[李景山php]thinkphp核心源码注释|Sqlite.class.php

<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK ]
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2014 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------
namespace Think\Cache\Driver;
use Think\Cache;
defined('THINK_PATH') or exit();
/**
* Sqlite缓存驱动
* 很小的一个数据库文件，不过不错，估计没什么大的创新
*/
class Sqlite extends Cache {

/**
* 架构函数
* @param array $options 缓存参数
* @access public
* 架构 构造函数
*/
public function __construct($options=array()) {
if ( !extension_loaded('sqlite') ) {
E(L('_NOT_SUPPORT_').':sqlite');
}
if(empty($options)) {
$options = array (
'db'        =>  ':memory:',
'table'     =>  'sharedmemory',
);
}
$this->options  =   $options;
$this->options['prefix']    =   isset($options['prefix'])?  $options['prefix']  :   C('DATA_CACHE_PREFIX');
$this->options['length']    =   isset($options['length'])?  $options['length']  :   0;
$this->options['expire']    =   isset($options['expire'])?  $options['expire']  :   C('DATA_CACHE_TIME');

$func = $this->options['persistent'] ? 'sqlite_popen' : 'sqlite_open';
$this->handler      = $func($this->options['db']);
}

/**
* 读取缓存
* @access public
* @param string $name 缓存变量名
* @return mixed
*
*/
public function get($name) {
N('cache_read',1);// 记录
$name   = $this->options['prefix'].sqlite_escape_string($name);
$sql    = 'SELECT value FROM '.$this->options['table'].' WHERE var=\''.$name.'\' AND (expire=0 OR expire >'.time().') LIMIT 1';
$result = sqlite_query($this->handler, $sql);// 看来你也是 sql 之中的一员啊
if (sqlite_num_rows($result)) {
$content   =  sqlite_fetch_single($result);// 系统函数
if(C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
//启用数据压缩
$content   =   gzuncompress($content);
}
return unserialize($content);
}
return false;
}

/**
* 写入缓存
* @access public
* @param string $name 缓存变量名
* @param mixed $value  存储数据
* @param integer $expire  有效时间（秒）
* @return boolean
*/
public function set($name, $value,$expire=null) {
N('cache_write',1);
$name  = $this->options['prefix'].sqlite_escape_string($name);
$value = sqlite_escape_string(serialize($value));
if(is_null($expire)) {
$expire  =  $this->options['expire'];
}
$expire	=	($expire==0)?0: (time()+$expire) ;//缓存有效期为0表示永久缓存
if( C('DATA_CACHE_COMPRESS') && function_exists('gzcompress')) {
//数据压缩
$value   =   gzcompress($value,3);
// var_dump( gzuncompress(gzcompress('lijingshan')) );
}
$sql  = 'REPLACE INTO '.$this->options['table'].' (var, value,expire) VALUES (\''.$name.'\', \''.$value.'\', \''.$expire.'\')';
if(sqlite_query($this->handler, $sql)){
if($this->options['length']>0) {
// 记录缓存队列
$this->queue($name);// 队列记录
}
return true;
}
return false;
}

/**
* 删除缓存
* @access public
* @param string $name 缓存变量名
* @return boolean
* 同样需要数据表的一个支持呢
*/
public function rm($name) {
$name  = $this->options['prefix'].sqlite_escape_string($name);
$sql  = 'DELETE FROM '.$this->options['table'].' WHERE var=\''.$name.'\'';
sqlite_query($this->handler, $sql);
return true;
}

/**
* 清除缓存
* @access public
* @return boolean
* 为什么不直接清空数据表呢
*/
public function clear() {
$sql  = 'DELETE FROM '.$this->options['table'];
sqlite_query($this->handler, $sql);
return ;
}
}
// 总结，没什么特殊的了，