Quelle ReadableByteStreamController.cpp Sprache: C

/* -*- 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/ReadableByteStreamController.h"

#include "ReadIntoRequest.h"
#include "js/ArrayBuffer.h"
#include "js/ErrorReport.h"
#include "js/Exception.h"
#include "js/TypeDecls.h"
#include "js/Value.h"
#include "js/ValueArray.h"
#include "js/experimental/TypedData.h"
#include "js/friend/ErrorMessages.h"
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Attributes.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/HoldDropJSObjects.h"
#include "mozilla/dom/ByteStreamHelpers.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/Promise-inl.h"
#include "mozilla/dom/ReadableByteStreamControllerBinding.h"
#include "mozilla/dom/ReadableStream.h"
#include "mozilla/dom/ReadableStreamBYOBReader.h"
#include "mozilla/dom/ReadableStreamBYOBRequest.h"
#include "mozilla/dom/ReadableStreamController.h"
#include "mozilla/dom/ReadableStreamDefaultController.h"
#include "mozilla/dom/ReadableStreamDefaultReader.h"
#include "mozilla/dom/ReadableStreamGenericReader.h"
#include "mozilla/dom/ToJSValue.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/dom/UnderlyingSourceCallbackHelpers.h"
#include "nsCycleCollectionParticipant.h"
#include "nsIGlobalObject.h"
#include "nsISupports.h"

#include <algorithm>  // std::min

namespace mozilla::dom {

using namespace streams_abstract;

// https://streams.spec.whatwg.org/#readable-byte-stream-queue-entry
struct ReadableByteStreamQueueEntry
    : LinkedListElement<RefPtr<ReadableByteStreamQueueEntry>> {
  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(
      ReadableByteStreamQueueEntry)
  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(
      ReadableByteStreamQueueEntry)

  ReadableByteStreamQueueEntry(JS::Handle<JSObject*> aBuffer,
                               size_t aByteOffset, size_t aByteLength)
      : mBuffer(aBuffer), mByteOffset(aByteOffset), mByteLength(aByteLength) {
    mozilla::HoldJSObjects(this);
  }

  JSObject* Buffer() const { return mBuffer; }
  void SetBuffer(JS::Handle<JSObject*> aBuffer) { mBuffer = aBuffer; }

  size_t ByteOffset() const { return mByteOffset; }
  void SetByteOffset(size_t aByteOffset) { mByteOffset = aByteOffset; }

  size_t ByteLength() const { return mByteLength; }
  void SetByteLength(size_t aByteLength) { mByteLength = aByteLength; }

private:
  // An ArrayBuffer, which will be a transferred version of the one originally
  // supplied by the underlying byte source.
  JS::Heap<JSObject*> mBuffer;

  // A nonnegative integer number giving the byte offset derived from the view
  // originally supplied by the underlying byte source
  size_t mByteOffset = 0;

  // A nonnegative integer number giving the byte length derived from the view
  // originally supplied by the underlying byte source
  size_t mByteLength = 0;

  ~ReadableByteStreamQueueEntry() { mozilla::DropJSObjects(this); }
};

NS_IMPL_CYCLE_COLLECTION_WITH_JS_MEMBERS(ReadableByteStreamQueueEntry, (),
                                         (mBuffer));

struct PullIntoDescriptor final
    : LinkedListElement<RefPtr<PullIntoDescriptor>> {
  NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(PullIntoDescriptor)
  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(PullIntoDescriptor)

  enum Constructor {
    DataView,
#define DEFINE_TYPED_CONSTRUCTOR_ENUM_NAMES(ExternalT, NativeT, Name) Name,
    JS_FOR_EACH_TYPED_ARRAY(DEFINE_TYPED_CONSTRUCTOR_ENUM_NAMES)
#undef DEFINE_TYPED_CONSTRUCTOR_ENUM_NAMES
  };

  static Constructor constructorFromScalar(JS::Scalar::Type type) {
    switch (type) {
#define REMAP_PULL_INTO_DESCRIPTOR_TYPE(ExternalT, NativeT, Name) \
  case JS::Scalar::Name:                                          \
    return Constructor::Name;
      JS_FOR_EACH_TYPED_ARRAY(REMAP_PULL_INTO_DESCRIPTOR_TYPE)
#undef REMAP

      case JS::Scalar::Int64:
      case JS::Scalar::Simd128:
      case JS::Scalar::MaxTypedArrayViewType:
        break;
    }
    MOZ_CRASH("Unexpected Scalar::Type");
  }

  PullIntoDescriptor(JS::Handle<JSObject*> aBuffer, uint64_t aBufferByteLength,
                     uint64_t aByteOffset, uint64_t aByteLength,
                     uint64_t aBytesFilled, uint64_t aMinimumFill,
                     uint64_t aElementSize, Constructor aViewConstructor,
                     ReaderType aReaderType)
      : mBuffer(aBuffer),
        mBufferByteLength(aBufferByteLength),
        mByteOffset(aByteOffset),
        mByteLength(aByteLength),
        mBytesFilled(aBytesFilled),
        mMinimumFill(aMinimumFill),
        mElementSize(aElementSize),
        mViewConstructor(aViewConstructor),
        mReaderType(aReaderType) {
    mozilla::HoldJSObjects(this);
  }

  JSObject* Buffer() const { return mBuffer; }
  void SetBuffer(JS::Handle<JSObject*> aBuffer) { mBuffer = aBuffer; }

  uint64_t BufferByteLength() const { return mBufferByteLength; }
  void SetBufferByteLength(const uint64_t aBufferByteLength) {
    mBufferByteLength = aBufferByteLength;
  }

  uint64_t ByteOffset() const { return mByteOffset; }
  void SetByteOffset(const uint64_t aByteOffset) { mByteOffset = aByteOffset; }

  uint64_t ByteLength() const { return mByteLength; }
  void SetByteLength(const uint64_t aByteLength) { mByteLength = aByteLength; }

  uint64_t BytesFilled() const { return mBytesFilled; }
  void SetBytesFilled(const uint64_t aBytesFilled) {
    mBytesFilled = aBytesFilled;
  }

  uint64_t MinimumFill() const { return mMinimumFill; }

  uint64_t ElementSize() const { return mElementSize; }
  void SetElementSize(const uint64_t aElementSize) {
    mElementSize = aElementSize;
  }

  Constructor ViewConstructor() const { return mViewConstructor; }

  // Note: Named GetReaderType to avoid name conflict with type.
  ReaderType GetReaderType() const { return mReaderType; }
  void SetReaderType(const ReaderType aReaderType) {
    mReaderType = aReaderType;
  }

private:
  JS::Heap<JSObject*> mBuffer;
  uint64_t mBufferByteLength = 0;
  uint64_t mByteOffset = 0;
  uint64_t mByteLength = 0;
  uint64_t mBytesFilled = 0;
  uint64_t mMinimumFill = 0;
  uint64_t mElementSize = 0;
  Constructor mViewConstructor;
  ReaderType mReaderType;

  ~PullIntoDescriptor() { mozilla::DropJSObjects(this); }
};

NS_IMPL_CYCLE_COLLECTION_WITH_JS_MEMBERS(PullIntoDescriptor, (), (mBuffer));

NS_IMPL_CYCLE_COLLECTION_CLASS(ReadableByteStreamController)
NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(ReadableByteStreamController,
                                                ReadableStreamController)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mByobRequest, mQueue, mPendingPullIntos)
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ReadableByteStreamController,
                                                  ReadableStreamController)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mByobRequest, mQueue, mPendingPullIntos)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(ReadableByteStreamController,
                                               ReadableStreamController)
  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_TRACE_END

NS_IMPL_ADDREF_INHERITED(ReadableByteStreamController, ReadableStreamController)
NS_IMPL_RELEASE_INHERITED(ReadableByteStreamController,
                          ReadableStreamController)
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ReadableByteStreamController)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
NS_INTERFACE_MAP_END_INHERITING(ReadableStreamController)

ReadableByteStreamController::ReadableByteStreamController(
    nsIGlobalObject* aGlobal)
    : ReadableStreamController(aGlobal) {}

ReadableByteStreamController::~ReadableByteStreamController() = default;

void ReadableByteStreamController::ClearQueue() { mQueue.clear(); }

void ReadableByteStreamController::ClearPendingPullIntos() {
  mPendingPullIntos.clear();
}

namespace streams_abstract {
// https://streams.spec.whatwg.org/#abstract-opdef-readablebytestreamcontrollergetbyobrequest
already_AddRefed<ReadableStreamBYOBRequest>
ReadableByteStreamControllerGetBYOBRequest(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv) {
  // Step 1.
  if (!aController->GetByobRequest() &&
      !aController->PendingPullIntos().isEmpty()) {
    // Step 1.1:
    PullIntoDescriptor* firstDescriptor =
        aController->PendingPullIntos().getFirst();

