FileStorage.php

<?php

namespace Drupal\file;

use Drupal\Core\Entity\Sql\SqlContentEntityStorage;

/**
 * File storage for files.
 */
class FileStorage extends SqlContentEntityStorage implements FileStorageInterface {
    
    /**
     * {@inheritdoc}
     */
    public function spaceUsed($uid = NULL, $status = FileInterface::STATUS_PERMANENT) {
        $query = $this->database
            ->select($this->entityType
            ->getBaseTable(), 'f')
            ->condition('f.status', $status);
        $query->addExpression('SUM([f].[filesize])', 'filesize');
        if (isset($uid)) {
            $query->condition('f.uid', $uid);
        }
        return $query->execute()
            ->fetchField();
    }

}