1 files changed, 68 insertions, 0 deletions
diff --git a/lib/private/Files/Stream/HashWrapper.php b/lib/private/Files/Stream/HashWrapper.php
new file mode 100644
index 00000000000..5956ad92549
--- /dev/null
+++ b/lib/private/Files/Stream/HashWrapper.php
@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\Files\Stream;
+
+use Icewind\Streams\Wrapper;
+
+class HashWrapper extends Wrapper {
+	protected $callback;
+	protected $hash;
+
+	public static function wrap($source, string $algo, callable $callback) {
+		$hash = hash_init($algo);
+		$context = stream_context_create([
+			'hash' => [
+				'source' => $source,
+				'callback' => $callback,
+				'hash' => $hash,
+			],
+		]);
+		return Wrapper::wrapSource($source, $context, 'hash', self::class);
+	}
+
+	protected function open() {
+		$context = $this->loadContext('hash');
+
+		$this->callback = $context['callback'];
+		$this->hash = $context['hash'];
+		return true;
+	}
+
+	public function dir_opendir($path, $options) {
+		return $this->open();
+	}
+
+	public function stream_open($path, $mode, $options, &$opened_path) {
+		return $this->open();
+	}
+
+	public function stream_read($count) {
+		$result = parent::stream_read($count);
+		hash_update($this->hash, $result);
+		return $result;
+	}
+
+	public function stream_close() {
+		if (is_callable($this->callback)) {
+			// if the stream is closed as a result of the end-of-request GC, the hash context might be cleaned up before this stream
+			if ($this->hash instanceof \HashContext) {
+				try {
+					$hash = @hash_final($this->hash);
+					if ($hash) {
+						call_user_func($this->callback, $hash);
+					}
+				} catch (\Throwable $e) {
+				}
+			}
+			// prevent further calls by potential PHP 7 GC ghosts
+			$this->callback = null;
+		}
+		return parent::stream_close();
+	}
+}