NFD for OS X

nfd_mac.go

package main

import (
	"fmt"
	"unicode/utf8"

	"golang.org/x/text/unicode/norm"
)

func main() {
	fmt.Printf("% x\n", "神")
	fmt.Printf("% x\n", NormString("神"))
	fmt.Printf("% x\n", "神")
}

func NormString(s string) string {
	var b [utf8.UTFMax]byte

	out := make([]byte, 0, len(s)*2)

	for _, r := range s {
		n := utf8.EncodeRune(b[:], r)

    // http://tama-san.com/hfsplus_normalize/
    
		switch {
		case r < 0x2000:
			out = norm.NFD.Append(out, b[:n]...)
		case r <= 0x2fff:
			out = append(out, b[:n]...)
		case r < 0xf900:
			out = norm.NFD.Append(out, b[:n]...)
		case r <= 0xfaff:
			out = append(out, b[:n]...)
		case r < 0x2f800:
			out = norm.NFD.Append(out, b[:n]...)
		case r <= 0x2fa1f:
			out = append(out, b[:n]...)
		default:
			out = norm.NFD.Append(out, b[:n]...)
		}
	}

	return string(out)
}