FetchStreamReader.h

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/* -*- 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/. */

#ifndef mozilla_dom_FetchStreamReader_h

#define mozilla_dom_FetchStreamReader_h

#include "js/RootingAPI.h"

#include "js/TypeDecls.h"

#include "mozilla/Attributes.h"

#include "mozilla/dom/FetchBinding.h"

#include "mozilla/dom/PromiseNativeHandler.h"

#include "nsIAsyncOutputStream.h"

#include "nsIGlobalObject.h"

namespace mozilla::dom {

class ReadableStream;

class ReadableStreamDefaultReader;

class StrongWorkerRef;

class FetchStreamReader final : public nsIOutputStreamCallback {

 public:

  NS_DECL_CYCLE_COLLECTING_ISUPPORTS

  NS_DECL_CYCLE_COLLECTION_CLASS(FetchStreamReader)

  NS_DECL_NSIOUTPUTSTREAMCALLBACK

  // This creates a nsIInputStream able to retrieve data from the ReadableStream

  // object. The reading starts when StartConsuming() is called.

  static nsresult Create(JSContext* aCx, nsIGlobalObject* aGlobal,

                         FetchStreamReader** aStreamReader,

                         nsIInputStream** aInputStream);

  MOZ_CAN_RUN_SCRIPT

  void ChunkSteps(JSContext* aCx, JS::Handle<JS::Value> aChunk,

                  ErrorResult& aRv);

  MOZ_CAN_RUN_SCRIPT

  void CloseSteps(JSContext* aCx, ErrorResult& aRv);

  MOZ_CAN_RUN_SCRIPT

  void ErrorSteps(JSContext* aCx, JS::Handle<JS::Value> aError,

                  ErrorResult& aRv);

  // Idempotently close the output stream and null out all state. If aCx is

  // provided, the reader will also be canceled.  aStatus must be a DOM error

  // as understood by DOMException because it will be provided as the

  // cancellation reason.

//

  // This is a script boundary minimize annotation changes required while

  // we figure out how to handle some more tricky annotation cases (for

  // example, the destructor of this class. Tracking under Bug 1750656)

  MOZ_CAN_RUN_SCRIPT_BOUNDARY

  void CloseAndRelease(JSContext* aCx, nsresult aStatus);

  void StartConsuming(JSContext* aCx, ReadableStream* aStream,

                      ErrorResult& aRv);

 private:

  explicit FetchStreamReader(nsIGlobalObject* aGlobal);

  ~FetchStreamReader();

  nsresult MaybeGrabStrongWorkerRef(JSContext* aCx);

  nsresult WriteBuffer();

  // Attempt to copy data from mBuffer into mPipeOut. Returns `true` if data was

  // written, and AsyncWait callbacks or FetchReadRequest calls have been set up

  // to write more data in the future, and `false` otherwise.

  MOZ_CAN_RUN_SCRIPT

  bool Process(JSContext* aCx);

  void ReportErrorToConsole(JSContext* aCx, JS::Handle<JS::Value> aValue);

  nsCOMPtr<nsIGlobalObject> mGlobal;

  nsCOMPtr<nsIEventTarget> mOwningEventTarget;

  nsCOMPtr<nsIAsyncOutputStream> mPipeOut;

  RefPtr<StrongWorkerRef> mWorkerRef;

  // This is an additional refcount we add to `mWorkerRef` when we have a

  // pending callback from mPipeOut.AsyncWait() which is guaranteed to fire when

  // either we can write to the pipe or the stream has been closed.  Because

  // this callback must run on our owning worker thread, we must ensure that the

  // worker thread lives long enough to process the runnable (and potentially

  // release the last reference to this non-thread-safe object on this thread).

//

  // By holding an additional refcount we can avoid creating a mini state

  // machine around mWorkerRef which hopefully improves clarity.

  RefPtr<StrongWorkerRef> mAsyncWaitWorkerRef;

  RefPtr<ReadableStreamDefaultReader> mReader;

  nsTArray<uint8_t> mBuffer;

  uint32_t mBufferRemaining = 0;

  uint32_t mBufferOffset = 0;

  bool mHasOutstandingReadRequest = false;

  bool mStreamClosed = false;

};

}  // namespace mozilla::dom

#endif  // mozilla_dom_FetchStreamReader_h