Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 951 insertions, 0 deletions

diff --git a/dom/fs/api/FileSystemWritableFileStream.cpp b/dom/fs/api/FileSystemWritableFileStream.cpp
new file mode 100644
index 0000000000..b19a0c9fe9
--- /dev/null
+++ b/dom/fs/api/FileSystemWritableFileStream.cpp
@@ -0,0 +1,951 @@
+/* -*- 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/. */
+
+#include "FileSystemWritableFileStream.h"
+
+#include "fs/FileSystemAsyncCopy.h"
+#include "fs/FileSystemShutdownBlocker.h"
+#include "fs/FileSystemThreadSafeStreamOwner.h"
+#include "mozilla/Buffer.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/InputStreamLengthHelper.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/TaskQueue.h"
+#include "mozilla/dom/Blob.h"
+#include "mozilla/dom/FileSystemHandle.h"
+#include "mozilla/dom/FileSystemLog.h"
+#include "mozilla/dom/FileSystemManager.h"
+#include "mozilla/dom/FileSystemWritableFileStreamBinding.h"
+#include "mozilla/dom/FileSystemWritableFileStreamChild.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerRef.h"
+#include "mozilla/dom/WritableStreamDefaultController.h"
+#include "mozilla/dom/fs/TargetPtrHolder.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "mozilla/ipc/RandomAccessStreamUtils.h"
+#include "nsAsyncStreamCopier.h"
+#include "nsIInputStream.h"
+#include "nsIRequestObserver.h"
+#include "nsISupportsImpl.h"
+#include "nsNetCID.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+
+namespace mozilla::dom {
+
+namespace {
+
+constexpr bool IsFileNotFoundError(const nsresult aRv) {
+  return NS_ERROR_DOM_FILE_NOT_FOUND_ERR == aRv ||
+         NS_ERROR_FILE_NOT_FOUND == aRv;
+}
+
+class WritableFileStreamUnderlyingSinkAlgorithms final
+    : public UnderlyingSinkAlgorithmsWrapper {
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(
+      WritableFileStreamUnderlyingSinkAlgorithms, UnderlyingSinkAlgorithmsBase)
+
+  explicit WritableFileStreamUnderlyingSinkAlgorithms(
+      FileSystemWritableFileStream& aStream)
+      : mStream(&aStream) {}
+
+  already_AddRefed<Promise> WriteCallback(
+      JSContext* aCx, JS::Handle<JS::Value> aChunk,
+      WritableStreamDefaultController& aController, ErrorResult& aRv) override;
+
+  already_AddRefed<Promise> CloseCallbackImpl(JSContext* aCx,
+                                              ErrorResult& aRv) override;
+
+  already_AddRefed<Promise> AbortCallbackImpl(
+      JSContext* aCx, const Optional<JS::Handle<JS::Value>>& aReason,
+      ErrorResult& aRv) override;
+
+  void ReleaseObjects() override;
+
+ private:
+  ~WritableFileStreamUnderlyingSinkAlgorithms() = default;
+
+  RefPtr<FileSystemWritableFileStream> mStream;
+};
+
+}  // namespace
+
+class FileSystemWritableFileStream::Command {
+ public:
+  explicit Command(RefPtr<FileSystemWritableFileStream> aWritableFileStream)
+      : mWritableFileStream(std::move(aWritableFileStream)) {
+    MOZ_ASSERT(mWritableFileStream);
+  }
+
+  NS_INLINE_DECL_REFCOUNTING(FileSystemWritableFileStream::Command)
+
+ private:
+  ~Command() { mWritableFileStream->NoteFinishedCommand(); }
+
+  RefPtr<FileSystemWritableFileStream> mWritableFileStream;
+};
+
+class FileSystemWritableFileStream::CloseHandler {
+  enum struct State : uint8_t { Initial = 0, Open, Closing, Closed };
+
+ public:
+  CloseHandler()
+      : mShutdownBlocker(fs::FileSystemShutdownBlocker::CreateForWritable()),
+        mClosePromiseHolder(),
+        mState(State::Initial) {}
+
+  NS_INLINE_DECL_REFCOUNTING(FileSystemWritableFileStream::CloseHandler)
+
+  /**
+   * @brief Are we not yet closing?
+   */
+  bool IsOpen() const { return State::Open == mState; }
+
+  /**
+   * @brief Are we already fully closed?
