Go Tour Exercises

rot13Reader_try1.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func (rot rot13Reader) Read(b []byte) (int, error) {
	n, err := rot.r.Read(b) // this is what will be returned
	
	if err != nil {
		return 0, err
	}

  // got this from the linked Wkipedia article
	input := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
	output := "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"

  // build a map from `input` and `output`
  inpOutMap := make(map[byte]byte)
	for i := range input {
		inpOutMap[input[i]] = output[i]
	}

	for i, c := range b {
		mappedChar, ok := inpOutMap[c]
		if !ok {
			b[i] = c
			continue
		}
		b[i] = mappedChar
	}

	return n, nil
}

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