    // Step 1.2:
    aRv.MightThrowJSException();
    JS::Rooted<JSObject*> buffer(aCx, firstDescriptor->Buffer());
    JS::Rooted<JSObject*> view(
        aCx, JS_NewUint8ArrayWithBuffer(
                 aCx, buffer,
                 firstDescriptor->ByteOffset() + firstDescriptor->BytesFilled(),
                 int64_t(firstDescriptor->ByteLength() -
                         firstDescriptor->BytesFilled())));
    if (!view) {
      aRv.StealExceptionFromJSContext(aCx);
      return nullptr;
    }

    // Step 1.3:
    RefPtr<ReadableStreamBYOBRequest> byobRequest =
        new ReadableStreamBYOBRequest(aController->GetParentObject());

    // Step 1.4:
    byobRequest->SetController(aController);

    // Step 1.5:
    byobRequest->SetView(view);

    // Step 1.6:
    aController->SetByobRequest(byobRequest);
  }

  // Step 2.
  RefPtr<ReadableStreamBYOBRequest> request(aController->GetByobRequest());
  return request.forget();
}
}  // namespace streams_abstract

already_AddRefed<ReadableStreamBYOBRequest>
ReadableByteStreamController::GetByobRequest(JSContext* aCx, ErrorResult& aRv) {
  return ReadableByteStreamControllerGetBYOBRequest(aCx, this, aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-get-desired-size
Nullable<double> ReadableByteStreamControllerGetDesiredSize(
    const ReadableByteStreamController* aController) {
  // Step 1.
  ReadableStream::ReaderState state = aController->Stream()->State();

  // Step 2.
  if (state == ReadableStream::ReaderState::Errored) {
    return nullptr;
  }

  // Step 3.
  if (state == ReadableStream::ReaderState::Closed) {
    return 0.0;
  }

  // Step 4.
  return aController->StrategyHWM() - aController->QueueTotalSize();
}

Nullable<double> ReadableByteStreamController::GetDesiredSize() const {
  // Step 1.
  return ReadableByteStreamControllerGetDesiredSize(this);
}

JSObject* ReadableByteStreamController::WrapObject(
    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
  return ReadableByteStreamController_Binding::Wrap(aCx, this, aGivenProto);
}

namespace streams_abstract {

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-invalidate-byob-request
static void ReadableByteStreamControllerInvalidateBYOBRequest(
    ReadableByteStreamController* aController) {
  // Step 1.
  if (!aController->GetByobRequest()) {
    return;
  }

  // Step 2.
  aController->GetByobRequest()->SetController(nullptr);

  // Step 3.
  aController->GetByobRequest()->SetView(nullptr);

  // Step 4.
  aController->SetByobRequest(nullptr);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-clear-pending-pull-intos
void ReadableByteStreamControllerClearPendingPullIntos(
    ReadableByteStreamController* aController) {
  // Step 1.
  ReadableByteStreamControllerInvalidateBYOBRequest(aController);

  // Step 2.
  aController->ClearPendingPullIntos();
}

// https://streams.spec.whatwg.org/#reset-queue
void ResetQueue(ReadableByteStreamController* aContainer) {
  // Step 1. Implied by type.
  // Step 2.
  aContainer->ClearQueue();

  // Step 3.
  aContainer->SetQueueTotalSize(0);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-clear-algorithms
void ReadableByteStreamControllerClearAlgorithms(
    ReadableByteStreamController* aController) {
  // Step 1. Set controller.[[pullAlgorithm]] to undefined.
  // Step 2. Set controller.[[cancelAlgorithm]] to undefined.
  aController->ClearAlgorithms();
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-error
void ReadableByteStreamControllerError(
    ReadableByteStreamController* aController, JS::Handle<JS::Value> aValue,
    ErrorResult& aRv) {
  // Step 1. Let stream be controller.[[stream]].
  ReadableStream* stream = aController->Stream();

  // Step 2. If stream.[[state]] is not "readable", return.
  if (stream->State() != ReadableStream::ReaderState::Readable) {
    return;
  }

  // Step 3. Perform
  // !ReadableByteStreamControllerClearPendingPullIntos(controller).
  ReadableByteStreamControllerClearPendingPullIntos(aController);

  // Step 4. Perform !ResetQueue(controller).
  ResetQueue(aController);

  // Step 5. Perform !ReadableByteStreamControllerClearAlgorithms(controller).
  ReadableByteStreamControllerClearAlgorithms(aController);

  // Step 6. Perform !ReadableStreamError(stream, e).
  AutoJSAPI jsapi;
  if (!jsapi.Init(aController->GetParentObject())) {
    return;
  }
  ReadableStreamError(jsapi.cx(), stream, aValue, aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-close
void ReadableByteStreamControllerClose(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv) {
  // Step 1.
  RefPtr<ReadableStream> stream = aController->Stream();

  // Step 2.
  if (aController->CloseRequested() ||
      stream->State() != ReadableStream::ReaderState::Readable) {
    return;
  }

  // Step 3.
  if (aController->QueueTotalSize() > 0) {
    // Step 3.1
    aController->SetCloseRequested(true);
    // Step 3.2
    return;
  }

  // Step 4.
  if (!aController->PendingPullIntos().isEmpty()) {
    // Step 4.1. Let firstPendingPullInto be controller.[[pendingPullIntos]][0].
    PullIntoDescriptor* firstPendingPullInto =
        aController->PendingPullIntos().getFirst();

    // Step 4.2. If the remainder after dividing firstPendingPullInto’s bytes
    // filled by firstPendingPullInto’s element size is not 0,
    if ((firstPendingPullInto->BytesFilled() %
         firstPendingPullInto->ElementSize()) != 0) {
      // Step 4.2.1
      ErrorResult rv;
      rv.ThrowTypeError("Leftover Bytes");

      JS::Rooted<JS::Value> exception(aCx);
      MOZ_ALWAYS_TRUE(ToJSValue(aCx, std::move(rv), &exception));

      // Step 4.2.2
      ReadableByteStreamControllerError(aController, exception, aRv);
      if (aRv.Failed()) {
        return;
      }

      aRv.MightThrowJSException();
      aRv.ThrowJSException(aCx, exception);
      return;
    }
  }

  // Step 5.
  ReadableByteStreamControllerClearAlgorithms(aController);

  // Step 6.
  ReadableStreamClose(aCx, stream, aRv);
}

}  // namespace streams_abstract

// https://streams.spec.whatwg.org/#rbs-controller-close
void ReadableByteStreamController::Close(JSContext* aCx, ErrorResult& aRv) {
  // Step 1.
  if (mCloseRequested) {
    aRv.ThrowTypeError("Close already requested");
    return;
  }

  // Step 2.
  if (Stream()->State() != ReadableStream::ReaderState::Readable) {
    aRv.ThrowTypeError("Closing un-readable stream controller");
    return;
  }

  // Step 3.
  ReadableByteStreamControllerClose(aCx, this, aRv);
}

namespace streams_abstract {

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-enqueue-chunk-to-queue
void ReadableByteStreamControllerEnqueueChunkToQueue(
    ReadableByteStreamController* aController,
    JS::Handle<JSObject*> aTransferredBuffer, size_t aByteOffset,
    size_t aByteLength) {
  // Step 1.
  RefPtr<ReadableByteStreamQueueEntry> queueEntry =
      new ReadableByteStreamQueueEntry(aTransferredBuffer, aByteOffset,
                                       aByteLength);
  aController->Queue().insertBack(queueEntry);

  // Step 2.
  aController->AddToQueueTotalSize(double(aByteLength));
}

// https://streams.spec.whatwg.org/#abstract-opdef-readablebytestreamcontrollerenqueueclonedchunktoqueue
void ReadableByteStreamControllerEnqueueClonedChunkToQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    JS::Handle<JSObject*> aBuffer, size_t aByteOffset, size_t aByteLength,
    ErrorResult& aRv) {
  // Step 1. Let cloneResult be CloneArrayBuffer(buffer, byteOffset, byteLength,
  // %ArrayBuffer%).
  aRv.MightThrowJSException();
  JS::Rooted<JSObject*> cloneResult(
      aCx, JS::ArrayBufferClone(aCx, aBuffer, aByteOffset, aByteLength));

  // Step 2. If cloneResult is an abrupt completion,
  if (!cloneResult) {
    JS::Rooted<JS::Value> exception(aCx);
    if (!JS_GetPendingException(aCx, &exception)) {
      // Uncatchable exception; we should mark aRv and return.
      aRv.StealExceptionFromJSContext(aCx);
      return;
    }
    JS_ClearPendingException(aCx);

    // Step 2.1. Perform ! ReadableByteStreamControllerError(controller,
    // cloneResult.[[Value]]).
    ReadableByteStreamControllerError(aController, exception, aRv);
    if (aRv.Failed()) {
      return;
    }

    // Step 2.2. Return cloneResult.
    aRv.ThrowJSException(aCx, exception);
    return;
  }

  // Step 3. Perform !
  // ReadableByteStreamControllerEnqueueChunkToQueue(controller,
  // cloneResult.[[Value]], 0, byteLength).
  ReadableByteStreamControllerEnqueueChunkToQueue(aController, cloneResult, 0,
                                                  aByteLength);
}

already_AddRefed<PullIntoDescriptor>
ReadableByteStreamControllerShiftPendingPullInto(
    ReadableByteStreamController* aController);