+   */
+  bool IsClosed() const { return State::Closed == mState; }
+
+  /**
+   * @brief Transition from open to closing state
+   *
+   * @return true if the state was open and became closing after the call
+   * @return false in all the other cases the previous state is preserved
+   */
+  bool TestAndSetClosing() {
+    const bool isOpen = State::Open == mState;
+
+    if (isOpen) {
+      mState = State::Closing;
+    }
+
+    return isOpen;
+  }
+
+  RefPtr<BoolPromise> GetClosePromise() const {
+    MOZ_ASSERT(State::Open != mState,
+               "Please call TestAndSetClosing before GetClosePromise");
+
+    if (State::Closing == mState) {
+      return mClosePromiseHolder.Ensure(__func__);
+    }
+
+    // Instant resolve for initial state due to early shutdown or closed state
+    return BoolPromise::CreateAndResolve(true, __func__);
+  }
+
+  /**
+   * @brief Transition from initial to open state. In initial state
+   *
+   */
+  void Open() {
+    MOZ_ASSERT(State::Initial == mState);
+    mShutdownBlocker->Block();
+
+    mState = State::Open;
+  }
+
+  /**
+   * @brief Transition to closed state and resolve all pending promises.
+   *
+   */
+  void Close() {
+    mShutdownBlocker->Unblock();
+    mState = State::Closed;
+    mClosePromiseHolder.ResolveIfExists(true, __func__);
+  }
+
+ protected:
+  virtual ~CloseHandler() = default;
+
+ private:
+  RefPtr<fs::FileSystemShutdownBlocker> mShutdownBlocker;
+
+  mutable MozPromiseHolder<BoolPromise> mClosePromiseHolder;
+
+  State mState;
+};
+
+FileSystemWritableFileStream::FileSystemWritableFileStream(
+    const nsCOMPtr<nsIGlobalObject>& aGlobal,
+    RefPtr<FileSystemManager>& aManager,
+    mozilla::ipc::RandomAccessStreamParams&& aStreamParams,
+    RefPtr<FileSystemWritableFileStreamChild> aActor,
+    already_AddRefed<TaskQueue> aTaskQueue,
+    const fs::FileSystemEntryMetadata& aMetadata)
+    : WritableStream(aGlobal, HoldDropJSObjectsCaller::Explicit),
+      mManager(aManager),
+      mActor(std::move(aActor)),
+      mTaskQueue(aTaskQueue),
+      mWorkerRef(),
+      mStreamParams(std::move(aStreamParams)),
+      mMetadata(std::move(aMetadata)),
+      mCloseHandler(MakeAndAddRef<CloseHandler>()),
+      mCommandActive(false) {
+  LOG(("Created WritableFileStream %p", this));
+
+  // Connect with the actor directly in the constructor. This way the actor
+  // can call `FileSystemWritableFileStream::ClearActor` when we call
+  // `PFileSystemWritableFileStreamChild::Send__delete__` even when
+  // FileSystemWritableFileStream::Create fails, in which case the not yet
+  // fully constructed FileSystemWritableFileStream is being destroyed.
+  mActor->SetStream(this);
+
+  mozilla::HoldJSObjects(this);
+}
+
+FileSystemWritableFileStream::~FileSystemWritableFileStream() {
+  MOZ_ASSERT(!mCommandActive);
+  MOZ_ASSERT(IsClosed());
+
+  mozilla::DropJSObjects(this);
+}
+
+// https://fs.spec.whatwg.org/#create-a-new-filesystemwritablefilestream
+// * This is fallible because of OOM handling of JSAPI. See bug 1762233.
+// XXX(krosylight): _BOUNDARY because SetUpNative here can't run script because
+// StartCallback here is no-op. Can we let the static check automatically detect
+// this situation?
+/* static */
+MOZ_CAN_RUN_SCRIPT_BOUNDARY
+Result<RefPtr<FileSystemWritableFileStream>, nsresult>
+FileSystemWritableFileStream::Create(
+    const nsCOMPtr<nsIGlobalObject>& aGlobal,
+    RefPtr<FileSystemManager>& aManager,
+    mozilla::ipc::RandomAccessStreamParams&& aStreamParams,
+    RefPtr<FileSystemWritableFileStreamChild> aActor,
+    const fs::FileSystemEntryMetadata& aMetadata) {
+  MOZ_ASSERT(aGlobal);
+
+  QM_TRY_UNWRAP(auto streamTransportService,
+                MOZ_TO_RESULT_GET_TYPED(nsCOMPtr<nsIEventTarget>,
+                                        MOZ_SELECT_OVERLOAD(do_GetService),
+                                        NS_STREAMTRANSPORTSERVICE_CONTRACTID));
+
+  RefPtr<TaskQueue> taskQueue =
+      TaskQueue::Create(streamTransportService.forget(), "WritableStreamQueue");
+  MOZ_ASSERT(taskQueue);
+
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(aGlobal)) {
+    return Err(NS_ERROR_FAILURE);
+  }
+  JSContext* cx = jsapi.cx();
+
+  // Step 1. Let stream be a new FileSystemWritableFileStream in realm.
