func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
	slice, err := b.readSlice(delim)
	// return a copy of slice. The buffer's backing array may
	// be overwritten by later calls.
	line = append(line, slice...)
	return line, err
}

// readSlice is like ReadBytes but returns a reference to internal buffer data.
func (b *Buffer) readSlice(delim byte) (line []byte, err error) {
	i := IndexByte(b.buf[b.off:], delim)

	}
	// Test error after ReadSlice.
	_, _, err = r.ReadRune() // reset state
	if err != nil {
		t.Error("unexpected error on ReadRune (4):", err)
	}
	_, err = r.ReadSlice(0)
	if err != io.EOF {
		t.Error("unexpected error on ReadSlice (4):", err)
	}
	if r.UnreadRune() == nil {
		t.Error("expected error after ReadSlice (4)")
	}
}

func TestUnreadRuneAtEOF(t *testing.T) {