1 files changed, 34 insertions, 0 deletions
diff --git a/xpcom/ds/nsArrayUtils.h b/xpcom/ds/nsArrayUtils.h
new file mode 100644
index 0000000000..6adad119c7
--- /dev/null
+++ b/xpcom/ds/nsArrayUtils.h
@@ -0,0 +1,34 @@
+/* -*- 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 nsArrayUtils_h__
+#define nsArrayUtils_h__
+
+#include "nsCOMPtr.h"
+#include "nsIArray.h"
+
+// helper class for do_QueryElementAt
+class MOZ_STACK_CLASS nsQueryArrayElementAt final : public nsCOMPtr_helper {
+ public:
+  nsQueryArrayElementAt(nsIArray* aArray, uint32_t aIndex, nsresult* aErrorPtr)
+      : mArray(aArray), mIndex(aIndex), mErrorPtr(aErrorPtr) {}
+
+  virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,
+                                          void**) const override;
+
+ private:
+  nsIArray* MOZ_NON_OWNING_REF mArray;
+  uint32_t mIndex;
+  nsresult* mErrorPtr;
+};
+
+inline const nsQueryArrayElementAt do_QueryElementAt(nsIArray* aArray,
+                                                     uint32_t aIndex,
+                                                     nsresult* aErrorPtr = 0) {
+  return nsQueryArrayElementAt(aArray, aIndex, aErrorPtr);
+}
+
+#endif  // nsArrayUtils_h__