Support weak references for bookmark / history / result observers. Bug 319324, r=darin.

This file was copied in CVS from the following location:
mozilla/browser/components/places/src/nsMaybeWeakPtr.h
Original committer: bryner%brianryner.com
Original revision: 1.1
Original date: 2005/12/08 22:23:52

toolkit/components/places/src/nsMaybeWeakPtr.h

@@ -0,0 +1,120 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla 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/MPL/
+ *
+ * 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 Places code.
+ *
+ * The Initial Developer of the Original Code is
+ * Google Inc.
+ * Portions created by the Initial Developer are Copyright (C) 2005
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Brian Ryner <bryner@brianryner.com> (original author)
+ *
+ * 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 MPL, 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 MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsMaybeWeakPtr_h_
+#define nsMaybeWeakPtr_h_
+
+#include "nsCOMPtr.h"
+#include "nsWeakReference.h"
+#include "nsTArray.h"
+
+// nsMaybeWeakPtr is a helper object to hold a strong-or-weak reference
+// to the template class.  It's pretty minimal, but sufficient.
+
+class nsMaybeWeakPtr_base
+{
+protected:
+  // Returns an addref'd pointer to the requested interface
+  void* GetValueAs(const nsIID& iid) const;
+
+  nsCOMPtr<nsISupports> mPtr;
+};
+
+template<class T>
+class nsMaybeWeakPtr : private nsMaybeWeakPtr_base
+{
+public:
+  nsMaybeWeakPtr(nsISupports *ref) { mPtr = ref; }
+  nsMaybeWeakPtr(const nsCOMPtr<nsIWeakReference> &ref) { mPtr = ref; }
+  nsMaybeWeakPtr(const nsCOMPtr<T> &ref) { mPtr = ref; }
+
+  PRBool operator==(const nsMaybeWeakPtr<T> &other) const {
+    return mPtr == other.mPtr;
+  }
+
+  operator const nsCOMPtr<T>() const { return GetValue(); }
+
+protected:
+  const nsCOMPtr<T> GetValue() const {
+    return nsCOMPtr<T>(dont_AddRef(NS_STATIC_CAST(T*,
+                                                  GetValueAs(NS_GET_IID(T)))));
+  }
+};
+
+// nsMaybeWeakPtrArray is an array of MaybeWeakPtr objects, that knows how to
+// grab a weak reference to a given object if requested.  It only allows a
+// given object to appear in the array once.
+
+class nsMaybeWeakPtrArray_base
+{
+protected:
+  static nsresult AppendWeakElementBase(nsTArray_base *aArray,
+                                        nsISupports *aElement, PRBool aWeak);
+  static nsresult RemoveWeakElementBase(nsTArray_base *aArray,
+                                         nsISupports *aElement);
+
+  typedef nsTArray< nsMaybeWeakPtr<nsISupports> > isupports_type;
+};
+
+template<class T>
+class nsMaybeWeakPtrArray : public nsTArray< nsMaybeWeakPtr<T> >,
+                            private nsMaybeWeakPtrArray_base
+{
+public:
+  nsresult AppendWeakElement(T *aElement, PRBool aOwnsWeak)
+  {
+    return AppendWeakElementBase(this, aElement, aOwnsWeak);
+  }
+
+  nsresult RemoveWeakElement(T *aElement)
+  {
+    return RemoveWeakElementBase(this, aElement);
+  }
+};
+
+// Call a method on each element in the array, but only if the element is
+// non-null.
+
+#define ENUMERATE_WEAKARRAY(array, type, method)                           \
+  for (PRUint32 array_idx = 0; array_idx < array.Length(); ++array_idx) {  \
+    const nsCOMPtr<type> &e = array.ElementAt(array_idx);                  \
+    if (e)                                                                 \
+      e->method;                                                           \
+  }
+
+#endif