+  // Step 2. Set stream.[[file]] to file. (Covered by the constructor)
+  RefPtr<FileSystemWritableFileStream> stream =
+      new FileSystemWritableFileStream(
+          aGlobal, aManager, std::move(aStreamParams), std::move(aActor),
+          taskQueue.forget(), aMetadata);
+
+  auto autoClose = MakeScopeExit([stream] {
+    stream->mCloseHandler->Close();
+    stream->mActor->SendClose();
+  });
+
+  QM_TRY_UNWRAP(
+      RefPtr<StrongWorkerRef> workerRef,
+      ([stream]() -> Result<RefPtr<StrongWorkerRef>, nsresult> {
+        WorkerPrivate* const workerPrivate = GetCurrentThreadWorkerPrivate();
+        if (!workerPrivate) {
+          return RefPtr<StrongWorkerRef>();
+        }
+
+        RefPtr<StrongWorkerRef> workerRef = StrongWorkerRef::Create(
+            workerPrivate, "FileSystemWritableFileStream::Create", [stream]() {
+              if (stream->IsOpen()) {
+                // We don't need the promise, we just
+                // begin the closing process.
+                Unused << stream->BeginClose();
+              }
+            });
+        QM_TRY(MOZ_TO_RESULT(workerRef));
+
+        return workerRef;
+      }()));
+
+  // Step 3 - 5
+  auto algorithms =
+      MakeRefPtr<WritableFileStreamUnderlyingSinkAlgorithms>(*stream);
+
+  // Step 8: Set up stream with writeAlgorithm set to writeAlgorithm,
+  // closeAlgorithm set to closeAlgorithm, abortAlgorithm set to
+  // abortAlgorithm, highWaterMark set to highWaterMark, and
+  // sizeAlgorithm set to sizeAlgorithm.
+  IgnoredErrorResult rv;
+  stream->SetUpNative(cx, *algorithms,
+                      // Step 6. Let highWaterMark be 1.
+                      Some(1),
+                      // Step 7. Let sizeAlgorithm be an algorithm
+                      // that returns 1. (nullptr returns 1, See
+                      // WritableStream::Constructor for details)
+                      nullptr, rv);
+  if (rv.Failed()) {
+    return Err(rv.StealNSResult());
+  }
+
+  autoClose.release();
+
+  stream->mWorkerRef = std::move(workerRef);
+  stream->mCloseHandler->Open();
+
+  // Step 9: Return stream.
+  return stream;
+}
+
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(FileSystemWritableFileStream,
+                                               WritableStream)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(FileSystemWritableFileStream)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(FileSystemWritableFileStream,
+                                                WritableStream)
+  // Per the comment for the FileSystemManager class, don't unlink mManager!
+  if (tmp->IsOpen()) {
+    Unused << tmp->BeginClose();
+  }
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(FileSystemWritableFileStream,
+                                                  WritableStream)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mManager)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+void FileSystemWritableFileStream::LastRelease() {
+  // We can't call `FileSystemWritableFileStream::Close` here because it may
+  // need to keep FileSystemWritableFileStream object alive which isn't possible
+  // when the object is about to be deleted. There are other mechanisms which
+  // ensure that the object is correctly closed before destruction. For example
+  // the object unlinking and the worker shutdown (we get notified about it via
+  // the callback passed to `StrongWorkerRef`) are used to close the object if
+  // it hasn't been closed yet.
