Fix reading empty files from objectstorage

Since we try to do range requests this will fail hard.
However since empty files are not that interesting to read anyways we
just read from an emptry memory stream.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

Author: rullzer

apps/files_external/lib/Lib/Storage/AmazonS3.php

@@ -507,6 +507,12 @@ public function fopen($path, $mode) {
 		switch ($mode) {
 			case 'r':
 			case 'rb':
+				// Don't try to fetch empty files
+				$stat = $this->stat($path);
+				if (is_array($stat) && isset($stat['size']) && $stat['size'] === '0') {
+					return fopen('php://memory', $mode);
+				}
+
 				try {
 					return $this->readObject($path);
 				} catch (S3Exception $e) {

lib/private/Files/ObjectStore/ObjectStoreStorage.php

@@ -286,6 +286,11 @@ public function fopen($path, $mode) {
 			case 'rb':
 				$stat = $this->stat($path);
 				if (is_array($stat)) {
+					// Reading 0 sized files is a waste of time
+					if (isset($stat['size']) && $stat['size'] === 0) {
+						return fopen('php://memory', $mode);
+					}
+
 					try {
 						return $this->objectStore->readObject($this->getURN($stat['fileid']));
 					} catch (NotFoundException $e) {