file_managed_file_save_upload($element, FormStateInterface $form_state) Saves any files that have been uploaded

file_cron() Implements

file_icon_map($mime_type) Determines the generic icon MIME package based on a file's MIME type.

public File::getOwner() Returns the entity

file_progress_implementation() Determines the preferred upload progress implementation.

file_schema() Implements

public File::getOwnerId() Returns the entity

public FileStorage::spaceUsed($uid = NULL, $status = FILE_STATUS_PERMANENT)

Provides helpers to operate on files and stream wrappers. Hierarchy class \Drupal\Core\File\

Defines the file schema handler. Hierarchy class \Drupal\Core\Entity\Sql\