fix: ban new Uint16Array(buffer) (#5838)

Due to typo, banned call has been executed.
Fixes typo and adds support to `Uint16Array` in `BufferUtils`.

build/conformance.textproto

@@ -120,7 +120,7 @@ requirement: {
     "function template(a) { new Uint8ClampedArray(a) }"
   value:
     "/** @param {BufferSource} a */"
-    "function template(a) { new Unt16Array(a) }"
+    "function template(a) { new Uint16Array(a) }"
   value:
     "/** @param {BufferSource} a */"
     "function template(a) { new Int16Array(a) }"

lib/util/buffer_utils.js

@@ -110,6 +110,23 @@ shaka.util.BufferUtils = class {
     return shaka.util.BufferUtils.view_(data, offset, length, Uint8Array);
   }
 
+  /**
+   * Creates a new Uint16Array view on the same buffer.  This clamps the values
+   * to be within the same view (i.e. you can't use this to move past the end
+   * of the view, even if the underlying buffer is larger).  However, you can
+   * pass a negative offset to access the data before the view.
+   *
+   * @param {BufferSource} data
+   * @param {number=} offset The offset from the beginning of this data's view
+   *   to start the new view at.
+   * @param {number=} length The byte length of the new view.
+   * @return {!Uint16Array}
+   * @export
+   */
+  static toUint16(data, offset = 0, length = Infinity) {
+    return shaka.util.BufferUtils.view_(data, offset, length, Uint16Array);
+  }
+
   /**
    * Creates a DataView over the given buffer.
    *
@@ -135,15 +152,20 @@ shaka.util.BufferUtils = class {
    */
   static view_(data, offset, length, Type) {
     const buffer = shaka.util.BufferUtils.unsafeGetArrayBuffer_(data);
+    let bytesPerElement = 1;
+    if ('BYTES_PER_ELEMENT' in Type) {
+      bytesPerElement = Type.BYTES_PER_ELEMENT;
+    }
     // Absolute end of the |data| view within |buffer|.
     /** @suppress {strictMissingProperties} */
-    const dataEnd = (data.byteOffset || 0) + data.byteLength;
+    const dataEnd = ((data.byteOffset || 0) + data.byteLength) /
+      bytesPerElement;
     // Absolute start of the result within |buffer|.
     /** @suppress {strictMissingProperties} */
-    const rawStart = (data.byteOffset || 0) + offset;
-    const start = Math.max(0, Math.min(rawStart, dataEnd));
+    const rawStart = ((data.byteOffset || 0) + offset) / bytesPerElement;
+    const start = Math.floor(Math.max(0, Math.min(rawStart, dataEnd)));
     // Absolute end of the result within |buffer|.
-    const end = Math.min(start + Math.max(length, 0), dataEnd);
+    const end = Math.floor(Math.min(start + Math.max(length, 0), dataEnd));
     return new Type(buffer, start, end - start);
   }
 };

lib/util/fairplay_utils.js

@@ -205,7 +205,7 @@ shaka.util.FairPlayUtils = class {
     const stringToArray = (string) => {
       // 2 bytes for each char
       const buffer = new ArrayBuffer(string.length * 2);
-      const array = new Uint16Array(buffer);
+      const array = shaka.util.BufferUtils.toUint16(buffer);
       for (let i = 0, strLen = string.length; i < strLen; i++) {
         array[i] = string.charCodeAt(i);
       }

test/util/buffer_utils_unit.js

@@ -42,7 +42,7 @@ describe('BufferUtils', () => {
 
     it('compares with same buffer', () => {
       const a = new Uint8Array([0, 1, 2, 3]);
-      const b = new Uint16Array(a.buffer);
+      const b = BufferUtils.toUint16(a);
       expect(BufferUtils.equal(a, b)).toBe(true);
     });