xpcom/glue/nsCategoryCache.h

   1 /* ***** BEGIN LICENSE BLOCK *****
   2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3  *
   4  * The contents of this file are subject to the Mozilla Public License Version
   5  * 1.1 (the "License"); you may not use this file except in compliance with
   6  * the License. You may obtain a copy of the License at
   7  * http://www.mozilla.org/MPL/
   8  *
   9  * Software distributed under the License is distributed on an "AS IS" basis,
  10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11  * for the specific language governing rights and limitations under the
  12  * License.
  13  *
  14  * The Original Code is a cache for services in a category.
  15  *
  16  * The Initial Developer of the Original Code is
  17  * Christian Biesinger <cbiesinger@web.de>.
  18  * Portions created by the Initial Developer are Copyright (C) 2005
  19  * the Initial Developer. All Rights Reserved.
  20  *
  21  * Contributor(s):
  22  *
  23  * Alternatively, the contents of this file may be used under the terms of
  24  * either the GNU General Public License Version 2 or later (the "GPL"), or
  25  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  26  * in which case the provisions of the GPL or the LGPL are applicable instead
  27  * of those above. If you wish to allow use of your version of this file only
  28  * under the terms of either the GPL or the LGPL, and not to allow others to
  29  * use your version of this file under the terms of the MPL, indicate your
  30  * decision by deleting the provisions above and replace them with the notice
  31  * and other provisions required by the GPL or the LGPL. If you do not delete
  32  * the provisions above, a recipient may use your version of this file under
  33  * the terms of any one of the MPL, the GPL or the LGPL.
  34  *
  35  * ***** END LICENSE BLOCK ***** */
  36
  37 #ifndef nsCategoryCache_h_
  38 #define nsCategoryCache_h_
  39
  40 #include "nsICategoryManager.h"
  41 #include "nsIObserver.h"
  42 #include "nsISimpleEnumerator.h"
  43 #include "nsISupportsPrimitives.h"
  44
  45 #include "nsServiceManagerUtils.h"
  46
  47 #include "nsAutoPtr.h"
  48 #include "nsCOMArray.h"
  49 #include "nsDataHashtable.h"
  50
  51 #include "nsXPCOM.h"
  52
  53 class NS_NO_VTABLE nsCategoryListener {
  54   protected:
  55     // no virtual destructor (people shouldn't delete through an
  56     // nsCategoryListener pointer)
  57     ~nsCategoryListener() {}
  58
  59   public:
  60     virtual void EntryAdded(const nsCString& aValue) = 0;
  61     virtual void EntryRemoved(const nsCString& aValue) = 0;
  62     virtual void CategoryCleared() = 0;
  63 };
  64
  65 class NS_COM_GLUE nsCategoryObserver : public nsIObserver {
  66   public:
  67     nsCategoryObserver(const char* aCategory,
  68                        nsCategoryListener* aCategoryListener);
  69     ~nsCategoryObserver();
  70
  71     void ListenerDied();
  72
  73     NS_DECL_ISUPPORTS
  74     NS_DECL_NSIOBSERVER
  75   private:
  76     nsDataHashtable<nsCStringHashKey, nsCString> mHash;
  77     nsCategoryListener*                          mListener;
  78     nsCString                                    mCategory;
  79 };
  80
  81 /**
  82  * This is a helper class that caches services that are registered in a certain
  83  * category. The intended usage is that a service stores a variable of type
  84  * nsCategoryCache<nsIFoo> in a member variable, where nsIFoo is the interface
  85  * that these services should implement. The constructor of this class should
  86  * then get the name of the category.
  87  */
  88 template<class T>
  89 class nsCategoryCache : protected nsCategoryListener {
  90   public:
  91     explicit nsCategoryCache(const char* aCategory);
  92     ~nsCategoryCache() { if (mObserver) mObserver->ListenerDied(); }
  93
  94     const nsCOMArray<T>& GetEntries() {
  95       // Lazy initialization, so that services in this category can't
  96       // cause reentrant getService (bug 386376)
  97       if (!mObserver)
  98         mObserver = new nsCategoryObserver(mCategoryName.get(), this);
  99       return mEntries;
 100     }
 101   protected:
 102     virtual void EntryAdded(const nsCString& aValue);
 103     virtual void EntryRemoved(const nsCString& aValue);
 104     virtual void CategoryCleared();
 105   private:
 106     friend class CategoryObserver;
 107
 108     // Not to be implemented
 109     nsCategoryCache(const nsCategoryCache<T>&);
 110
 111     nsCString mCategoryName;
 112     nsCOMArray<T> mEntries;
 113     nsRefPtr<nsCategoryObserver> mObserver;
 114 };
 115
 116 // -----------------------------------
 117 // Implementation
 118
 119 template<class T>
 120 nsCategoryCache<T>::nsCategoryCache(const char* aCategory)
 121 : mCategoryName(aCategory)
 122 {
 123 }
 124
 125 template<class T>
 126 void nsCategoryCache<T>::EntryAdded(const nsCString& aValue) {
 127   nsCOMPtr<T> catEntry = do_GetService(aValue.get());
 128   if (catEntry)
 129     mEntries.AppendObject(catEntry);
 130 }
 131
 132 template<class T>
 133 void nsCategoryCache<T>::EntryRemoved(const nsCString& aValue) {
 134   nsCOMPtr<T> catEntry = do_GetService(aValue.get());
 135   if (catEntry)
 136     mEntries.RemoveObject(catEntry);
 137 }
 138
 139 template<class T>
 140 void nsCategoryCache<T>::CategoryCleared() {
 141   mEntries.Clear();
 142 }
 143
 144 #endif