+
+  if (mActor) {
+    PFileSystemWritableFileStreamChild::Send__delete__(mActor);
+    MOZ_ASSERT(!mActor);
+  }
+}
+
+RefPtr<FileSystemWritableFileStream::Command>
+FileSystemWritableFileStream::CreateCommand() {
+  MOZ_ASSERT(!mCommandActive);
+
+  mCommandActive = true;
+
+  return MakeRefPtr<Command>(this);
+}
+
+bool FileSystemWritableFileStream::IsCommandActive() const {
+  return mCommandActive;
+}
+
+void FileSystemWritableFileStream::ClearActor() {
+  MOZ_ASSERT(mActor);
+
+  mActor = nullptr;
+}
+
+bool FileSystemWritableFileStream::IsOpen() const {
+  return mCloseHandler->IsOpen();
+}
+
+bool FileSystemWritableFileStream::IsClosed() const {
+  return mCloseHandler->IsClosed();
+}
+
+RefPtr<BoolPromise> FileSystemWritableFileStream::BeginClose() {
+  using ClosePromise = PFileSystemWritableFileStreamChild::ClosePromise;
+  if (mCloseHandler->TestAndSetClosing()) {
+    Finish()
+        ->Then(mTaskQueue, __func__,
+               [selfHolder = fs::TargetPtrHolder(this)]() mutable {
+                 if (selfHolder->mStreamOwner) {
+                   selfHolder->mStreamOwner->Close();
+                 } else {
+                   // If the stream was not deserialized, `mStreamParams` still
+                   // contains a pre-opened file descriptor which needs to be
+                   // closed here by moving `mStreamParams` to a local variable
+                   // (the file descriptor will be closed for real when
+                   // `streamParams` goes out of scope).
+
+                   mozilla::ipc::RandomAccessStreamParams streamParams(
+                       std::move(selfHolder->mStreamParams));
+                 }
+
+                 return BoolPromise::CreateAndResolve(true, __func__);
+               })
+        ->Then(GetCurrentSerialEventTarget(), __func__,
+               [self = RefPtr(this)](const BoolPromise::ResolveOrRejectValue&) {
+                 return self->mTaskQueue->BeginShutdown();
+               })
+        ->Then(GetCurrentSerialEventTarget(), __func__,
+               [self = RefPtr(this)](
+                   const ShutdownPromise::ResolveOrRejectValue& /* aValue */) {
+                 if (!self->mActor) {
+                   return ClosePromise::CreateAndResolve(void_t(), __func__);
+                 }
+
+                 return self->mActor->SendClose();
+               })
+        ->Then(GetCurrentSerialEventTarget(), __func__,
+               [self = RefPtr(this)](
+                   const ClosePromise::ResolveOrRejectValue& aValue) {
+                 self->mWorkerRef = nullptr;
+                 self->mCloseHandler->Close();
+
+                 QM_TRY(OkIf(aValue.IsResolve()), QM_VOID);
+               });
+  }
+
+  return mCloseHandler->GetClosePromise();
+}
+
+already_AddRefed<Promise> FileSystemWritableFileStream::Write(
+    JSContext* aCx, JS::Handle<JS::Value> aChunk, ErrorResult& aError) {
+  // https://fs.spec.whatwg.org/#create-a-new-filesystemwritablefilestream
+  // Step 3. Let writeAlgorithm be an algorithm which takes a chunk argument
+  // and returns the result of running the write a chunk algorithm with stream
+  // and chunk.
+
+  // https://fs.spec.whatwg.org/#write-a-chunk
+  // Step 1. Let input be the result of converting chunk to a
+  // FileSystemWriteChunkType.
+
+  aError.MightThrowJSException();
+
+  ArrayBufferViewOrArrayBufferOrBlobOrUTF8StringOrWriteParams data;
+  if (!data.Init(aCx, aChunk)) {
+    aError.StealExceptionFromJSContext(aCx);
+    return nullptr;
+  }
+
+  // Step 2. Let p be a new promise.
+  RefPtr<Promise> promise = Promise::Create(GetParentObject(), aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  if (!IsOpen()) {
+    promise->MaybeRejectWithTypeError("WritableFileStream closed");
+    return promise.forget();
+  }
+
+  // Step 3.3. Let command be input.type if input is a WriteParams, ...
+  if (data.IsWriteParams()) {
+    const WriteParams& params = data.GetAsWriteParams();
+    switch (params.mType) {
+      // Step 3.4. If command is "write":
+      case WriteCommandType::Write: {
+        if (!params.mData.WasPassed()) {
+          promise->MaybeRejectWithSyntaxError("write() requires data");
+          return promise.forget();
+        }
+
+        // Step 3.4.2. If data is undefined, reject p with a TypeError and
+        // abort.
