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-rw-r--r--xpcom/glue/nsWeakReference.cpp164
1 files changed, 164 insertions, 0 deletions
diff --git a/xpcom/glue/nsWeakReference.cpp b/xpcom/glue/nsWeakReference.cpp
new file mode 100644
index 000000000..57f372641
--- /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;
+ }
+}
+