/*
* This method deletes a particular page from file.
*
* params: File* file, const PageId PageNo
*/
void BufMgr::disposePage(File* file, const PageId PageNo)
{
// Should we delete page if pincount is not zero? currently do not check pincount
try{
FrameId frame = -1;
// find if the page is in the buffer pool
hashTable->lookup(file, PageNo, frame);
// page is within the hashtable
BufDesc* bufDesc = &(bufDescTable[frame]);
/*if(bufDesc->pinCnt>0)
{
throw PagePinnedException("abc", PageNo, frame);
}*/
// Clear the frame
bufDesc->Clear();
// delete from buffer pool
hashTable->remove(file, PageNo);
}
// Page is not in the buffer pool
catch(HashNotFoundException) {
}
file->deletePage(PageNo);
}
/*
* 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);
}
}
void BufMgr::flushFile(const File* file)
{
for(FrameId i = 0; i < numBufs; i++){
BufDesc* temp = &(bufDescTable[i]);
if (temp->file == file){
if(temp->pinCnt > 0){
throw PagePinnedException(file->filename(), temp->pageNo, temp->frameNo);
}
if(temp->valid == false){
temp->pinCnt = 0;
throw BadBufferException(temp->frameNo, temp->dirty, temp->valid, temp->refbit);
}
// (a)
if (temp->dirty){
temp->file -> writePage(bufPool[i]); // flushes the page to disk
temp->dirty = false; // sets dirty bit to false
}
//(b)
try{
hashTable->remove(file, bufDescTable[i].pageNo);
} catch(HashNotFoundException e){
return;
}
//(c)
temp->Clear(); // clears frame
//bufDescTable[i].valid = false;
//bufDescTable[i].pinCnt = 0;
}
}
}
//Flushes out all dirty pages and deallocates the buffer pool and the BufDesc table.
BufMgr::~BufMgr()
{
BufDesc* bufdesc;
File * tmpfile;
Page * frame;
for (std::uint32_t i = 0; i < numBufs; i++)
{
bufdesc = &(bufDescTable[i]);
if(bufdesc->valid && bufdesc->dirty) {
//write frame from buffer onto disk
tmpfile = bufdesc->file;
frame = &(bufPool[bufdesc->frameNo]);
tmpfile->writePage(*frame);
}
//clear entry from BufDesc
bufdesc->Clear();
}
//deallocate BufDesc table
delete [] &bufDescTable;
//deallocates BufferPool
for(std::uint32_t i = 0; i < numBufs; i++) {
//guess there is no harm in leaving old information in pool
}
delete [] &bufPool;
}
/*
* print buffer management including total number of valid frames
*/
void BufMgr::printSelf(void)
{
BufDesc* tmpbuf;
int validFrames = 0;
for (std::uint32_t i = 0; i < numBufs; i++)
{
tmpbuf = &(bufDescTable[i]);
std::cout << "FrameNo:" << i << " ";
tmpbuf->Print();
if (tmpbuf->valid == true)
validFrames++;
}
std::cout << "Total Number of Valid Frames:" << validFrames << "\n";
}
/*
* 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";
}
