return (r1-surr1)<<10 | (r2 - surr2) + surrSelf
	}
	return replacementChar
}

// EncodeRune returns the UTF-16 surrogate pair r1, r2 for the given rune.
// If the rune is not a valid Unicode code point or does not need encoding,
// EncodeRune returns U+FFFD, U+FFFD.
func EncodeRune(r rune) (r1, r2 rune) {
	if r < surrSelf || r > maxRune {
		return replacementChar, replacementChar
	}
	r -= surrSelf

	for i, tt := range encodeTests {
		j := 0
		for _, r := range tt.in {
			r1, r2 := EncodeRune(r)
			if r < 0x10000 || r > unicode.MaxRune {
				if j >= len(tt.out) {
					t.Errorf("#%d: ran out of tt.out", i)
					break
				}
				if r1 != unicode.ReplacementChar || r2 != unicode.ReplacementChar {
					t.Errorf("EncodeRune(%#x) = %#x, %#x; want 0xfffd, 0xfffd", r, r1, r2)
				}
				j++
			} else {

		// No-op.
	} else if x := entity[string(entityName)]; x != 0 {
		return dst + utf8.EncodeRune(b[dst:], x), src + i
	} else if x := entity2[string(entityName)]; x[0] != 0 {
		dst1 := dst + utf8.EncodeRune(b[dst:], x[0])
		return dst1 + utf8.EncodeRune(b[dst1:], x[1]), src + i
	} else if !attribute {
		maxLen := len(entityName) - 1
		if maxLen > longestEntityWithoutSemicolon {

	}
	// Output:
	// H 1
	// e 1
	// l 1
	// l 1
	// o 1
	// , 1
	//   1
	// 世 3
	// 界 3
}

func ExampleEncodeRune() {
	r := '世'
	buf := make([]byte, 3)

	n := utf8.EncodeRune(buf, r)

	fmt.Println(buf)
	fmt.Println(n)
	// Output:
	// [228 184 150]
	// 3
}

func ExampleEncodeRune_outOfRange() {
	runes := []rune{
		// Less than 0, out of range.
		-1,

			pos += 4
			if rune3Max < r && r <= maxRune {
				return
			}
		}
	}

	return runeError, k + 1
}

// encoderune writes into p (which must be large enough) the UTF-8 encoding of the rune.
// It returns the number of bytes written.
func encoderune(p []byte, r rune) int {
	// Negative values are erroneous. Making it unsigned addresses the problem.
	switch i := uint32(r); {
	case i <= rune1Max:

			//   unicode ::= '\' [0-9a-fA-F]{1,6} wc?
			j := 2
			for j < len(s) && j < 7 && isHex(s[j]) {
				j++
			}
			r := hexDecode(s[1:j])
			if r > unicode.MaxRune {
				r, j = r/16, j-1
			}
			n := utf8.EncodeRune(b[len(b):cap(b)], r)
			// The optional space at the end allows a hex
			// sequence to be followed by a literal hex.
			// string(decodeCSS([]byte(`\A B`))) == "\nB"
			b, s = b[:len(b)+n], skipCSSSpace(s[j:])
		} else {

	0x8: FSI, // U+2068 FirstStrongIsolate,
	0x9: PDI, // U+2069 PopDirectionalIsolate,
}

// LookupRune returns properties for r.
func LookupRune(r rune) (p Properties, size int) {
	var buf [4]byte
	n := utf8.EncodeRune(buf[:], r)
	return Lookup(buf[:n])
}

// TODO: these lookup methods are based on the generated trie code. The returned
// sizes have slightly different semantics from the generated code, in that it