// https://streams.spec.whatwg.org/#abstract-opdef-readablebytestreamcontrollerenqueuedetachedpullintotoqueue
void ReadableByteStreamControllerEnqueueDetachedPullIntoToQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    PullIntoDescriptor* aPullIntoDescriptor, ErrorResult& aRv) {
  // Step 1. Assert: pullIntoDescriptor’s reader type is "none".
  MOZ_ASSERT(aPullIntoDescriptor->GetReaderType() == ReaderType::None);

  // Step 2. If pullIntoDescriptor’s bytes filled > 0,
  // perform ? ReadableByteStreamControllerEnqueueClonedChunkToQueue(controller,
  // pullIntoDescriptor’s buffer, pullIntoDescriptor’s byte offset,
  // pullIntoDescriptor’s bytes filled).
  if (aPullIntoDescriptor->BytesFilled() > 0) {
    JS::Rooted<JSObject*> buffer(aCx, aPullIntoDescriptor->Buffer());
    ReadableByteStreamControllerEnqueueClonedChunkToQueue(
        aCx, aController, buffer, aPullIntoDescriptor->ByteOffset(),
        aPullIntoDescriptor->BytesFilled(), aRv);
    if (aRv.Failed()) {
      return;
    }
  }

  // Step 3. Perform !
  // ReadableByteStreamControllerShiftPendingPullInto(controller).
  RefPtr<PullIntoDescriptor> discarded =
      ReadableByteStreamControllerShiftPendingPullInto(aController);
  (void)discarded;
}

// https://streams.spec.whatwg.org/#readable-stream-get-num-read-into-requests
static size_t ReadableStreamGetNumReadIntoRequests(ReadableStream* aStream) {
  // Step 1.
  MOZ_ASSERT(ReadableStreamHasBYOBReader(aStream));

  // Step 2.
  return aStream->GetReader()->AsBYOB()->ReadIntoRequests().length();
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-should-call-pull
bool ReadableByteStreamControllerShouldCallPull(
    ReadableByteStreamController* aController) {
  // Step 1. Let stream be controller.[[stream]].
  ReadableStream* stream = aController->Stream();

  // Step 2. If stream.[[state]] is not "readable", return false.
  if (stream->State() != ReadableStream::ReaderState::Readable) {
    return false;
  }

  // Step 3. If controller.[[closeRequested]] is true, return false.
  if (aController->CloseRequested()) {
    return false;
  }

  // Step 4. If controller.[[started]] is false, return false.
  if (!aController->Started()) {
    return false;
  }

  // Step 5. If ! ReadableStreamHasDefaultReader(stream) is true
  // and ! ReadableStreamGetNumReadRequests(stream) > 0, return true.
  if (ReadableStreamHasDefaultReader(stream) &&
      ReadableStreamGetNumReadRequests(stream) > 0) {
    return true;
  }

  // Step 6. If ! ReadableStreamHasBYOBReader(stream) is true
  // and ! ReadableStreamGetNumReadIntoRequests(stream) > 0, return true.
  if (ReadableStreamHasBYOBReader(stream) &&
      ReadableStreamGetNumReadIntoRequests(stream) > 0) {
    return true;
  }

  // Step 7. Let desiredSize be
  // ! ReadableByteStreamControllerGetDesiredSize(controller).
  Nullable<double> desiredSize =
      ReadableByteStreamControllerGetDesiredSize(aController);

  // Step 8. Assert: desiredSize is not null.
  MOZ_ASSERT(!desiredSize.IsNull());

  // Step 9. If desiredSize > 0, return true.
  // Step 10. Return false.
  return desiredSize.Value() > 0;
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-call-pull-if-needed
void ReadableByteStreamControllerCallPullIfNeeded(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv) {
  // Step 1.
  bool shouldPull = ReadableByteStreamControllerShouldCallPull(aController);

  // Step 2.
  if (!shouldPull) {
    return;
  }

  // Step 3.
  if (aController->Pulling()) {
    aController->SetPullAgain(true);
    return;
  }

  // Step 4.
  MOZ_ASSERT(!aController->PullAgain());

  // Step 5.
  aController->SetPulling(true);

  // Step 6.
  RefPtr<ReadableStreamController> controller(aController);
  RefPtr<UnderlyingSourceAlgorithmsBase> algorithms =
      aController->GetAlgorithms();
  RefPtr<Promise> pullPromise = algorithms->PullCallback(aCx, *controller, aRv);
  if (aRv.Failed()) {
    return;
  }

  // Steps 7+8
  pullPromise->AddCallbacksWithCycleCollectedArgs(
      [](JSContext* aCx, JS::Handle<JS::Value> aValue, ErrorResult& aRv,
         ReadableByteStreamController* aController)
          MOZ_CAN_RUN_SCRIPT_BOUNDARY {
            // Step 7.1
            aController->SetPulling(false);
            // Step 7.2
            if (aController->PullAgain()) {
              // Step 7.2.1
              aController->SetPullAgain(false);

              // Step 7.2.2
              ReadableByteStreamControllerCallPullIfNeeded(
                  aCx, MOZ_KnownLive(aController), aRv);
            }
          },
      [](JSContext* aCx, JS::Handle<JS::Value> aValue, ErrorResult& aRv,
         ReadableByteStreamController* aController) {
        // Step 8.1
        ReadableByteStreamControllerError(aController, aValue, aRv);
      },
      RefPtr(aController));
}

bool ReadableByteStreamControllerFillPullIntoDescriptorFromQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    PullIntoDescriptor* aPullIntoDescriptor, ErrorResult& aRv);

JSObject* ReadableByteStreamControllerConvertPullIntoDescriptor(
    JSContext* aCx, PullIntoDescriptor* pullIntoDescriptor, ErrorResult& aRv);

// https://streams.spec.whatwg.org/#readable-stream-fulfill-read-into-request
MOZ_CAN_RUN_SCRIPT
void ReadableStreamFulfillReadIntoRequest(JSContext* aCx,
                                          ReadableStream* aStream,
                                          JS::Handle<JS::Value> aChunk,
                                          bool done, ErrorResult& aRv) {
  // Step 1. Assert: !ReadableStreamHasBYOBReader(stream) is true.
  MOZ_ASSERT(ReadableStreamHasBYOBReader(aStream));

  // Step 2. Let reader be stream.[[reader]].
  ReadableStreamBYOBReader* reader = aStream->GetReader()->AsBYOB();

  // Step 3. Assert: reader.[[readIntoRequests]] is not empty.
  MOZ_ASSERT(!reader->ReadIntoRequests().isEmpty());

  // Step 4. Let readIntoRequest be reader.[[readIntoRequests]][0].
  // Step 5. Remove readIntoRequest from reader.[[readIntoRequests]].
  RefPtr<ReadIntoRequest> readIntoRequest =
      reader->ReadIntoRequests().popFirst();

  // Step 6. If done is true, perform readIntoRequest’s close steps, given
  // chunk.
  if (done) {
    readIntoRequest->CloseSteps(aCx, aChunk, aRv);
    return;
  }

  // Step 7. Otherwise, perform readIntoRequest’s chunk steps, given chunk.
  readIntoRequest->ChunkSteps(aCx, aChunk, aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-commit-pull-into-descriptor
MOZ_CAN_RUN_SCRIPT
void ReadableByteStreamControllerCommitPullIntoDescriptor(
    JSContext* aCx, ReadableStream* aStream,
    PullIntoDescriptor* pullIntoDescriptor, ErrorResult& aRv) {
  // Step 1. Assert: stream.[[state]] is not "errored".
  MOZ_ASSERT(aStream->State() != ReadableStream::ReaderState::Errored);

  // Step 2. Assert: pullIntoDescriptor.reader type is not "none".
  MOZ_ASSERT(pullIntoDescriptor->GetReaderType() != ReaderType::None);

  // Step 3. Let done be false.
  bool done = false;

  // Step 4. If stream.[[state]] is "closed",
  if (aStream->State() == ReadableStream::ReaderState::Closed) {
    // Step 4.1. Assert: the remainder after dividing pullIntoDescriptor’s bytes
    // filled by pullIntoDescriptor’s element size is 0.
    MOZ_ASSERT((pullIntoDescriptor->BytesFilled() %
                pullIntoDescriptor->ElementSize()) == 0);

    // Step 4.2. Set done to true.
    done = true;
  }

  // Step 5. Let filledView be !
  // ReadableByteStreamControllerConvertPullIntoDescriptor(pullIntoDescriptor).
  JS::Rooted<JSObject*> filledView(
      aCx, ReadableByteStreamControllerConvertPullIntoDescriptor(
               aCx, pullIntoDescriptor, aRv));
  if (aRv.Failed()) {
    return;
  }
  JS::Rooted<JS::Value> filledViewValue(aCx, JS::ObjectValue(*filledView));

