public Object getPage(long pagePlusOffsetAddress) {
        if (tungstenMemoryMode == MemoryMode.ON_HEAP) {
            final int pageNumber = decodePageNumber(pagePlusOffsetAddress);
            assert (pageNumber >= 0 && pageNumber < PAGE_TABLE_SIZE);
            final MemoryBlock page = pageTable[pageNumber];
            assert (page != null);
            assert (page.getBaseObject() != null);
            return page.getBaseObject();
        } else {
            return null;
        }
    }
Get the page associated with an address encoded by
{@link TaskMemoryManager#encodePageNumberAndOffset(MemoryBlock, long)}
indexr-query-opt/src/main/java/org/apache/spark/memory/TaskMemoryManager.java