diff --git a/mozilla/xpcom/ds/nsArray.cpp b/mozilla/xpcom/ds/nsArray.cpp
new file mode 100644
index 00000000000..53b8236cab1
--- /dev/null
+++ b/mozilla/xpcom/ds/nsArray.cpp
@@ -0,0 +1,142 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: NPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is 
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or 
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the NPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the NPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include "nsArray.h"
+
+// used by IndexOf()
+struct findIndexOfClosure
+{
+    nsISupports *targetElement;
+    PRUint32 startIndex;
+    PRUint32 resultIndex;
+};
+
+NS_IMPL_ISUPPORTS2(nsArray, nsIArray, nsIMutableArray)
+
+nsArray::~nsArray()
+{
+    Clear();
+}
+    
+NS_IMETHODIMP
+nsArray::GetLength(PRUint32* aLength)
+{
+    *aLength = mArray.Count();
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsArray::QueryElementAt(PRUint32 aIndex,
+                        const nsIID& aIID,
+                        void ** aResult)
+{
+    nsISupports * obj = mArray.ObjectAt(aIndex);
+    if (!obj) return NS_ERROR_UNEXPECTED;
+
+    return obj->QueryInterface(aIID, aResult);
+}
+
+NS_IMETHODIMP
+nsArray::IndexOf(PRUint32 aStartIndex, nsISupports* aElement,
+                 PRUint32* aResult)
+{
+    if (aStartIndex == 0) {
+        *aResult = mArray.IndexOf(aElement);
+        if (*aResult == -1)
+            return NS_ERROR_FAILURE;
+        return NS_OK;
+    }
+
+    findIndexOfClosure closure = { aElement, aStartIndex, 0 };
+    PRBool notFound = mArray.EnumerateForwards(FindElementCallback, &closure);
+    if (notFound)
+        return NS_ERROR_FAILURE;
+
+    *aResult = closure.resultIndex;
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsArray::Enumerate(nsISimpleEnumerator **aResult)
+{
+    return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+// nsIMutableArray implementation
+
+NS_IMETHODIMP
+nsArray::AppendElement(nsISupports* aElement)
+{
+    PRBool result = mArray.AppendObject(aElement);
+    return result ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsArray::RemoveElementAt(PRUint32 aIndex)
+{
+    PRBool result = mArray.RemoveObjectAt(aIndex);
+    return result ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsArray::InsertElementAt(nsISupports* element, PRUint32 aIndex)
+{
+    PRBool result = mArray.InsertObjectAt(element, aIndex);
+    return result ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsArray::Clear()
+{
+    mArray.Clear();
+    return NS_OK;
+}
+
+nsArray::FindElementCallback(void *aElement, void* aClosure)
+{
+    findIndexOfClosure* closure =
+        NS_STATIC_CAST(findIndexOfClosure*, aClosure);
+
+    // don't start searching until we're past the startIndex
+    if (closure->resultIndex >= closure->startIndex &&
+        aElement == closure->targetElement) {
+        return PR_FALSE;    // stop! We found it
+    }
+    closure->resultIndex++;
+
+    return PR_TRUE;
+}
diff --git a/mozilla/xpcom/ds/nsArray.h b/mozilla/xpcom/ds/nsArray.h
new file mode 100644
index 00000000000..bc4c2f98bb7
--- /dev/null
+++ b/mozilla/xpcom/ds/nsArray.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: NPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is 
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or 
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the NPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the NPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsArray_h__
+#define nsArray_h__
+
+#include "nsIArray.h"
+#include "nsCOMArray.h"
+
+#define NS_ARRAY_CLASSNAME \
+  "nsIArray implementation"
+
+// {35C66FD1-95E9-4e0a-80C5-C3BD2B375481}
+#define NS_ARRAY_CID \
+{ 0x35c66fd1, 0x95e9, 0x4e0a, \
+  { 0x80, 0xc5, 0xc3, 0xbd, 0x2b, 0x37, 0x54, 0x81 } }
+
+#define NS_ARRAY_CONTRACTID \
+  "@mozilla.org/array;1"
+
+// adapter class to map nsIArray->nsCOMArray
+// do NOT declare this as a stack or member variable, use
+// nsCOMArray instead
+class nsArray : public nsIMutableArray
+{
+public:
+    nsArray() { NS_INIT_ISUPPORTS(); }
+    virtual ~nsArray();
+
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIARRAY
+    NS_DECL_NSIMUTABLEARRAY
+
+private:
+    static PRBool FindElementCallback(void* aElement, void* aClosure);
+    nsCOMArray<nsISupports> mArray;
+};
+
+
+
+#endif
diff --git a/mozilla/xpcom/ds/nsCOMArray.h b/mozilla/xpcom/ds/nsCOMArray.h
new file mode 100644
index 00000000000..c0dcef9f466
--- /dev/null
+++ b/mozilla/xpcom/ds/nsCOMArray.h
@@ -0,0 +1,140 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: NPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/NPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is mozilla.org code.
