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/gecko_api/include/nsIWeakReferenceUtils.h

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  1/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
  2/* ***** BEGIN LICENSE BLOCK *****
  3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  4 *
  5 * The contents of this file are subject to the Mozilla Public License Version
  6 * 1.1 (the "License"); you may not use this file except in compliance with
  7 * the License. You may obtain a copy of the License at
  8 * http://www.mozilla.org/MPL/
  9 *
 10 * Software distributed under the License is distributed on an "AS IS" basis,
 11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 12 * for the specific language governing rights and limitations under the
 13 * License.
 14 *
 15 * The Original Code is mozilla.org code.
 16 *
 17 * The Initial Developer of the Original Code is
 18 * Netscape Communications Corporation.
 19 * Portions created by the Initial Developer are Copyright (C) 1998
 20 * the Initial Developer. All Rights Reserved.
 21 *
 22 * Contributor(s):
 23 *   Scott Collins <scc@mozilla.org> (Original Author)
 24 *
 25 * Alternatively, the contents of this file may be used under the terms of
 26 * either of the GNU General Public License Version 2 or later (the "GPL"),
 27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 28 * in which case the provisions of the GPL or the LGPL are applicable instead
 29 * of those above. If you wish to allow use of your version of this file only
 30 * under the terms of either the GPL or the LGPL, and not to allow others to
 31 * use your version of this file under the terms of the MPL, indicate your
 32 * decision by deleting the provisions above and replace them with the notice
 33 * and other provisions required by the GPL or the LGPL. If you do not delete
 34 * the provisions above, a recipient may use your version of this file under
 35 * the terms of any one of the MPL, the GPL or the LGPL.
 36 *
 37 * ***** END LICENSE BLOCK ***** */
 38
 39#ifndef nsIWeakReferenceUtils_h__
 40#define nsIWeakReferenceUtils_h__
 41
 42#ifndef nsCOMPtr_h__
 43#include "nsCOMPtr.h"
 44#endif
 45
 46typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
 47
 48/**
 49 *
 50 */
 51
 52// a type-safe shortcut for calling the |QueryReferent()| member function
 53// T must inherit from nsIWeakReference, but the cast may be ambiguous.
 54template <class T, class DestinationType>
 55inline
 56nsresult
 57CallQueryReferent( T* aSource, DestinationType** aDestination )
 58  {
 59    NS_PRECONDITION(aSource, "null parameter");
 60    NS_PRECONDITION(aDestination, "null parameter");
 61
 62    return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
 63                                  reinterpret_cast<void**>(aDestination));
 64  }
 65
 66
 67class NS_COM_GLUE nsQueryReferent : public nsCOMPtr_helper
 68  {
 69    public:
 70      nsQueryReferent( nsIWeakReference* aWeakPtr, nsresult* error )
 71          : mWeakPtr(aWeakPtr),
 72            mErrorPtr(error)
 73        {
 74          // nothing else to do here
 75        }
 76
 77      virtual nsresult NS_FASTCALL operator()( const nsIID& aIID, void** ) const;
 78
 79    private:
 80      nsIWeakReference*  mWeakPtr;
 81      nsresult*          mErrorPtr;
 82  };
 83
 84inline
 85const nsQueryReferent
 86do_QueryReferent( nsIWeakReference* aRawPtr, nsresult* error = 0 )
 87  {
 88    return nsQueryReferent(aRawPtr, error);
 89  }
 90
 91
 92  /**
 93   * Deprecated, use |do_GetWeakReference| instead.
 94   */
 95extern NS_COM_GLUE
 96nsIWeakReference*
 97NS_GetWeakReference( nsISupports* , nsresult* aResult=0 );
 98
 99  /**
100   * |do_GetWeakReference| is a convenience function that bundles up all the work needed
101   * to get a weak reference to an arbitrary object, i.e., the |QueryInterface|, test, and
102   * call through to |GetWeakReference|, and put it into your |nsCOMPtr|.
103   * It is specifically designed to cooperate with |nsCOMPtr| (or |nsWeakPtr|) like so:
104   * |nsWeakPtr myWeakPtr = do_GetWeakReference(aPtr);|.
105   */
106inline
107already_AddRefed<nsIWeakReference>
108do_GetWeakReference( nsISupports* aRawPtr, nsresult* error = 0 )
109  {
110    return NS_GetWeakReference(aRawPtr, error);
111  }
112
113inline
114void
115do_GetWeakReference( nsIWeakReference* aRawPtr, nsresult* error = 0 )
116  {
117    // This signature exists solely to _stop_ you from doing a bad thing.
118    //  Saying |do_GetWeakReference()| on a weak reference itself,
119    //  is very likely to be a programmer error.
120  }
121
122template <class T>
123inline
124void
125do_GetWeakReference( already_AddRefed<T>& )
126  {
127    // This signature exists solely to _stop_ you from doing the bad thing.
128    //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
129    //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
130  }
131
132template <class T>
133inline
134void
135do_GetWeakReference( already_AddRefed<T>&, nsresult* )
136  {
137    // This signature exists solely to _stop_ you from doing the bad thing.
138    //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
139    //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
140  }
141
142#endif