+        if (params.mData.Value().IsNull()) {
+          promise->MaybeRejectWithTypeError("write() of null data");
+          return promise.forget();
+        }
+
+        Maybe<uint64_t> position;
+
+        if (params.mPosition.WasPassed()) {
+          if (params.mPosition.Value().IsNull()) {
+            promise->MaybeRejectWithTypeError("write() with null position");
+            return promise.forget();
+          }
+
+          position = Some(params.mPosition.Value().Value());
+        }
+
+        Write(params.mData.Value().Value(), position, promise);
+        return promise.forget();
+      }
+
+      // Step 3.5. Otherwise, if command is "seek":
+      case WriteCommandType::Seek:
+        if (!params.mPosition.WasPassed()) {
+          promise->MaybeRejectWithSyntaxError("seek() requires a position");
+          return promise.forget();
+        }
+
+        // Step 3.5.1. If chunk.position is undefined, reject p with a
+        // TypeError and abort.
+        if (params.mPosition.Value().IsNull()) {
+          promise->MaybeRejectWithTypeError("seek() with null position");
+          return promise.forget();
+        }
+
+        Seek(params.mPosition.Value().Value(), promise);
+        return promise.forget();
+
+      // Step 3.6. Otherwise, if command is "truncate":
+      case WriteCommandType::Truncate:
+        if (!params.mSize.WasPassed()) {
+          promise->MaybeRejectWithSyntaxError("truncate() requires a size");
+          return promise.forget();
+        }
+
+        // Step 3.6.1. If chunk.size is undefined, reject p with a TypeError
+        // and abort.
+        if (params.mSize.Value().IsNull()) {
+          promise->MaybeRejectWithTypeError("truncate() with null size");
+          return promise.forget();
+        }
+
+        Truncate(params.mSize.Value().Value(), promise);
+        return promise.forget();
+
+      default:
+        MOZ_CRASH("Bad WriteParams value!");
+    }
+  }
+
+  // Step 3.3. ... and "write" otherwise.
+  // Step 3.4. If command is "write":
+  Write(data, Nothing(), promise);
+  return promise.forget();
+}
+
+// WebIDL Boilerplate
+
+JSObject* FileSystemWritableFileStream::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return FileSystemWritableFileStream_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+// WebIDL Interface
+
+already_AddRefed<Promise> FileSystemWritableFileStream::Write(
+    const ArrayBufferViewOrArrayBufferOrBlobOrUTF8StringOrWriteParams& aData,
+    ErrorResult& aError) {
+  // https://fs.spec.whatwg.org/#dom-filesystemwritablefilestream-write
+  // Step 1. Let writer be the result of getting a writer for this.
+  RefPtr<WritableStreamDefaultWriter> writer = GetWriter(aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  // Step 2. Let result be the result of writing a chunk to writer given data.
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(GetParentObject())) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  JSContext* cx = jsapi.cx();
+
+  JS::Rooted<JSObject*> global(cx, JS::CurrentGlobalOrNull(cx));
+
+  JS::Rooted<JS::Value> val(cx);
+  if (!aData.ToJSVal(cx, global, &val)) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  RefPtr<Promise> promise = writer->Write(cx, val, aError);
+
+  // Step 3. Release writer.
+  writer->ReleaseLock(cx);
+
+  // Step 4. Return result.
+  return promise.forget();
+}
+
+already_AddRefed<Promise> FileSystemWritableFileStream::Seek(
+    uint64_t aPosition, ErrorResult& aError) {
+  // https://fs.spec.whatwg.org/#dom-filesystemwritablefilestream-seek
+  // Step 1. Let writer be the result of getting a writer for this.
+  RefPtr<WritableStreamDefaultWriter> writer = GetWriter(aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  // Step 2. Let result be the result of writing a chunk to writer given
+  // «[ "type" → "seek", "position" → position ]».
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(GetParentObject())) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  JSContext* cx = jsapi.cx();
+
+  RootedDictionary<WriteParams> writeParams(cx);
+  writeParams.mType = WriteCommandType::Seek;
+  writeParams.mPosition.Construct(aPosition);
+
+  JS::Rooted<JS::Value> val(cx);
+  if (!ToJSValue(cx, writeParams, &val)) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  RefPtr<Promise> promise = writer->Write(cx, val, aError);
+
+  // Step 3. Release writer.
+  writer->ReleaseLock(cx);
+
+  // Step 4. Return result.
+  return promise.forget();
+}
+
+already_AddRefed<Promise> FileSystemWritableFileStream::Truncate(
+    uint64_t aSize, ErrorResult& aError) {
+  // https://fs.spec.whatwg.org/#dom-filesystemwritablefilestream-truncate
+  // Step 1. Let writer be the result of getting a writer for this.
