1 files changed, 145 insertions, 0 deletions
diff --git a/toolkit/components/places/nsMaybeWeakPtr.h b/toolkit/components/places/nsMaybeWeakPtr.h
new file mode 100644
index 0000000000..ce52e5090d
--- /dev/null
+++ b/toolkit/components/places/nsMaybeWeakPtr.h
@@ -0,0 +1,145 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsMaybeWeakPtr_h_
+#define nsMaybeWeakPtr_h_
+
+#include "mozilla/Attributes.h"
+#include "nsCOMPtr.h"
+#include "nsWeakReference.h"
+#include "nsTArray.h"
+#include "nsCycleCollectionNoteChild.h"
+
+// nsMaybeWeakPtr is a helper object to hold a strong-or-weak reference
+// to the template class.  It's pretty minimal, but sufficient.
+
+template<class T>
+class nsMaybeWeakPtr
+{
+public:
+  MOZ_IMPLICIT nsMaybeWeakPtr(nsISupports* aRef) : mPtr(aRef) {}
+  MOZ_IMPLICIT nsMaybeWeakPtr(const nsCOMPtr<nsIWeakReference>& aRef) : mPtr(aRef) {}
+  MOZ_IMPLICIT nsMaybeWeakPtr(const nsCOMPtr<T>& aRef) : mPtr(aRef) {}
+
+  bool operator==(const nsMaybeWeakPtr<T> &other) const {
+    return mPtr == other.mPtr;
+  }
+
+  nsISupports* GetRawValue() const { return mPtr.get(); }
+
+  const nsCOMPtr<T> GetValue() const;
+
+private:
+  nsCOMPtr<nsISupports> mPtr;
+};
+
+// nsMaybeWeakPtrArray is an array of MaybeWeakPtr objects, that knows how to
+// grab a weak reference to a given object if requested.  It only allows a
+// given object to appear in the array once.
+
+template<class T>
+class nsMaybeWeakPtrArray : public nsTArray<nsMaybeWeakPtr<T>>
+{
+  typedef nsTArray<nsMaybeWeakPtr<T>> MaybeWeakArray;
+
+public:
+  nsresult AppendWeakElement(T* aElement, bool aOwnsWeak)
+  {
+    nsCOMPtr<nsISupports> ref;
+    if (aOwnsWeak) {
+      ref = do_GetWeakReference(aElement);
+    } else {
+      ref = aElement;
+    }
+
+    if (MaybeWeakArray::Contains(ref.get())) {
+      return NS_ERROR_INVALID_ARG;
+    }
+    if (!MaybeWeakArray::AppendElement(ref)) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    return NS_OK;
+  }
+
+  nsresult RemoveWeakElement(T* aElement)
+  {
+    if (MaybeWeakArray::RemoveElement(aElement)) {
+      return NS_OK;
+    }
+
+    // Don't use do_GetWeakReference; it should only be called if we know
+    // the object supports weak references.
+    nsCOMPtr<nsISupportsWeakReference> supWeakRef = do_QueryInterface(aElement);
+    NS_ENSURE_TRUE(supWeakRef, NS_ERROR_INVALID_ARG);
+
+    nsCOMPtr<nsIWeakReference> weakRef;
+    nsresult rv = supWeakRef->GetWeakReference(getter_AddRefs(weakRef));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    if (MaybeWeakArray::RemoveElement(weakRef)) {
+      return NS_OK;
+    }
+
+    return NS_ERROR_INVALID_ARG;
+  }
+};
+
+template<class T>
+const nsCOMPtr<T>
+nsMaybeWeakPtr<T>::GetValue() const
+{
+  if (!mPtr) {
+    return nullptr;
+  }
+
+  nsresult rv;
+  nsCOMPtr<T> ref = do_QueryInterface(mPtr, &rv);
+  if (NS_SUCCEEDED(rv)) {
+    return ref;
+  }
+
+  nsCOMPtr<nsIWeakReference> weakRef = do_QueryInterface(mPtr);
+  if (weakRef) {
+    ref = do_QueryReferent(weakRef, &rv);
+    if (NS_SUCCEEDED(rv)) {
+      return ref;
+    }
+  }
+
+  return nullptr;
+}
+
+template <typename T>
+inline void
+ImplCycleCollectionUnlink(nsMaybeWeakPtrArray<T>& aField)
+{
+  aField.Clear();
+}
+
+template <typename E>
+inline void
+ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
+                            nsMaybeWeakPtrArray<E>& aField,
+                            const char* aName,
+                            uint32_t aFlags = 0)
+{
+  aFlags |= CycleCollectionEdgeNameArrayFlag;
+  size_t length = aField.Length();
+  for (size_t i = 0; i < length; ++i) {
+    CycleCollectionNoteChild(aCallback, aField[i].GetRawValue(), aName, aFlags);
+  }
+}
+
+// Call a method on each element in the array, but only if the element is
+// non-null.
+
+#define ENUMERATE_WEAKARRAY(array, type, method)                           \
+  for (uint32_t array_idx = 0; array_idx < array.Length(); ++array_idx) {  \
+    const nsCOMPtr<type> &e = array.ElementAt(array_idx).GetValue();       \
+    if (e)                                                                 \
+      e->method;                                                           \
+  }
+
+#endif