From ea4d941f39fade35487baf4fca09d46e28f1e494 Mon Sep 17 00:00:00 2001
From: Joey Parrish <joeyparrish@google.com>
Date: Wed, 15 May 2019 12:30:40 -0700
Subject: [PATCH] Clean up EBML size constants

Instead of using an array of Uint8Arrays, which could trigger a
load-time failure on very old browsers, store an array of number
arrays.  This is equivalent for the purpose of comparison, and it
cannot fail at load-time.

This cleanup seems to fix minor test flake in the EBML parser tests
that was observed with upgraded node modules.

Issue #1694

Change-Id: I87b2307bceddb3a21dfc81d4fe9828afd9508617
---
 lib/util/ebml_parser.js      | 37 +++++++++++++++++-------------------
 lib/util/uint8array_utils.js |  7 +++++--
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/lib/util/ebml_parser.js b/lib/util/ebml_parser.js
index 36e874958..0f3f39033 100644
--- a/lib/util/ebml_parser.js
+++ b/lib/util/ebml_parser.js
@@ -37,26 +37,23 @@ shaka.util.EbmlParser = function(dataView) {
   this.reader_ = new shaka.util.DataViewReader(
       dataView,
       shaka.util.DataViewReader.Endianness.BIG_ENDIAN);
-
-  // If not already constructed, build a list of EBML dynamic size constants.
-  // This is not done at load-time to avoid exceptions on unsupported browsers.
-  if (!shaka.util.EbmlParser.DYNAMIC_SIZES) {
-    shaka.util.EbmlParser.DYNAMIC_SIZES = [
-      new Uint8Array([0xff]),
-      new Uint8Array([0x7f, 0xff]),
-      new Uint8Array([0x3f, 0xff, 0xff]),
-      new Uint8Array([0x1f, 0xff, 0xff, 0xff]),
-      new Uint8Array([0x0f, 0xff, 0xff, 0xff, 0xff]),
-      new Uint8Array([0x07, 0xff, 0xff, 0xff, 0xff, 0xff]),
-      new Uint8Array([0x03, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
-      new Uint8Array([0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
-    ];
-  }
 };
 
 
-/** @const {!Array.<!Uint8Array>} */
-shaka.util.EbmlParser.DYNAMIC_SIZES;
+/**
+ * A list of EBML dynamic size constants.
+ * @const {!Array.<!Array.<number>>}
+ */
+shaka.util.EbmlParser.DYNAMIC_SIZES = [
+  [0xff],
+  [0x7f, 0xff],
+  [0x3f, 0xff, 0xff],
+  [0x1f, 0xff, 0xff, 0xff],
+  [0x0f, 0xff, 0xff, 0xff, 0xff],
+  [0x07, 0xff, 0xff, 0xff, 0xff, 0xff],
+  [0x03, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff],
+  [0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff],
+];
 
 
 /**
@@ -225,10 +222,10 @@ shaka.util.EbmlParser.getVintValue_ = function(vint) {
  */
 shaka.util.EbmlParser.isDynamicSizeValue_ = function(vint) {
   const EbmlParser = shaka.util.EbmlParser;
-  const uint8ArrayEqual = shaka.util.Uint8ArrayUtils.equal;
+  const Uint8ArrayUtils = shaka.util.Uint8ArrayUtils;
 
-  for (let i = 0; i < EbmlParser.DYNAMIC_SIZES.length; i++) {
-    if (uint8ArrayEqual(vint, EbmlParser.DYNAMIC_SIZES[i])) {
+  for (const dynamicSizeConst of EbmlParser.DYNAMIC_SIZES) {
+    if (Uint8ArrayUtils.equal(vint, dynamicSizeConst)) {
       return true;
     }
   }
diff --git a/lib/util/uint8array_utils.js b/lib/util/uint8array_utils.js
index 899f9c147..713ca9679 100644
--- a/lib/util/uint8array_utils.js
+++ b/lib/util/uint8array_utils.js
@@ -109,8 +109,11 @@ shaka.util.Uint8ArrayUtils.toHex = function(arr) {
 
 /**
  * Compare two Uint8Arrays for equality.
- * @param {Uint8Array} arr1
- * @param {Uint8Array} arr2
+ * For convenience, this also accepts Arrays, so that one can trivially compare
+ * a Uint8Array to an Array of numbers.
+ *
+ * @param {(Uint8Array|Array.<number>)} arr1
+ * @param {(Uint8Array|Array.<number>)} arr2
  * @return {boolean}
  * @export
  */