nextcloud-server/lib/private/Preview/Storage/ObjectStorePreviewStorage.php

<?php

namespace OC\Preview\Storage;

use Icewind\Streams\CountWrapper;
use OC\Preview\Db\Preview;
use OCP\Files\ObjectStore\IObjectStore;

class ObjectStorePreviewStorage implements IPreviewStorage {
	private string $objectPrefix = 'urn:oid:preview:';

	/**
	 * @param array{objectPrefix: ?string} $parameters
	 */
	public function __construct(private IObjectStore $objectStore, array $parameters) {
		if (isset($parameters['objectPrefix'])) {
			$this->objectPrefix = $parameters['objectPrefix'] . 'preview:';
		}
	}

	public function writePreview(Preview $preview, $stream): false|int {
		if (!is_resource($stream)) {
			$fh = fopen('php://temp', 'w+');
			fwrite($fh, $stream);
			rewind($fh);

			$stream = $fh;
		}

		$size = 0;
		$countStream = CountWrapper::wrap($stream, function (int $writtenSize) use (&$size): void {
			$size = $writtenSize;
		});

		$this->objectStore->writeObject($this->constructUrn($preview), $countStream);
		return $size;
	}

	public function readPreview(Preview $preview) {
		return $this->objectStore->readObject($this->constructUrn($preview));
	}

	public function deletePreview(Preview $preview) {
		return $this->objectStore->deleteObject($this->constructUrn($preview));
	}

	private function constructUrn(Preview $preview): string {
		return $this->objectPrefix . $preview->getId();
	}
}