t3 = 0xE0 // 1110 0000
	t4 = 0xF0 // 1111 0000
	t5 = 0xF8 // 1111 1000

	maskx = 0x3F // 0011 1111
	mask2 = 0x1F // 0001 1111
	mask3 = 0x0F // 0000 1111
	mask4 = 0x07 // 0000 0111

	rune1Max = 1<<7 - 1
	rune2Max = 1<<11 - 1
	rune3Max = 1<<16 - 1

	// The default lowest and highest continuation byte.
	locb = 0x80 // 1000 0000
	hicb = 0xBF // 1011 1111
)

// countrunes returns the number of runes in s.

	"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
// UTF-16 encoding of s.
func encodeWTF16(s string, buf []uint16) []uint16 {
	for i := 0; i < len(s); {