unquote nginx hex string in golang

unquote_nginx.go

package main

import (
	"bytes"
	"encoding/hex"
	"fmt"
)

func UnquoteHex(str string) ([]byte, error) {
	var (
		ret     bytes.Buffer
		isQuote = false
	)
	for i := 0; i < len(str); i++ {
		s := str[i]
		if isQuote { // start dequote
			if s == 'x' || s == 'X' {
				if i+3 > len(str) {
					return nil, fmt.Errorf("line hex is error")
				}
				hs, err := hex.DecodeString(str[i+1 : i+3])
				if err != nil {
					return nil, err
				}
				ret.WriteByte(hs[0])
				i += 2 // the default i will be increased again, so it's 2
				isQuote = false
			} else {
				return nil, fmt.Errorf("illegal dequote at [%v:%v]", i, s)
			}
		} else {
			if s == '\\' {
				isQuote = true // mark the dequote as starting
			} else {
				// it's not quoted
				isQuote = false
				if err := ret.WriteByte(byte(s)); err != nil {
					return nil, err
				}
			}
		}
	}
	return ret.Bytes(), nil
}

func main() {
	testStr := `\x08\x16 \x02*` // you have to notice this using `, not to using ", if your declare a variable using ", golang will dequote \x automatically
	desBytes, err := UnquoteHex(testStr)
	if err != nil {
		panic(err)
	}
	fmt.Println(desBytes) // [8 22 32 2 42]
}