@Override
    protected TimestampOffset parseEntry(ByteBuffer buffer, int n) {
        return new TimestampOffset(timestamp(buffer, n), baseOffset() + relativeOffset(buffer, n));
    }
@Test
    public void testParseEntry() {
        idx.maybeAppend(1, 1 + baseOffset);
        assertEquals(new TimestampOffset(1, baseOffset + 1), idx.parseEntry(idx.mmap(), 0));
    }