buffer.h

#pragma once

#include "file.h"
#include "bufHashTbl.h"

namespace badgerdb {

class BufMgr;

class BufDesc {

  friend class BufMgr;

 private:
  File* file;

  PageId pageNo;

  FrameId frameNo;

  int pinCnt;

  bool dirty;

  bool valid;

  bool refbit;

  void Clear()
  {
    pinCnt = 0;
  file = NULL;
  pageNo = Page::INVALID_NUMBER;
    dirty = false;
    refbit = false;
  valid = false;
  };

  void Set(File* filePtr, PageId pageNum)
  { 
  file = filePtr;
    pageNo = pageNum;
    pinCnt = 1;
    dirty = false;
    valid = true;
    refbit = true;
  }

  void Print()
  {
    if(file)
    {
      std::cout << "file:" << file->filename() << " ";
      std::cout << "pageNo:" << pageNo << " ";
    }
    else
      std::cout << "file:NULL ";

    std::cout << "valid:" << valid << " ";
    std::cout << "pinCnt:" << pinCnt << " ";
    std::cout << "dirty:" << dirty << " ";
    std::cout << "refbit:" << refbit << "\n";
  }

  BufDesc()
  {
    Clear();
  }
};


struct BufStats
{
  int accesses;

  int diskreads;

  int diskwrites;

  void clear()
  {
    accesses = diskreads = diskwrites = 0;
  }
      
  BufStats()
  {
    clear();
  }
};


class BufMgr 
{
 private:
  FrameId clockHand;

  std::uint32_t numBufs;
  
  BufHashTbl *hashTable;

  BufDesc *bufDescTable;

  BufStats bufStats;

  void advanceClock();

  void allocBuf(FrameId & frame);

 public:
  Page* bufPool;

  BufMgr(std::uint32_t bufs);
  
  ~BufMgr();

  void readPage(File* file, const PageId PageNo, Page*& page);

  void unPinPage(File* file, const PageId PageNo, const bool dirty);

  void allocPage(File* file, PageId &PageNo, Page*& page); 

  void flushFile(const File* file);

  void disposePage(File* file, const PageId PageNo);

  void  printSelf();

  BufStats & getBufStats()
  {
    return bufStats;
  }

  void clearBufStats() 
  {
    bufStats.clear();
  }
};

}