From b495ca492408c3560e654e0137fcae35ff35a576 Mon Sep 17 00:00:00 2001
From: Vincent Petry <pvince81@owncloud.com>
Date: Wed, 11 Feb 2015 16:26:03 +0100
Subject: [PATCH] Added part files for when writing chunks

Whenever a chunk is being written, it is now written to a part file
first. This is to avoid a concurrent chunk upload to believe that the
former chunk already exists, even though it's not fully written.

This makes sure that the final file assembly is only done when all
chunks were successfully written.

Also added an extra unique id to chunk parts in case the same chunk is
uploaded twice concurrently.
---
 lib/private/cache/file.php | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/private/cache/file.php b/lib/private/cache/file.php
index 6fa7686ea9..8ec048ccba 100644
--- a/lib/private/cache/file.php
+++ b/lib/private/cache/file.php
@@ -11,6 +11,7 @@ namespace OC\Cache;
 
 use OC\Files\Filesystem;
 use OC\Files\View;
+use OCP\Security\ISecureRandom;
 
 class File {
 	protected $storage;
@@ -79,12 +80,22 @@ class File {
 		$storage = $this->getStorage();
 		$result = false;
 		$proxyStatus = \OC_FileProxy::$enabled;
+		// unique id to avoid chunk collision, just in case
+		$uniqueId = \OC::$server->getSecureRandom()->getLowStrengthGenerator()->generate(
+			16,
+			ISecureRandom::CHAR_DIGITS . ISecureRandom::CHAR_LOWER . ISecureRandom::CHAR_UPPER
+		);
+
+		// use part file to prevent hasKey() to find the key
+		// while it is being written
+		$keyPart = $key . '.' . $uniqueId . '.part';
 		\OC_FileProxy::$enabled = false;
-		if ($storage and $storage->file_put_contents($key, $value)) {
+		if ($storage and $storage->file_put_contents($keyPart, $value)) {
 			if ($ttl === 0) {
 				$ttl = 86400; // 60*60*24
 			}
-			$result = $storage->touch($key, time() + $ttl);
+			$result = $storage->touch($keyPart, time() + $ttl);
+			$result &= $storage->rename($keyPart, $key);
 		}
 		\OC_FileProxy::$enabled = $proxyStatus;
 		return $result;