  // Step 6. If pullIntoDescriptor’s reader type is "default",
  if (pullIntoDescriptor->GetReaderType() == ReaderType::Default) {
    // Step 6.1. Perform !ReadableStreamFulfillReadRequest(stream, filledView,
    // done).
    ReadableStreamFulfillReadRequest(aCx, aStream, filledViewValue, done, aRv);
    return;
  }

  // Step 7.1. Assert: pullIntoDescriptor’s reader type is "byob".
  MOZ_ASSERT(pullIntoDescriptor->GetReaderType() == ReaderType::BYOB);

  // Step 7.2 Perform !ReadableStreamFulfillReadIntoRequest(stream, filledView,
  // done).
  ReadableStreamFulfillReadIntoRequest(aCx, aStream, filledViewValue, done,
                                       aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-process-pull-into-descriptors-using-queue
MOZ_CAN_RUN_SCRIPT
void ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    nsTArray<RefPtr<PullIntoDescriptor>>& aFilledPullIntos, ErrorResult& aRv) {
  // Step 1. Assert: controller.[[closeRequested]] is false.
  MOZ_ASSERT(!aController->CloseRequested());

  // Step 2. Let filledPullIntos be a new empty list.
  MOZ_ASSERT(aFilledPullIntos.IsEmpty());

  // Step 3. While controller.[[pendingPullIntos]] is not empty,
  while (!aController->PendingPullIntos().isEmpty()) {
    // Step 3.1. If controller.[[queueTotalSize]] is 0, then break.
    if (aController->QueueTotalSize() == 0) {
      break;
    }

    // Step 3.2. Let pullIntoDescriptor be controller.[[pendingPullIntos]][0].
    RefPtr<PullIntoDescriptor> pullIntoDescriptor =
        aController->PendingPullIntos().getFirst();

    // Step 3.3. If
    // !ReadableByteStreamControllerFillPullIntoDescriptorFromQueue(controller,
    // pullIntoDescriptor) is true,
    bool ready = ReadableByteStreamControllerFillPullIntoDescriptorFromQueue(
        aCx, aController, pullIntoDescriptor, aRv);
    if (aRv.Failed()) {
      return;
    }

    if (ready) {
      //  Step 3.3.1. Perform
      //  !ReadableByteStreamControllerShiftPendingPullInto(controller).
      RefPtr<PullIntoDescriptor> discardedPullIntoDescriptor =
          ReadableByteStreamControllerShiftPendingPullInto(aController);

      // Step 3.3.2. Append pullIntoDescriptor to filledPullIntos.
      aFilledPullIntos.AppendElement(pullIntoDescriptor);
    }
  }

  // Step 4: Return filledPullIntos. (Implicit)
}

MOZ_CAN_RUN_SCRIPT
void ReadableByteStreamControllerHandleQueueDrain(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv);

// https://streams.spec.whatwg.org/#abstract-opdef-readablebytestreamcontrollerfillreadrequestfromqueue
MOZ_CAN_RUN_SCRIPT void ReadableByteStreamControllerFillReadRequestFromQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    ReadRequest* aReadRequest, ErrorResult& aRv) {
  // Step 1. Assert: controller.[[queueTotalSize]] > 0.
  MOZ_ASSERT(aController->QueueTotalSize() > 0);
  // Also assert that the queue has a non-zero length;
  MOZ_ASSERT(aController->Queue().length() > 0);

  // Step 2. Let entry be controller.[[queue]][0].
  // Step 3. Remove entry from controller.[[queue]].
  RefPtr<ReadableByteStreamQueueEntry> entry = aController->Queue().popFirst();

  // Assert that we actually got an entry.
  MOZ_ASSERT(entry);

  // Step 4. Set controller.[[queueTotalSize]] to controller.[[queueTotalSize]]
  // − entry’s byte length.
  aController->SetQueueTotalSize(aController->QueueTotalSize() -
                                 double(entry->ByteLength()));

  // Step 5. Perform ! ReadableByteStreamControllerHandleQueueDrain(controller).
  ReadableByteStreamControllerHandleQueueDrain(aCx, aController, aRv);
  if (aRv.Failed()) {
    return;
  }

  // Step 6. Let view be ! Construct(%Uint8Array%, « entry’s buffer, entry’s
  // byte offset, entry’s byte length »).
  aRv.MightThrowJSException();
  JS::Rooted<JSObject*> buffer(aCx, entry->Buffer());
  JS::Rooted<JSObject*> view(
      aCx, JS_NewUint8ArrayWithBuffer(aCx, buffer, entry->ByteOffset(),
                                      int64_t(entry->ByteLength())));
  if (!view) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }

  // Step 7. Perform readRequest’s chunk steps, given view.
  JS::Rooted<JS::Value> viewValue(aCx, JS::ObjectValue(*view));
  aReadRequest->ChunkSteps(aCx, viewValue, aRv);
}

MOZ_CAN_RUN_SCRIPT void
ReadableByteStreamControllerProcessReadRequestsUsingQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv) {
  // Step 1. Let reader be controller.[[stream]].[[reader]].
  // Step 2. Assert: reader implements ReadableStreamDefaultReader.
  RefPtr<ReadableStreamDefaultReader> reader =
      aController->Stream()->GetDefaultReader();

  // Step 3. While reader.[[readRequests]] is not empty,
  while (!reader->ReadRequests().isEmpty()) {
    // Step 3.1. If controller.[[queueTotalSize]] is 0, return.
    if (aController->QueueTotalSize() == 0) {
      return;
    }

    // Step 3.2. Let readRequest be reader.[[readRequests]][0].
    // Step 3.3. Remove readRequest from reader.[[readRequests]].
    RefPtr<ReadRequest> readRequest = reader->ReadRequests().popFirst();

    // Step 3.4. Perform !
    // ReadableByteStreamControllerFillReadRequestFromQueue(controller,
    // readRequest).
    ReadableByteStreamControllerFillReadRequestFromQueue(aCx, aController,
                                                         readRequest, aRv);
    if (aRv.Failed()) {
      return;
    }
  }
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-enqueue
void ReadableByteStreamControllerEnqueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    JS::Handle<JSObject*> aChunk, ErrorResult& aRv) {
  aRv.MightThrowJSException();

  // Step 1.
  RefPtr<ReadableStream> stream = aController->Stream();

  // Step 2.
  if (aController->CloseRequested() ||
      stream->State() != ReadableStream::ReaderState::Readable) {
    return;
  }

  // Step 3.
  bool isShared;
  JS::Rooted<JSObject*> buffer(
      aCx, JS_GetArrayBufferViewBuffer(aCx, aChunk, &isShared));
  if (!buffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }

  // Step 4.
  size_t byteOffset = JS_GetArrayBufferViewByteOffset(aChunk);

  // Step 5.
  size_t byteLength = JS_GetArrayBufferViewByteLength(aChunk);

  // Step 6.
  if (JS::IsDetachedArrayBufferObject(buffer)) {
    aRv.ThrowTypeError("Detached Array Buffer");
    return;
  }

  // Step 7.
  JS::Rooted<JSObject*> transferredBuffer(aCx,
                                          TransferArrayBuffer(aCx, buffer));
  if (!transferredBuffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }

  // Step 8.
  if (!aController->PendingPullIntos().isEmpty()) {
    // Step 8.1
    RefPtr<PullIntoDescriptor> firstPendingPullInto =
        aController->PendingPullIntos().getFirst();

    // Step 8.2
    JS::Rooted<JSObject*> pendingBuffer(aCx, firstPendingPullInto->Buffer());
    if (JS::IsDetachedArrayBufferObject(pendingBuffer)) {
      aRv.ThrowTypeError("Pending PullInto has detached buffer");
      return;
    }

    // Step 8.3. Perform !
    // ReadableByteStreamControllerInvalidateBYOBRequest(controller).
    ReadableByteStreamControllerInvalidateBYOBRequest(aController);

    // Step 8.4. Set firstPendingPullInto’s buffer to !
    // TransferArrayBuffer(firstPendingPullInto’s buffer).
    pendingBuffer = TransferArrayBuffer(aCx, pendingBuffer);
    if (!pendingBuffer) {
      aRv.StealExceptionFromJSContext(aCx);
      return;
    }
    firstPendingPullInto->SetBuffer(pendingBuffer);

    // Step 8.5. If firstPendingPullInto’s reader type is "none", perform ?
    // ReadableByteStreamControllerEnqueueDetachedPullIntoToQueue(controller,
    // firstPendingPullInto).
    if (firstPendingPullInto->GetReaderType() == ReaderType::None) {
      ReadableByteStreamControllerEnqueueDetachedPullIntoToQueue(
          aCx, aController, firstPendingPullInto, aRv);
      if (aRv.Failed()) {
        return;
      }
    }
  }

  // Step 9. If ! ReadableStreamHasDefaultReader(stream) is true,
  if (ReadableStreamHasDefaultReader(stream)) {
    // Step 9.1. Perform !
    // ReadableByteStreamControllerProcessReadRequestsUsingQueue(controller).
    ReadableByteStreamControllerProcessReadRequestsUsingQueue(aCx, aController,
                                                              aRv);
    if (aRv.Failed()) {
      return;
    }

