startBufSize = 4096 // Size of initial allocation for buffer.
)

// NewScanner returns a new [Scanner] to read from r.
// The split function defaults to [ScanLines].
func NewScanner(r io.Reader) *Scanner {
	return &Scanner{
		r:            r,
		split:        ScanLines,
		maxTokenSize: MaxScanTokenSize,
	}
}

// Err returns the first non-EOF error that was encountered by the [Scanner].
func (s *Scanner) Err() error {

		genLine(tmp, lineNum, j, true)
		if j < smallMaxTokenSize {
			j++
		} else {
			j--
		}
		buf.Write(tmp.Bytes())
		lineNum++
	}
	s := NewScanner(&slowReader{1, buf})
	s.Split(ScanLines)
	s.MaxTokenSize(smallMaxTokenSize)
	j = 0
	for lineNum := 0; s.Scan(); lineNum++ {
		genLine(tmp, lineNum, j, false)
		if j < smallMaxTokenSize {
			j++
		} else {
			j--
		}