Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 62 insertions, 0 deletions

diff --git a/parser/html/nsHtml5StreamListener.h b/parser/html/nsHtml5StreamListener.h
new file mode 100644
index 0000000000..46056eacee
--- /dev/null
+++ b/parser/html/nsHtml5StreamListener.h
@@ -0,0 +1,62 @@
+/* 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 nsHtml5StreamListener_h
+#define nsHtml5StreamListener_h
+
+#include "nsIStreamListener.h"
+#include "nsIThreadRetargetableStreamListener.h"
+#include "nsHtml5StreamParser.h"
+#include "mozilla/ReentrantMonitor.h"
+
+/**
+ * The purpose of this class is to reconcile the problem that
+ * nsHtml5StreamParser is a cycle collection participant, which means that it
+ * can only be refcounted on the main thread, but
+ * nsIThreadRetargetableStreamListener can be refcounted from another thread,
+ * so nsHtml5StreamParser being an nsIThreadRetargetableStreamListener was
+ * a memory corruption problem.
+ *
+ * mDelegate is an nsHtml5StreamParserPtr, which releases the object that it
+ * points to from a runnable on the main thread. DropDelegate() is only called
+ * on the main thread. This call will finish before the main-thread derefs the
+ * nsHtml5StreamListener itself, so there is no risk of another thread making
+ * the refcount of nsHtml5StreamListener go to zero and running the destructor
+ * concurrently. Other than that, the thread-safe nsISupports implementation
+ * takes care of the destructor not running concurrently from different
+ * threads, so there is no need to have a mutex around nsHtml5StreamParserPtr to
+ * prevent it from double-releasing nsHtml5StreamParser.
+ */
+class nsHtml5StreamListener : public nsIStreamListener,
+                              public nsIThreadRetargetableStreamListener {
+ public:
+  explicit nsHtml5StreamListener(nsHtml5StreamParser* aDelegate);
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIREQUESTOBSERVER
+  NS_DECL_NSISTREAMLISTENER
+  NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
+
+  // Main-thread-only
+  nsHtml5StreamParser* GetDelegate();
+
+  // Main-thread-only
+  void DropDelegate();
+
+ private:
+  void DropDelegateImpl();
+  virtual ~nsHtml5StreamListener();
+
+  // ReentrantMonitor instead of Mutex, because `GetDelegate()`
+  // can be called from within the Necko callbacks when Necko events
+  // are delivered on the main thread.
+  mozilla::ReentrantMonitor mDelegateMonitor MOZ_UNANNOTATED;
+  // Owning pointer with manually-managed refcounting, protected by
+  // mDelegateMonitor.   Access to it is Atomic, which avoids getting a lock
+  // to check if it's set or to return the pointer.   Access to the data within
+  // it needs the monitor.   MOZ_PT_GUARDED_BY() can't be used with Atomic<...*>
+  mozilla::Atomic<nsHtml5StreamParser*, mozilla::ReleaseAcquire> mDelegate;
+};
+
+#endif  // nsHtml5StreamListener_h