golang初学之接口---rot13Reader

package main

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

type rot13Reader struct {
	r io.Reader
}
func (reader rot13Reader) Read(b []byte) (int, error) {
	n, err := reader.r.Read(b)
	for i:=0; i<n; i++{
		switch {
		case b[i] >= 'A' && b[i] <'N' :
			b[i] += 13
		case b[i]>='N' && b[i] <='Z':
			b[i] -=13
		case b[i] >= 'a' && b[i] <'n' :
			b[i] += 13
		case b[i]>='n' && b[i] <='z':
			b[i] -=13
		}
	}
	return n, err
}
func main() {
	s := strings.NewReader("Lbh penpxrq gur pbqr!")
	r := rot13Reader{s}
	io.Copy(os.Stdout, &r)
}