[转]改进的PHP文本数据库类

改进的PHP文本数据库类

作者：bpns
来源：http://space.tju.cn/site/redboy/index.php?item=read&blogID=4&id=11

找了些时间，改进了自己文本数据库系统，从空间利用效率和并发性能两个方面着手，搞高了程序性能。

在空间利用率上，做了两点改进，一是在删除记录的时候，如果记录的存放位置在数据库的末端，就自动修改数据库末端指针，而不是将此记录的空间作为一个闲置块存入闲置块记录中，这样就可以继续在数据文件尾分配任意长度的空间而不是像以前那样将这个删除记录的空间整块分配给下一次请求空间的新记录；第二点改进是在从闲置块中请求空间的时候，不仅继续采用原来的最佳适应法，而且在请求到合适的闲置块的时候并不是将整个块而是将其部分划分给新记录，这样又进一部提高了空间的利用率。

在并发性能上，增加了数据库的打开模式这个选项。为了保持文本数据库操作的原子性，以前都以写模式打开数据库，用户无论是从数据库中读数据或写数据，系统都会锁定数据库而禁止其它用户并发的读写操作，而大多情况下，用户都是浏览网页而不是POST数据，禁止对数据库的并行的读操作，势必成为网页浏览速度的瓶颈，为了加速网页生成速度，在数据库中加入了打开模式这一选项，在只读模式下，可以允许不同的用户并发地从数据库中申请数据，使得网页并发性能得到了一定程序上的提高。

下面给出新文本数据库类的部分代码，其相关注释可以从原来的文章：http://202.113.13.169/site/redboy/index.php?item=read&id=1&blogID=4中获得。

源代码：

<?
classTxtDB
{
var$name='';//文本数据库名
var$path='';
var$minLen=20;
var$isError;
var$dbh;
var$indxh;
var$lfth;
var$lckh;
var$rcdCnt=0;
var$maxID=0;
var$leftCnt=0;
var$DBend=0;
var$mod='w';

functionTxtDB($name,$mod='w',$path='bpns_dbm')
{
$this->name=$name;
$this->path=$path.'/'.$name;
$this->isError=0;
$this->mod=$mod;
$path=$this->path;
if($name!='')
{
@mkdir($this->path,0777);
if(!file_exists($path.'/'.$name.'.tdb'))$this->dbh=fopen($this->path.'/'.$name.'.tdb','w+');
else$this->dbh=fopen($path.'/'.$name.'.tdb','r+');
if(!file_exists($path.'/'.$name.'.indx'))$this->indxh=fopen($this->path.'/'.$name.'.indx','w+');
else$this->indxh=fopen($path.'/'.$name.'.indx','r+');
if(!file_exists($path.'/'.$name.'.lft'))$this->lfth=fopen($this->path.'/'.$name.'.lft','w+');
else$this->lfth=fopen($this->path.'/'.$name.'.lft','r+');
if($this->mod=='w')
{
$this->lckh=fopen($this->path.'/'.$name.'.lck','w');
flock($this->lckh,2);
fwrite($this->lckh,'lck');//lockthedatebase
}
$rcd=$this->getRcd(0);
$this->rcdCnt=$rcd[id];
$this->maxID=$rcd[loc];
$this->DBend=$rcd[len];
$rcd=$this->getLeft(0);
$this->leftCnt=$rcd[loc];
}
else$this->isError=1;
}

functionsetRcd($rid,$id,$loc,$len)
{
fseek($this->indxh,$rid*12);
$str=pack('III',$id,$loc,$len);
fwrite($this->indxh,$str,12);
}

functiongetRcd($rid)
{
fseek($this->indxh,$rid*12);
$str=fread($this->indxh,12);
$rcd=array();
$rcd[id]=str2int($str);
$rcd[loc]=str2int(substr($str,4,4));
$rcd[len]=str2int(substr($str,8,4));
return$rcd;
}

functionsetLeft($lid,$loc,$len)
{
fseek($this->lfth,$lid*8);
$str=pack('II',$loc,$len);
fwrite($this->lfth,$str,8);
}

functiongetLeft($lid)
{
fseek($this->lfth,$lid*8);
$str=fread($this->lfth,8);
$rcd[loc]=str2int($str);
$rcd[len]=str2int(substr($str,4,4));
return$rcd;
}

functionclear()
{
$this->setRcd(0,0,0,0);
$this->setLeft(0,0,0);
}

functionclose()
{
@fclose($this->dbh);
@fclose($this->indxh);
@fclose($this->lfth);
@fclose($this->lckh);
}

functionseekSpace($len)
{
$res=array('loc'=>0,'len'=>0);
if($this->leftCnt<1)return$res;
$find=0;
$min=1000000;
for($i=$this->leftCnt;$i>0;$i--)
{
$res=$this->getLeft($i);
if($res[len]==$len){$find=$i;break;}
elseif($res[len]>$len)
{
if($res[len]-$len<$min)
{
$min=$res[len]-$len;
$find=$i;
}
}
}
if($find)
{
$res=$this->getLeft($find);
if($res[len]<2*$len)
{
fseek($this->lfth,($find+1)*8);
$str=fread($this->lfth,($this->leftCnt-$find)*8);
fseek($this->lfth,$find*8);
fwrite($this->lfth,$str);
$this->leftCnt--;
$this->setLeft(0,$this->leftCnt,0);
return$res;
}
else
{
$rs=array();
$rs[loc]=$res[loc];
$rs[len]=$len;
$res[loc]+=$len;
$this->setLeft($find,$res[loc],$res[len]-$len);
return$rs;
}
}
else//fail
{
$res[len]=0;
return$res;
}
}

