httpHelper.go

package main

// Revised after seeing pkg/http/url.go

import (
	"fmt";
	"strings";
)

func shouldEscape(c int) bool {
	if c == 95 || c > 44 && c < 47 || c > 47 && c < 58 || c > 64 && c < 91 || c > 96 && c < 123 {
		return false
	}
	return true;
}

func unicodeLen(c int) int {
	switch {
	case c < 128:
		return 1
	case c < 2048:
		return 2
	case c < 65536:
		return 3
	default:	// c < 1114112,
		return 4
	}
	return 4;
}

func URLEscape(s string) string {
	spaceFlag := false;
	hexCount, multibyteCount := 0, 0;
	for _, c := range s {
		switch shouldEscape(c) {
		case c == ' ':
			spaceFlag = true
		default:
			hexCount += unicodeLen(c);		// extra hex pairs
			multibyteCount += (unicodeLen(c) - 1);	// extra percent signs
		}
	}

	if !spaceFlag && hexCount == 0 {
		return s
	}

	t := make([]byte, len(s)+2*hexCount+multibyteCount);
	j := 0;
	for _, c := range s {
		switch {
		case c == ' ':
			t[j] = '+';
			j++;
		case shouldEscape(c) && c < 128:
			t[j] = '%';
			t[j+1] = "0123456789abcdef"[c>>4];
			t[j+2] = "0123456789abcdef"[c&15];
			j += 3;
		case c < 128:
			t[j] = uint8(c);
			j++;
		default:
			r := strings.Bytes(string(c));
			for _, b := range r {
				t[j] = '%';
				t[j+1] = "0123456789abcdef"[b>>4];
				t[j+2] = "0123456789abcdef"[b&15];
				j += 3;
			}
		}
	}
	return string(t);
}

func main()	{ fmt.Println(URLEscape("a b ç")) }