TwigPhpStorageCache.php

<?php

namespace Drupal\Core\Template;

use Drupal\Component\Utility\Crypt;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\PhpStorage\PhpStorageFactory;
use Twig\Cache\CacheInterface;

/**
 * Provides an alternate cache storage for Twig using PhpStorage.
 *
 * This class is designed to work on setups with multiple webheads using a local
 * filesystem for the twig cache. When generating the cache key, a hash value
 * depending on the enabled extensions is included. This prevents stale
 * templates from being reused when twig extensions are enabled or disabled.
 *
 * @see \Drupal\Core\DependencyInjection\Compiler\TwigExtensionPass
 */
class TwigPhpStorageCache implements CacheInterface {
    
    /**
     * The maximum length for each part of the cache key suffix.
     */
    const SUFFIX_SUBSTRING_LENGTH = 25;
    
    /**
     * The cache object used for auto-refresh via mtime.
     *
     * @var \Drupal\Core\Cache\CacheBackendInterface
     */
    protected $cache;
    
    /**
     * The PhpStorage object used for storing the templates.
     *
     * @var \Drupal\Component\PhpStorage\PhpStorageInterface
     */
    protected $storage;
    
    /**
     * The template cache filename prefix.
     *
     * @var string
     */
    protected $templateCacheFilenamePrefix;
    
    /**
     * Store cache backend and other information internally.
     *
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache
     *   The cache bin.
     * @param string $twig_cache_prefix
     *   A Twig cache file prefix that changes when Twig extensions change.
     */
    public function __construct(CacheBackendInterface $cache, $twig_cache_prefix) {
        $this->cache = $cache;
        $this->templateCacheFilenamePrefix = $twig_cache_prefix;
    }
    
    /**
     * Gets the PHP code storage object to use for the compiled Twig files.
     *
     * @return \Drupal\Component\PhpStorage\PhpStorageInterface
     */
    protected function storage() {
        if (!isset($this->storage)) {
            $this->storage = PhpStorageFactory::get('twig');
        }
        return $this->storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public function generateKey($name, $className) {
        if (strpos($name, '{# inline_template_start #}') === 0) {
            // $name is an inline template, and can have characters that are not valid
            // for a filename. $suffix is unique for each inline template so we just
            // use the generic name 'inline-template' here.
            $name = 'inline-template';
        }
        else {
            $name = basename($name);
        }
        // Windows (and some encrypted Linux systems) only support 255 characters in
        // a path. On Windows a requirements error is displayed and installation is
        // blocked if Drupal's public files path is longer than 120 characters.
        // Thus, to always be less than 255, file paths may not be more than 135
        // characters long. Using the default PHP file storage class, the Twig cache
        // file path will be 124 characters long at most, which provides a margin of
        // safety.
        $suffix = substr($name, 0, self::SUFFIX_SUBSTRING_LENGTH) . '_';
        $suffix .= substr(Crypt::hashBase64($className), 0, self::SUFFIX_SUBSTRING_LENGTH);
        // The cache prefix is what gets invalidated.
        return $this->templateCacheFilenamePrefix . '_' . $suffix;
    }
    
    /**
     * {@inheritdoc}
     */
    public function load($key) {
        $this->storage()
            ->load($key);
    }
    
    /**
     * {@inheritdoc}
     */
    public function write($key, $content) {
        $this->storage()
            ->save($key, $content);
        // Save the last mtime.
        $cid = 'twig:' . $key;
        $this->cache
            ->set($cid, REQUEST_TIME);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTimestamp($key) {
        $cid = 'twig:' . $key;
        if ($cache = $this->cache
            ->get($cid)) {
            return $cache->data;
        }
        else {
            return 0;
        }
    }

}