Learn Go

io.Reader+Writer Exploration 2

package main

import (
	"bytes"
	"fmt"
	"io"
)

type Maker interface {
	WriteIn(data []byte) (int, error)
	ReadOut() ([]byte, error)
}

type Duck struct {
	*bytes.Buffer
}

func (d *Duck) WriteIn(data []byte) (int, error) {
	n, err := d.Write(data)
	if n > 0 {
		return n, nil
	}
	return 0, err
}

func (d *Duck) ReadOut() ([]byte, error) {
	p := make([]byte, d.Len())
	n, err := d.Read(p)
	if n > 0 {
		return p, nil
	}
	return p, err
}

func NewDuck(d []byte) *Duck {
	return &Duck{
		bytes.NewBuffer(d),
	}
}

func main() {
	tinyDuck := NewDuck([]byte(""))
	in, err := tinyDuck.WriteIn([]byte("#WriteTo data"))
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(in)
	out, err := tinyDuck.ReadOut()
	if err != nil {
		fmt.Println(err)
	}
	fmt.Println(string(out))
	Extract(tinyDuck)
	out, _ = tinyDuck.ReadOut()
	fmt.Println(string(out))
}

func ReadFrom(w io.Reader, num int) ([]byte, error) {
	p := make([]byte, num)
	n, err := w.Read(p)
	if n > 0 {
		return p[:n], nil
	}
	return p, err
}

func WriteTo(w io.Writer, data []byte) (int, error) {
	n, err := w.Write(data)
	if n > 0 {
		return n, nil
	}
	return 0, err
}

func Extract(m ...Maker) {
	for _, d := range m {
		n, err := d.WriteIn([]byte("Some Data"))
		if err != nil {
			fmt.Println(err)
		}
		fmt.Println("- ", n, "Written to maker")
	}
}