michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef nsMaybeWeakPtr_h_
michael@0: #define nsMaybeWeakPtr_h_
michael@0: 
michael@0: #include "nsCOMPtr.h"
michael@0: #include "nsWeakReference.h"
michael@0: #include "nsTArray.h"
michael@0: #include "nsCycleCollectionNoteChild.h"
michael@0: 
michael@0: // nsMaybeWeakPtr is a helper object to hold a strong-or-weak reference
michael@0: // to the template class.  It's pretty minimal, but sufficient.
michael@0: 
michael@0: class nsMaybeWeakPtr_base
michael@0: {
michael@0: protected:
michael@0:   // Returns an addref'd pointer to the requested interface
michael@0:   void* GetValueAs(const nsIID& iid) const;
michael@0: 
michael@0:   nsCOMPtr<nsISupports> mPtr;
michael@0: };
michael@0: 
michael@0: template<class T>
michael@0: class nsMaybeWeakPtr : private nsMaybeWeakPtr_base
michael@0: {
michael@0: public:
michael@0:   nsMaybeWeakPtr(nsISupports *ref) { mPtr = ref; }
michael@0:   nsMaybeWeakPtr(const nsCOMPtr<nsIWeakReference> &ref) { mPtr = ref; }
michael@0:   nsMaybeWeakPtr(const nsCOMPtr<T> &ref) { mPtr = ref; }
michael@0: 
michael@0:   bool operator==(const nsMaybeWeakPtr<T> &other) const {
michael@0:     return mPtr == other.mPtr;
michael@0:   }
michael@0: 
michael@0:   operator const nsCOMPtr<T>() const { return GetValue(); }
michael@0: 
michael@0: protected:
michael@0:   const nsCOMPtr<T> GetValue() const {
michael@0:     return nsCOMPtr<T>(dont_AddRef(static_cast<T*>
michael@0:                                               (GetValueAs(NS_GET_TEMPLATE_IID(T)))));
michael@0:   }
michael@0: };
michael@0: 
michael@0: // nsMaybeWeakPtrArray is an array of MaybeWeakPtr objects, that knows how to
michael@0: // grab a weak reference to a given object if requested.  It only allows a
michael@0: // given object to appear in the array once.
michael@0: 
michael@0: typedef nsTArray< nsMaybeWeakPtr<nsISupports> > isupports_array_type;
michael@0: nsresult NS_AppendWeakElementBase(isupports_array_type *aArray,
michael@0:                                   nsISupports *aElement, bool aWeak);
michael@0: nsresult NS_RemoveWeakElementBase(isupports_array_type *aArray,
michael@0:                                   nsISupports *aElement);
michael@0: 
michael@0: template<class T>
michael@0: class nsMaybeWeakPtrArray : public nsTArray< nsMaybeWeakPtr<T> >
michael@0: {
michael@0: public:
michael@0:   nsresult AppendWeakElement(T *aElement, bool aOwnsWeak)
michael@0:   {
michael@0:     return NS_AppendWeakElementBase(
michael@0:       reinterpret_cast<isupports_array_type*>(this), aElement, aOwnsWeak);
michael@0:   }
michael@0: 
michael@0:   nsresult RemoveWeakElement(T *aElement)
michael@0:   {
michael@0:     return NS_RemoveWeakElementBase(
michael@0:       reinterpret_cast<isupports_array_type*>(this), aElement);
michael@0:   }
michael@0: };
michael@0: 
michael@0: template <typename T>
michael@0: inline void
michael@0: ImplCycleCollectionUnlink(nsMaybeWeakPtrArray<T>& aField)
michael@0: {
michael@0:   aField.Clear();
michael@0: }
michael@0: 
michael@0: template <typename E>
michael@0: inline void
michael@0: ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
michael@0:                             nsMaybeWeakPtrArray<E>& aField,
michael@0:                             const char* aName,
michael@0:                             uint32_t aFlags = 0)
michael@0: {
michael@0:   aFlags |= CycleCollectionEdgeNameArrayFlag;
michael@0:   size_t length = aField.Length();
michael@0:   for (size_t i = 0; i < length; ++i) {
michael@0:     CycleCollectionNoteChild(aCallback, aField[i].get(), aName, aFlags);
michael@0:   }
michael@0: }
michael@0: 
michael@0: // Call a method on each element in the array, but only if the element is
michael@0: // non-null.
michael@0: 
michael@0: #define ENUMERATE_WEAKARRAY(array, type, method)                           \
michael@0:   for (uint32_t array_idx = 0; array_idx < array.Length(); ++array_idx) {  \
michael@0:     const nsCOMPtr<type> &e = array.ElementAt(array_idx);                  \
michael@0:     if (e)                                                                 \
michael@0:       e->method;                                                           \
michael@0:   }
michael@0: 
michael@0: #endif