perf(toolkit/uuid): use faster algorithm to generate UUID

closes #162

projects/scion/toolkit/uuid/src/public_api.ts

@@ -14,4 +14,4 @@
  *
  * @see https://github.com/ng-packagr/ng-packagr/blob/master/docs/secondary-entrypoints.md
  */
-export {UUID} from './uuid.util';
+export * as UUID from './uuid.util';

projects/scion/toolkit/uuid/src/uuid.spec.ts

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2018-2023 Swiss Federal Railways
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ *  SPDX-License-Identifier: EPL-2.0
+ */
+
+import {randomUUID} from './uuid.util';
+
+describe('UUID', () => {
+
+  it('should generate an UUID with 36 characters', () => {
+    const uuid = randomUUID();
+    expect(uuid).not.toBeNull();
+    expect(uuid.length === 36).toBeTrue();
+  });
+
+  it('should generate 500_000 unique UUIDs', () => {
+    // check uniqueness of 500.000 UUIDs
+    const uuids = new Set();
+    for (let i = 0; i < 500_000; i++) {
+      const uuid = randomUUID();
+      expect(uuids.has(uuid)).toBeFalse();
+      uuids.add(uuid);
+    }
+  });
+});

projects/scion/toolkit/uuid/src/uuid.util.ts

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2019 Swiss Federal Railways
+ * Copyright (c) 2018-2023 Swiss Federal Railways
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -8,27 +8,32 @@
  *  SPDX-License-Identifier: EPL-2.0
  */
 
-/**
- * Allows generating pseudo-random identifiers.
- */
-export class UUID {
+const uuidIterator = generateUUID();
 
-  private constructor() {
+function* generateUUID(): IterableIterator<string> {
+  const lut = [];
+  for (let i = 0; i < 256; i++) {
+    lut[i] = (i < 16 ? '0' : '') + (i).toString(16);
   }
 
-  /**
-   * Generates a 'pseudo-random' identifier.
-   */
-  public static randomUUID(): string {
-    let now = Date.now();
-    if (typeof window !== 'undefined' && typeof window.performance !== 'undefined' && typeof window.performance.now === 'function') {
-      now += performance.now(); // use high-precision timer if available
-    }
+  while (true) {
+    const d0 = Math.random() * 0xffffffff | 0;
+    const d1 = Math.random() * 0xffffffff | 0;
+    const d2 = Math.random() * 0xffffffff | 0;
+    const d3 = Math.random() * 0xffffffff | 0;
 
-    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, char => {
-      const random = (now + Math.random() * 16) % 16 | 0;
-      now = Math.floor(now / 16);
-      return (char === 'x' ? random : (random & 0x3 | 0x8)).toString(16);
-    });
+    const uuid = lut[d0 & 0xff] + lut[d0 >> 8 & 0xff] + lut[d0 >> 16 & 0xff] + lut[d0 >> 24 & 0xff] + '-' +
+      lut[d1 & 0xff] + lut[d1 >> 8 & 0xff] + '-' + lut[d1 >> 16 & 0x0f | 0x40] + lut[d1 >> 24 & 0xff] + '-' +
+      lut[d2 & 0x3f | 0x80] + lut[d2 >> 8 & 0xff] + '-' + lut[d2 >> 16 & 0xff] + lut[d2 >> 24 & 0xff] +
+      lut[d3 & 0xff] + lut[d3 >> 8 & 0xff] + lut[d3 >> 16 & 0xff] + lut[d3 >> 24 & 0xff];
+
+    yield uuid;
   }
 }
+
+/**
+ * Generates a UUID (universally unique identifier) compliant with the RFC 4122 version 4.
+ */
+export function randomUUID(): string {
+  return uuidIterator.next().value;
+}