A Tour of Go, exercise rot13Reader

exercise.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func (rot *rot13Reader) Read(p []byte) (n int, err error) {
	n, err = rot.r.Read(p)
	for i := 0; i < len(p); i++ {
		if p[i] >= 'A' && p[i] < 'Z' {
			p[i] = 65 + (((p[i] - 65) + 13) % 26)
		} else if p[i] >= 'a' && p[i] <= 'z' {
			p[i] = 97 + (((p[i] - 97) + 13) % 26)
		}
	}
	return
}

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

package main

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

type rot13Reader struct {
	r io.Reader
}

const (
        lowerMap = "nopqrstuvwxyzabcdefghijklm"
        upperMap = "NOPQRSTUVWXYZABCDEFGHIJKLM"
)

func rotateBytes(bytes []byte) {
	for i := range bytes {
	    if unicode.IsLower(rune(bytes[i])) {
                    bytes[i] = lowerMap[bytes[i]-'a']
	    } else if unicode.IsUpper(rune(bytes[i])) {
		    bytes[i] = upperMap[bytes[i]-'A']
	    }
	}
}

func (rot13 *rot13Reader) Read(bytes []byte) (int, error) {
	n, err := rot13.r.Read(bytes)
	rotateBytes(bytes)
	return n, err
}

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