1 files changed, 164 insertions, 0 deletions
diff --git a/xpcom/glue/nsWeakReference.cpp b/xpcom/glue/nsWeakReference.cpp
new file mode 100644
index 0000000000..57f372641e
--- /dev/null
+++ b/xpcom/glue/nsWeakReference.cpp
@@ -0,0 +1,164 @@
+/* -*- 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"
+
+#ifdef MOZ_THREAD_SAFETY_OWNERSHIP_CHECKS_SUPPORTED
+
+#define MOZ_WEAKREF_DECL_OWNINGTHREAD nsAutoOwningThread _mWeakRefOwningThread;
+#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD \
+  NS_CheckThreadSafe(_mWeakRefOwningThread.GetThread(), "nsWeakReference not thread-safe")
+#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(that) \
+  NS_CheckThreadSafe((that)->_mWeakRefOwningThread.GetThread(), "nsWeakReference not thread-safe")
+
+#else
+
+#define MOZ_WEAKREF_DECL_OWNINGTHREAD
+#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD do { } while (false)
+#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(that) do { } while (false)
+
+#endif
+
+class nsWeakReference final : public nsIWeakReference
+{
+public:
+  // nsISupports...
+  NS_DECL_ISUPPORTS
+
+  // nsIWeakReference...
+  NS_DECL_NSIWEAKREFERENCE
+  virtual size_t SizeOfOnlyThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
+
+private:
+  MOZ_WEAKREF_DECL_OWNINGTHREAD
+
+  friend class nsSupportsWeakReference;
+
+  explicit nsWeakReference(nsSupportsWeakReference* aReferent)
+    : mReferent(aReferent)
+    // ...I can only be constructed by an |nsSupportsWeakReference|
+  {
+  }
+
+  ~nsWeakReference()
+  // ...I will only be destroyed by calling |delete| myself.
+  {
+    MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+    if (mReferent) {
+      mReferent->NoticeProxyDestruction();
+    }
+  }
+
+  void
+  NoticeReferentDestruction()
+  // ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
+  {
+    MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+    mReferent = nullptr;
+  }
+
+  nsSupportsWeakReference* MOZ_NON_OWNING_REF mReferent;
+};
+
+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*  // 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);
+  }
+  *aInstancePtr = mProxy;
+
+  nsresult status;
+  if (!*aInstancePtr) {
+    status = NS_ERROR_OUT_OF_MEMORY;
+  } else {
+    NS_ADDREF(*aInstancePtr);
+    status = NS_OK;
+  }
+
+  return status;
+}
+
+NS_IMPL_ISUPPORTS(nsWeakReference, nsIWeakReference)
+
+NS_IMETHODIMP
+nsWeakReference::QueryReferent(const nsIID& aIID, void** aInstancePtr)
+{
+  MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
+
+  return mReferent ? mReferent->QueryInterface(aIID, aInstancePtr) :
+                     NS_ERROR_NULL_POINTER;
+}
+
+size_t
+nsWeakReference::SizeOfOnlyThis(mozilla::MallocSizeOf aMallocSizeOf) const
+{
+  return aMallocSizeOf(this);
+}
+
+void
+nsSupportsWeakReference::ClearWeakReferences()
+{
+  if (mProxy) {
+    mProxy->NoticeReferentDestruction();
+    mProxy = nullptr;
+  }
+}
+