Golang Exercise: rot13Reader

package main

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

type rot13Reader struct {
 r io.Reader
}

func (p rot13Reader) Read(b []byte) (n int, err error) {
 n, err = p.r.Read(b)
 for i := 0; i < n; i++ {
  b[i] = b[i] + 13
  if b[i] > 'z' || (b[i] > 'Z' && b[i] < 'a') {
   b[i] = b[i] - 26
  }
  fmt.Printf("b[%v] = %q\n", i, b[i])
 }
 n = len(b)
 return n, err
}

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

Output:

b[0] = 'Y'
b[1] = 'o'
b[2] = 'u'
b[3] = '-'
b[4] = 'c'
b[5] = 'r'
b[6] = 'a'
b[7] = 'c'
b[8] = 'k'
b[9] = 'e'
b[10] = 'd'
b[11] = '-'
b[12] = 't'
b[13] = 'h'
b[14] = 'e'
b[15] = '-'
b[16] = 'c'
b[17] = 'o'
b[18] = 'd'
b[19] = 'e'
b[20] = '.'
You-cracked-the-code.You-cracked-the-code.
Program exited.

Reference:

http://tour.golang.org/methods/12