badgerdb::BufHashTbl Class Reference

Hash table class to keep track of pages in the buffer pool. More...

#include <bufHashTbl.h>

Public Member Functions
	BufHashTbl (const int htSize)
	~BufHashTbl ()
void	insert (const File *file, const PageId pageNo, const FrameId frameNo)
bool	lookup (const File *file, const PageId pageNo, FrameId &frameNo)
void	remove (const File *file, const PageId pageNo)

Detailed Description

Hash table class to keep track of pages in the buffer pool.

Warning

This class is not threadsafe.

Definition at line 45 of file bufHashTbl.h.

Constructor & Destructor Documentation

badgerdb::BufHashTbl::BufHashTbl

(

const int

htSize

)

Constructor of BufHashTbl class

Definition at line 26 of file bufHashTbl.cpp.

  : HTSIZE(htSize)
{
  // allocate an array of pointers to hashBuckets
  ht = new hashBucket* [htSize];
  for(int i=0; i < HTSIZE; i++)
    ht[i] = NULL;
}

badgerdb::BufHashTbl::~BufHashTbl

(

)

Destructor of BufHashTbl class

Definition at line 35 of file bufHashTbl.cpp.

{
  for(int i = 0; i < HTSIZE; i++) {
    hashBucket* tmpBuf = ht[i];
    while (ht[i]) {
      tmpBuf = ht[i];
      ht[i] = ht[i]->next;
      delete tmpBuf;
    }
  }
  delete [] ht;
}

Member Function Documentation

void badgerdb::BufHashTbl::insert	(	const File *	file,
		const PageId	pageNo,
		const FrameId	frameNo
	)

Insert entry into hash table mapping (file, pageNo) to frameNo.

Parameters

file	File object
pageNo	Page number in the file
frameNo	Frame number assigned to that page of the file

Exceptions

HashAlreadyPresentException	if the corresponding page already exists in the hash table
HashTableException	(optional) if could not create a new bucket as running of memory

Definition at line 48 of file bufHashTbl.cpp.

{
  int index = hash(file, pageNo);

  hashBucket* tmpBuc = ht[index];
  while (tmpBuc) {
    if (tmpBuc->file == file && tmpBuc->pageNo == pageNo)
      throw HashAlreadyPresentException(tmpBuc->file->filename(), tmpBuc->pageNo, tmpBuc->frameNo);
    tmpBuc = tmpBuc->next;
  }

  tmpBuc = new hashBucket;
  if (!tmpBuc)
    throw HashTableException();

  tmpBuc->file = (File*) file;
  tmpBuc->pageNo = pageNo;
  tmpBuc->frameNo = frameNo;
  tmpBuc->next = ht[index];
  ht[index] = tmpBuc;
}

bool badgerdb::BufHashTbl::lookup	(	const File *	file,
		const PageId	pageNo,
		FrameId &	frameNo
	)

Check if (file, pageNo) is currently in the buffer pool (ie. in the hash table). If so, assign the value to frameNo and return true.

Parameters

file	File object
pageNo	Page number in the file
frameNo	Frame number reference that is assigned if (file, pageNo) is present

Returns

true if (file, pageNo) is present. Else false.

Definition at line 70 of file bufHashTbl.cpp.

{
  int index = hash(file, pageNo);
  hashBucket* tmpBuc = ht[index];
  while (tmpBuc) {
    if (tmpBuc->file == file && tmpBuc->pageNo == pageNo)
    {
      frameNo = tmpBuc->frameNo; // 'return' frameNo by reference
      return true;
    }
    tmpBuc = tmpBuc->next;
  }
  return false;
}

void badgerdb::BufHashTbl::remove	(	const File *	file,
		const PageId	pageNo
	)

Delete entry (file,pageNo) from hash table.

Parameters

file	File object
pageNo	Page number in the file

Exceptions

HashNotFoundException

if the page entry is not found in the hash table

Definition at line 85 of file bufHashTbl.cpp.

                                                             {

  int index = hash(file, pageNo);
  hashBucket* tmpBuc = ht[index];
  hashBucket* prevBuc = NULL;

  while (tmpBuc)
  {
    if (tmpBuc->file == file && tmpBuc->pageNo == pageNo)
    {
      if(prevBuc) 
        prevBuc->next = tmpBuc->next;
      else
        ht[index] = tmpBuc->next;

      delete tmpBuc;
      return;
    }
    else
    {
      prevBuc = tmpBuc;
      tmpBuc = tmpBuc->next;
    }
  }

  throw HashNotFoundException(file->filename(), pageNo);
}

---

The documentation for this class was generated from the following files:

• /afs/cs.wisc.edu/u/h/a/haiyun/private/cs564-spr17/projects/p2/BufMgr/src/bufHashTbl.h
• /afs/cs.wisc.edu/u/h/a/haiyun/private/cs564-spr17/projects/p2/BufMgr/src/bufHashTbl.cpp