return &Writer{cw: &countWriter{w: bufio.NewWriter(w)}}
}

// SetOffset sets the offset of the beginning of the zip data within the
// underlying writer. It should be used when the zip data is appended to an
// existing file, such as a binary executable.
// It must be called before any data is written.
func (w *Writer) SetOffset(n int64) {
	if w.cw.count != 0 {
		panic("zip: SetOffset called after data was written")
	}
	w.cw.count = n
}

		writeTests[1].Data = nil
	}()

	// write a zip file
	buf := new(bytes.Buffer)
	existingData := []byte{1, 2, 3, 1, 2, 3, 1, 2, 3}
	n, _ := buf.Write(existingData)
	w := NewWriter(buf)
	w.SetOffset(int64(n))

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

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

	// read it back

	{"asmcgocall<>(SB)", "asmcgocall<>(SB)"},
	{"b+24(FP)", "b+24(FP)"},
	{"b_len+32(FP)", "b_len+32(FP)"},
	{"racecall<>(SB)", "racecall<>(SB)"},
	{"rcv_name+20(FP)", "rcv_name+20(FP)"},
	{"retoffset+28(FP)", "retoffset+28(FP)"},
	{"runtime·_GetStdHandle(SB)", "runtime._GetStdHandle(SB)"},
	{"sync\u2215atomic·AddInt64(SB)", "sync/atomic.AddInt64(SB)"},
	{"timeout+20(FP)", "timeout+20(FP)"},
	{"ts+16(FP)", "ts+16(FP)"},