import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

xpcom/glue/nsArrayUtils.h

@@ -0,0 +1,40 @@
+/* -*- 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__