Group member:
Dan Ye
Peng Du

Some clarifications of our method:

1. To run the Unit Test provided in the submission, please modify the ¡®path¡¯ variable in the BufferQunit.cc line 37.

2. When a handle is generated intially, it's assigned a nullptr. Only when it calls readByte() or writeByte will it be assigned real page in the buffer pool.

3. When the whole buffer pool is occupied by pinned pages, any other allocation of a new page in the buffer pool will be reported as an exception.

4. For the strategy of the LRU, when a pinned page is unpinned, it will become the first to be evicted in the future.