ROT13 Tour

implement-image.go

package main

import (
	"golang.org/x/tour/pic"
	"image"
	"image/color"
)

type Image struct{}

func (Image) ColorModel() color.Model {
	return color.RGBAModel
}

func (Image) Bounds() image.Rectangle {
	return image.Rect(0, 0, 100, 100)
}

func (Image) At(x, y int) color.Color {
	return color.RGBA{uint8(x), uint8(y), uint8(x), 255}
}

func main() {
	m := Image{}
	pic.ShowImage(m)
}

rot13.go

package main

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

type rot13Reader struct {
	r io.Reader
}

func position(alphabet string, b byte, offset int) (changed bool, result byte) {
	index := strings.IndexByte(alphabet, b)
	if index >= 0 {
		pos := index + offset
		if pos >= len(alphabet) {
			pos -= len(alphabet)
		}
		return true, alphabet[pos]
	} else {
		return false, b
	}
}

func (re rot13Reader) Read(b []byte) (read int, e error) {
	read_from_underlying, underlying_error := re.r.Read(b);
	
	if underlying_error == nil {
		for i := 0; i < read_from_underlying; i ++ {
			changed, n := position("ABCDEFGHIJKLMNOPQRSTUVWXYZ", b[i], 13)
			
			if !changed {
				_, n = position("abcdefghijklmnopqrstuvwxyz", b[i], 13)
			}
			
			b[i] = n
		}
	}
	
	return read_from_underlying, underlying_error
}

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