args.go
func decodeArgAppendNoPlus(dst, src []byte) []byte {
	if bytes.IndexByte(src, '%') < 0 {
		// fast path: src doesn't contain encoded chars
		return append(dst, src...)
	}

	// slow path
	for i := 0; i < len(src); i++ {
		c := src[i]
		if c == '%' {
			if i+2 >= len(src) {
				return append(dst, src[i:]...)
			}
			x2 := hex2intTable[src[i+2]]
			x1 := hex2intTable[src[i+1]]
			if x1 == 16 || x2 == 16 {
				dst = append(dst, '%')
			} else {
				dst = append(dst, x1<<4|x2)
				i += 2
			}
		} else {
			dst = append(dst, c)
		}
	}
	return dst
}
func decodeArgAppendNoPlus(dst, src []byte) []byte {
	if bytes.IndexByte(src, '%') < 0 {
		// fast path: src doesn't contain encoded chars
		return append(dst, src...)
	}

	// slow path
	for i := 0; i < len(src); i++ {
		c := src[i]
		if c == '%' {
			if i+2 >= len(src) {
				return append(dst, src[i:]...)
			}
			x2 := hex2intTable[src[i+2]]
			x1 := hex2intTable[src[i+1]]
			if x1 == 16 || x2 == 16 {
				dst = append(dst, '%')
			} else {
				dst = append(dst, x1<<4|x2)
				i += 2
			}
		} else {
			dst = append(dst, c)
		}
	}
	return dst
}
// decodeArgAppendNoPlus is almost identical to decodeArgAppend, but it doesn't
// substitute '+' with ' '.
//
// The function is copy-pasted from decodeArgAppend due to the performance
// reasons only.