fix DCS handler

src/common/TypedArrayUtils.test.ts

@@ -3,21 +3,20 @@
  * @license MIT
  */
 import { assert } from 'chai';
-import { fillFallback } from './TypedArrayUtils';
+import { fillFallback, concat, utf16ToString } from './TypedArrayUtils';
 
 type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
   | Int8Array | Int16Array | Int32Array
   | Float32Array | Float64Array;
 
-describe('polyfill conformance tests', function(): void {
-
-  function deepEquals(a: TypedArray, b: TypedArray): void {
-    assert.equal(a.length, b.length);
-    for (let i = 0; i < a.length; ++i) {
-      assert.equal(a[i], b[i]);
-    }
+function deepEquals(a: TypedArray, b: TypedArray): void {
+  assert.equal(a.length, b.length);
+  for (let i = 0; i < a.length; ++i) {
+    assert.equal(a[i], b[i]);
   }
+}
 
+describe('polyfill conformance tests', function(): void {
   describe('TypedArray.fill', function(): void {
     it('should work with all typed array types', function(): void {
       const u81 = new Uint8Array(5);
@@ -87,3 +86,20 @@ describe('polyfill conformance tests', function(): void {
     });
   });
 });
+
+describe('typed array convenience functions', () => {
+  it('concat', () => {
+    const a = new Uint8Array([1, 2, 3, 4, 5]);
+    const b = new Uint8Array([6, 7, 8, 9, 0]);
+    const merged = concat(a, b);
+    deepEquals(merged, new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]));
+  });
+  it('utf16ToString', () => {
+    const s = 'abcdefg';
+    const data = new Uint16Array(s.length);
+    for (let i = 0; i < s.length; ++i) {
+      data[i] = s.charCodeAt(i);
+    }
+    assert.equal(utf16ToString(data), s);
+  });
+});

src/common/TypedArrayUtils.ts

@@ -3,15 +3,14 @@
  * @license MIT
  */
 
-/**
- * polyfill for TypedArray.fill
- * This is needed to support .fill in all safari versions and IE 11.
- */
-
 type TypedArray = Uint8Array | Uint16Array | Uint32Array | Uint8ClampedArray
   | Int8Array | Int16Array | Int32Array
   | Float32Array | Float64Array;
 
+/**
+ * polyfill for TypedArray.fill
+ * This is needed to support .fill in all safari versions and IE 11.
+ */
 export function fill<T extends TypedArray>(array: T, value: number, start?: number, end?: number): T {
   // all modern engines that support .fill
   if (array.fill) {
@@ -39,3 +38,28 @@ export function fillFallback<T extends TypedArray>(array: T, value: number, star
   }
   return array;
 }
+
+/**
+ * Concat two typed arrays `a` and `b`.
+ * Returns a new typed array.
+ */
+export function concat<T extends TypedArray>(a: T, b: T): T {
+  const result = new (a.constructor as any)(a.length + b.length);
+  result.set(a);
+  result.set(b, a.length);
+  return result;
+}
+
+/**
+ * Convert UTF16 char codes into JS string.
+ * Note the typed array is not limited to Uint16Array, make sure to align
+ * the values to 0-65535 integer for other typed array types, otherwise
+ * the conversion will fail.
+ */
+export function utf16ToString<T extends TypedArray>(data: T): string {
+  let s = '';
+  for (let i = 0; i < data.length; ++i) {
+    s += String.fromCharCode(data[i]);
+  }
+  return s;
+}