// The return value n is the number of bytes written; it always fits into an
// int, but it is int64 to match the [io.WriterTo] interface. Any error
// encountered during the write is also returned.
func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
	b.lastRead = opInvalid
	if nBytes := b.Len(); nBytes > 0 {
		m, e := w.Write(b.buf[b.off:])
		if m > nBytes {
			panic("bytes.Buffer.WriteTo: invalid Write count")
		}

	for r := rune(0); r < NRune; r++ {
		size := utf8.EncodeRune(b[n:], r)
		nbytes, err := buf.WriteRune(r)
		if err != nil {
			t.Fatalf("WriteRune(%U) error: %s", r, err)
		}
		if nbytes != size {
			t.Fatalf("WriteRune(%U) expected %d, got %d", r, size, nbytes)
		}
		n += size
	}
	b = b[0:n]

	// Check the resulting bytes
	if !Equal(buf.Bytes(), b) {

// Package bytes implements functions for the manipulation of byte slices.
// It is analogous to the facilities of the [strings] package.
package bytes

import (
	"internal/bytealg"
	"math/bits"
	"unicode"
	"unicode/utf8"
	_ "unsafe" // for linkname
)

// Equal reports whether a and b
// are the same length and contain the same bytes.
// A nil argument is equivalent to an empty slice.

func (b *Reader) readErr() error {
	err := b.err
	b.err = nil
	return err
}

// Peek returns the next n bytes without advancing the reader. The bytes stop
// being valid at the next read call. If necessary, Peek will read more bytes
// into the buffer in order to make n bytes available. If Peek returns fewer
// than n bytes, it also returns an error explaining why the read is short.

		genLine(tmp, lineNum, j, false)
		if j < smallMaxTokenSize {
			j++
		} else {
			j--
		}
		line := tmp.Bytes()
		if !bytes.Equal(s.Bytes(), line) {
			t.Errorf("%d: bad line: %d %d\n%.100q\n%.100q\n", lineNum, len(s.Bytes()), len(line), s.Bytes(), line)
		}
	}
	err := s.Err()
	if err != ErrTooLong {
		t.Fatalf("expected ErrTooLong; got %s", err)
	}
}

// suffixSaver is an io.Writer & io.ReaderAt that remembers the last 0
// to 'keep' bytes of data written to it. Call Suffix to get the
// suffix bytes.
type suffixSaver struct {
	keep  int
	buf   []byte
	start int
	size  int64
}

func (ss *suffixSaver) Size() int64 { return ss.size }

var errDiscardedBytes = errors.New("ReadAt of discarded bytes")

func (ss *suffixSaver) ReadAt(p []byte, off int64) (n int, err error) {

	defer func() {
		writeTests[1].Data = nil
	}()

	// write a zip file
	buf := new(bytes.Buffer)
	w := NewWriter(buf)

	for _, wt := range writeTests {
		testCreate(t, w, &wt)
	}

	if err := w.Close(); err != nil {
		t.Fatal(err)
	}

	// read it back
	r, err := NewReader(bytes.NewReader(buf.Bytes()), int64(buf.Len()))
	if err != nil {
		t.Fatal(err)
	}
	for i, wt := range writeTests {

pkg bytes, func FieldsFuncSeq([]uint8, func(int32) bool) iter.Seq[[]uint8] #61901
pkg bytes, func FieldsSeq([]uint8) iter.Seq[[]uint8] #61901
pkg bytes, func Lines([]uint8) iter.Seq[[]uint8] #61901
pkg bytes, func SplitAfterSeq([]uint8, []uint8) iter.Seq[[]uint8] #61901
pkg bytes, func SplitSeq([]uint8, []uint8) iter.Seq[[]uint8] #61901
pkg crypto/cipher, func NewCFBDecrypter //deprecated #69445
pkg crypto/cipher, func NewCFBEncrypter //deprecated #69445

	}

	// xattr bar should always appear before others
	indices := []int{
		bytes.Index(buf.Bytes(), []byte("bar=bar")),
		bytes.Index(buf.Bytes(), []byte("baz=baz")),
		bytes.Index(buf.Bytes(), []byte("foo=foo")),
		bytes.Index(buf.Bytes(), []byte("qux=qux")),
	}
	if !slices.IsSorted(indices) {
		t.Fatal("PAX headers are not sorted")
	}
}

func TestUSTARLongName(t *testing.T) {

	}
	if nb := tw.curr.logicalRemaining(); nb > 0 {
		return fmt.Errorf("archive/tar: missed writing %d bytes", nb)
	}
	if _, tw.err = tw.w.Write(zeroBlock[:tw.pad]); tw.err != nil {
		return tw.err
	}
	tw.pad = 0
	return nil
}

// WriteHeader writes hdr and prepares to accept the file's contents.
// The Header.Size determines how many bytes can be written for the next file.