Solution of Exercise: rot13Reader

exercise-rot-reader.go

package main

import (
	"io"
	"os"
	"strings"
)

type rot13Reader struct {
	r io.Reader
}

//ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
const src string = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
//NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm
const dest string = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"

func (r *rot13Reader) Read (b []byte) (n int, err error) {
	m, err := r.r.Read(b)
	for i := 0; i < m; i++ {
		if b[i] >= 'A' && b[i] <= 'Z' ||  b[i] >= 'a' && b[i] <= 'z' {
			b[i] = dest[strings.IndexByte(src, b[i])]
		}
	}
	return m, err
	
}

func main() {
	s := strings.NewReader("Lbh penpxrq gur pbqr!")
	r := rot13Reader{s}
	io.Copy(os.Stdout, &r)
}