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nsUrlListenerManager.h
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00037 
00038 #ifndef nsUrlListenerManager_h___
00039 #define nsUrlListenerManager_h___
00040 
00041 #include "nsIUrlListenerManager.h"
00042 #include "nsISupportsArray.h"
00043 #include "nsCOMPtr.h"
00044 
00045 /********************************************************************************************
00046        The url listener manager is a helper class used by all of our subclassed urls to implement
00047        registration and broadcasting of changes to all of their registered url listeners. I envision
00048        every url implementation to have a has a relationship with a nsIUrlListenerManager. All
00049        url listener register/unregister calls are forwarded to the listener manager. In addition,
00050        the url listener manager handles broadcasting of event changes on the url.
00051 
00052   mscott --> hmm now that I think about it this class is probably going to have to be made
00053        thread safe. It might have to proxy notification calls into another thread....
00054  ********************************************************************************************/
00055 
00056 typedef enum {
00057        nsUrlNotifyStartRunning = 0,
00058        nsUrlNotifyStopRunning
00059 } nsUrlNotifyType;
00060 
00061 class nsUrlListenerManager : public nsIUrlListenerManager {
00062 public:
00063        NS_DECL_ISUPPORTS
00064        NS_DECL_NSIURLLISTENERMANAGER
00065     nsUrlListenerManager();
00066        virtual ~nsUrlListenerManager();
00067     
00068 protected:
00069   // mscott --> for the longest time, I had m_listeners as a nsVoidArray to prevent
00070   // circular references when the url listener owned the url which owned the manager
00071   // which owned the url listener. By using a void array, were the manager didn't own
00072   // the listeners, we got out of this problem. But this made the model very difficult
00073   // to use for folks when it came to maintenance. Why? Because they would have a url
00074   // listener which didn't own the url. And they had no way of knowing how to keep
00075   // their object alive until the listener manager said the url was done. As a result,
00076   // folks were using strange ref counting techniques on their objects such that they 
00077   // would addref themselves before adding their listener to the url. Then, when they
00078   // received a on stop running url, they would throw a random release in there.
00079   // Needless to say, this is far from ideal so I've decided to change this to 
00080   // an nsISupportsArray and cleanup the caller's ref counting hacks to get this to work.
00081   // The danger is of course still the circular reference problem. In order to get around
00082   // this, when we issue a on stop running url through the manager, I'm going to release
00083   // all our url listeners. This should break the circle.
00084        // nsVoidArray * m_listeners;
00085   nsCOMPtr<nsISupportsArray> m_listeners;
00086 
00087        // helper function used to enumerate ISupportsArray and broadcast the change
00088        nsresult BroadcastChange(nsIURI * aUrl, nsUrlNotifyType notification, nsresult aErrorCode);
00089   void ReleaseListeners();
00090 };
00091 
00092 #endif /* nsUrlListenerManager_h___ */