    // Step 9.2. If ! ReadableStreamGetNumReadRequests(stream) is 0,
    if (ReadableStreamGetNumReadRequests(stream) == 0) {
      // Step 9.2.1 Assert: controller.[[pendingPullIntos]] is empty.
      MOZ_ASSERT(aController->PendingPullIntos().isEmpty());

      // Step 9.2.2. Perform !
      // ReadableByteStreamControllerEnqueueChunkToQueue(controller,
      // transferredBuffer, byteOffset, byteLength).
      ReadableByteStreamControllerEnqueueChunkToQueue(
          aController, transferredBuffer, byteOffset, byteLength);

      // Step 9.3. Otherwise,
    } else {
      // Step 9.3.1 Assert: controller.[[queue]] is empty.
      MOZ_ASSERT(aController->Queue().isEmpty());

      // Step 9.3.2. If controller.[[pendingPullIntos]] is not empty,
      if (!aController->PendingPullIntos().isEmpty()) {
        // Step 9.3.2.1. Assert: controller.[[pendingPullIntos]][0]'s reader
        // type is "default".
        MOZ_ASSERT(
            aController->PendingPullIntos().getFirst()->GetReaderType() ==
            ReaderType::Default);

        // Step 9.3.2.2. Perform !
        // ReadableByteStreamControllerShiftPendingPullInto(controller).
        RefPtr<PullIntoDescriptor> pullIntoDescriptor =
            ReadableByteStreamControllerShiftPendingPullInto(aController);
        (void)pullIntoDescriptor;
      }

      // Step 9.3.3. Let transferredView be ! Construct(%Uint8Array%, «
      // transferredBuffer, byteOffset, byteLength »).
      JS::Rooted<JSObject*> transferredView(
          aCx, JS_NewUint8ArrayWithBuffer(aCx, transferredBuffer, byteOffset,
                                          int64_t(byteLength)));
      if (!transferredView) {
        aRv.StealExceptionFromJSContext(aCx);
        return;
      }

      // Step 9.3.4. Perform ! ReadableStreamFulfillReadRequest(stream,
      // transferredView, false).
      JS::Rooted<JS::Value> transferredViewValue(
          aCx, JS::ObjectValue(*transferredView));
      ReadableStreamFulfillReadRequest(aCx, stream, transferredViewValue, false,
                                       aRv);
      if (aRv.Failed()) {
        return;
      }
    }

    // Step 10. Otherwise, if ! ReadableStreamHasBYOBReader(stream) is true,
  } else if (ReadableStreamHasBYOBReader(stream)) {
    // Step 10.1. Perform !
    // ReadableByteStreamControllerEnqueueChunkToQueue(controller,
    // transferredBuffer, byteOffset, byteLength).
    ReadableByteStreamControllerEnqueueChunkToQueue(
        aController, transferredBuffer, byteOffset, byteLength);

    // Step 10.2. Let filledPullIntos be the result of performing !
    // ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(controller).
    nsTArray<RefPtr<PullIntoDescriptor>> filledPullIntos;
    ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(
        aCx, aController, filledPullIntos, aRv);
    if (aRv.Failed()) {
      return;
    }

    // Step 10.3. For each filledPullInto of filledPullIntos,
    for (auto& filledPullInto : filledPullIntos) {
      // Step 10.3.1. Perform !
      // ReadableByteStreamControllerCommitPullIntoDescriptor(stream,
      // filledPullInto).
      ReadableByteStreamControllerCommitPullIntoDescriptor(
          aCx, stream, MOZ_KnownLive(filledPullInto), aRv);
      if (aRv.Failed()) {
        return;
      }
    }

    // Step 11. Otherwise,
  } else {
    // Step 11.1. Assert: ! IsReadableStreamLocked(stream) is false.
    MOZ_ASSERT(!IsReadableStreamLocked(stream));

    // Step 11.2. Perform !
    // ReadableByteStreamControllerEnqueueChunkToQueue(controller,
    // transferredBuffer, byteOffset, byteLength).
    ReadableByteStreamControllerEnqueueChunkToQueue(
        aController, transferredBuffer, byteOffset, byteLength);
  }

  // Step 12. Perform !
  // ReadableByteStreamControllerCallPullIfNeeded(controller).
  ReadableByteStreamControllerCallPullIfNeeded(aCx, aController, aRv);
}

}  // namespace streams_abstract

// https://streams.spec.whatwg.org/#rbs-controller-enqueue
void ReadableByteStreamController::Enqueue(JSContext* aCx,
                                           const ArrayBufferView& aChunk,
                                           ErrorResult& aRv) {
  // Step 1.
  JS::Rooted<JSObject*> chunk(aCx, aChunk.Obj());
  if (JS_GetArrayBufferViewByteLength(chunk) == 0) {
    aRv.ThrowTypeError("Zero Length View");
    return;
  }

  // Step 2.
  bool isShared;
  JS::Rooted<JSObject*> viewedArrayBuffer(
      aCx, JS_GetArrayBufferViewBuffer(aCx, chunk, &isShared));
  if (!viewedArrayBuffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }

  if (JS::GetArrayBufferByteLength(viewedArrayBuffer) == 0) {
    aRv.ThrowTypeError("Zero Length Buffer");
    return;
  }

  // Step 3.
  if (CloseRequested()) {
    aRv.ThrowTypeError("close requested");
    return;
  }

  // Step 4.
  if (Stream()->State() != ReadableStream::ReaderState::Readable) {
    aRv.ThrowTypeError("Not Readable");
    return;
  }

  // Step 5.
  ReadableByteStreamControllerEnqueue(aCx, this, chunk, aRv);
}

// https://streams.spec.whatwg.org/#rbs-controller-error
void ReadableByteStreamController::Error(JSContext* aCx,
                                         JS::Handle<JS::Value> aErrorValue,
                                         ErrorResult& aRv) {
  // Step 1.
  ReadableByteStreamControllerError(this, aErrorValue, aRv);
}

// https://streams.spec.whatwg.org/#rbs-controller-private-cancel
already_AddRefed<Promise> ReadableByteStreamController::CancelSteps(
    JSContext* aCx, JS::Handle<JS::Value> aReason, ErrorResult& aRv) {
  // Step 1.
  ReadableByteStreamControllerClearPendingPullIntos(this);

  // Step 2.
  ResetQueue(this);

  // Step 3.
  Optional<JS::Handle<JS::Value>> reason(aCx, aReason);
  RefPtr<UnderlyingSourceAlgorithmsBase> algorithms = mAlgorithms;
  RefPtr<Promise> result = algorithms->CancelCallback(aCx, reason, aRv);
  if (NS_WARN_IF(aRv.Failed())) {
    return nullptr;
  }
  // Step 4.
  ReadableByteStreamControllerClearAlgorithms(this);

  // Step 5.
  return result.forget();
}

namespace streams_abstract {
// https://streams.spec.whatwg.org/#readable-byte-stream-controller-handle-queue-drain
void ReadableByteStreamControllerHandleQueueDrain(
    JSContext* aCx, ReadableByteStreamController* aController,
    ErrorResult& aRv) {
  // Step 1.
  MOZ_ASSERT(aController->Stream()->State() ==
             ReadableStream::ReaderState::Readable);

  // Step 2.
  if (aController->QueueTotalSize() == 0 && aController->CloseRequested()) {
    // Step 2.1
    ReadableByteStreamControllerClearAlgorithms(aController);

    // Step 2.2
    RefPtr<ReadableStream> stream = aController->Stream();
    ReadableStreamClose(aCx, stream, aRv);
    return;
  }

  // Step 3.1
  ReadableByteStreamControllerCallPullIfNeeded(aCx, aController, aRv);
}
}  // namespace streams_abstract

// https://streams.spec.whatwg.org/#rbs-controller-private-pull
void ReadableByteStreamController::PullSteps(JSContext* aCx,
                                             ReadRequest* aReadRequest,
                                             ErrorResult& aRv) {
  // Step 1. Let stream be this.[[stream]].
  ReadableStream* stream = Stream();

  // Step 2. Assert: ! ReadableStreamHasDefaultReader(stream) is true.
  MOZ_ASSERT(ReadableStreamHasDefaultReader(stream));

  // Step 3. If this.[[queueTotalSize]] > 0,
  if (QueueTotalSize() > 0) {
    // Step 3.1. Assert: ! ReadableStreamGetNumReadRequests ( stream ) is 0.
    MOZ_ASSERT(ReadableStreamGetNumReadRequests(stream) == 0);

    // Step 3.2. Perform !
    // ReadableByteStreamControllerFillReadRequestFromQueue(this, readRequest).
    ReadableByteStreamControllerFillReadRequestFromQueue(aCx, this,
                                                         aReadRequest, aRv);

    // Step 3.3. Return.
    return;
  }

  // Step 4. Let autoAllocateChunkSize be this.[[autoAllocateChunkSize]].
  Maybe<uint64_t> autoAllocateChunkSize = AutoAllocateChunkSize();

