[A Tour of Go] Exercise: rot13Reader

exercise-rot-reader.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func rot13(b byte) byte {
	if b <= 'A' || b > 'z' {
		return b
	}
	if b >= 'a' {
		return (((b - 'a') + 13) % 26) + 'a'
	} else {
		return (((b - 'A') + 13) % 26) + 'A'
	}
}

func (r rot13Reader) Read(p []byte) (n int, err error) {
	n, err = r.r.Read(p)
	for i := range p {
		p[i] = rot13(p[i])
	}
	return
}

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