{[]rune{1, 2, 3, 4}, []uint16{1, 2, 3, 4}},
	{[]rune{0xffff, 0x10000, 0x10001, 0x12345, 0x10ffff},
		[]uint16{0xffff, 0xd800, 0xdc00, 0xd800, 0xdc01, 0xd808, 0xdf45, 0xdbff, 0xdfff}},
	{[]rune{'a', 'b', 0xd7ff, 0xd800, 0xdfff, 0xe000, 0x110000, -1},
		[]uint16{'a', 'b', 0xd7ff, 0xfffd, 0xfffd, 0xe000, 0xfffd, 0xfffd}},
}

func TestEncode(t *testing.T) {
	for _, tt := range encodeTests {
		out := Encode(tt.in)

		wstr: []uint16{0xD800, 0xD800},
	},
	{
		// "High surrogate followed by a symbol that is not a surrogate"
		str:  string([]byte{0xED, 0xA0, 0x80, 0xA}),
		wstr: []uint16{0xD800, 0xA},
	},
	{
		// "Unmatched high surrogate, followed by a surrogate pair, followed by an unmatched high surrogate"
		str:  string([]byte{0xED, 0xA0, 0x80, 0xF0, 0x9D, 0x8C, 0x86, 0xED, 0xA0, 0x80}),
		wstr: []uint16{0xD800, 0xD834, 0xDF06, 0xD800},
	},
	{

	assert(s, "\xef\xbf\xbd", "too-large rune constant")
	s = string(0xD800)
	assert(s, "\xef\xbf\xbd", "surrogate rune min constant")
	s = string(0xDFFF)
	assert(s, "\xef\xbf\xbd", "surrogate rune max constant")
	s = string(-1)
	assert(s, "\xef\xbf\xbd", "negative rune")

	// the large rune tests yet again, with a slice.
	rs := []rune{0x10ffff, 0x10ffff + 1, 0xD800, 0xDFFF, -1}
	s = string(rs)

	maxRune         = '\U0010FFFF' // Maximum valid Unicode code point.
)

const (
	// 0xd800-0xdc00 encodes the high 10 bits of a pair.
	// 0xdc00-0xe000 encodes the low 10 bits of a pair.
	// the value is those 20 bits plus 0x10000.
	surr1 = 0xd800
	surr2 = 0xdc00
	surr3 = 0xe000

	surrSelf = 0x10000
)

// IsSurrogate reports whether the specified Unicode code point

//
// See go.dev/issues/59971 for more info.

package syscall

import (
	"unicode/utf16"
	"unicode/utf8"
)

const (
	surr1 = 0xd800
	surr2 = 0xdc00
	surr3 = 0xe000

	tx    = 0b10000000
	t3    = 0b11100000
	maskx = 0b00111111
	mask3 = 0b00001111

	rune1Max = 1<<7 - 1
	rune2Max = 1<<11 - 1
)

// encodeWTF16 returns the potentially ill-formed

	{0x0800, "\xe0\xa0\x80"},
	{0x0801, "\xe0\xa0\x81"},
	{0x1000, "\xe1\x80\x80"},
	{0xd000, "\xed\x80\x80"},
	{0xd7ff, "\xed\x9f\xbf"}, // last code point before surrogate half.
	{0xe000, "\xee\x80\x80"}, // first code point after surrogate half.
	{0xfffe, "\xef\xbf\xbe"},
	{0xffff, "\xef\xbf\xbf"},
	{0x10000, "\xf0\x90\x80\x80"},
	{0x10001, "\xf0\x90\x80\x81"},
	{0x40000, "\xf1\x80\x80\x80"},
	{0x10fffe, "\xf4\x8f\xbf\xbe"},

byte('\'')
math.Float64frombits(0x7ff8000000000002)
math.Float32frombits(0x7fc00001)`,
		},
		{
			desc: "rune validation",
			in: `go test fuzz v1
rune(0)
rune(0x41)
rune(-1)
rune(0xfffd)
rune(0xd800)
rune(0x10ffff)
rune(0x110000)
`,
			want: `go test fuzz v1
rune('\x00')
rune('A')
int32(-1)
rune('�')
int32(55296)
rune('\U0010ffff')
int32(1114112)`,
		},
		{

	runeSelf  = 0x80         // characters below runeSelf are represented as themselves in a single byte.
	maxRune   = '\U0010FFFF' // Maximum valid Unicode code point.
)

// Code points in the surrogate range are not valid for UTF-8.
const (
	surrogateMin = 0xD800
	surrogateMax = 0xDFFF
)

const (
	t1 = 0x00 // 0000 0000
	tx = 0x80 // 1000 0000
	t2 = 0xC0 // 1100 0000

			}
			break
		}

		if i <= 3 { // No characters matched.
			b[dst] = b[src]
			return dst + 1, src + 1
		}

		if 0x80 <= x && x <= 0x9F {
			// Replace characters from Windows-1252 with UTF-8 equivalents.
			x = replacementTable[x-0x80]
		} else if x == 0 || (0xD800 <= x && x <= 0xDFFF) || x > 0x10FFFF {
			// Replace invalid characters with the replacement character.
			x = '\uFFFD'
		}

		{'A', true},
		{'Z', true},
		{'a', true},
		{'z', true},
		{'_', true},
		{'-', true},
		{':', false},
		{';', false},
		{' ', false},
		{0x7f, false},
		{0x80, true},
		{0x1234, true},
		{0xd800, false},
		{0xdc00, false},
		{0xfffe, false},
		{0x10000, true},
		{0x110000, false},
	}
	for _, test := range tests {
		got := isCSSNmchar(test.rune)
		if got != test.want {