rot13Reader

README.md

Hackish first attempt at the rot13Reader exercise of the go tour.

Not as concise or elegant as the official solution.

rot13.go

package main

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

// rot13Map constructor used in rot13 method
// m["A"] == "N"
// m["z"] == "m"
func NewRot13Map() map[byte]byte {
    p := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
    q := "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"
	m := make(map[byte]byte)
	for i, c := range p {
		m[byte(c)] = q[byte(i)]
	}
	return m
}

var rot13Map = NewRot13Map()

type rot13Reader struct {
    reader io.Reader
    rot13Map map[byte]byte
}

// rotate alphabetic byte chars by 13 positions (A to N, z to m)
func (r *rot13Reader) rot13(c byte) byte {
    if c >= 'A' && c <= 'z' {
        return r.rot13Map[c]
    }
    return c
}

func (r *rot13Reader) Read(b []byte) (int, error) {
    n, err := r.reader.Read(b)
    for i, c := range b {
        b[i] = r.rot13(c)
    }
    return n, err
}

// rot13Reader construtor
func NewRot13Reader(r io.Reader) *rot13Reader {
    return &rot13Reader{r, rot13Map}
}

func main() {
    s := strings.NewReader("Lbh penpxrq gur pbqr!")
    r := NewRot13Reader(s)
    io.Copy(os.Stdout, r) //You cracked the code!
}