+  RefPtr<WritableStreamDefaultWriter> writer = GetWriter(aError);
+  if (aError.Failed()) {
+    return nullptr;
+  }
+
+  // Step 2. Let result be the result of writing a chunk to writer given
+  // «[ "type" → "truncate", "size" → size ]».
+  AutoJSAPI jsapi;
+  if (!jsapi.Init(GetParentObject())) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  JSContext* cx = jsapi.cx();
+
+  RootedDictionary<WriteParams> writeParams(cx);
+  writeParams.mType = WriteCommandType::Truncate;
+  writeParams.mSize.Construct(aSize);
+
+  JS::Rooted<JS::Value> val(cx);
+  if (!ToJSValue(cx, writeParams, &val)) {
+    aError.ThrowUnknownError("Internal error");
+    return nullptr;
+  }
+
+  RefPtr<Promise> promise = writer->Write(cx, val, aError);
+
+  // Step 3. Release writer.
+  writer->ReleaseLock(cx);
+
+  // Step 4. Return result.
+  return promise.forget();
+}
+
+template <typename T>
+void FileSystemWritableFileStream::Write(const T& aData,
+                                         const Maybe<uint64_t> aPosition,
+                                         const RefPtr<Promise>& aPromise) {
+  MOZ_ASSERT(IsOpen());
+
+  auto rejectAndReturn = [&aPromise](const nsresult rv) {
+    if (IsFileNotFoundError(rv)) {
+      aPromise->MaybeRejectWithNotFoundError("File not found");
+      return;
+    }
+    aPromise->MaybeReject(rv);
+  };
+
+  nsCOMPtr<nsIInputStream> inputStream;
+
+  // https://fs.spec.whatwg.org/#write-a-chunk
+  // Step 3.4.6 If data is a BufferSource, let dataBytes be a copy of data.
+  if (aData.IsArrayBuffer() || aData.IsArrayBufferView()) {
+    const auto dataSpan = [&aData]() -> mozilla::Span<uint8_t> {
+      if (aData.IsArrayBuffer()) {
+        const ArrayBuffer& buffer = aData.GetAsArrayBuffer();
+        buffer.ComputeState();
+        return Span{buffer.Data(), buffer.Length()};
+      }
+
+      const ArrayBufferView& buffer = aData.GetAsArrayBufferView();
+      buffer.ComputeState();
+      return Span{buffer.Data(), buffer.Length()};
+    }();
+
+    // Here we copy
+
+    QM_TRY(MOZ_TO_RESULT(NS_NewByteInputStream(getter_AddRefs(inputStream),
+                                               AsChars(dataSpan),
+                                               NS_ASSIGNMENT_COPY)),
+           rejectAndReturn);
+
+    WriteImpl(std::move(inputStream), aPosition, aPromise);
+    return;
+  }
+
+  // Step 3.4.7 Otherwise, if data is a Blob ...
+  if (aData.IsBlob()) {
+    Blob& blob = aData.GetAsBlob();
+
+    ErrorResult error;
+    blob.CreateInputStream(getter_AddRefs(inputStream), error);
+    QM_TRY((MOZ_TO_RESULT(!error.Failed()).mapErr([&error](const nsresult rv) {
+             return error.StealNSResult();
+           })),
+           rejectAndReturn);
+
+    WriteImpl(std::move(inputStream), aPosition, aPromise);
+    return;
+  }
+
+  // Step 3.4.8 Otherwise ...
