buffer.h

#pragma once

#include "include/file.h"
#include "bufferHashTable.h"

namespace wiscdb {

class BufferManager;

class Frame {

  friend class BufferManager;

 private:
  File* file;

  PageId pageNo;

  FrameId  frameNo;

  int pinCnt;

  bool dirty;

  bool valid;

  bool refbit;

  void reset();

  void load(File* filePtr, PageId pageNum);

  void print();

  Frame();
};


struct BufferStats
{
  int accesses;

  int diskreads;

  int diskwrites;

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


class BufferManager 
{
 private:
  FrameId clockHand;

  std::uint32_t numFrames;
  
  BufferHashTable *hashTable;

  Frame *frameTable;

  BufferStats bufferStats;

  void advanceClock();

  void allocateFrame(FrameId & frame);

 public:
  Page* bufPool;

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

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

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

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

  void flushFile(const File* file);

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

  void  printSelf();

  BufferStats & getBufferStats()
  {
    return bufferStats;
  }

  void clearBufferStats() 
  {
    bufferStats.clear();
  }
};

}