Cache Handler Function
缓冲处理函数
As an alternative to using the default file-based caching mechanism, you can
specify a custom cache handling function that will be used to read, write
and clear cached files.
作为一个可选择使用的默认基于文本的缓冲机制，你可以定制或者自定义缓冲处理函数来进行读、写、清除缓冲文件。
Create a function in your application that Smarty will use as a cache handler.
Set the name of it in the $cache_handler_func class variable. Smarty will now use this to handle cached data. The first argument
is the action, which will be one of 'read', 'write' and 'clear'. The second
parameter is the Smarty object. The third parameter is the cached content.
Upon a write, Smarty passes the cached content in these parameters. Upon a
'read', Smarty expects your function to accept this parameter by reference
and populate it with the cached data. Upon a 'clear', pass a dummy variable
here since it is not used. The fourth parameter is the name of the template
file (needed for read/write), the fifth parameter is the cache_id (optional),
and the sixth is the compile_id (optional).
如果要在应用程序下建立一个函数，SMARTY将会使用一个缓冲处理。设置这个函数名为 $cache
handler func 中类变量名。Smarty将使用这个函数来处理缓冲数据。第一个参数不管是‘读’，‘写’，‘清除’，都是动态的。第二个参数是
Smarty 对象。第三个参数是缓冲的内容。在进行写操作之前，Smarty 传递这些缓冲内容给这些参量。在进行读操作之前，Smarty预处理那些缓冲数据相关或者封装好了的函数。在进行清除操作之前，从他没有使用起，就传递一个虚拟变量。第四个参数是模板文件名（需要读和写的文件），第五个函数是缓冲ID（额外选项），然后第六个参数是编译的ID（额外选项）。
Note: The last parameter ($exp_time) was added in Smarty-2.6.0.
注意：最新的参数名 （$exp_time) 在Smarty-2.6.0中才加入的。
Example 15-5. example using MySQL as a cache source
<?php
function mysql_cache_handler($action, &$smarty_obj, &$cache_content, $tpl_file=null, $cache_id=null, $compile_id=null, $exp_time=null)
{
// set db host, user and pass here
$db_host = 'localhost';
$db_user = 'myuser';
$db_pass = 'mypass';
$db_name = 'SMARTY_CACHE';
$use_gzip = false;
// create unique cache id
$CacheID = md5($tpl_file.$cache_id.$compile_id);
if(! $link = mysql_pconnect($db_host, $db_user, $db_pass)) {
$smarty_obj->_trigger_error_msg("cache_handler: could not connect to database");
return false;
}
mysql_select_db($db_name);
switch ($action) {
case 'read':
// save cache to database
$results = mysql_query("select CacheContents from CACHE_PAGES where CacheID='$CacheID'");
if(!$results) {
$smarty_obj->_trigger_error_msg("cache_handler: query failed.");
}
$row = mysql_fetch_array($results,MYSQL_ASSOC);
if($use_gzip && function_exists("gzuncompress")) {
$cache_contents = gzuncompress($row["CacheContents"]);
} else {
$cache_contents = $row["CacheContents"];
}
$return = $results;
break;
case 'write':
// save cache to database
if($use_gzip && function_exists("gzcompress")) {
// compress the contents for storage efficiency
$contents = gzcompress($cache_content);
} else {
$contents = $cache_content;
}
$results = mysql_query("replace into CACHE_PAGES values(
'$CacheID',
'".addslashes($contents)."')
");
if(!$results) {
$smarty_obj->_trigger_error_msg("cache_handler: query failed.");
}
$return = $results;
break;
case 'clear':
// clear cache info
if(empty($cache_id) && empty($compile_id) && empty($tpl_file)) {
// clear them all
$results = mysql_query("delete from CACHE_PAGES");
} else {
$results = mysql_query("delete from CACHE_PAGES where CacheID='$CacheID'");
}
if(!$results) {
$smarty_obj->_trigger_error_msg("cache_handler: query failed.");
}
$return = $results;
break;
default:
// error, unknown action
$smarty_obj->_trigger_error_msg("cache_handler: unknown action \"$action\"");
$return = false;
break;
}
mysql_close($link);
return $return;
}
?>
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