Merge branch 'master' into gl-geo-marchingcubes

src/mol-util/index.ts

@@ -10,6 +10,7 @@ import StringBuilder from './string-builder'
 import UUID from './uuid'
 import Mask from './mask'
 
+export * from './value-cell'
 export { BitFlags, StringBuilder, UUID, Mask }
 
 export function arrayEqual<T>(arr1: T[], arr2: T[]) {

src/mol-util/value-cell.ts

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author David Sehnal <david.sehnal@gmail.com>
+ */
+
+/** A mutable value cell. */
+interface ValueCell<T> { value: T }
+/** Create a mutable value cell. */
+function ValueCell<T>(value: T): ValueCell<T> { return { value }; }
+
+let _valueBoxId = 0;
+function getNextId() {
+    return _valueBoxId++ % 0x7FFFFFFF;
+}
+
+/** An immutable value box that also holds a version of the attribute. */
+interface ValueBox<T> {
+    // Unique identifier in the range 0 to 0x7FFFFFFF
+    readonly id: number,
+    readonly version: number,
+    readonly value: T
+}
+/** Create a new box with the specified value and version = 0 */
+function ValueBox<T>(value: T): ValueBox<T>
+/** Create a new box by updating the value of an old box and incrementing the version number. */
+function ValueBox<T>(box: ValueBox<T>, value: T): ValueBox<T>
+function ValueBox<T>(boxOrValue: T | ValueBox<T>, value?: T): ValueBox<T> {
+    if (arguments.length === 2) return { id: (boxOrValue as ValueBox<T>).id, version: (boxOrValue as ValueBox<T>).version + 1, value: value! };
+    return { id: getNextId(), version: 0, value: boxOrValue as T };
+}
+
+export { ValueCell, ValueBox };
+