From de912385e00eae5c32445ae934c1c111f90961b2 Mon Sep 17 00:00:00 2001
From: Morris Jobke <hey@morrisjobke.de>
Date: Thu, 26 Oct 2017 16:47:54 +0200
Subject: [PATCH] Fix seeking on object storage

Seeking is not needed if the $from is 0, because then the pointer is already at the correct position. Additionally another fallback is added, that if the fseek fails it just uses an fread to skip the beginning of the file until it is at the correct position. This skipping is done with a chunked fread.

Signed-off-by: Morris Jobke <hey@morrisjobke.de>
---
 lib/private/Files/View.php | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/lib/private/Files/View.php b/lib/private/Files/View.php
index 7fee0883a2..d69f3b45fd 100644
--- a/lib/private/Files/View.php
+++ b/lib/private/Files/View.php
@@ -447,8 +447,28 @@ class View {
 		@ob_end_clean();
 		$handle = $this->fopen($path, 'rb');
 		if ($handle) {
-			if (fseek($handle, $from) === 0) {
-				$chunkSize = 8192; // 8 kB chunks
+			$chunkSize = 8192; // 8 kB chunks
+			$startReading = true;
+
+			if ($from !== 0 && $from !== '0' && fseek($handle, $from) !== 0) {
+				// forward file handle via chunked fread because fseek seem to have failed
+
+				$end = $from + 1;
+				while (!feof($handle) && ftell($handle) < $end) {
+					$len = $from - ftell($handle);
+					if ($len > $chunkSize) {
+						$len = $chunkSize;
+					}
+					$result = fread($handle, $len);
+
+					if ($result === false) {
+						$startReading = false;
+						break;
+					}
+				}
+			}
+
+			if ($startReading) {
 				$end = $to + 1;
 				while (!feof($handle) && ftell($handle) < $end) {
 					$len = $end - ftell($handle);