// returning nil instead of empty slice if all spaces.
		return nil
	}
	return s[start:stop]
}

// Runes interprets s as a sequence of UTF-8-encoded code points.
// It returns a slice of runes (Unicode code points) equivalent to s.
func Runes(s []byte) []rune {
	t := make([]rune, utf8.RuneCount(s))
	i := 0
	for len(s) > 0 {
		r, l := utf8.DecodeRune(s)
		t[i] = r
		i++

// The opening parenthesis has been absorbed.
func (in *Input) argsFor(macro *Macro) map[string][]Token {
	var args [][]Token
	// One macro argument per iteration. Collect them all and check counts afterwards.
	for argNum := 0; ; argNum++ {
		tokens, tok := in.collectArgument(macro)
		args = append(args, tokens)
		if tok == ')' {
			break
		}
	}
	// Zero-argument macros are tricky.

			} else if nextReg != int(reg) {
				p.errorf("incontiguous register in ARM64 register list: %s", name)
			}
			regCnt++
			nextReg = (nextReg + 1) % 32
		case sys.ARM:
			// Parse the upper and lower bounds.
			lo := p.registerNumber(tok.String())
			hi := lo
			if p.peek() == '-' {
				p.next()
				hi = p.registerNumber(p.next().String())
			}
			if hi < lo {
				lo, hi = hi, lo
			}

			t.Fatalf("ReadRune(0x%x) got 0x%x,%d not 0x%x,%d (err=%s)", r1, nr, nbytes, r1, size, err)
		}
	}
}

func TestWriteInvalidRune(t *testing.T) {
	// Invalid runes, including negative ones, should be written as the
	// replacement character.
	for _, r := range []rune{-1, utf8.MaxRune + 1} {
		var buf strings.Builder
		w := NewWriter(&buf)
		w.WriteRune(r)
		w.Flush()

// if it becomes too large, WriteRune will panic with [ErrTooLarge].
func (b *Buffer) WriteRune(r rune) (n int, err error) {
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		b.WriteByte(byte(r))
		return 1, nil
	}
	b.lastRead = opInvalid
	m, ok := b.tryGrowByReslice(utf8.UTFMax)
	if !ok {
		m = b.grow(utf8.UTFMax)
	}

	Uid   int    // User ID of owner
	Gid   int    // Group ID of owner
	Uname string // User name of owner
	Gname string // Group name of owner

	// If the Format is unspecified, then Writer.WriteHeader rounds ModTime
	// to the nearest second and ignores the AccessTime and ChangeTime fields.
	//
	// To use AccessTime or ChangeTime, specify the Format as PAX or GNU.
	// To use sub-second resolution, specify the Format as PAX.

	// Keep a list of all the functions, to remove the ones
	// only used as expressions and avoid generating bridge
	// code for them.
	functions := make(map[string]bool)

	for _, n := range f.Name {
		if n.Kind == "func" {
			functions[n.Go] = false
		}
	}

	// Now that we have all the name types filled in,
	// scan through the Refs to identify the ones that
	// are trying to do a ,err call. Also check that

		}
	}
}

// Test that the rune splitter returns same sequence of runes (not bytes) as for range string.
func TestScanRune(t *testing.T) {
	for n, test := range scanTests {
		buf := strings.NewReader(test)
		s := NewScanner(buf)
		s.Split(ScanRunes)
		var i, runeCount int
		var expect rune
		// Use a string range loop to validate the sequence of runes.
		for i, expect = range test {
			if !s.Scan() {
				break
			}

}

// WriteRune writes a single Unicode code point, returning
// the number of bytes written and any error.
func (b *Writer) WriteRune(r rune) (size int, err error) {
	// Compare as uint32 to correctly handle negative runes.
	if uint32(r) < utf8.RuneSelf {
		err = b.WriteByte(byte(r))
		if err != nil {
			return 0, err
		}
		return 1, nil
	}
	if b.err != nil {
		return 0, b.err
	}
	n := b.Available()