+ *
+ * The Initial Developer of the Original Code is 
+ * Netscape Communications Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 1998
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or 
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the NPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the NPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsCOMArray_h__
+#define nsCOMArray_h__
+
+#include "nsVoidArray.h"
+#include "nsISupports.h"
+
+// a non-XPCOM, refcounting array of XPCOM objects
+// used as a member variable or stack variable - this object is NOT
+// refcounted, but the objects that it holds are
+template <class T>
+class NS_COM nsCOMArray
+{
+ public:
+    nsCOMArray() {}
+    nsCOMArray(PRInt32 aCount) : mArray(aCount) {}
+
+    ~nsCOMArray() {}
+
+    // these do NOT refcount on the way out, for speed
+    T* ObjectAt(PRInt32 aIndex) const {
+        return NS_STATIC_CAST(T*,mArray.ElementAt(aIndex));
+    }
+    
+    T* operator[](PRInt32 aIndex) const {
+        return ObjectAt(aIndex);
+    }
+
+    PRInt32 IndexOf(T* aObject) {
+        return mArray.IndexOf(aObject);
+    }
+    
+    PRBool InsertObjectAt(T* aObject, PRInt32 aIndex) {
+        PRBool result = mArray.InsertElementAt(aObject, aIndex);
+        if (result)
+            NS_ADDREF(aObject);
+        return result;
+    }
+    
+    PRBool ReplaceObjectAt(T* aObject, PRInt32 aIndex) {
+        T *oldObject = ObjectAt(aIndex);
+        NS_IF_RELEASE(oldObject);
+        PRBool result = mArray.ReplaceElementAt(aObject, aIndex);
+        if (result)
+            NS_ADDREF(aObject);
+        return result;
+    }
+
+    // override nsVoidArray stuff so that they can be accessed by
+    // other methods
+    PRInt32 Count() const {
+        return mArray.Count();
+    }
+
+    void Clear() {
+        mArray.EnumerateForwards(ClearObjectsCallback, nsnull);
+        mArray.Clear();
+    }
+
+    PRBool EnumerateForwards(nsVoidArrayEnumFunc aFunc, void* aData) {
+        return mArray.EnumerateForwards(aFunc, aData);
+    }
+    
+    PRBool AppendObject(T *aObject) {
+        PRBool result = InsertObjectAt(aObject, Count());
+        if (result)
+            NS_ADDREF(aObject);
+        return result;
+    }
+
+    PRBool RemoveObject(T *aObject) {
+        PRBool result = mArray.RemoveElement(aObject);
+        if (result)
+            NS_RELEASE(aObject);
+        return result;
+    }
+    
+    PRBool RemoveObjectAt(PRInt32 aIndex) {
+        T* element = ObjectAt(aIndex);
+        if (element) {
+            PRBool result = mArray.RemoveElementAt(aIndex);
+            if (result)
+                NS_RELEASE(element);
+            return result;
+        }
+        return PR_FALSE;
+    }
+
+
+ private:
+    
+    static PRBool ClearObjectsCallback(void *aElement, void*) {
+        T* element = NS_STATIC_CAST(nsISupports*, aElement);
+        NS_RELEASE(element);
+        return PR_TRUE;
+    }
+
+    nsCOMArray(const nsCOMArray& other);
+    nsCOMArray& operator=(const nsCOMArray& other);
+    nsVoidArray mArray;
+};
+
+
+#endif
diff --git a/mozilla/xpcom/ds/nsIArray.idl b/mozilla/xpcom/ds/nsIArray.idl
index 20012a8d8fd..fbc2eee635a 100644
--- a/mozilla/xpcom/ds/nsIArray.idl
+++ b/mozilla/xpcom/ds/nsIArray.idl
@@ -63,7 +63,7 @@ interface nsIArray : nsISupports
     /**
      * number of elements in the array
      */
-    attribute unsigned long length;
+    readonly attribute unsigned long length;
 
     /**
      * Retrieve a specific element of the array
@@ -113,7 +113,7 @@ interface nsIMutableArray : nsIArray
     /**
      *
      */
-    void insertElementAt(in unsigned long index, in nsISupports element);
+    void insertElementAt(in nsISupports element, in unsigned long index);
     
     /**
      * clear the entire array