1 files changed, 174 insertions, 0 deletions
diff --git a/lib/private/Files/Stream/SeekableHttpStream.php b/lib/private/Files/Stream/SeekableHttpStream.php
new file mode 100644
index 00000000000..80f05f7ea09
--- /dev/null
+++ b/lib/private/Files/Stream/SeekableHttpStream.php
@@ -0,0 +1,174 @@
+<?php
+/**
+ *
+ * @copyright Copyright (c) 2020, Lukas Stabe (lukas@stabe.de)
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\Files\Stream;
+
+use Icewind\Streams\File;
+
+/**
+ * A stream wrapper that uses http range requests to provide a seekable stream for http reading
+ */
+class SeekableHttpStream implements File {
+	private const PROTOCOL = 'httpseek';
+
+	private static $registered = false;
+
+	/**
+	 * Registers the stream wrapper using the `httpseek://` url scheme
+	 * $return void
+	 */
+	private static function registerIfNeeded() {
+		if (!self::$registered) {
+			stream_wrapper_register(
+				self::PROTOCOL,
+				self::class
+			);
+			self::$registered = true;
+		}
+	}
+
+	/**
+	 * Open a readonly-seekable http stream
+	 *
+	 * The provided callback will be called with byte range and should return an http stream for the requested range
+	 *
+	 * @param callable $callback
+	 * @return false|resource
+	 */
+	public static function open(callable $callback) {
+		$context = stream_context_create([
+			SeekableHttpStream::PROTOCOL => [
+				'callback' => $callback
+			],
+		]);
+
+		SeekableHttpStream::registerIfNeeded();
+		return fopen(SeekableHttpStream::PROTOCOL . '://', 'r', false, $context);
+	}
+
+	/** @var resource */
+	public $context;
+
+	/** @var callable */
+	private $openCallback;
+
+	/** @var resource */
+	private $current;
+	/** @var int */
+	private $offset = 0;
+
+	private function reconnect($range) {
+		if ($this->current != null) {
+			fclose($this->current);
+		}
+
+		$this->current = ($this->openCallback)($range);
+
+		if ($this->current === false) {
+			return false;
+		}
+
+		$responseHead = stream_get_meta_data($this->current)['wrapper_data'];
+		$contentRange = array_values(array_filter($responseHead, function ($v) {
+			return preg_match('#^content-range:#i', $v) === 1;
+		}))[0];
+
+		$content = trim(explode(':', $contentRange)[1]);
+		$range = trim(explode(' ', $content)[1]);
+		$begin = explode('-', $range)[0];
+		$this->offset = intval($begin);
+
+		return true;
+	}
+
+	function stream_open($path, $mode, $options, &$opened_path) {
+		$options = stream_context_get_options($this->context)[self::PROTOCOL];
+		$this->openCallback = $options['callback'];
+
+		return $this->reconnect('0-');
+	}
+
+	function stream_read($count) {
+		if (!$this->current) {
+			return false;
+		}
+		$ret = fread($this->current, $count);
+		$this->offset += strlen($ret);
+		return $ret;
+	}
+
+	function stream_seek($offset, $whence = SEEK_SET) {
+		switch ($whence) {
+			case SEEK_SET:
+				if ($offset === $this->offset) {
+					return true;
+				}
+				return $this->reconnect($offset . '-');
+			case SEEK_CUR:
+				if ($offset === 0) {
+					return true;
+				}
+				return $this->reconnect(($this->offset + $offset) . '-');
+			case SEEK_END:
+				return false;
+		}
+		return false;
+	}
+
+	function stream_tell() {
+		return $this->offset;
+	}
+
+	function stream_stat() {
+		return fstat($this->current);
+	}
+
+	function stream_eof() {
+		return feof($this->current);
+	}
+
+	function stream_close() {
+		fclose($this->current);
+	}
+
+	public function stream_write($data) {
+		return false;
+	}
+
+	public function stream_set_option($option, $arg1, $arg2) {
+		return false;
+	}
+
+	public function stream_truncate($size) {
+		return false;
+	}
+
+	public function stream_lock($operation) {
+		return false;
+	}
+
+	public function stream_flush() {
+		return; //noop because readonly stream
+	}
+
+
+}