+  MOZ_ASSERT(aData.IsUTF8String());
+
+  // Here we copy
+  nsCString dataString;
+  if (!dataString.Assign(aData.GetAsUTF8String(), mozilla::fallible)) {
+    rejectAndReturn(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+
+  // Input stream takes ownership
+  QM_TRY(MOZ_TO_RESULT(NS_NewCStringInputStream(getter_AddRefs(inputStream),
+                                                std::move(dataString))),
+         rejectAndReturn);
+
+  WriteImpl(std::move(inputStream), aPosition, aPromise);
+}
+
+void FileSystemWritableFileStream::WriteImpl(
+    nsCOMPtr<nsIInputStream> aInputStream, const Maybe<uint64_t> aPosition,
+    const RefPtr<Promise>& aPromise) {
+  auto command = CreateCommand();
+
+  InvokeAsync(
+      mTaskQueue, __func__,
+      [selfHolder = fs::TargetPtrHolder(this),
+       inputStream = std::move(aInputStream), aPosition]() {
+        QM_TRY(MOZ_TO_RESULT(selfHolder->EnsureStream()),
+               CreateAndRejectInt64Promise);
+
+        if (aPosition.isSome()) {
+          LOG(("%p: Seeking to %" PRIu64, selfHolder->mStreamOwner.get(),
+               aPosition.value()));
+
+          QM_TRY(
+              MOZ_TO_RESULT(selfHolder->mStreamOwner->Seek(aPosition.value())),
+              CreateAndRejectInt64Promise);
+        }
+
+        nsCOMPtr<nsIOutputStream> streamSink =
+            selfHolder->mStreamOwner->OutputStream();
+
+        auto written = std::make_shared<int64_t>(0);
+        auto writingProgress = [written](uint32_t aDelta) {
+          *written += static_cast<int64_t>(aDelta);
+        };
+
+        auto promiseHolder = MakeUnique<MozPromiseHolder<Int64Promise>>();
+        RefPtr<Int64Promise> promise = promiseHolder->Ensure(__func__);
+
+        auto writingCompletion =
+            [written,
+             promiseHolder = std::move(promiseHolder)](nsresult aStatus) {
+              if (NS_SUCCEEDED(aStatus)) {
+                promiseHolder->ResolveIfExists(*written, __func__);
+                return;
+              }
+
+              promiseHolder->RejectIfExists(aStatus, __func__);
+            };
+
+        QM_TRY(MOZ_TO_RESULT(fs::AsyncCopy(
+                   inputStream, streamSink, selfHolder->mTaskQueue,
+                   nsAsyncCopyMode::NS_ASYNCCOPY_VIA_READSEGMENTS,
+                   /* aCloseSource */ true, /* aCloseSink */ false,
+                   std::move(writingProgress), std::move(writingCompletion))),
+               CreateAndRejectInt64Promise);
+
+        return promise;
+      })
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [command,
+           aPromise](const Int64Promise::ResolveOrRejectValue& aValue) {
+            if (aValue.IsResolve()) {
+              aPromise->MaybeResolve(aValue.ResolveValue());
+              return;
+            }
+
+            if (IsFileNotFoundError(aValue.RejectValue())) {
+              aPromise->MaybeRejectWithNotFoundError("File not found");
+            } else if (aValue.RejectValue() == NS_ERROR_FILE_NO_DEVICE_SPACE) {
+              aPromise->MaybeRejectWithQuotaExceededError("Quota exceeded");
+            } else {
+              aPromise->MaybeReject(aValue.RejectValue());
+            }
+
+            aPromise->MaybeReject(aValue.RejectValue());
+          });
+}
+
+void FileSystemWritableFileStream::Seek(uint64_t aPosition,
+                                        const RefPtr<Promise>& aPromise) {
+  MOZ_ASSERT(IsOpen());
+
+  LOG_VERBOSE(("%p: Seeking to %" PRIu64, mStreamOwner.get(), aPosition));
+
+  auto command = CreateCommand();
+
+  InvokeAsync(mTaskQueue, __func__,
+              [selfHolder = fs::TargetPtrHolder(this), aPosition]() mutable {
+                QM_TRY(MOZ_TO_RESULT(selfHolder->EnsureStream()),
+                       CreateAndRejectBoolPromise);
+
+                QM_TRY(MOZ_TO_RESULT(selfHolder->mStreamOwner->Seek(aPosition)),
+                       CreateAndRejectBoolPromise);
+
+                return BoolPromise::CreateAndResolve(true, __func__);
+              })
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [command, aPromise](const BoolPromise::ResolveOrRejectValue& aValue) {
+            if (aValue.IsReject()) {
+              auto rv = aValue.RejectValue();
+              if (IsFileNotFoundError(rv)) {
+                aPromise->MaybeRejectWithNotFoundError("File not found");
+                return;
+              }
+              aPromise->MaybeReject(rv);
+              return;
+            }
+            MOZ_ASSERT(aValue.IsResolve());
