package main

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

type rot13Reader struct {
	r io.Reader
}

var ROT13_FROM = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
var ROT13_TO = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"

func (in rot13Reader) Read(p []byte) (n int, err os.Error) {
	n, err = in.r.Read(p)
	if n > 0 {
		for x := 0; x < n; x++ {
			char := p[x]
			
			pos := -1
			for y := 0; y < len(ROT13_FROM); y++ {
				if ROT13_FROM[y] == char {
					pos = y;
					break
				}
			}
			if pos > -1 {
				p[x] = ROT13_TO[pos]
			}

		}
	}
	return n, err
}

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