  // Step 5. If autoAllocateChunkSize is not undefined,
  if (autoAllocateChunkSize) {
    // Step 5.1.  Let buffer be Construct(%ArrayBuffer%, « autoAllocateChunkSize
    // »).
    aRv.MightThrowJSException();
    JS::Rooted<JSObject*> buffer(
        aCx, JS::NewArrayBuffer(aCx, *autoAllocateChunkSize));

    // Step 5.2. If buffer is an abrupt completion,
    if (!buffer) {
      // Step 5.2.1. Perform readRequest’s error steps, given buffer.[[Value]].
      JS::Rooted<JS::Value> bufferError(aCx);
      if (!JS_GetPendingException(aCx, &bufferError)) {
        // Uncatchable exception; we should mark aRv and return.
        aRv.StealExceptionFromJSContext(aCx);
        return;
      }

      // It's not explicitly stated, but I assume the intention here is that
      // we perform a normal completion here.
      JS_ClearPendingException(aCx);

      aReadRequest->ErrorSteps(aCx, bufferError, aRv);

      // Step 5.2.2. Return.
      return;
    }

    // Step 5.3 Let pullIntoDescriptor be a new pull-into descriptor with
    //  buffer              buffer.[[Value]]
    //  buffer byte length  autoAllocateChunkSize
    //  byte offset         0
    //  byte length         autoAllocateChunkSize
    //  bytes filled        0
    //  minimum fill        1
    //  element size        1
    //  view constructor    %Uint8Array%
    //  reader type         "default"
    RefPtr<PullIntoDescriptor> pullIntoDescriptor = new PullIntoDescriptor(
        buffer, /* aBufferByteLength */ *autoAllocateChunkSize,
        /*aByteOffset */ 0, /* aByteLength */ *autoAllocateChunkSize,
        /* aBytesFilled */ 0, /* aMinimumFill */ 1, /* aElementSize */ 1,
        PullIntoDescriptor::Constructor::Uint8, ReaderType::Default);

    //  Step 5.4. Append pullIntoDescriptor to this.[[pendingPullIntos]].
    PendingPullIntos().insertBack(pullIntoDescriptor);
  }

  // Step 6. Perform ! ReadableStreamAddReadRequest(stream, readRequest).
  ReadableStreamAddReadRequest(stream, aReadRequest);

  // Step 7. Perform ! ReadableByteStreamControllerCallPullIfNeeded(this).
  ReadableByteStreamControllerCallPullIfNeeded(aCx, this, aRv);
}

// https://streams.spec.whatwg.org/#abstract-opdef-readablebytestreamcontroller-releasesteps
void ReadableByteStreamController::ReleaseSteps() {
  // Step 1. If this.[[pendingPullIntos]] is not empty,
  if (!PendingPullIntos().isEmpty()) {
    // Step 1.1. Let firstPendingPullInto be this.[[pendingPullIntos]][0].
    RefPtr<PullIntoDescriptor> firstPendingPullInto =
        PendingPullIntos().popFirst();

    // Step 1.2. Set firstPendingPullInto’s reader type to "none".
    firstPendingPullInto->SetReaderType(ReaderType::None);

    // Step 1.3. Set this.[[pendingPullIntos]] to the list «
    // firstPendingPullInto ».
    PendingPullIntos().clear();
    PendingPullIntos().insertBack(firstPendingPullInto);
  }
}

namespace streams_abstract {

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-shift-pending-pull-into
already_AddRefed<PullIntoDescriptor>
ReadableByteStreamControllerShiftPendingPullInto(
    ReadableByteStreamController* aController) {
  // Step 1.
  MOZ_ASSERT(!aController->GetByobRequest());

  // Step 2 + 3
  RefPtr<PullIntoDescriptor> descriptor =
      aController->PendingPullIntos().popFirst();

  // Step 4.
  return descriptor.forget();
}

JSObject* ConstructFromPullIntoConstructor(
    JSContext* aCx, PullIntoDescriptor::Constructor constructor,
    JS::Handle<JSObject*> buffer, size_t byteOffset, size_t length) {
  switch (constructor) {
    case PullIntoDescriptor::Constructor::DataView:
      return JS_NewDataView(aCx, buffer, byteOffset, length);
      break;

#define CONSTRUCT_TYPED_ARRAY_TYPE(ExternalT, NativeT, Name)      \
  case PullIntoDescriptor::Constructor::Name:                     \
    return JS_New##Name##ArrayWithBuffer(aCx, buffer, byteOffset, \
                                         int64_t(length));        \
    break;

      JS_FOR_EACH_TYPED_ARRAY(CONSTRUCT_TYPED_ARRAY_TYPE)

#undef CONSTRUCT_TYPED_ARRAY_TYPE

    default:
      MOZ_ASSERT_UNREACHABLE("Unknown PullIntoDescriptor::Constructor");
      return nullptr;
  }
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-convert-pull-into-descriptor
JSObject* ReadableByteStreamControllerConvertPullIntoDescriptor(
    JSContext* aCx, PullIntoDescriptor* pullIntoDescriptor, ErrorResult& aRv) {
  // Step 1. Let bytesFilled be pullIntoDescriptor’s bytes filled.
  uint64_t bytesFilled = pullIntoDescriptor->BytesFilled();

  // Step 2. Let elementSize be pullIntoDescriptor’s element size.
  uint64_t elementSize = pullIntoDescriptor->ElementSize();

  // Step 3. Assert: bytesFilled ≤ pullIntoDescriptor’s byte length.
  MOZ_ASSERT(bytesFilled <= pullIntoDescriptor->ByteLength());

  // Step 4. Assert: the remainder after dividing bytesFilled by elementSize is
  // 0.
  MOZ_ASSERT(bytesFilled % elementSize == 0);

  // Step 5. Let buffer be ! TransferArrayBuffer(pullIntoDescriptor’s buffer).
  aRv.MightThrowJSException();
  JS::Rooted<JSObject*> srcBuffer(aCx, pullIntoDescriptor->Buffer());
  JS::Rooted<JSObject*> buffer(aCx, TransferArrayBuffer(aCx, srcBuffer));
  if (!buffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return nullptr;
  }

  // Step 6. Return ! Construct(pullIntoDescriptor’s view constructor,
  //  « buffer, pullIntoDescriptor’s byte offset, bytesFilled ÷ elementSize »).
  JS::Rooted<JSObject*> res(
      aCx, ConstructFromPullIntoConstructor(
               aCx, pullIntoDescriptor->ViewConstructor(), buffer,
               pullIntoDescriptor->ByteOffset(), bytesFilled / elementSize));
  if (!res) {
    aRv.StealExceptionFromJSContext(aCx);
    return nullptr;
  }
  return res;
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-respond-in-closed-state
MOZ_CAN_RUN_SCRIPT
static void ReadableByteStreamControllerRespondInClosedState(
    JSContext* aCx, ReadableByteStreamController* aController,
    RefPtr<PullIntoDescriptor>& aFirstDescriptor, ErrorResult& aRv) {
  // Step 1. Assert: the remainder after dividing firstDescriptor’s bytes filled
  // by firstDescriptor’s element size is 0.
  MOZ_ASSERT(
      (aFirstDescriptor->BytesFilled() % aFirstDescriptor->ElementSize()) == 0);

  // Step 2. If firstDescriptor’s reader type is "none",
  // perform ! ReadableByteStreamControllerShiftPendingPullInto(controller).
  if (aFirstDescriptor->GetReaderType() == ReaderType::None) {
    RefPtr<PullIntoDescriptor> discarded =
        ReadableByteStreamControllerShiftPendingPullInto(aController);
    (void)discarded;
  }

  // Step 3. Let stream be controller.[[stream]].
  RefPtr<ReadableStream> stream = aController->Stream();

  // Step 4. If ! ReadableStreamHasBYOBReader(stream) is true,
  if (ReadableStreamHasBYOBReader(stream)) {
    // Step 4.1. Let filledPullIntos be a new empty list.
    nsTArray<RefPtr<PullIntoDescriptor>> filledPullIntos;

    // Step 4.2. While |filledPullInto|'s [=list/size=] < !
    // ReadableStreamGetNumReadIntoRequests(stream),
    while (filledPullIntos.Length() <
           ReadableStreamGetNumReadIntoRequests(stream)) {
      // Step 4.2.1. Let pullIntoDescriptor be !
      // ReadableByteStreamControllerShiftPendingPullInto(controller).
      RefPtr<PullIntoDescriptor> pullIntoDescriptor =
          ReadableByteStreamControllerShiftPendingPullInto(aController);

      // Step 4.2.2. Append pullIntoDescriptor to filledPullIntos.
      filledPullIntos.AppendElement(pullIntoDescriptor);
    }