+            aPromise->MaybeResolveWithUndefined();
+          });
+}
+
+void FileSystemWritableFileStream::Truncate(uint64_t aSize,
+                                            const RefPtr<Promise>& aPromise) {
+  MOZ_ASSERT(IsOpen());
+
+  auto command = CreateCommand();
+
+  InvokeAsync(mTaskQueue, __func__,
+              [selfHolder = fs::TargetPtrHolder(this), aSize]() mutable {
+                QM_TRY(MOZ_TO_RESULT(selfHolder->EnsureStream()),
+                       CreateAndRejectBoolPromise);
+
+                QM_TRY(MOZ_TO_RESULT(selfHolder->mStreamOwner->Truncate(aSize)),
+                       CreateAndRejectBoolPromise);
+
+                return BoolPromise::CreateAndResolve(true, __func__);
+              })
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [command, aPromise](const BoolPromise::ResolveOrRejectValue& aValue) {
+            if (aValue.IsReject()) {
+              aPromise->MaybeReject(aValue.RejectValue());
+              return;
+            }
+
+            aPromise->MaybeResolveWithUndefined();
+          });
+}
+
+nsresult FileSystemWritableFileStream::EnsureStream() {
+  if (!mStreamOwner) {
+    QM_TRY_UNWRAP(MovingNotNull<nsCOMPtr<nsIRandomAccessStream>> stream,
+                  DeserializeRandomAccessStream(mStreamParams),
+                  NS_ERROR_FAILURE);
+
+    mozilla::ipc::RandomAccessStreamParams streamParams(
+        std::move(mStreamParams));
+
+    mStreamOwner = MakeRefPtr<fs::FileSystemThreadSafeStreamOwner>(
+        this, std::move(stream));
+  }
+
+  return NS_OK;
+}
+
+void FileSystemWritableFileStream::NoteFinishedCommand() {
+  MOZ_ASSERT(mCommandActive);
+
+  mCommandActive = false;
+
+  mFinishPromiseHolder.ResolveIfExists(true, __func__);
+}
+
+RefPtr<BoolPromise> FileSystemWritableFileStream::Finish() {
+  if (!mCommandActive) {
+    return BoolPromise::CreateAndResolve(true, __func__);
+  }
+
+  return mFinishPromiseHolder.Ensure(__func__);
+}
+
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(
+    WritableFileStreamUnderlyingSinkAlgorithms, UnderlyingSinkAlgorithmsBase)
+NS_IMPL_CYCLE_COLLECTION_INHERITED(WritableFileStreamUnderlyingSinkAlgorithms,
+                                   UnderlyingSinkAlgorithmsBase, mStream)
+
+// Step 3 of
+// https://fs.spec.whatwg.org/#create-a-new-filesystemwritablefilestream
+already_AddRefed<Promise>
+WritableFileStreamUnderlyingSinkAlgorithms::WriteCallback(
+    JSContext* aCx, JS::Handle<JS::Value> aChunk,
+    WritableStreamDefaultController& aController, ErrorResult& aRv) {
+  return mStream->Write(aCx, aChunk, aRv);
+}
+
+// Step 4 of
+// https://fs.spec.whatwg.org/#create-a-new-filesystemwritablefilestream
+already_AddRefed<Promise>
+WritableFileStreamUnderlyingSinkAlgorithms::CloseCallbackImpl(
+    JSContext* aCx, ErrorResult& aRv) {
+  RefPtr<Promise> promise = Promise::Create(mStream->GetParentObject(), aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  if (!mStream->IsOpen()) {
+    promise->MaybeRejectWithTypeError("WritableFileStream closed");
+    return promise.forget();
+  }
+
+  mStream->BeginClose()->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [promise](const BoolPromise::ResolveOrRejectValue& aValue) {
+        // Step 2.3. Return a promise resolved with undefined.
+        if (aValue.IsResolve()) {
+          promise->MaybeResolveWithUndefined();
+          return;
+        }
+        promise->MaybeRejectWithAbortError(
+            "Internal error closing file stream");
+      });
+
+  return promise.forget();
+}
+
+// Step 5 of
+// https://fs.spec.whatwg.org/#create-a-new-filesystemwritablefilestream
+already_AddRefed<Promise>
+WritableFileStreamUnderlyingSinkAlgorithms::AbortCallbackImpl(
+    JSContext* aCx, const Optional<JS::Handle<JS::Value>>& /* aReason */,
+    ErrorResult& aRv) {
+  // https://streams.spec.whatwg.org/#writablestream-set-up
+  // Step 3. Let abortAlgorithmWrapper be an algorithm that runs these steps:
+  // Step 3.3. Return a promise resolved with undefined.
+
+  return CloseCallbackImpl(aCx, aRv);
+}
+
+void WritableFileStreamUnderlyingSinkAlgorithms::ReleaseObjects() {
+  // XXX We shouldn't be calling close here. We should just release the lock.
+  // However, calling close here is not a big issue for now because we don't
+  // write to a temporary file which would atomically replace the real file
+  // during close.
+  if (mStream->IsOpen()) {
+    Unused << mStream->BeginClose();
+  }
+}
+
+}  // namespace mozilla::dom