1 files changed, 62 insertions, 0 deletions
diff --git a/dom/bindings/ProxyHandlerUtils.h b/dom/bindings/ProxyHandlerUtils.h
new file mode 100644
index 0000000000..b9a9e4a579
--- /dev/null
+++ b/dom/bindings/ProxyHandlerUtils.h
@@ -0,0 +1,62 @@
+/* -*- 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/. */
+
+#ifndef mozilla_dom_ProxyHandlerUtils_h
+#define mozilla_dom_ProxyHandlerUtils_h
+
+#include "mozilla/Likely.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TextUtils.h"
+
+#include "js/Id.h"
+#include "js/Object.h"  // JS::GetClass
+#include "js/PropertyDescriptor.h"
+#include "js/String.h"  // JS::AtomToLinearString, JS::GetLinearString{CharAt,Length}
+#include "js/TypeDecls.h"
+
+#include "jsfriendapi.h"  // js::StringIsArrayIndex
+
+namespace mozilla::dom {
+
+extern jsid s_length_id;
+
+// A return value of UINT32_MAX indicates "not an array index".  Note, in
+// particular, that UINT32_MAX itself is not a valid array index in general.
+inline uint32_t GetArrayIndexFromId(JS::Handle<jsid> id) {
+  // Much like js::IdIsIndex, except with a fast path for "length" and another
+  // fast path for starting with a lowercase ascii char.  Is that second one
+  // really needed?  I guess it is because StringIsArrayIndex is out of line...
+  // as of now, use id.get() instead of id otherwise operands mismatch error
+  // occurs.
+  if (MOZ_LIKELY(id.isInt())) {
+    return id.toInt();
+  }
+  if (MOZ_LIKELY(id.get() == s_length_id)) {
+    return UINT32_MAX;
+  }
+  if (MOZ_UNLIKELY(!id.isAtom())) {
+    return UINT32_MAX;
+  }
+
+  JSLinearString* str = JS::AtomToLinearString(id.toAtom());
+  if (MOZ_UNLIKELY(JS::GetLinearStringLength(str) == 0)) {
+    return UINT32_MAX;
+  }
+
+  char16_t firstChar = JS::GetLinearStringCharAt(str, 0);
+  if (MOZ_LIKELY(IsAsciiLowercaseAlpha(firstChar))) {
+    return UINT32_MAX;
+  }
+
+  uint32_t i;
+  return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;
+}
+
+inline bool IsArrayIndex(uint32_t index) { return index < UINT32_MAX; }
+
+}  // namespace mozilla::dom
+
+#endif /* mozilla_dom_ProxyHandlerUtils_h */