buf.c

linux 下用c++ 开发的一个小型数据库系统

#include <memory.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <fcntl.h>
#include <iostream>
#include <stdio.h>
#include "page.h"
#include "buf.h"

#define ASSERT(c)  { if (!(c)) { \
		       cerr << "At line " << __LINE__ << ":" << endl << "  "; \
                       cerr << "This condition should hold: " #c << endl; \
                       exit(1); \
		     } \
                   }

//----------------------------------------
// Constructor of the class BufMgr
//----------------------------------------

BufMgr::BufMgr(const int bufs)
{
  numBufs = bufs ;

  hashTable = new BufHashTbl(bufs * 2) ;
  bufTable = new BufDesc[bufs] ;
  bufPool = new Page[bufs] ;

  bufTable[0].next = &bufTable[1] ;
  bufTable[0].prior = NULL ;
  bufTable[0].frameNo = 0 ;
  for (int i = 1; i < bufs - 1; i++){
    bufTable[i].next = &bufTable[i+1] ;
    bufTable[i].prior = &bufTable[i-1] ;
    bufTable[i].frameNo = i ;
  }
  bufTable[bufs - 1].next = NULL ;
  bufTable[bufs - 1].prior = &bufTable[bufs-2] ;
  bufTable[bufs - 1].frameNo = numBufs - 1 ;

  rearUPL = &bufTable[0] ;
  frontUPL = &bufTable[bufs-1] ;   
}

BufMgr::~BufMgr() 
{
    BufDesc *tmpbuf = NULL ;

    for (int i = 0; i < numBufs; i++){
      tmpbuf = &bufTable[i] ;      
      if (tmpbuf->valid == true && tmpbuf->dirty == true)
        tmpbuf->file->writePage( tmpbuf->pageNo, &bufPool[i]) ;
    }

    delete hashTable ;
    delete []bufTable ;
    delete []bufPool ;
}

void BufMgr::BufDump() 
{
// late



}


const Status BufMgr::allocBuf(int& frame) 
{
  BufDesc *mybuf = NULL ;

  if (rearUPL == NULL) return BUFFEREXCEEDED ;
  mybuf = rearUPL ;

  if (rearUPL == frontUPL) rearUPL = frontUPL = NULL ;
  else{
    rearUPL = rearUPL->next ;
    rearUPL->prior = NULL ;
  }

  if (mybuf->dirty){
    mybuf->file->writePage(mybuf->pageNo,&bufPool[mybuf->frameNo]) ;
    hashTable->remove(mybuf->file, mybuf->pageNo) ;
  }
  
  if (mybuf->valid == true)
    hashTable->remove(mybuf->file, mybuf->pageNo) ;  
 
  mybuf->Clear() ;
  frame = mybuf->frameNo ;

  return OK ;
}

// release an unused buffer frame - used in error conditions
const void BufMgr::releaseBuf(int frame) 
{
    rearUPL->prior = &bufTable[frame] ;
    bufTable[frame].next = rearUPL ;
    rearUPL = &bufTable[frame] ;
    rearUPL->prior = NULL ;
}

const Status BufMgr::readPage(File* file, const int PageNo, Page*& page)
{
  int myframeNo ;
//  cout<<file<<" "<<PageNo<<endl ;
  if (hashTable->lookup(file,PageNo,myframeNo) == OK){
   
    if (bufTable[myframeNo].pinCnt >= 1) bufTable[myframeNo].pinCnt++ ;
    else{
      if (&bufTable[myframeNo] == rearUPL) rearUPL = bufTable[myframeNo].next ;
      if (&bufTable[myframeNo] == frontUPL) frontUPL = bufTable[myframeNo].prior ;
      if (bufTable[myframeNo].prior != NULL)
        bufTable[myframeNo].prior->next = bufTable[myframeNo].next ;
      if (bufTable[myframeNo].next != NULL)
        bufTable[myframeNo].next->prior = bufTable[myframeNo].prior ;

      bufTable[myframeNo].next = bufTable[myframeNo].prior = NULL ; 
      bufTable[myframeNo].pinCnt = 1 ;
    }
   
    page = &bufPool[myframeNo] ;

