Go tour rot13Reader

r13Reader.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func (reader *rot13Reader) Read(p []byte) (int, error) {
	b := make([]byte, 8)
	n, err := reader.r.Read(b)
	//fmt.Printf("n=%v err=%v b=%s\n", n, err, b[:n])
	if err == io.EOF {
		return 0, io.EOF
	}
	
	i := 0
	for ; i < n; i++ {
		p[i] = rot13Decode(b[i])
	}
	//fmt.Printf("decoded=%s\n", p[:n])
	return i, nil
}

func rot13Decode(b byte) byte {
	if b >= 'A' && b <= 'Z' {
		return ((b - 'A' + 13) % 26) + 'A'
	}
	if b >= 'a' && b <= 'z' {
		return ((b - 'a' + 13) % 26) + 'a'
	}
	return b
}

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