func TestBadReader(t *testing.T) {
	scanner := NewScanner(endlessZeros{})
	for scanner.Scan() {
		t.Fatal("read should fail")
	}
	err := scanner.Err()
	if err != io.ErrNoProgress {
		t.Errorf("unexpected error: %v", err)
	}
}

func TestScanWordsExcessiveWhiteSpace(t *testing.T) {
	const word = "ipsum"
	s := strings.Repeat(" ", 4*smallMaxTokenSize) + word
	scanner := NewScanner(strings.NewReader(s))

func ExampleScanner_lines() {
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		fmt.Println(scanner.Text()) // Println will add back the final '\n'
	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "reading standard input:", err)
	}
}

// Return the most recent call to Scan as a []byte.
func ExampleScanner_Bytes() {
	scanner := bufio.NewScanner(strings.NewReader("gopher"))
	for scanner.Scan() {

	largeInput  = make([]byte, 1024*1024*128) // 128MB
)

func TestScanner(t *testing.T) {
	data := []byte("abcdefghijklmnopqrstuvwxyz0123456789")

	var i int
	r := bytes.NewReader(data)
	scanner := newScanner(r)
	for scanner.pos < atomic.LoadInt64(&scanner.end) {
		c := scanner.next()
		if scanner.readerErr != nil {
			t.Fatal(scanner.readerErr)
		}
		if c != data[i] {

	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Fatalf("%v: %v\n%s", cmd, err, string(out))
	}
	syms := make(map[string]string)
	scanner := bufio.NewScanner(bytes.NewReader(out))
	for scanner.Scan() {
		f := strings.Fields(scanner.Text())
		if len(f) < 3 {
			continue
		}
		syms[f[2]] = f[0]
	}
	if err := scanner.Err(); err != nil {

	nbuf      [chunk]byte     // next internal buffer
	fillReq   chan struct{}
	fillReady chan int64
	readerErr error // underlying reader error, if any
}

func newScanner(r io.Reader) *scanner {
	sr := &scanner{
		end:       maxInt,
		fillReq:   make(chan struct{}),
		fillReady: make(chan int64),
	}

	go func() {
		var rpos int64 // total bytes read into buffer

	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	tab, err := f.PCLineTable()
	if err != nil {
		log.Fatalf("reading %s: %v", flag.Arg(0), err)
	}

	stdin := bufio.NewScanner(os.Stdin)
	stdout := bufio.NewWriter(os.Stdout)

	for stdin.Scan() {
		p := stdin.Text()
		if strings.Contains(p, ":") {
			// Reverse translate file:line to pc.

		}
		break
	}

	// Parse trailers.
	wantTrailers := make(map[string]struct{}, len(cr.trailers))
	for k := range cr.trailers {
		wantTrailers[strings.ToLower(k)] = struct{}{}
	}
	input := bufio.NewScanner(bytes.NewReader(valueBuffer.Bytes()))
	for input.Scan() {
		line := strings.TrimSpace(input.Text())
		if line == "" {
			continue
		}
		// Find first separator.

	}

	bf := bytes.Buffer{}

	save := func(s string) {
		bf.WriteString(s + "\n")
	}
	reset := func() {
		bf.Reset()
	}

	ret := make(map[time.Duration][]string)

	s := bufio.NewScanner(f)
	s.Split(bufio.ScanLines)

	var (
		t            time.Duration
		skip, record bool
	)

	for s.Scan() {
		line := s.Text()
		switch {
		case skip && line != "":
		case skip && line == "":

	result := make(map[string]string)

	mountInfo, err := os.Open("/proc/self/mountinfo")
	if err != nil {
		return nil, err
	}
	defer mountInfo.Close()

	scanner := bufio.NewScanner(mountInfo)
	for scanner.Scan() {
		s := strings.Split(scanner.Text(), " ")
		if len(s) != 11 {
			return nil, errors.New("unsupported /proc/self/mountinfo format")
		}
		result[s[2]] = s[9]
	}

	// may need to include, for instance, a newline.
	MaxScanTokenSize = 64 * 1024

	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,
	}
}