t.Errorf("r.Len(): got %d, want %d", got, want)
	}
	if n, err := r.Read(make([]byte, 10)); err != nil || n != 10 {
		t.Errorf("Read failed: read %d %v", n, err)
	}
	if got, want := r.Len(), 1; got != want {
		t.Errorf("r.Len(): got %d, want %d", got, want)
	}
	if n, err := r.Read(make([]byte, 1)); err != nil || n != 1 {
		t.Errorf("Read failed: read %d %v; want 1, nil", n, err)
	}
	if got, want := r.Len(), 0; got != want {

// The result is unaffected by any method calls except [Reader.Reset].
func (r *Reader) Size() int64 { return int64(len(r.s)) }

// Read implements the [io.Reader] interface.
func (r *Reader) Read(b []byte) (n int, err error) {
	if r.i >= int64(len(r.s)) {
		return 0, io.EOF
	}
	r.prevRune = -1
	n = copy(b, r.s[r.i:])
	r.i += int64(n)
	return
}

	for i := 0; i < chunks; i++ {
		_, err := io.ReadFull(rc, chunk)
		if err != nil {
			t.Fatal("read:", err)
		}
	}
	if frag := int(size % chunkSize); frag > 0 {
		_, err := io.ReadFull(rc, chunk[:frag])
		if err != nil {
			t.Fatal("read:", err)
		}
	}
	gotEnd, err := io.ReadAll(rc)
	if err != nil {
		t.Fatal("read end:", err)
	}
	if !bytes.Equal(gotEnd, end) {

	}
	n, err := tw.curr.Write(b)
	if err != nil && err != ErrWriteTooLong {
		tw.err = err
	}
	return n, err
}

// readFrom populates the content of the current file by reading from r.
// The bytes read must match the number of remaining bytes in the current file.
//
// If the current file is sparse and r is an io.ReadSeeker,
// then readFrom uses Seek to skip past holes defined in Header.SparseHoles,

	// Distinguish these cases using the column number, since we don't
	// see the space itself. Note that text/scanner reports the position at the
	// end of the token. It's where you are now, and you just read this token.
	if tok == '(' && in.Stack.Col() == prevCol+1 {
		// Macro has arguments. Scan list of formals.
		acceptArg := true
		args = []string{} // Zero length but not nil.
	Loop:
		for {

type dirReader struct {
	err error
}

func (r *dirReader) Read([]byte) (int, error) {
	return 0, r.err
}

func (r *dirReader) Close() error {
	return nil
}

type checksumReader struct {
	rc    io.ReadCloser
	hash  hash.Hash32
	nread uint64 // number of bytes read so far
	f     *File
	desr  io.Reader // if non-nil, where to read the data descriptor
	err   error     // sticky error
}

			s.buf = newBuf
			s.end -= s.start
			s.start = 0
		}
		// Finally we can read some input. Make sure we don't get stuck with
		// a misbehaving Reader. Officially we don't need to do this, but let's
		// be extra careful: Scanner is for safe, simple jobs.
		for loop := 0; ; {
			n, err := s.r.Read(s.buf[s.end:len(s.buf)])
			if n < 0 || len(s.buf)-s.end < n {
				s.setErr(ErrBadReadCount)
				break

		panic(fmt.Errorf(format, args...))
	}
	if p.lineNum == p.errorLine {
		// Only one error per line.
		return
	}
	p.errorLine = p.lineNum
	if p.lex != nil {
		// Put file and line information on head of message.
		format = "%s:%d: " + format + "\n"
		args = append([]interface{}{p.lex.File(), p.lineNum}, args...)
	}
	fmt.Fprintf(p.errorWriter, format, args...)
	p.errorCount++
	if p.errorCount > 10 && !*flags.AllErrors {

	buf := make([]byte, 1)
	if _, err := b.Read(nil); err != nil {
		t.Fatalf("1st nil Read = %v; want nil", err)
	}
	if _, err := b.Read(buf); err != errFake {
		t.Fatalf("1st Read = %v; want errFake", err)
	}
	if _, err := b.Read(nil); err != nil {
		t.Fatalf("2nd nil Read = %v; want nil", err)
	}
	if _, err := b.Read(buf); err != nil {
		t.Fatalf("3rd Read with buffer = %v; want nil", err)
	}

	// check not at EOF
	b.WriteString("abcdefghijklmnopqrstuvwxyz")

	// after unsuccessful read
	if n, err := b.Read(nil); n != 0 || err != nil {
		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
	}
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after Read(nil): got no error")
	}

	// after successful read
	if _, err := b.ReadBytes('m'); err != nil {
		t.Fatalf("ReadBytes: %v", err)
	}