go-tourの#61を解いてみる ref: http://qiita.com/kamatama_41/items/192f96d05c675135d9b9

file0.go

package main

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

type rot13Reader struct {
    r io.Reader
}

func (reader rot13Reader) Read(p []byte) (n int, err error) {
    tmp1 := make([]byte, 10)
    n, err = reader.r.Read(tmp1)
    tmp2 := bytes.Map(func(r rune) rune {
            switch {
            case ('a' <= r && r <= 'z'):
                return 'a' + (r-'a'+13)%26
            case ('A' <= r && r <= 'Z'):
                return 'A' + (r-'A'+13)%26
            default:
                return r
            }
        }, tmp1)
    copy(p, tmp2)
    return
}

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

}