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     NS_HIDDEN_(void) RemoveObservers();
  77
  78     nsDataHashtable<nsCStringHashKey, nsCString> mHash;
  79     nsCategoryListener*                          mListener;
  80     nsCString                                    mCategory;
  81     bool                                         mObserversRemoved;
  82 };
  83
  84 /**
  85  * This is a helper class that caches services that are registered in a certain
  86  * category. The intended usage is that a service stores a variable of type
  87  * nsCategoryCache<nsIFoo> in a member variable, where nsIFoo is the interface
  88  * that these services should implement. The constructor of this class should
  89  * then get the name of the category.
  90  */
  91 template<class T>
  92 class nsCategoryCache : protected nsCategoryListener {
  93   public:
  94     explicit nsCategoryCache(const char* aCategory);
  95     ~nsCategoryCache() { if (mObserver) mObserver->ListenerDied(); }
  96
  97     const nsCOMArray<T>& GetEntries() {
  98       // Lazy initialization, so that services in this category can't
  99       // cause reentrant getService (bug 386376)
 100       if (!mObserver)
 101         mObserver = new nsCategoryObserver(mCategoryName.get(), this);
 102       return mEntries;
 103     }
 104   protected:
 105     virtual void EntryAdded(const nsCString& aValue);
 106     virtual void EntryRemoved(const nsCString& aValue);
 107     virtual void CategoryCleared();
 108   private:
 109     friend class CategoryObserver;
 110
 111     // Not to be implemented
 112     nsCategoryCache(const nsCategoryCache<T>&);
 113
 114     nsCString mCategoryName;
 115     nsCOMArray<T> mEntries;
 116     nsRefPtr<nsCategoryObserver> mObserver;
 117 };
 118
 119 // -----------------------------------
 120 // Implementation
 121
 122 template<class T>
 123 nsCategoryCache<T>::nsCategoryCache(const char* aCategory)
 124 : mCategoryName(aCategory)
 125 {
 126 }
 127
 128 template<class T>
 129 void nsCategoryCache<T>::EntryAdded(const nsCString& aValue) {
 130   nsCOMPtr<T> catEntry = do_GetService(aValue.get());
 131   if (catEntry)
 132     mEntries.AppendObject(catEntry);
 133 }
 134
 135 template<class T>
 136 void nsCategoryCache<T>::EntryRemoved(const nsCString& aValue) {
 137   nsCOMPtr<T> catEntry = do_GetService(aValue.get());
 138   if (catEntry)
 139     mEntries.RemoveObject(catEntry);
 140 }
 141
 142 template<class T>
 143 void nsCategoryCache<T>::CategoryCleared() {
 144   mEntries.Clear();
 145 }
 146
 147 #endif