functioninsert($content,$len=0)//returnwithrecordid
{
$res=array('loc'=>0);
if($this->mod!='w')return0;
if(!$len)$len=strlen($content);
if($len<$this->minLen)$len=$this->minLen;
if($this->leftCnt)$res=$this->seekSpace($len);
if(!$res[len])
{
$res[loc]=$this->DBend;
$res[len]=$len;
}
if($res[loc]+$res[len]>$this->DBend)$this->DBend=$res[loc]+$res[len];
//echo$this->DBend.'<br>';
$this->maxID++;
$this->rcdCnt++;
$this->setRcd(0,$this->rcdCnt,$this->maxID,$this->DBend);
$this->setRcd($this->rcdCnt,$this->maxID,$res[loc],$res[len]);
fseek($this->dbh,$res[loc]);
fwrite($this->dbh,$content,$len);
return$this->maxID;
}

functionfindByID($id)
{
if($id<1or$id>$this->maxIDor$this->rcdCnt<1)return0;
$left=1;
$right=$this->rcdCnt;
while($left<$right)
{
$mid=(int)(($left+$right)/2);
if($mid==$leftor$mid==$right)break;
$rcd=$this->getRcd($mid);
if($rcd[id]==$id)return$mid;
elseif($id<$rcd[id])$right=$mid;
else$left=$mid;
}
//$rcd=$this->getRcd($mid);
//if($rcd[id]==$id)return$mid;
$rcd=$this->getRcd($left);
if($rcd[id]==$id)return$left;
$rcd=$this->getRcd($right);
if($rcd[id]==$id)return$right;
return0;
}

functiondelete($id)
{
if($this->mod!='w')return0;
$rid=$this->findByID($id);
if(!$rid)return;
$res=$this->getRcd($rid);
fseek($this->indxh,($rid+1)*12);
$str=fread($this->indxh,($this->rcdCnt-$i)*12);
fseek($this->indxh,$rid*12);
fwrite($this->indxh,$str);
$this->rcdCnt--;
if($res[loc]+$res[len]==$this->DBend)
{
$this->DBend=$res[loc];
$this->setRcd(0,$this->rcdCnt,$this->maxID,$this->DBend);
}
else
{
$this->setRcd(0,$this->rcdCnt,$this->maxID,$this->DBend);
$this->leftCnt++;
$this->setLeft(0,$this->leftCnt,0);
$this->setLeft($this->leftCnt,$res[loc],$res[len]);
}
}

functionupdate($id,$newcontent,$len=0)
{
if($this->mod!='w')return;
$rid=$this->findByID($id);
if(!$rid)return;
if(!$len)$len=strlen($newcontent);
$rcd=$this->getRcd($rid);
if($rcd[len]<$len)
{
$this->leftCnt++;
$this->setLeft(0,$this->leftCnt,0);
$this->setLeft($this->leftCnt,$rcd[loc],$rcd[len]);
$rcd[loc]=$this->DBend;
$rcd[len]=$len;
$this->DBend+=$len;
$this->setRcd(0,$this->rcdCnt,$this->maxID,$this->DBend);
$this->setRcd($rid,$rcd[id],$rcd[loc],$rcd[len]);
}
fseek($this->dbh,$rcd[loc]);
fwrite($this->dbh,$newcontent,$len);
//echo$id.'<br>'.$content.'<br>'.$len;
}

functionselectByRid($rid)
{
$res=array('id'=>0,'content'=>'');
if($rid<1or$rid>$this->rcdCnt)return$res;
else$rcd=$this->getRcd($rid);
$res[id]=$rcd[id];
$res[len]=$rcd[len];
fseek($this->dbh,$rcd[loc]);
$res[content]=fread($this->dbh,$rcd[len]);
//$res[rid]=$rid;
return$res;
}

functionselect($id)
{
return$this->selectByRid($this->findByID($id));
}

functionbackup()
{
copy($this->path.'/'.$this->name.'.tdb',$this->path.'/'.$this->name.'.tdb.bck');
copy($this->path.'/'.$this->name.'.indx',$this->path.'/'.$this->name.'.indx.bck');
copy($this->path.'/'.$this->name.'.lft',$this->path.'/'.$this->name.'.lft.bck');
}

functionrecover()
{
copy($this->path.'/'.$this->name.'.tdb.bck',$this->path.'/'.$this->name.'.tdb');
copy($this->path.'/'.$this->name.'.indx.bck',$this->path.'/'.$this->name.'.indx');
copy($this->path.'/'.$this->name.'.lft.bck',$this->path.'/'.$this->name.'.lft');
}
}

?>

PS: 其他可以参考上一篇文章：http://blog.csdn.net/heiyeshuwu/archive/2006/06/16/804265.aspx