[wip] Enable fseek for files in S3 storage

lib/private/Files/ObjectStore/S3ObjectTrait.php

@@ -49,27 +49,16 @@ abstract protected function getConnection();
 	 * @since 7.0.0
 	 */
 	function readObject($urn) {
-		$client = $this->getConnection();
-		$command = $client->getCommand('GetObject', [
-			'Bucket' => $this->bucket,
-			'Key' => $urn
+		$context = stream_context_create([
+			's3seek' => [
+				'client' => $this->getConnection(),
+				'bucket' => $this->bucket,
+				'urn' => $urn,
+			],
 		]);
-		$request = \Aws\serialize($command);
-		$headers = [];
-		foreach ($request->getHeaders() as $key => $values) {
-			foreach ($values as $value) {
-				$headers[] = "$key: $value";
-			}
-		}
-		$opts = [
-			'http' => [
-				'protocol_version'  => 1.1,
-				'header' => $headers
-			]
-		];
 
-		$context = stream_context_create($opts);
-		return fopen($request->getUri(), 'r', false, $context);
+		S3SeekableReadStream::registerIfNeeded();
+		return fopen('s3seek://', 'r', false, $context);
 	}
 
 	/**

lib/private/Files/ObjectStore/S3SeekableReadStream.php

@@ -0,0 +1,139 @@
+<?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\ObjectStore;
+
+/**
+ * A stream wrapper that uses http range requests to provide a seekable
+ * stream of a file in S3 storage.
+ */
+class S3SeekableReadStream {
+	private static $registered = false;
+
+	/**
+	 * Registers the stream wrapper using the `s3seek://` url scheme
+	 * $return void
+	 */
+	public static function registerIfNeeded() {
+		if (!self::$registered) {
+			stream_wrapper_register(
+				's3seek',
+				'OC\Files\ObjectStore\S3SeekableReadStream'
+			);
+			self::$registered = true;
+		}
+	}
+
+	private $client;
+	private $bucket;
+	private $urn;
+
+	private $current;
+	private $offset = 0;
+
+	private function reconnect($range) {
+		if ($this->current != null) {
+			fclose($this->current);
+		}
+
+		$command = $this->client->getCommand('GetObject', [
+			'Bucket' => $this->bucket,
+			'Key' => $this->urn,
+			'Range' => 'bytes=' . $range,
+		]);
+		$request = \Aws\serialize($command);
+		$headers = [];
+		foreach ($request->getHeaders() as $key => $values) {
+			foreach ($values as $value) {
+				$headers[] = "$key: $value";
+			}
+		}
+		$opts = [
+			'http' => [
+				'protocol_version' => 1.1,
+				'header' => $headers,
+			],
+		];
+
+		$context = stream_context_create($opts);
+		$this->current = fopen($request->getUri(), 'r', false, $context);
+
+		if ($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) {
+		$o = stream_context_get_options($this->context)['s3seek'];
+		$this->bucket = $o['bucket'];
+		$this->urn = $o['urn'];
+		$this->client = $o['client'];
+
+		return $this->reconnect('0-');
+	}
+
+	function stream_read($count) {
+		$ret = fread($this->current, $count);
+		$this->offset += strlen($ret);
+		return $ret;
+	}
+
+	function stream_seek($offset, $whence) {
+		switch ($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);
+	}
+}