fmt.Fprintf(&buf, "\t%#04x,\n", r-0x10000)
	}
	fmt.Fprintf(&buf, "}\n\n")

	// The list of graphic but not "printable" runes is short. Just make one easy table.
	fmt.Fprintf(&buf, "// isGraphic lists the graphic runes not matched by IsPrint.\n")
	fmt.Fprintf(&buf, "var isGraphic = []uint16{\n")
	for r := rune(0); r <= unicode.MaxRune; r++ {
		if unicode.IsPrint(r) != unicode.IsGraphic(r) {
			// Sanity check.

	r = -1
	s = string(r)
	assert(s, "\xef\xbf\xbd", "negative rune")

	// the large rune tests again, this time using constants instead of a variable.
	// these conversions will be done at compile time.
	s = string(0x10ffff) // largest rune value
	assert(s, "\xf4\x8f\xbf\xbf", "largest rune constant")
	s = string(0x10ffff + 1)
	assert(s, "\xef\xbf\xbd", "too-large rune constant")
	s = string(0xD800)

	rBuffer := make([]rune, nRunes)
	buf := bytes.NewBuffer([]byte(string(rBuffer)))

	seed := time.Now().UnixNano()
	t.Logf("rand seed: %v", seed)
	rng := rand.New(rand.NewSource(seed))

	for i := 0; i < 50; i++ {
		// Generate a random string of runes.
		buf.Reset()
		for buf.Len() < sys.ExecArgLengthLimit+1 {
			var r rune
			for {
				r = rune(rng.Intn(utf8.MaxRune + 1))
				if utf8.ValidRune(r) {

func decodeWTF16(s []uint16, buf []byte) []byte {
	for i := 0; i < len(s); i++ {
		var ar rune
		switch r := s[i]; {
		case r < surr1, surr3 <= r:
			// normal rune
			ar = rune(r)
		case surr1 <= r && r < surr2 && i+1 < len(s) &&
			surr2 <= s[i+1] && s[i+1] < surr3:
			// valid surrogate sequence
			ar = utf16.DecodeRune(rune(r), rune(s[i+1]))
			i++
		default:
			// WTF-8 fallback.

func (p Properties) CCC() uint8 {
	if p.index >= firstCCCZeroExcept {
		return 0
	}
	return ccc[p.ccc]
}

// LeadCCC returns the CCC of the first rune in the decomposition.
// If there is no decomposition, LeadCCC equals CCC.
func (p Properties) LeadCCC() uint8 {
	return ccc[p.ccc]
}

// TrailCCC returns the CCC of the last rune in the decomposition.

		if n := runtimeRuneCount(ts); n != count {
			t.Errorf("%q: len([]rune()) counted %d runes; got %d from RuneCountInString", ts, n, count)
			break
		}

		runes := []rune(ts)
		if n := len(runes); n != count {
			t.Errorf("%q: []rune() has length %d; got %d from RuneCountInString", ts, n, count)
			break
		}
		i := 0
		for _, r := range ts {
			if r != runes[i] {

func (p Properties) CCC() uint8 {
	if p.index >= firstCCCZeroExcept {
		return 0
	}
	return ccc[p.ccc]
}

// LeadCCC returns the CCC of the first rune in the decomposition.
// If there is no decomposition, LeadCCC equals CCC.
func (p Properties) LeadCCC() uint8 {
	return ccc[p.ccc]
}

// TrailCCC returns the CCC of the last rune in the decomposition.

// written, not just their values. Particularly useful for runes.
func f8(r rune) {
	const x = 10
	switch r {
	case 33, 33: // ERROR "duplicate case (33 in switch)?"
	case 34, '"': // ERROR "duplicate case '"' .value 34. in switch"
	case 35, rune('#'): // ERROR "duplicate case (rune.'#'. .value 35. in switch)?"
	case 36, rune(36): // ERROR "duplicate case (rune.36. .value 36. in switch)?"

func Decode(s []uint16) []rune {
	// Preallocate capacity to hold up to 64 runes.
	// Decode inlines, so the allocation can live on the stack.
	buf := make([]rune, 0, 64)
	return decode(s, buf)
}

// decode appends to buf the Unicode code point sequence represented
// by the UTF-16 encoding s and return the extended buffer.
func decode(s []uint16, buf []rune) []rune {
	for i := 0; i < len(s); i++ {

// is undesirable for our purposes. ICU prevents breaks in such cases as well.

// isBreak returns whether this rune should introduce a break.
func (c info) isBreak() bool {
	return c.cccVal() == cccBreak
}

// isLetter returns whether the rune is of break type ALetter, Hebrew_Letter,
// Numeric, ExtendNumLet, or Extend.
func (c info) isLetter() bool {
	ccc := c.cccVal()
	if ccc == cccZero {