How to encode and decode data using a custom binary format in Go?

To encode and decode data using a custom binary format in Go, you can use the encoding/binary package. Here is an example of how to encode and decode data using a custom binary format:

Define the struct representing your data:

type MyData struct {
    ID     uint32
    Name   string
    Active bool
}

Implement the Encoding and Decoding functions for your struct:

func (d *MyData) Encode() ([]byte, error) {
    buf := new(bytes.Buffer)
    
    // Write ID
    err := binary.Write(buf, binary.LittleEndian, d.ID)
    if err != nil {
        return nil, err
    }
    
    // Write Name
    err = binary.Write(buf, binary.LittleEndian, uint32(len(d.Name)))
    if err != nil {
        return nil, err
    }
    _, err = buf.WriteString(d.Name)
    if err != nil {
        return nil, err
    }
    
    // Write Active
    err = binary.Write(buf, binary.LittleEndian, d.Active)
    if err != nil {
        return nil, err
    }
    
    return buf.Bytes(), nil
}

func (d *MyData) Decode(data []byte) error {
    buf := bytes.NewBuffer(data)
    
    // Read ID
    err := binary.Read(buf, binary.LittleEndian, &d.ID)
    if err != nil {
        return err
    }
    
    // Read Name
    var nameLen uint32
    err = binary.Read(buf, binary.LittleEndian, &nameLen)
    if err != nil {
        return err
    }
    nameBytes := make([]byte, nameLen)
    _, err = buf.Read(nameBytes)
    if err != nil {
        return err
    }
    d.Name = string(nameBytes)
    
    // Read Active
    err = binary.Read(buf, binary.LittleEndian, &d.Active)
    if err != nil {
        return err
    }
    
    return nil
}

Now you can encode and decode your data:

data := MyData{
    ID:     42,
    Name:   "John Doe",
    Active: true,
}

// Encode data
encoded, err := data.Encode()
if err != nil {
    log.Fatal(err)
}

// Decode data
decoded := MyData{}
err = decoded.Decode(encoded)
if err != nil {
    log.Fatal(err)
}

fmt.Printf("%+v\n", decoded)

This example demonstrates a custom binary format where we encode the ID as a little-endian 32-bit unsigned integer, the Name as a 32-bit unsigned integer specifying the length followed by the Name string itself, and the Active field as a boolean value.