<?php
/**
* Zend Framework (http://framework.zend.com/)
*
* @link http://github.com/zendframework/zf2 for the canonical source repository
* @copyright Copyright (c) 2005-2014 Zend Technologies USA Inc. (http://www.zend.com)
* @license http://framework.zend.com/license/new-bsd New BSD License
*/
namespace Zend\Memory;
use Zend\Cache\Storage\ClearByNamespaceInterface as ClearByNamespaceCacheStorage;
use Zend\Cache\Storage\FlushableInterface as FlushableCacheStorage;
use Zend\Cache\Storage\StorageInterface as CacheStorage;
/**
* Memory manager
*
* This class encapsulates memory menagement operations, when PHP works
* in limited memory mode.
*/
class MemoryManager
{
/**
* Storage cache object
*
* @var CacheStorage
*/
private $cache = null;
/**
* Memory grow limit.
* Default value is 2/3 of memory_limit php.ini variable
* Negative value means no limit
*
* @var int
*/
private $memoryLimit = -1;
/**
* Minimum value size to be swapped.
* Default value is 16K
* Negative value means that memory objects are never swapped
*
* @var int
*/
private $minSize = 16384;
/**
* Overall size of memory, used by values
*
* @var int
*/
private $memorySize = 0;
/**
* Id for next Zend\Memory object
*
* @var int
*/
private $nextId = 0;
/**
* List of candidates to unload
*
* It also represents objects access history. Last accessed objects are moved to the end of array
*
* array(
* <id> => <memory container object>,
* ...
* )
*
* @var array
*/
private $unloadCandidates = array();
/**
* List of object sizes.
*
* This list is used to calculate modification of object sizes
*
* array( <id> => <size>, ...)
*
* @var array
*/
private $sizes = array();
/**
* Last modified object
*
* It's used to reduce number of calls necessary to trace objects' modifications
* Modification is not processed by memory manager until we do not switch to another
* object.
* So we have to trace only _first_ object modification and do nothing for others
*
* @var \Zend\Memory\Container\Movable
*/
private $lastModified = null;
/**
* Unique memory manager id
*
* @var int
*/
private $managerId;
/**
* This function is intended to generate unique id, used by memory manager
*/
private function _generateMemManagerId()
{
/**
* @todo !!!
* uniqid() php function doesn't really guarantee the id to be unique
* it should be changed by something else
* (Ex. backend interface should be extended to provide this functionality)
*/
$this->managerId = str_replace('.', '_', uniqid('ZendMemManager', true)) . '_';
}
/**
* Memory manager constructor
*
* If cache is not specified, then memory objects are never swapped
*
* @param CacheStorage $cache
*/
public function __construct(CacheStorage $cache = null)
{
if ($cache === null) {
return;
}
$this->cache = $cache;
$this->_generateMemManagerId();
$memoryLimitStr = trim(ini_get('memory_limit'));
if ($memoryLimitStr != '' && $memoryLimitStr != -1) {
$this->memoryLimit = (int) $memoryLimitStr;
switch (strtolower($memoryLimitStr[strlen($memoryLimitStr) - 1])) {
case 'g':
$this->memoryLimit *= 1024;
// no break
case 'm':
$this->memoryLimit *= 1024;
// no break
case 'k':
$this->memoryLimit *= 1024;
break;
default:
break;
}
$this->memoryLimit = (int) ($this->memoryLimit*2/3);
} // No limit otherwise
}
/**
* Object destructor
*
* Clean up cache storage
*/
public function __destruct()
{
if ($this->cache !== null) {
if ($this->cache instanceof ClearByNamespaceCacheStorage) {
$this->cache->clearByNamespace($this->cache->getOptions()->getNamespace());
} elseif ($this->cache instanceof FlushableCacheStorage) {
$this->cache->flush();
}
}
}
/**
* Set memory grow limit
*
* @param int $newLimit
*/
public function setMemoryLimit($newLimit)
{
$this->memoryLimit = $newLimit;
$this->_swapCheck();
}
/**
* Get memory grow limit
*
* @return int
*/
public function getMemoryLimit()
{
return $this->memoryLimit;
}
/**
* Set minimum size of values, which may be swapped
*
* @param int $newSize
*/
public function setMinSize($newSize)
{
$this->minSize = $newSize;
}
/**
* Get minimum size of values, which may be swapped
*
* @return int
*/
public function getMinSize()
{
return $this->minSize;
}
/**
* Create new Zend\Memory value container
*
* @param string $value
* @return Container\ContainerInterface
* @throws Exception\ExceptionInterface
*/
public function create($value = '')
{
return $this->_create($value, false);
}
/**
* Create new Zend\Memory value container, which has value always
* locked in memory
*
* @param string $value