    // Step 4.3. For each filledPullInto of filledPullIntos,
    for (auto& filledPullInto : filledPullIntos) {
      // Step 4.3.1. Perform !
      // ReadableByteStreamControllerCommitPullIntoDescriptor(stream,
      // filledPullInto).
      ReadableByteStreamControllerCommitPullIntoDescriptor(
          aCx, stream, MOZ_KnownLive(filledPullInto), aRv);
      if (aRv.Failed()) {
        return;
      }
    }
  }
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-fill-head-pull-into-descriptor
void ReadableByteStreamControllerFillHeadPullIntoDescriptor(
    ReadableByteStreamController* aController, size_t aSize,
    PullIntoDescriptor* aPullIntoDescriptor) {
  // Step 1. Assert: either controller.[[pendingPullIntos]] is empty, or
  // controller.[[pendingPullIntos]][0] is pullIntoDescriptor.
  MOZ_ASSERT(aController->PendingPullIntos().isEmpty() ||
             aController->PendingPullIntos().getFirst() == aPullIntoDescriptor);

  // Step 2. Assert: controller.[[byobRequest]] is null.
  MOZ_ASSERT(!aController->GetByobRequest());

  // Step 3. Set pullIntoDescriptor’s bytes filled to bytes filled + size.
  aPullIntoDescriptor->SetBytesFilled(aPullIntoDescriptor->BytesFilled() +
                                      aSize);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-respond-in-readable-state
MOZ_CAN_RUN_SCRIPT
static void ReadableByteStreamControllerRespondInReadableState(
    JSContext* aCx, ReadableByteStreamController* aController,
    uint64_t aBytesWritten, PullIntoDescriptor* aPullIntoDescriptor,
    ErrorResult& aRv) {
  // Step 1. Assert: pullIntoDescriptor’s bytes filled + bytesWritten ≤
  // pullIntoDescriptor’s byte length.
  MOZ_ASSERT(aPullIntoDescriptor->BytesFilled() + aBytesWritten <=
             aPullIntoDescriptor->ByteLength());

  // Step 2. Perform
  // !ReadableByteStreamControllerFillHeadPullIntoDescriptor(controller,
  // bytesWritten, pullIntoDescriptor).
  ReadableByteStreamControllerFillHeadPullIntoDescriptor(
      aController, aBytesWritten, aPullIntoDescriptor);

  // Step 3. If pullIntoDescriptor’s reader type is "none",
  if (aPullIntoDescriptor->GetReaderType() == ReaderType::None) {
    // Step 3.1. Perform ?
    // ReadableByteStreamControllerEnqueueDetachedPullIntoToQueue(controller,
    // pullIntoDescriptor).
    ReadableByteStreamControllerEnqueueDetachedPullIntoToQueue(
        aCx, aController, aPullIntoDescriptor, aRv);
    if (aRv.Failed()) {
      return;
    }

    // Step 3.2. Let filledPullIntos be the result of performing !
    // ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(controller).
    nsTArray<RefPtr<PullIntoDescriptor>> filledPullIntos;
    ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(
        aCx, aController, filledPullIntos, aRv);
    if (aRv.Failed()) {
      return;
    }

    // Step 3.3. For each filledPullInto of filledPullIntos,
    for (auto& filledPullInto : filledPullIntos) {
      // Step 3.3.1. Perform !
      // ReadableByteStreamControllerCommitPullIntoDescriptor(controller.[[stream]],
      // filledPullInto).
      ReadableByteStreamControllerCommitPullIntoDescriptor(
          aCx, MOZ_KnownLive(aController->Stream()),
          MOZ_KnownLive(filledPullInto), aRv);
      if (aRv.Failed()) {
        return;
      }
    }

    // Step 3.4. Return.
    return;
  }

  // Step 4. If pullIntoDescriptor’s bytes filled < pullIntoDescriptor’s minimum
  // fill, return.
  if (aPullIntoDescriptor->BytesFilled() < aPullIntoDescriptor->MinimumFill()) {
    return;
  }

  // Step 5. Perform
  // !ReadableByteStreamControllerShiftPendingPullInto(controller).
  RefPtr<PullIntoDescriptor> pullIntoDescriptor =
      ReadableByteStreamControllerShiftPendingPullInto(aController);
  (void)pullIntoDescriptor;

  // Step 6. Let remainderSize be the remainder after dividing
  // pullIntoDescriptor’s bytes filled by pullIntoDescriptor’s element size.
  size_t remainderSize =
      aPullIntoDescriptor->BytesFilled() % aPullIntoDescriptor->ElementSize();

  // Step 7. If remainderSize > 0,
  if (remainderSize > 0) {
    // Step 7.1. Let end be pullIntoDescriptor’s byte offset +
    // pullIntoDescriptor’s bytes filled.
    size_t end =
        aPullIntoDescriptor->ByteOffset() + aPullIntoDescriptor->BytesFilled();

    // Step 7.2. Perform ?
    // ReadableByteStreamControllerEnqueueClonedChunkToQueue(controller,
    // pullIntoDescriptor’s buffer, end − remainderSize, remainderSize).
    JS::Rooted<JSObject*> pullIntoBuffer(aCx, aPullIntoDescriptor->Buffer());
    ReadableByteStreamControllerEnqueueClonedChunkToQueue(
        aCx, aController, pullIntoBuffer, end - remainderSize, remainderSize,
        aRv);
    if (aRv.Failed()) {
      return;
    }
  }

  // Step 8. Set pullIntoDescriptor’s bytes filled to pullIntoDescriptor’s bytes
  // filled − remainderSize.
  aPullIntoDescriptor->SetBytesFilled(aPullIntoDescriptor->BytesFilled() -
                                      remainderSize);

  // Step 9. Let filledPullIntos be the result of performing !
  // ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(controller).
  nsTArray<RefPtr<PullIntoDescriptor>> filledPullIntos;
  ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue(
      aCx, aController, filledPullIntos, aRv);
  if (aRv.Failed()) {
    return;
  }

  // Step 10. Perform
  // !ReadableByteStreamControllerCommitPullIntoDescriptor(controller.[[stream]],
  // pullIntoDescriptor).
  RefPtr<ReadableStream> stream(aController->Stream());
  ReadableByteStreamControllerCommitPullIntoDescriptor(
      aCx, stream, aPullIntoDescriptor, aRv);
  if (aRv.Failed()) {
    return;
  }

  // Step 11. For each filledPullInto of filledPullIntos,
  for (auto& filledPullInto : filledPullIntos) {
    // Step 11.1. Perform !
    // ReadableByteStreamControllerCommitPullIntoDescriptor(controller.[[stream]],
    // filledPullInto).
    ReadableByteStreamControllerCommitPullIntoDescriptor(
        aCx, stream, MOZ_KnownLive(filledPullInto), aRv);
    if (aRv.Failed()) {
      return;
    }
  }
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-respond-internal
void ReadableByteStreamControllerRespondInternal(
    JSContext* aCx, ReadableByteStreamController* aController,
    uint64_t aBytesWritten, ErrorResult& aRv) {
  // Step 1.
  RefPtr<PullIntoDescriptor> firstDescriptor =
      aController->PendingPullIntos().getFirst();

  // Step 2.
  JS::Rooted<JSObject*> buffer(aCx, firstDescriptor->Buffer());
#ifdef DEBUG
  bool canTransferBuffer = CanTransferArrayBuffer(aCx, buffer, aRv);
  MOZ_ASSERT(!aRv.Failed());
  MOZ_ASSERT(canTransferBuffer);
#endif

  // Step 3.
  ReadableByteStreamControllerInvalidateBYOBRequest(aController);

  // Step 4.
  auto state = aController->Stream()->State();

  // Step 5.
  if (state == ReadableStream::ReaderState::Closed) {
    // Step 5.1
    MOZ_ASSERT(aBytesWritten == 0);

    // Step 5.2
    ReadableByteStreamControllerRespondInClosedState(aCx, aController,
                                                     firstDescriptor, aRv);
    if (aRv.Failed()) {
      return;
    }
  } else {
    // Step 6.1
    MOZ_ASSERT(state == ReadableStream::ReaderState::Readable);

    // Step 6.2.
    MOZ_ASSERT(aBytesWritten > 0);

    // Step 6.3
    ReadableByteStreamControllerRespondInReadableState(
        aCx, aController, aBytesWritten, firstDescriptor, aRv);
    if (aRv.Failed()) {
      return;
    }
  }
  // Step 7.
  ReadableByteStreamControllerCallPullIfNeeded(aCx, aController, aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-respond
void ReadableByteStreamControllerRespond(
    JSContext* aCx, ReadableByteStreamController* aController,
    uint64_t aBytesWritten, ErrorResult& aRv) {
  // Step 1.
  MOZ_ASSERT(!aController->PendingPullIntos().isEmpty());

  // Step 2.
  PullIntoDescriptor* firstDescriptor =
      aController->PendingPullIntos().getFirst();

  // Step 3.
  auto state = aController->Stream()->State();

  // Step 4.
  if (state == ReadableStream::ReaderState::Closed) {
    // Step 4.1
    if (aBytesWritten != 0) {
      aRv.ThrowTypeError("bytesWritten not zero on closed stream");
      return;
    }
  } else {
    // Step 5.1
    MOZ_ASSERT(state == ReadableStream::ReaderState::Readable);

    // Step 5.2
    if (aBytesWritten == 0) {
      aRv.ThrowTypeError("bytesWritten 0");
      return;
    }

