sbWeakReference.h

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/*
 *=BEGIN SONGBIRD GPL
 *
 * This file is part of the Songbird web player.
 *
 * Copyright(c) 2005-2010 POTI, Inc.
 * http://www.songbirdnest.com
 *
 * This file may be licensed under the terms of of the
 * GNU General Public License Version 2 (the ``GPL'').
 *
 * Software distributed under the License is distributed
 * on an ``AS IS'' basis, WITHOUT WARRANTY OF ANY KIND, either
 * express or implied. See the GPL for the specific language
 * governing rights and limitations.
 *
 * You should have received a copy of the GPL along with this
 * program. If not, go to http://www.gnu.org/licenses/gpl.html
 * or write to the Free Software Foundation, Inc.,
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 *=END SONGBIRD GPL
 */

#ifndef __SB_WEAKREFERENCE_H__
#define __SB_WEAKREFERENCE_H__

#include <nsIWeakReference.h>
#include <nsIWeakReferenceUtils.h>

#include <nsAutoLock.h>

class sbWeakReference;

// Set IMETHOD_VISIBILITY to empty so that the class-level NS_COM declaration
// controls member method visibility.
#undef  IMETHOD_VISIBILITY
#define IMETHOD_VISIBILITY NS_COM_GLUE

class NS_COM_GLUE sbSupportsWeakReference : public nsISupportsWeakReference
{
public:
  sbSupportsWeakReference() 
    : mProxy(nsnull)
    , mProxyLock(nsnull) {
    mProxyLock = nsAutoLock::NewLock("sbSupportsWeakReference::mProxyLock");
    NS_WARN_IF_FALSE(mProxyLock, "Failed to create lock.");
  }

  NS_DECL_NSISUPPORTSWEAKREFERENCE

protected:
  inline ~sbSupportsWeakReference();

private:
  friend class sbWeakReference;

  void NoticeProxyDestruction() {
    NS_ENSURE_TRUE(mProxyLock, /*void*/);
    nsAutoLock lock(mProxyLock);
    // ...called (only) by an |nsWeakReference| from _its_ dtor.
    mProxy = nsnull;
  }

  sbWeakReference* mProxy;
  // Lock to protect mProxy.
  PRLock*          mProxyLock;

protected:
  void ClearWeakReferences();
  PRBool HasWeakReferences() const {
    NS_ENSURE_TRUE(mProxyLock, PR_FALSE);
    nsAutoLock lock(mProxyLock);
    return mProxy != 0; 
  }
};

#undef  IMETHOD_VISIBILITY
#define IMETHOD_VISIBILITY NS_VISIBILITY_HIDDEN

inline
sbSupportsWeakReference::~sbSupportsWeakReference() {
  ClearWeakReferences();
  
  if (mProxyLock) {
    nsAutoLock::DestroyLock(mProxyLock);
  }
}

#endif // __SB_WEAKREFERENCE_H__