1 files changed, 151 insertions, 0 deletions
diff --git a/xpcom/base/nsWeakReference.cpp b/xpcom/base/nsWeakReference.cpp
new file mode 100644
index 0000000000..958ef08451
--- /dev/null
+++ b/xpcom/base/nsWeakReference.cpp
@@ -0,0 +1,151 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+// nsWeakReference.cpp
+
+#include "mozilla/Attributes.h"
+
+#include "nsWeakReference.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+
+class nsWeakReference final : public nsIWeakReference {
+ public:
+  // nsISupports...
+  NS_DECL_ISUPPORTS
+
+  // nsIWeakReference...
+  NS_DECL_NSIWEAKREFERENCE
+
+ private:
+  friend class nsSupportsWeakReference;
+
+  explicit nsWeakReference(nsSupportsWeakReference* aReferent)
+      : nsIWeakReference(aReferent)
+  // ...I can only be constructed by an |nsSupportsWeakReference|
+  {}
+
+  ~nsWeakReference()
+  // ...I will only be destroyed by calling |delete| myself.
+  {
+    MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+    if (mObject) {
+      static_cast<nsSupportsWeakReference*>(mObject)->NoticeProxyDestruction();
+    }
+  }
+
+  void NoticeReferentDestruction()
+  // ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
+  {
+    MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+    mObject = nullptr;
+  }
+};
+
+nsresult nsQueryReferent::operator()(const nsIID& aIID, void** aAnswer) const {
+  nsresult status;
+  if (mWeakPtr) {
+    if (NS_FAILED(status = mWeakPtr->QueryReferent(aIID, aAnswer))) {
+      *aAnswer = 0;
+    }
+  } else {
+    status = NS_ERROR_NULL_POINTER;
+  }
+
+  if (mErrorPtr) {
+    *mErrorPtr = status;
+  }
+  return status;
+}
+
+nsIWeakReference* NS_GetWeakReference(nsISupportsWeakReference* aInstancePtr,
+                                      nsresult* aErrorPtr) {
+  nsresult status;
+
+  nsIWeakReference* result = nullptr;
+
+  if (aInstancePtr) {
+    status = aInstancePtr->GetWeakReference(&result);
+  } else {
+    status = NS_ERROR_NULL_POINTER;
+  }
+
+  if (aErrorPtr) {
+    *aErrorPtr = status;
+  }
+
+  return result;
+}
+
+nsIWeakReference*  // or else |already_AddRefed<nsIWeakReference>|
+NS_GetWeakReference(nsISupports* aInstancePtr, nsresult* aErrorPtr) {
+  nsresult status;
+
+  nsIWeakReference* result = nullptr;
+
+  if (aInstancePtr) {
+    nsCOMPtr<nsISupportsWeakReference> factoryPtr =
+        do_QueryInterface(aInstancePtr, &status);
+    if (factoryPtr) {
+      status = factoryPtr->GetWeakReference(&result);
+    }
+    // else, |status| has already been set by |do_QueryInterface|
+  } else {
+    status = NS_ERROR_NULL_POINTER;
+  }
+
+  if (aErrorPtr) {
+    *aErrorPtr = status;
+  }
+  return result;
+}
+
+nsresult nsSupportsWeakReference::GetWeakReference(
+    nsIWeakReference** aInstancePtr) {
+  if (!aInstancePtr) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  if (!mProxy) {
+    mProxy = new nsWeakReference(this);
+  } else {
+    MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(mProxy);
+  }
+  RefPtr<nsWeakReference> rval = mProxy;
+  rval.forget(aInstancePtr);
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(nsWeakReference, nsIWeakReference)
+
+NS_IMETHODIMP
+nsWeakReference::QueryReferentFromScript(const nsIID& aIID,
+                                         void** aInstancePtr) {
+  return QueryReferent(aIID, aInstancePtr);
+}
+
+nsresult nsIWeakReference::QueryReferent(const nsIID& aIID,
+                                         void** aInstancePtr) {
+  MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+
+  if (!mObject) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  return mObject->QueryInterface(aIID, aInstancePtr);
+}
+
+size_t nsWeakReference::SizeOfOnlyThis(mozilla::MallocSizeOf aMallocSizeOf) {
+  return aMallocSizeOf(this);
+}
+
+void nsSupportsWeakReference::ClearWeakReferences() {
+  if (mProxy) {
+    mProxy->NoticeReferentDestruction();
+    mProxy = nullptr;
+  }
+}