1 files changed, 37 insertions, 0 deletions
diff --git a/apps/files/js/semaphore.js b/apps/files/js/semaphore.js
new file mode 100644
index 00000000000..044f0af23f3
--- /dev/null
+++ b/apps/files/js/semaphore.js
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2018
+ *
+ * This file is licensed under the Affero General Public License version 3
+ * or later.
+ *
+ * See the COPYING-README file.
+ *
+ */
+
+(function(){
+	var Semaphore = function(max) {
+		var counter = 0;
+		var waiting = [];
+
+		this.acquire = function() {
+			if(counter < max) {
+				counter++;
+				return new Promise(function(resolve) { resolve(); });
+			} else {
+				return new Promise(function(resolve) { waiting.push(resolve); });
+			}
+		};
+
+		this.release = function() {
+			counter--;
+			if (waiting.length > 0 && counter < max) {
+				counter++;
+				var promise = waiting.shift();
+				promise();
+			}
+		};
+	};
+
+	OCA.Files.Semaphore = Semaphore;
+
+})();