class EntityFile

class EntityFile extends EntityContentBase {
    
    /**
     * {@inheritdoc}
     */
    protected function getEntity(Row $row, array $old_destination_id_values) {
        // For stub rows, there is no real file to deal with, let the stubbing
        // process take its default path.
        if ($row->isStub()) {
            return parent::getEntity($row, $old_destination_id_values);
        }
        // By default the entity key (fid) would be used, but we want to make sure
        // we're loading the matching URI.
        $destination = $row->getDestinationProperty('uri');
        if (empty($destination)) {
            throw new MigrateException('Destination property uri not provided');
        }
        $entity = $this->storage
            ->loadByProperties([
            'uri' => $destination,
        ]);
        if ($entity) {
            return reset($entity);
        }
        else {
            return parent::getEntity($row, $old_destination_id_values);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function processStubRow(Row $row) {
        // We stub the uri value ourselves so we can create a real stub file for it.
        if (!$row->getDestinationProperty('uri')) {
            $field_definitions = $this->entityFieldManager
                ->getFieldDefinitions($this->storage
                ->getEntityTypeId(), $this->getKey('bundle'));
            $value = UriItem::generateSampleValue($field_definitions['uri']);
            if (empty($value)) {
                throw new MigrateException('Stubbing failed, unable to generate value for field uri');
            }
            // generateSampleValue() wraps the value in an array.
            $value = reset($value);
            // Make it into a proper public file uri, stripping off the existing
            // scheme if present.
            $value = 'public://' . preg_replace('|^[a-z]+://|i', '', $value);
            $value = mb_substr($value, 0, $field_definitions['uri']->getSetting('max_length'));
            // Create a real file, so File::preSave() can do filesize() on it.
            touch($value);
            $row->setDestinationProperty('uri', $value);
        }
        parent::processStubRow($row);
    }

}