class FilesystemCache

1. 8.x drupal/core/vendor/kriswallsmith/assetic/src/Assetic/Cache/FilesystemCache.php \Assetic\Cache\FilesystemCache
2. 8.x drupal/core/vendor/doctrine/common/lib/Doctrine/Common/Cache/FilesystemCache.php \Doctrine\Common\Cache\FilesystemCache

FilesystemCacheTest.php in drupal/core/vendor/doctrine/common/tests/Doctrine/Tests/Common/Cache/FilesystemCacheTest.php

class FilesystemCache extends FileCache {
  const EXTENSION = '.doctrinecache.data';

  /**
   * {@inheritdoc}
   */
  protected $extension = self::EXTENSION;

  /**
   * {@inheritdoc}
   */
  protected function doFetch($id) {
    $data = '';
    $lifetime = -1;
    $filename = $this
      ->getFilename($id);
    if (!file_exists($filename)) {
      return false;
    }
    $resource = fopen($filename, "r");
    if (false !== ($line = fgets($resource))) {
      $lifetime = (int) $line;
    }
    if ($lifetime !== 0 && $lifetime < time()) {
      fclose($resource);
      return false;
    }
    while (false !== ($line = fgets($resource))) {
      $data .= $line;
    }
    fclose($resource);
    return unserialize($data);
  }

  /**
   * {@inheritdoc}
   */
  protected function doContains($id) {
    $lifetime = -1;
    $filename = $this
      ->getFilename($id);
    if (!file_exists($filename)) {
      return false;
    }
    $resource = fopen($filename, "r");
    if (false !== ($line = fgets($resource))) {
      $lifetime = (int) $line;
    }
    fclose($resource);
    return $lifetime === 0 || $lifetime > time();
  }

  /**
   * {@inheritdoc}
   */
  protected function doSave($id, $data, $lifeTime = 0) {
    if ($lifeTime > 0) {
      $lifeTime = time() + $lifeTime;
    }
    $data = serialize($data);
    $filename = $this
      ->getFilename($id);
    $filepath = pathinfo($filename, PATHINFO_DIRNAME);
    if (!is_dir($filepath)) {
      mkdir($filepath, 0777, true);
    }
    return file_put_contents($filename, $lifeTime . PHP_EOL . $data);
  }

}