/*
* Decrements the pinCnt of the frame containing (file, PageNo)
*
* Throws HashNotFoundException when page is not in the buffer pool,
* on the hashtable to get a frame number.
* params: File* file, const PageId pageNo, Page*& page
*/
void BufMgr::readPage(File* file, const PageId pageNo, Page*& page)
{
FrameId frame = -1;
// look up hashtable
try{
hashTable->lookup(file, pageNo, frame);
// page is within the hashtable
BufDesc* bufDesc = &(bufDescTable[frame]);
bufDesc->refbit = true;
bufDesc->pinCnt = bufDesc->pinCnt + 1;
page = &(bufPool[frame]);
}
// Page is not in the buffer pool
catch(HashNotFoundException) {
// calling this first to see if the page is valid
file->readPage(pageNo);
// Allocate frame
FrameId frame = -1;
allocBuf(frame);
page = &(bufPool[frame]);
*page = file->readPage(pageNo);
// insert into hash table
hashTable->insert(file, pageNo, frame);
// call Set()
BufDesc* bufDesc = &(bufDescTable[frame]);
bufDesc->Set(file, pageNo);
}
}
/*
* This method is to to allocate an empty page in the specified file.
*
* params: File* file, PageId &pageNo, Page*& page
*/
void BufMgr::allocPage(File* file, PageId &pageNo, Page*& page)
{
// get a new page and allocate frame
Page newPage = file->allocatePage();
pageNo = newPage.page_number();
FrameId frame = -1;
allocBuf(frame);
page = &(bufPool[frame]);
*page = file->readPage(pageNo);
// insert into hash table
hashTable->insert(file, pageNo, frame);
// call Set()
BufDesc* bufDesc = &(bufDescTable[frame]);
bufDesc->Set(file, pageNo);
//std::cout << "Allocated new page: " << frame << "\n";
}