    return OK ;
  }
  else{
    if (allocBuf(myframeNo) != OK) return BUFFEREXCEEDED ;
    if (file->readPage(PageNo,&bufPool[myframeNo]) != OK){
      releaseBuf(myframeNo) ;
      return UNIXERR ;
    }
//    cout<<"n read page ="<<(char *)&bufPool[myframeNo]<<endl ; 
    bufTable[myframeNo].Set(file,PageNo) ;
    if(hashTable->insert(file,PageNo,myframeNo) != OK) return HASHTBLERROR ;

    page = &bufPool[myframeNo] ;

    return OK ;
  }
}


const Status BufMgr::unPinPage(const File* file, const int PageNo, 
			       const bool dirty, const bool loveIt)
{
  int myframeNo;

  if (hashTable->lookup(file,PageNo,myframeNo) != OK) return HASHNOTFOUND ;
//  cout<<"relese frame ="<<myframeNo<<endl ;

  if(dirty) bufTable[myframeNo].dirty = dirty ;
//  cout<<"frame ="<<myframeNo<<"  info =" ;
//  cout<<(char *)&bufPool[myframeNo]<<endl ;

  if (bufTable[myframeNo].pinCnt == 0) return PAGENOTPINNED ;

  bufTable[myframeNo].pinCnt-- ;

  if(bufTable[myframeNo].pinCnt != 0) return OK ;

  if ((rearUPL == NULL) && (frontUPL == NULL)){
    rearUPL = frontUPL = &bufTable[myframeNo] ;

    return OK ;
  }

  if (loveIt == false) releaseBuf(myframeNo) ;
  else{
    frontUPL->next = &bufTable[myframeNo] ;
    bufTable[myframeNo].prior = frontUPL ;
    frontUPL = &bufTable[myframeNo] ;
    frontUPL->next = NULL ;
  }

  return OK ;
}


const Status BufMgr::flushFile(const File* file) 
{
  for (int i = 0; i < numBufs; i++){

    if (bufTable[i].file == file){

      if (bufTable[i].pinCnt != 0)
        return PAGEPINNED ;

      if (bufTable[i].dirty)
        (bufTable[i].file)->writePage(bufTable[i].pageNo,&bufPool[bufTable[i].frameNo]) ;

      if (bufTable[i].valid)
        hashTable->remove( file, bufTable[i].pageNo) ;

      bufTable[i].valid = false ;   
      bufTable[i].dirty = false ;
    }
  }
      

  return OK ;
}


const Status BufMgr::disposePage(File* file, const int pageNo) 
{
  int myframeNo ;

  if (hashTable->lookup(file,pageNo,myframeNo) != OK)
    return HASHTBLERROR ;

  if (bufTable[myframeNo].pinCnt != 0)
    return PAGEPINNED ;

  hashTable->remove(file,pageNo) ;
  releaseBuf(myframeNo) ;
  
  if (file->disposePage(pageNo) != OK) return UNIXERR ;

  return OK ;
}


const Status BufMgr::allocPage(File* file, int& pageNo, Page*& page) 
{
  int myframeNo ;

  if (file->allocatePage(pageNo) != OK) return UNIXERR ;

  if (allocBuf(myframeNo) != OK) return BUFFEREXCEEDED ;
//  cout<<"alloc frame="<<myframeNo<<endl ;

  if (hashTable->insert (file, pageNo, myframeNo) != OK){
    releaseBuf(myframeNo) ;
    return HASHTBLERROR ;
  }

  bufTable[myframeNo].Set( file, pageNo) ;
  page = &bufPool[myframeNo] ;

  return OK ;
}

void BufMgr::printSelf(void) {

  cout<<"rearUPL framNo="<<rearUPL->frameNo<<endl ;
  cout<<"frontUPL frameNo="<<frontUPL->frameNo<<endl ;
  BufDesc* tmpbuf;
  int i = 1 ;
  cout << endl << "Print buffer...\n";
    tmpbuf = rearUPL;
  do{
    cout << tmpbuf->frameNo << "\t" << (char*)(&bufPool[tmpbuf->frameNo]) 
              << "\tpinCnt: " << tmpbuf->pinCnt ;
    if (tmpbuf->valid == true)
      cout << "\tvalid" ;
    if (tmpbuf->dirty == true)
      cout << "\tdirty\n" ; 
    cout << endl;
    tmpbuf = tmpbuf->next ;
    i = i + 1 ;
  }while(tmpbuf != NULL) ;
  cout<<"ky buf num = "<<i<<endl ;
}