go语言Exercise: Rot13 Reader

A common pattern is an io.Reader that wraps another

io.Reader

,
modifying the stream in some way.
For example, the gzip.NewReader function takes an

io.Reader

(a
stream of gzipped data) and returns a

*gzip.Reader

that also implements

io.Reader

(a stream of
the decompressed data).
Implement a

rot13Reader

that implements

io.Reader

and
reads from an

io.Reader

, modifying the stream by applying the ROT13substitution cipher to all alphabetical characters.
The

rot13Reader

type is provided for you. Make it an

io.Reader

by
implementing its

Read

method.
加密方法：凯撒加密，key为13

package main

import (

"io"

"os"

"strings"

)

type rot13Reader struct {

r io.Reader

}

func Rot13(b byte) byte {

switch {

case 'A' <= b && b <= 'M':

b = b + 13

case 'M' < b && b <= 'Z':

b = b - 13

case 'a' <= b && b <= 'm':

b = b + 13

case 'm' < b && b <= 'z':

b = b - 13

}

return b

}

func (read *rot13Reader) Read(p []byte) (n int, err error){

n, err = read.r.Read(p)

for i, value := range p {

p[i] = Rot13(value)

}

return

}

func main() {

s := strings.NewReader(

"Lbh penpxrq gur pbqr!")

r := rot13Reader{s}

io.Copy(os.Stdout, &r)

}