content/2013/bestpractices/shortercode6.go

// +build ignore,OMIT

package main

import (
	"bytes"
	"encoding/binary"
	"io"
	"log"
	"os"
)

type Gopher struct {
	Name     string
	AgeYears int
}

type binWriter struct {
	w   io.Writer
	buf bytes.Buffer // HL
	err error
}

// Write writes a value to the provided writer in little endian form.
func (w *binWriter) Write(v interface{}) {
	if w.err != nil {
		return
	}
	switch x := v.(type) {
	case string:
		w.Write(int32(len(x)))
		w.Write([]byte(x))
	case int:
		w.Write(int64(x))
	default:
		w.err = binary.Write(&w.buf, binary.LittleEndian, v) // HL
	}
}

// Flush writes any pending values into the writer if no error has occurred.
// If an error has occurred, earlier or with a write by Flush, the error is
// returned.
func (w *binWriter) Flush() (int64, error) {
	if w.err != nil {
		return 0, w.err
	}
	return w.buf.WriteTo(w.w)
}

func (g *Gopher) WriteTo(w io.Writer) (int64, error) {
	bw := &binWriter{w: w}
	bw.Write(g.Name)
	bw.Write(g.AgeYears)
	return bw.Flush() // HL
}

func main() {
	g := &Gopher{
		Name:     "Gophertiti",
		AgeYears: 3382,
	}

	if _, err := g.WriteTo(os.Stdout); err != nil {
		log.Printf("DumpBinary: %v\n", err)
	}
}