summaryrefslogtreecommitdiffstats
path: root/dom/bindings/RootedOwningNonNull.h
diff options
context:
space:
mode:
Diffstat (limited to 'dom/bindings/RootedOwningNonNull.h')
-rw-r--r--dom/bindings/RootedOwningNonNull.h73
1 files changed, 73 insertions, 0 deletions
diff --git a/dom/bindings/RootedOwningNonNull.h b/dom/bindings/RootedOwningNonNull.h
new file mode 100644
index 000000000..890afd74f
--- /dev/null
+++ b/dom/bindings/RootedOwningNonNull.h
@@ -0,0 +1,73 @@
+/* -*- 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/. */
+
+/**
+ * An implementation of Rooted for OwningNonNull<T>. This works by assuming
+ * that T has a Trace() method defined on it which will trace whatever things
+ * inside the T instance need tracing.
+ *
+ * This implementation has one serious drawback: operator= doesn't work right
+ * because it's declared on Rooted directly and expects the type Rooted is
+ * templated over.
+ */
+
+#ifndef mozilla_RootedOwningNonNull_h__
+#define mozilla_RootedOwningNonNull_h__
+
+#include "mozilla/OwningNonNull.h"
+#include "js/GCPolicyAPI.h"
+#include "js/RootingAPI.h"
+
+namespace JS {
+template<typename T>
+struct GCPolicy<mozilla::OwningNonNull<T>>
+{
+ typedef mozilla::OwningNonNull<T> SmartPtrType;
+
+ static SmartPtrType initial()
+ {
+ return SmartPtrType();
+ }
+
+ static void trace(JSTracer* trc, SmartPtrType* tp,
+ const char* name)
+ {
+ // We have to be very careful here. Normally, OwningNonNull can't be null.
+ // But binding code can end up in a situation where it sets up a
+ // Rooted<OwningNonNull> and then before it gets a chance to assign to it
+ // (e.g. from the constructor of the thing being assigned) a GC happens. So
+ // we can land here when *tp stores a null pointer because it's not
+ // initialized.
+ //
+ // So we need to check for that before jumping.
+ if ((*tp).isInitialized()) {
+ (*tp)->Trace(trc);
+ }
+ }
+};
+} // namespace JS
+
+namespace js {
+template<typename T>
+struct RootedBase<mozilla::OwningNonNull<T>>
+{
+ typedef mozilla::OwningNonNull<T> SmartPtrType;
+
+ operator SmartPtrType& () const
+ {
+ auto& self = *static_cast<const JS::Rooted<SmartPtrType>*>(this);
+ return self.get();
+ }
+
+ operator T& () const
+ {
+ auto& self = *static_cast<const JS::Rooted<SmartPtrType>*>(this);
+ return self.get();
+ }
+};
+} // namespace js
+
+#endif /* mozilla_RootedOwningNonNull_h__ */