diff -r 000000000000 -r 6474c204b198 mfbt/Array.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/Array.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* A compile-time constant-length array with bounds-checking assertions. */
+
+#ifndef mozilla_Array_h
+#define mozilla_Array_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+
+#include <stddef.h>
+
+namespace mozilla {
+
+template<typename T, size_t Length>
+class Array
+{
+    T arr[Length];
+
+  public:
+    T& operator[](size_t i) {
+      MOZ_ASSERT(i < Length);
+      return arr[i];
+    }
+
+    const T& operator[](size_t i) const {
+      MOZ_ASSERT(i < Length);
+      return arr[i];
+    }
+};
+
+template<typename T>
+class Array<T, 0>
+{
+  public:
+    T& operator[](size_t i) {
+      MOZ_ASSUME_UNREACHABLE("indexing into zero-length array");
+    }
+
+    const T& operator[](size_t i) const {
+      MOZ_ASSUME_UNREACHABLE("indexing into zero-length array");
+    }
+};
+
+}  /* namespace mozilla */
+
+#endif /* mozilla_Array_h */