A Tour of Go - Exercise: Rot13 Reader

rot13_reader.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func (r rot13Reader) Read(p []byte) (n int, err error) {
    n, err = r.r.Read(p)
    for i := 0; i < n; i++ {
        if p[i] >= 'a' && p[i] <= 'z' {
            p[i] = ((p[i] - 'a' + 13) % ('z' - 'a' + 1)) + 'a'
        } else if p[i] >= 'A' && p[i] <= 'Z' {
            p[i] = ((p[i] - 'A' + 13) % ('Z' - 'A' + 1)) + 'A'
        }
    }
    return n, err
}

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