1 files changed, 109 insertions, 0 deletions
diff --git a/dom/streams/UnderlyingSourceCallbackHelpers.cpp b/dom/streams/UnderlyingSourceCallbackHelpers.cpp
new file mode 100644
index 0000000000..2fef2fd12e
--- /dev/null
+++ b/dom/streams/UnderlyingSourceCallbackHelpers.cpp
@@ -0,0 +1,109 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/. */
+
+#include "mozilla/dom/ReadableStreamDefaultController.h"
+#include "mozilla/dom/UnderlyingSourceCallbackHelpers.h"
+#include "mozilla/dom/UnderlyingSourceBinding.h"
+
+namespace mozilla::dom {
+
+// UnderlyingSourceAlgorithmsBase
+NS_IMPL_CYCLE_COLLECTION(UnderlyingSourceAlgorithmsBase)
+NS_IMPL_CYCLE_COLLECTING_ADDREF(UnderlyingSourceAlgorithmsBase)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(UnderlyingSourceAlgorithmsBase)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(UnderlyingSourceAlgorithmsBase)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED_WITH_JS_MEMBERS(
+    UnderlyingSourceAlgorithms, UnderlyingSourceAlgorithmsBase,
+    (mGlobal, mStartCallback, mPullCallback, mCancelCallback),
+    (mUnderlyingSource))
+NS_IMPL_ADDREF_INHERITED(UnderlyingSourceAlgorithms,
+                         UnderlyingSourceAlgorithmsBase)
+NS_IMPL_RELEASE_INHERITED(UnderlyingSourceAlgorithms,
+                          UnderlyingSourceAlgorithmsBase)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(UnderlyingSourceAlgorithms)
+NS_INTERFACE_MAP_END_INHERITING(UnderlyingSourceAlgorithmsBase)
+
+// https://streams.spec.whatwg.org/#set-up-readable-stream-default-controller-from-underlying-source
+void UnderlyingSourceAlgorithms::StartCallback(
+    JSContext* aCx, ReadableStreamController& aController,
+    JS::MutableHandle<JS::Value> aRetVal, ErrorResult& aRv) {
+  if (!mStartCallback) {
+    // Step 2: Let startAlgorithm be an algorithm that returns undefined.
+    aRetVal.setUndefined();
+    return;
+  }
+
+  // Step 5: If underlyingSourceDict["start"] exists, then set startAlgorithm to
+  // an algorithm which returns the result of invoking
+  // underlyingSourceDict["start"] with argument list « controller » and
+  // callback this value underlyingSource.
+  JS::Rooted<JSObject*> thisObj(aCx, mUnderlyingSource);
+  ReadableStreamDefaultControllerOrReadableByteStreamController controller;
+  if (aController.IsDefault()) {
+    controller.SetAsReadableStreamDefaultController() = aController.AsDefault();
+  } else {
+    controller.SetAsReadableByteStreamController() = aController.AsByte();
+  }
+
+  return mStartCallback->Call(thisObj, controller, aRetVal, aRv,
+                              "UnderlyingSource.start",
+                              CallbackFunction::eRethrowExceptions);
+}
+
+// https://streams.spec.whatwg.org/#set-up-readable-stream-default-controller-from-underlying-source
+already_AddRefed<Promise> UnderlyingSourceAlgorithms::PullCallback(
+    JSContext* aCx, ReadableStreamController& aController, ErrorResult& aRv) {
+  JS::Rooted<JSObject*> thisObj(aCx, mUnderlyingSource);
+  if (!mPullCallback) {
+    // Step 3: Let pullAlgorithm be an algorithm that returns a promise resolved
+    // with undefined.
+    return Promise::CreateResolvedWithUndefined(mGlobal, aRv);
+  }
+
+  // Step 6: If underlyingSourceDict["pull"] exists, then set pullAlgorithm to
+  // an algorithm which returns the result of invoking
+  // underlyingSourceDict["pull"] with argument list « controller » and callback
+  // this value underlyingSource.
+  ReadableStreamDefaultControllerOrReadableByteStreamController controller;
+  if (aController.IsDefault()) {
+    controller.SetAsReadableStreamDefaultController() = aController.AsDefault();
+  } else {
+    controller.SetAsReadableByteStreamController() = aController.AsByte();
+  }
+
+  RefPtr<Promise> promise =
+      mPullCallback->Call(thisObj, controller, aRv, "UnderlyingSource.pull",
+                          CallbackFunction::eRethrowExceptions);
+
+  return promise.forget();
+}
+
+// https://streams.spec.whatwg.org/#set-up-readable-stream-default-controller-from-underlying-source
+already_AddRefed<Promise> UnderlyingSourceAlgorithms::CancelCallback(
+    JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aReason,
+    ErrorResult& aRv) {
+  if (!mCancelCallback) {
+    // Step 4: Let cancelAlgorithm be an algorithm that returns a promise
+    // resolved with undefined.
+    return Promise::CreateResolvedWithUndefined(mGlobal, aRv);
+  }
+
+  // Step 7: If underlyingSourceDict["cancel"] exists, then set cancelAlgorithm
+  // to an algorithm which takes an argument reason and returns the result of
+  // invoking underlyingSourceDict["cancel"] with argument list « reason » and
+  // callback this value underlyingSource.
+  JS::Rooted<JSObject*> thisObj(aCx, mUnderlyingSource);
+  RefPtr<Promise> promise =
+      mCancelCallback->Call(thisObj, aReason, aRv, "UnderlyingSource.cancel",
+                            CallbackFunction::eRethrowExceptions);
+
+  return promise.forget();
+}
+
+}  // namespace mozilla::dom