1 files changed, 47 insertions, 0 deletions
diff --git a/js/src/builtin/streams/WritableStream-inl.h b/js/src/builtin/streams/WritableStream-inl.h
new file mode 100644
index 0000000000..f2832d1ec1
--- /dev/null
+++ b/js/src/builtin/streams/WritableStream-inl.h
@@ -0,0 +1,47 @@
+/* -*- 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/. */
+
+/* Class WritableStream. */
+
+#ifndef builtin_streams_WritableStream_inl_h
+#define builtin_streams_WritableStream_inl_h
+
+#include "builtin/streams/WritableStream.h"
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/Attributes.h"  // MOZ_MUST_USE
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+#include "builtin/streams/WritableStreamDefaultWriter.h"  // js::WritableStreamDefaultWriter
+#include "js/RootingAPI.h"                                // JS::Handle
+#include "js/Value.h"                                     // JS::{,Object}Value
+
+#include "vm/Compartment-inl.h"  // js::UnwrapInternalSlot
+
+struct JS_PUBLIC_API JSContext;
+
+namespace js {
+
+/**
+ * Returns the writer associated with the given stream.
+ *
+ * Must only be called on WritableStreams that already have a writer
+ * associated with them.
+ *
+ * If the writer is a wrapper, it will be unwrapped, so the result might not be
+ * an object from the currently active compartment.
+ */
+inline MOZ_MUST_USE WritableStreamDefaultWriter* UnwrapWriterFromStream(
+    JSContext* cx, JS::Handle<WritableStream*> unwrappedStream) {
+  MOZ_ASSERT(unwrappedStream->hasWriter());
+  return UnwrapInternalSlot<WritableStreamDefaultWriter>(
+      cx, unwrappedStream, WritableStream::Slot_Writer);
+}
+
+}  // namespace js
+
+#endif  // builtin_streams_WritableStream_inl_h