    // Step 5.3
    if (firstDescriptor->BytesFilled() + aBytesWritten >
        firstDescriptor->ByteLength()) {
      aRv.ThrowRangeError("bytesFilled + bytesWritten > byteLength");
      return;
    }
  }

  // Step 6.
  aRv.MightThrowJSException();
  JS::Rooted<JSObject*> buffer(aCx, firstDescriptor->Buffer());
  JS::Rooted<JSObject*> transferredBuffer(aCx,
                                          TransferArrayBuffer(aCx, buffer));
  if (!transferredBuffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }
  firstDescriptor->SetBuffer(transferredBuffer);

  // Step 7.
  ReadableByteStreamControllerRespondInternal(aCx, aController, aBytesWritten,
                                              aRv);
}

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-respond-with-new-view
void ReadableByteStreamControllerRespondWithNewView(
    JSContext* aCx, ReadableByteStreamController* aController,
    JS::Handle<JSObject*> aView, ErrorResult& aRv) {
  aRv.MightThrowJSException();

  // Step 1.
  MOZ_ASSERT(!aController->PendingPullIntos().isEmpty());

  // Step 2.
  bool isSharedMemory;
  JS::Rooted<JSObject*> viewedArrayBuffer(
      aCx, JS_GetArrayBufferViewBuffer(aCx, aView, &isSharedMemory));
  if (!viewedArrayBuffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }
  MOZ_ASSERT(!JS::IsDetachedArrayBufferObject(viewedArrayBuffer));

  // Step 3.
  RefPtr<PullIntoDescriptor> firstDescriptor =
      aController->PendingPullIntos().getFirst();

  // Step 4.
  ReadableStream::ReaderState state = aController->Stream()->State();

  // Step 5.
  if (state == ReadableStream::ReaderState::Closed) {
    // Step 5.1
    if (JS_GetArrayBufferViewByteLength(aView) != 0) {
      aRv.ThrowTypeError("View has non-zero length in closed stream");
      return;
    }
  } else {
    // Step 6.1
    MOZ_ASSERT(state == ReadableStream::ReaderState::Readable);

    // Step 6.2
    if (JS_GetArrayBufferViewByteLength(aView) == 0) {
      aRv.ThrowTypeError("View has zero length in readable stream");
      return;
    }
  }

  // Step 7.
  if (firstDescriptor->ByteOffset() + firstDescriptor->BytesFilled() !=
      JS_GetArrayBufferViewByteOffset(aView)) {
    aRv.ThrowRangeError("Invalid Offset");
    return;
  }

  // Step 8.
  if (firstDescriptor->BufferByteLength() !=
      JS::GetArrayBufferByteLength(viewedArrayBuffer)) {
    aRv.ThrowRangeError("Mismatched buffer byte lengths");
    return;
  }

  // Step 9.
  if (firstDescriptor->BytesFilled() + JS_GetArrayBufferViewByteLength(aView) >
      firstDescriptor->ByteLength()) {
    aRv.ThrowRangeError("Too many bytes");
    return;
  }

  // Step 10. Let viewByteLength be view.[[ByteLength]].
  size_t viewByteLength = JS_GetArrayBufferViewByteLength(aView);

  // Step 11. Set firstDescriptor’s buffer to ?
  // TransferArrayBuffer(view.[[ViewedArrayBuffer]]).
  JS::Rooted<JSObject*> transferedBuffer(
      aCx, TransferArrayBuffer(aCx, viewedArrayBuffer));
  if (!transferedBuffer) {
    aRv.StealExceptionFromJSContext(aCx);
    return;
  }
  firstDescriptor->SetBuffer(transferedBuffer);

  // Step 12. Perform ? ReadableByteStreamControllerRespondInternal(controller,
  // viewByteLength).
  ReadableByteStreamControllerRespondInternal(aCx, aController, viewByteLength,
                                              aRv);
}

#ifdef DEBUG
// https://streams.spec.whatwg.org/#abstract-opdef-cancopydatablockbytes
bool CanCopyDataBlockBytes(JS::Handle<JSObject*> aToBuffer, size_t aToIndex,
                           JS::Handle<JSObject*> aFromBuffer, size_t aFromIndex,
                           size_t aCount) {
  // Step 1. Assert: toBuffer is an Object.
  // Step 2. Assert: toBuffer has an [[ArrayBufferData]] internal slot.
  MOZ_ASSERT(JS::IsArrayBufferObject(aToBuffer));

  // Step 3. Assert: fromBuffer is an Object.
  // Step 4. Assert: fromBuffer has an [[ArrayBufferData]] internal slot.
  MOZ_ASSERT(JS::IsArrayBufferObject(aFromBuffer));

  // Step 5. If toBuffer is fromBuffer, return false.
  // Note: JS API makes it safe to just compare the pointers.
  if (aToBuffer == aFromBuffer) {
    return false;
  }

  // Step 6. If ! IsDetachedBuffer(toBuffer) is true, return false.
  if (JS::IsDetachedArrayBufferObject(aToBuffer)) {
    return false;
  }

  // Step 7. If ! IsDetachedBuffer(fromBuffer) is true, return false.
  if (JS::IsDetachedArrayBufferObject(aFromBuffer)) {
    return false;
  }

  // Step 8. If toIndex + count > toBuffer.[[ArrayBufferByteLength]], return
  // false.
  if (aToIndex + aCount > JS::GetArrayBufferByteLength(aToBuffer)) {
    return false;
  }
  // (Not in the spec) also check overflow.
  if (aToIndex + aCount < aToIndex) {
    return false;
  }

  // Step 9. If fromIndex + count > fromBuffer.[[ArrayBufferByteLength]], return
  // false.
  if (aFromIndex + aCount > JS::GetArrayBufferByteLength(aFromBuffer)) {
    return false;
  }
  // (Not in the spec) also check overflow.
  if (aFromIndex + aCount < aFromIndex) {
    return false;
  }

  // Step 10. Return true.
  return true;
}
#endif

// https://streams.spec.whatwg.org/#readable-byte-stream-controller-fill-pull-into-descriptor-from-queue
bool ReadableByteStreamControllerFillPullIntoDescriptorFromQueue(
    JSContext* aCx, ReadableByteStreamController* aController,
    PullIntoDescriptor* aPullIntoDescriptor, ErrorResult& aRv) {
  // Step 1. Let maxBytesToCopy be min(controller.[[queueTotalSize]],
  // pullIntoDescriptor’s byte length − pullIntoDescriptor’s bytes filled).
  size_t maxBytesToCopy =
      std::min(static_cast<size_t>(aController->QueueTotalSize()),
               static_cast<size_t>((aPullIntoDescriptor->ByteLength() -
                                    aPullIntoDescriptor->BytesFilled())));

  // Step 2. Let maxBytesFilled be pullIntoDescriptor’s bytes filled +
  // maxBytesToCopy.
  size_t maxBytesFilled = aPullIntoDescriptor->BytesFilled() + maxBytesToCopy;

  // Step 3. Let totalBytesToCopyRemaining be maxBytesToCopy.
  size_t totalBytesToCopyRemaining = maxBytesToCopy;

  // Step 4. Let ready be false.
  bool ready = false;

  // Step 5. Assert: ! IsDetachedBuffer(pullIntoDescriptor ’s buffer) is false.
  MOZ_ASSERT(!JS::IsDetachedArrayBufferObject(aPullIntoDescriptor->Buffer()));

  // Step 6. Assert: pullIntoDescriptor’s bytes filled < pullIntoDescriptor’s
  // minimum fill.
  MOZ_ASSERT(aPullIntoDescriptor->BytesFilled() <
             aPullIntoDescriptor->MinimumFill());

  // Step 7. Let remainderBytes be the remainder after dividing maxBytesFilled
  // by pullIntoDescriptor’s element size.
  size_t remainderBytes = maxBytesFilled % aPullIntoDescriptor->ElementSize();

  // Step 8. Let maxAlignedBytes be maxBytesFilled − remainderBytes.
  size_t maxAlignedBytes = maxBytesFilled - remainderBytes;

  // Step 9. If maxAlignedBytes ≥ pullIntoDescriptor’s minimum fill,
  if (maxAlignedBytes >= aPullIntoDescriptor->MinimumFill()) {
    // Step 9.1. Set totalBytesToCopyRemaining to maxAlignedBytes −
    // pullIntoDescriptor’s bytes filled.
    totalBytesToCopyRemaining =
        maxAlignedBytes - aPullIntoDescriptor->BytesFilled();
    // Step 9.2. Set ready to true.
    ready = true;
  }

  // Step 10. Let queue be controller.[[queue]].
  LinkedList<RefPtr<ReadableByteStreamQueueEntry>>& queue =
      aController->Queue();

  // Step 11. While totalBytesToCopyRemaining > 0,
  while (totalBytesToCopyRemaining > 0) {
    // Step 11.1  Let headOfQueue be queue[0].
    ReadableByteStreamQueueEntry* headOfQueue = queue.getFirst();

    // Step 11.2. Let bytesToCopy be min(totalBytesToCopyRemaining,
    // headOfQueue’s byte length).
--> --------------------

--> maximum size reached

--> --------------------

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