func (s *scratch) add(c byte) {
	if s.fill+1 >= cap(s.data) {
		s.grow()
	}

	s.data[s.fill] = c
	s.fill++
}

// append encoded rune to scratch buffer
func (s *scratch) addRune(r rune) int {
	if s.fill+utf8.UTFMax >= cap(s.data) {
		s.grow()
	}

	n := utf8.EncodeRune(s.data[s.fill:], r)
	s.fill += n
	return n

package bufio

// Exported for testing only.
import (
	"unicode/utf8"
)

var IsSpace = isSpace

const DefaultBufSize = defaultBufSize

func (s *Scanner) MaxTokenSize(n int) {
	if n < utf8.UTFMax || n > 1e9 {
		panic("bad max token size")
	}
	if n < len(s.buf) {
		s.buf = make([]byte, n)
	}
	s.maxTokenSize = n
}

// ErrOrEOF is like Err, but returns EOF. Used to test a corner case.