dom/streams/TransformerCallbackHelpers.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "TransformerCallbackHelpers.h"
   8
   9 #include "mozilla/dom/Promise.h"
  10 #include "mozilla/dom/TransformStreamDefaultController.h"
  11
  12 using namespace mozilla::dom;
  13
  14 NS_IMPL_CYCLE_COLLECTION_WITH_JS_MEMBERS(TransformerAlgorithms,
  15                                          (mGlobal, mTransformCallback,
  16                                           mFlushCallback),
  17                                          (mTransformer))
  18 NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(TransformerAlgorithms, AddRef)
  19 NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(TransformerAlgorithms, Release)
  20
  21 // https://streams.spec.whatwg.org/#set-up-transform-stream-default-controller-from-transformer
  22 already_AddRefed<Promise> TransformerAlgorithms::TransformCallback(
  23     JSContext* aCx, JS::Handle<JS::Value> aChunk,
  24     TransformStreamDefaultController& aController, ErrorResult& aRv) {
  25   if (!mTransformCallback) {
  26     // Step 2.1. Let result be
  27     // TransformStreamDefaultControllerEnqueue(controller, chunk).
  28     aController.Enqueue(aCx, aChunk, aRv);
  29
  30     // Step 2.2. If result is an abrupt completion, return a promise rejected
  31     // with result.[[Value]].
  32     if (aRv.MaybeSetPendingException(aCx)) {
  33       JS::Rooted<JS::Value> error(aCx);
  34       if (!JS_GetPendingException(aCx, &error)) {
  35         // Uncatchable exception; we should mark aRv and return.
  36         aRv.StealExceptionFromJSContext(aCx);
  37         return nullptr;
  38       }
  39       JS_ClearPendingException(aCx);
  40
  41       RefPtr<Promise> promise =
  42           Promise::Create(aController.GetParentObject(), aRv);
  43       if (aRv.Failed()) {
  44         return nullptr;
  45       }
  46       promise->MaybeReject(error);
  47       return promise.forget();
  48     }
  49
  50     // Step 2.3. Otherwise, return a promise resolved with undefined.
  51     return Promise::CreateResolvedWithUndefined(aController.GetParentObject(),
  52                                                 aRv);
  53   }
  54   // Step 4. If transformerDict["transform"] exists, set transformAlgorithm to
  55   // an algorithm which takes an argument chunk and returns the result of
  56   // invoking transformerDict["transform"] with argument list « chunk,
  57   // controller » and callback this value transformer.
  58   JS::Rooted<JSObject*> thisObj(aCx, mTransformer);
  59   return MOZ_KnownLive(mTransformCallback)
  60       ->Call(thisObj, aChunk, aController, aRv,
  61              "TransformStreamDefaultController.[[transformAlgorithm]]",
  62              CallbackObject::eRethrowExceptions);
  63 }
  64
  65 // https://streams.spec.whatwg.org/#set-up-transform-stream-default-controller-from-transformer
  66 already_AddRefed<Promise> TransformerAlgorithms::FlushCallback(
  67     JSContext* aCx, TransformStreamDefaultController& aController,
  68     ErrorResult& aRv) {
  69   if (!mFlushCallback) {
  70     // Step 3. Let flushAlgorithm be an algorithm which returns a promise
  71     // resolved with undefined.
  72     return Promise::CreateResolvedWithUndefined(aController.GetParentObject(),
  73                                                 aRv);
  74   }
  75   // Step 5. If transformerDict["flush"] exists, set flushAlgorithm to an
  76   // algorithm which returns the result of invoking transformerDict["flush"]
  77   // with argument list « controller » and callback this value transformer.
  78   JS::Rooted<JSObject*> thisObj(aCx, mTransformer);
  79   return MOZ_KnownLive(mFlushCallback)
  80       ->Call(thisObj, aController, aRv,
  81              "TransformStreamDefaultController.[[flushAlgorithm]]",
  82              CallbackObject::eRethrowExceptions);
  83 }