All: Optimised Nextcloud sync delta functionality

ReactNativeClient/lib/ArrayUtils.js

@@ -13,4 +13,28 @@ ArrayUtils.removeElement = function(array, element) {
 	return array;
 }
 
+// https://stackoverflow.com/a/10264318/561309
+ArrayUtils.binarySearch = function(items, value) {
+
+	var startIndex  = 0,
+		stopIndex   = items.length - 1,
+		middle      = Math.floor((stopIndex + startIndex)/2);
+
+	while(items[middle] != value && startIndex < stopIndex){
+
+		//adjust search area
+		if (value < items[middle]){
+			stopIndex = middle - 1;
+		} else if (value > items[middle]){
+			startIndex = middle + 1;
+		}
+
+		//recalculate middle
+		middle = Math.floor((stopIndex + startIndex)/2);
+	}
+
+	//make sure it's the right value
+	return (items[middle] != value) ? -1 : middle;
+}
+
 module.exports = ArrayUtils;