2","weight":182.15},{"sku":"item3","name":"test item 3","weight":23717.85},{"sku":"item2","name":"test item 4","weight":10}],"metadata":["one","two","three","four","five"],"tags":[{"id":"tag1","name":"Home Improvement"},{"id":"tag2","name":"Digital Goods"}]}