* @return Container\ContainerInterface
* @throws Exception\ExceptionInterface
*/
public function createLocked($value = '')
{
return $this->_create($value, true);
}
/**
* Create new Zend\Memory object
*
* @param string $value
* @param bool $locked
* @return \Zend\Memory\Container\ContainerInterface
* @throws \Zend\Memory\Exception\ExceptionInterface
*/
private function _create($value, $locked)
{
$id = $this->nextId++;
if ($locked || ($this->cache === null) /* Use only memory locked objects if backend is not specified */) {
return new Container\Locked($value);
}
// Commit other objects modifications
$this->_commit();
$valueObject = new Container\Movable($this, $id, $value);
// Store last object size as 0
$this->sizes[$id] = 0;
// prepare object for next modifications
$this->lastModified = $valueObject;
return new Container\AccessController($valueObject);
}
/**
* Unlink value container from memory manager
*
* Used by Memory container destroy() method
*
* @internal
* @param Container\Movable $container
* @param int $id
* @return null
*/
public function unlink(Container\Movable $container, $id)
{
if ($this->lastModified === $container) {
// Drop all object modifications
$this->lastModified = null;
unset($this->sizes[$id]);
return;
}
if (isset($this->unloadCandidates[$id])) {
unset($this->unloadCandidates[$id]);
}
$this->memorySize -= $this->sizes[$id];
unset($this->sizes[$id]);
}
/**
* Process value update
*
* @internal
* @param \Zend\Memory\Container\Movable $container
* @param int $id
*/
public function processUpdate(Container\Movable $container, $id)
{
/**
* This method is automatically invoked by memory container only once per
* "modification session", but user may call memory container touch() method
* several times depending on used algorithm. So we have to use this check
* to optimize this case.
*/
if ($container === $this->lastModified) {
return;
}
// Remove just updated object from list of candidates to unload
if (isset($this->unloadCandidates[$id])) {
unset($this->unloadCandidates[$id]);
}
// Reduce used memory mark
$this->memorySize -= $this->sizes[$id];
// Commit changes of previously modified object if necessary
$this->_commit();
$this->lastModified = $container;
}
/**
* Commit modified object and put it back to the loaded objects list
*/
private function _commit()
{
if (($container = $this->lastModified) === null) {
return;
}
$this->lastModified = null;
$id = $container->getId();
// Calculate new object size and increase used memory size by this value
$this->memorySize += ($this->sizes[$id] = strlen($container->getRef()));
if ($this->sizes[$id] > $this->minSize) {
// Move object to "unload candidates list"
$this->unloadCandidates[$id] = $container;
}
$container->startTrace();
$this->_swapCheck();
}
/**
* Check and swap objects if necessary
*
* @throws Exception\RuntimeException
*/
private function _swapCheck()
{
if ($this->memoryLimit < 0 || $this->memorySize < $this->memoryLimit) {
// Memory limit is not reached
// Do nothing
return;
}
// walk through loaded objects in access history order
foreach ($this->unloadCandidates as $id => $container) {
$this->_swap($container, $id);
unset($this->unloadCandidates[$id]);
if ($this->memorySize < $this->memoryLimit) {
// We've swapped enough objects
return;
}
}
throw new Exception\RuntimeException('Memory manager can\'t get enough space.');
}
/**
* Swap object data to disk
* Actually swaps data or only unloads it from memory,
* if object is not changed since last swap
*
* @param \Zend\Memory\Container\Movable $container
* @param int $id
*/
private function _swap(Container\Movable $container, $id)
{
if ($container->isLocked()) {
return;
}
if (!$container->isSwapped()) {
$this->cache->setItem($this->managerId . $id, $container->getRef());
}
$this->memorySize -= $this->sizes[$id];
$container->markAsSwapped();
$container->unloadValue();
}
/**
* Load value from swap file.
*
* @internal
* @param \Zend\Memory\Container\Movable $container
* @param int $id
*/
public function load(Container\Movable $container, $id)
{
$value = $this->cache->getItem($this->managerId . $id);
// Try to swap other objects if necessary
// (do not include specified object into check)
$this->memorySize += strlen($value);
$this->_swapCheck();
// Add loaded object to the end of loaded objects list
$container->setValue($value);
if ($this->sizes[$id] > $this->minSize) {
// Add object to the end of "unload candidates list"
$this->unloadCandidates[$id] = $container;
}
}
}