<?php
namespace JLaso\ToolsLib;
class PreEmptiveCache
{
const OLDEST_MODE = 1; // remove from cache first the oldest item
const LESS_MODE = 2; // remove from cache first the less accessed item
const LESS_OLDEST_MODE = 3; // remove from cache first the oldest item from the less accessed items
/** @var array */
protected $items = array();
/** @var array */
protected $metaInfo = array();
/** @var \Closure */
protected $callable;
/** @var int */
protected $mode;
/** @var int */
protected $maxRecordsCached;
/** @var bool */
protected $debug;
/** @var int */
protected $baseTime = 0;
/**
* @param \Closure $callable
* @param array $options
*/
public function __construct($callable, $options = array())
{
$this->callable = $callable;
$options = array_merge(array(
"mode" => self::OLDEST_MODE,
"maxRecordsCached" => 500,
"debug" => false,
), $options);
$this->debug = $options["debug"];
$this->mode = $options["mode"];
$this->maxRecordsCached = isset($options["maxRecordsCached"]) ? $options["maxRecordsCached"] : -1;
$this->baseTime = $this->getTimeStamp();
}
/**
* @return int
*/
protected function getTimeStamp()
{
return intval(1000000*microtime(true)) - $this->baseTime;
}
/**
* @param $id
* @return mixed
*/
public function fetch($id)
{
if (!isset($this->items[$id])) {
if (count($this->items) >= $this->maxRecordsCached){
if ($this->debug){
print (sprintf("max mem exceeded (%d bytes) with %d items!\n", $this->currentMemUsed, count($this->items)));
}
$this->findCandidateAndRemoveFromCache();
}
$this->items[$id] = call_user_func_array($this->callable, array($id));
$this->metaInfo[$id]['id'] = $id;
$this->metaInfo[$id]['inMem'] = true;
$this->metaInfo[$id]['lastAccess'] = $this->getTimeStamp();
$this->metaInfo[$id]['numAccess'] = isset($this->metaInfo[$id]['numAccess']) ? $this->metaInfo[$id]['numAccess']+1 : 1;
}
return $this->items[$id];
}
/**
* @return bool
*/
protected function findCandidateAndRemoveFromCache()
{
$candidate = null;
switch ($this->mode){
case self::LESS_MODE:
$less = 9999999;
foreach ($this->metaInfo as $metaInfo){
if (($metaInfo['numAccess'] < $less) && $metaInfo['inMem']){
$less = $metaInfo['numAccess'];
$candidate = $metaInfo;
if ($less == 1){
break;
}
}
}
break;
case self::LESS_OLDEST_MODE:
$less = 9999999;
// calculate the min value for numAccess
foreach ($this->metaInfo as $metaInfo){
if (($metaInfo['numAccess'] < $less) && $metaInfo['inMem']){
$less = $metaInfo['numAccess'];
}
}
$oldest = $this->getTimeStamp();
foreach ($this->metaInfo as &$metaInfo){
if (($less == $metaInfo['numAccess']) && $metaInfo['inMem'] && ($metaInfo['lastAccess'] < $oldest)){
$oldest = $metaInfo['lastAccess'];
$candidate = $metaInfo;
}
}
break;
case self::OLDEST_MODE:
$oldest = date("U");
foreach ($this->metaInfo as $metaInfo){
if (($metaInfo['lastAccess'] < $oldest) && $metaInfo['inMem']){
$oldest = $metaInfo['lastAccess'];
$candidate = $metaInfo;
}
}
break;
}
if ($this->debug){
var_dump($candidate);
}
if ($candidate){
if ($this->debug){
$this->dumpMetaInfo();
print sprintf("freeing item %d from memory\n", $candidate['id']);
}
$this->metaInfo[$candidate['id']]['inMem'] = false;
unset($this->items[$candidate['id']]);
if ($this->debug){
$this->dumpMetaInfo();
}
return true;
}
}
/**
* Only with debug purposes
*/
protected function dumpMetaInfo()
{
$text = "";
$temp = $this->metaInfo;
sort($temp);
foreach($temp as $metaInfo){
$text .= sprintf("%d[%d]%s,", $metaInfo['id'], $metaInfo['numAccess'], ($metaInfo['inMem']?'*':''));
}
print $text."\n";
}
}
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