TextEncoder polyfill

Apparently Safari doesn't sport a TextEncoder, so here's a polyfill for it.

test/utils/TextDecoderPolyfill-test.js

@@ -0,0 +1,85 @@
+/*
+Copyright 2017 Vector Creations Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+"use strict";
+
+import TextDecoderPolyfill from 'utils/TextDecoderPolyfill';
+
+import * as testUtils from '../test-utils';
+import expect from 'expect';
+
+describe('textDecoderPolyfill', function() {
+    beforeEach(function() {
+        testUtils.beforeEach(this);
+    });
+
+    it('should correctly decode a range of strings', function() {
+        const decoder = new TextDecoderPolyfill();
+
+        expect(decoder.decode(Uint8Array.of(65, 66, 67))).toEqual('ABC');
+        expect(decoder.decode(Uint8Array.of(0xC3, 0xA6))).toEqual('æ');
+        expect(decoder.decode(Uint8Array.of(0xE2, 0x82, 0xAC))).toEqual('€');
+        expect(decoder.decode(Uint8Array.of(0xF0, 0x9F, 0x92, 0xA9))).toEqual('\uD83D\uDCA9');
+    });
+
+    it('should ignore byte-order marks', function() {
+        const decoder = new TextDecoderPolyfill();
+        expect(decoder.decode(Uint8Array.of(0xEF, 0xBB, 0xBF, 65)))
+            .toEqual('A');
+    });
+
+    it('should not ignore byte-order marks in the middle of the array', function() {
+        const decoder = new TextDecoderPolyfill();
+        expect(decoder.decode(Uint8Array.of(65, 0xEF, 0xBB, 0xBF, 66)))
+            .toEqual('A\uFEFFB');
+    });
+
+    it('should reject overlong encodings', function() {
+        const decoder = new TextDecoderPolyfill();
+
+        // euro, as 4 bytes
+        expect(decoder.decode(Uint8Array.of(65, 0xF0, 0x82, 0x82, 0xAC, 67)))
+            .toEqual('A\uFFFD\uFFFD\uFFFD\uFFFDC');
+    });
+
+    it('should reject 5 and 6-byte encodings', function() {
+        const decoder = new TextDecoderPolyfill();
+
+        expect(decoder.decode(Uint8Array.of(65, 0xF8, 0x82, 0x82, 0x82, 0x82, 67)))
+            .toEqual('A\uFFFD\uFFFD\uFFFD\uFFFD\uFFFDC');
+    });
+
+    it('should reject code points beyond 0x10000', function() {
+        const decoder = new TextDecoderPolyfill();
+
+        expect(decoder.decode(Uint8Array.of(0xF4, 0xA0, 0x80, 0x80)))
+            .toEqual('\uFFFD\uFFFD\uFFFD\uFFFD');
+    });
+
+    it('should cope with end-of-string', function() {
+        const decoder = new TextDecoderPolyfill();
+
+        expect(decoder.decode(Uint8Array.of(65, 0xC3)))
+            .toEqual('A\uFFFD');
+
+        expect(decoder.decode(Uint8Array.of(65, 0xE2, 0x82)))
+            .toEqual('A\uFFFD\uFFFD');
+
+        expect(decoder.decode(Uint8Array.of(65, 0xF0, 0x9F, 0x92)))
+            .toEqual('A\uFFFD\uFFFD\uFFFD');
+    });
+
+});