Fixes

Author: Alexander Belov

src/lib/math/nearest-highest-power-of-two-result/nearest-highest-power-of-two-result.spec.ts

@@ -0,0 +1,24 @@
+// tslint:disable:no-expression-statement
+import test from 'ava';
+import { nearestHighestPowerOfTwoResult } from './nearest-highest-power-of-two-result';
+
+test('exponentiation of nearest highest power of two', t => {
+  const tests = [
+    [1, 2 ** 0],
+    [2, 2 ** 1],
+    [3, 2 ** 2],
+    [5, 2 ** 3],
+    [11, 2 ** 4],
+    [1023, 2 ** 10],
+    [1024, 2 ** 10],
+    [1025, 2 ** 11],
+    [2 ** 31 - 1, 2 ** 31],
+    [2 ** 78 - 1, 2 ** 78]
+  ];
+
+  for (const v of tests) {
+    const [value, power] = v;
+
+    t.is(nearestHighestPowerOfTwoResult(value), power);
+  }
+});

src/lib/math/nearest-highest-power-of-two-result/nearest-highest-power-of-two-result.ts

@@ -0,0 +1,20 @@
+/**
+ * Returns the result of exponentiation
+ * 2 ^ (nearest highest power of two from specific number)
+ *
+ * Produces better performance than 2 ^ nearestHighestPowerOfTwo(v) in average
+ *
+ * @link http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+ *
+ * @param {number} v
+ * @returns {number}
+ */
+export function nearestHighestPowerOfTwoResult(v: number): number {
+  v--;
+  v |= v >> 1;
+  v |= v >> 2;
+  v |= v >> 4;
+  v |= v >> 8;
+  v |= v >> 16;
+  return ++v;
+}