Quelle  ActorsChild.cpp   Sprache: C

/* -*- 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 <type_traits>

#include "ActorsChild.h"
#include "BackgroundChildImpl.h"
#include "IDBDatabase.h"
#include "IDBEvents.h"
#include "IDBFactory.h"
#include "IDBIndex.h"
#include "IDBObjectStore.h"
#include "IDBRequest.h"
#include "IDBTransaction.h"
#include "IndexedDatabase.h"
#include "IndexedDatabaseInlines.h"
#include "IndexedDBCommon.h"
#include "js/Array.h"               // JS::NewArrayObject, JS::SetArrayLength
#include "js/Date.h"                // JS::NewDateObject, JS::TimeClip
#include "js/PropertyAndElement.h"  // JS_DefineElement, JS_DefineProperty
#include <mozIRemoteLazyInputStream.h>
#include "mozilla/ArrayAlgorithm.h"
#include "mozilla/BasicEvents.h"
#include "mozilla/CycleCollectedJSRuntime.h"
#include "mozilla/Maybe.h"
#include "mozilla/ResultExtensions.h"
#include "mozilla/dom/BlobImpl.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/Event.h"
#include "mozilla/dom/PermissionMessageUtils.h"
#include "mozilla/dom/BrowserChild.h"
#include "mozilla/dom/indexedDB/PBackgroundIDBDatabaseFileChild.h"
#include "mozilla/dom/IPCBlobUtils.h"
#include "mozilla/dom/WorkerPrivate.h"
#include "mozilla/dom/WorkerRunnable.h"
#include "mozilla/dom/quota/ResultExtensions.h"
#include "mozilla/Encoding.h"
#include "mozilla/ipc/BackgroundUtils.h"
#include "mozilla/ProfilerLabels.h"
#include "mozilla/TaskQueue.h"
#include "nsCOMPtr.h"
#include "nsContentUtils.h"
#include "nsIAsyncInputStream.h"
#include "nsIEventTarget.h"
#include "nsIFileStreams.h"
#include "nsNetCID.h"
#include "nsPIDOMWindow.h"
#include "nsThreadUtils.h"
#include "nsTraceRefcnt.h"
#include "ProfilerHelpers.h"
#include "ReportInternalError.h"
#include "ThreadLocal.h"

#ifdef DEBUG
#  include "IndexedDatabaseManager.h"
#endif

#define GC_ON_IPC_MESSAGES 0

#if defined(DEBUG) || GC_ON_IPC_MESSAGES

#  include "js/GCAPI.h"
#  include "nsJSEnvironment.h"

#  define BUILD_GC_ON_IPC_MESSAGES

#endif  // DEBUG || GC_ON_IPC_MESSAGES

namespace mozilla {

using ipc::PrincipalInfo;

namespace dom::indexedDB {

/*******************************************************************************
 * ThreadLocal
 ******************************************************************************/

ThreadLocal::ThreadLocal(const nsID& aBackgroundChildLoggingId)
    : mLoggingInfo(aBackgroundChildLoggingId, 1, -1, 1),
      mLoggingIdString(aBackgroundChildLoggingId) {
  MOZ_COUNT_CTOR(mozilla::dom::indexedDB::ThreadLocal);
}

ThreadLocal::~ThreadLocal() {
  MOZ_COUNT_DTOR(mozilla::dom::indexedDB::ThreadLocal);
}

/*******************************************************************************
 * Helpers
 ******************************************************************************/

namespace {

void MaybeCollectGarbageOnIPCMessage() {
#ifdef BUILD_GC_ON_IPC_MESSAGES
  static const bool kCollectGarbageOnIPCMessages =
#  if GC_ON_IPC_MESSAGES
      true;
#  else
      false;
#  endif  // GC_ON_IPC_MESSAGES

  if (!kCollectGarbageOnIPCMessages) {
    return;
  }

  static bool haveWarnedAboutGC = false;
  static bool haveWarnedAboutNonMainThread = false;

  if (!haveWarnedAboutGC) {
    haveWarnedAboutGC = true;
    NS_WARNING("IndexedDB child actor GC debugging enabled!");
  }

  if (!NS_IsMainThread()) {
    if (!haveWarnedAboutNonMainThread) {
      haveWarnedAboutNonMainThread = true;
      NS_WARNING("Don't know how to GC on a non-main thread yet.");
    }
    return;
  }

  nsJSContext::GarbageCollectNow(JS::GCReason::DOM_IPC);
  nsJSContext::CycleCollectNow(CCReason::API);
#endif  // BUILD_GC_ON_IPC_MESSAGES
}

class MOZ_STACK_CLASS AutoSetCurrentTransaction final {
  using BackgroundChildImpl = mozilla::ipc::BackgroundChildImpl;

  Maybe<IDBTransaction&> const mTransaction;
  Maybe<IDBTransaction&> mPreviousTransaction;
  ThreadLocal* mThreadLocal;

 public:
  AutoSetCurrentTransaction(const AutoSetCurrentTransaction&) = delete;
  AutoSetCurrentTransaction(AutoSetCurrentTransaction&&) = delete;
  AutoSetCurrentTransaction& operator=(const AutoSetCurrentTransaction&) =
      delete;
  AutoSetCurrentTransaction& operator=(AutoSetCurrentTransaction&&) = delete;

  explicit AutoSetCurrentTransaction(Maybe<IDBTransaction&> aTransaction)
      : mTransaction(aTransaction), mThreadLocal(nullptr) {
    if (aTransaction) {
      BackgroundChildImpl::ThreadLocal* threadLocal =
          BackgroundChildImpl::GetThreadLocalForCurrentThread();
      MOZ_ASSERT(threadLocal);

      // Hang onto this for resetting later.
      mThreadLocal = threadLocal->mIndexedDBThreadLocal.get();
      MOZ_ASSERT(mThreadLocal);

      // Save the current value.
      mPreviousTransaction = mThreadLocal->MaybeCurrentTransactionRef();

      // Set the new value.
      mThreadLocal->SetCurrentTransaction(aTransaction);
    }
  }

  ~AutoSetCurrentTransaction() {
    MOZ_ASSERT_IF(mThreadLocal, mTransaction);
    MOZ_ASSERT_IF(mThreadLocal,
                  ReferenceEquals(mThreadLocal->MaybeCurrentTransactionRef(),
                                  mTransaction));

    if (mThreadLocal) {
      // Reset old value.
      mThreadLocal->SetCurrentTransaction(mPreviousTransaction);
    }
  }
};

template <typename T>
void SetResultAndDispatchSuccessEvent(
    const NotNull<RefPtr<IDBRequest>>& aRequest,
    const SafeRefPtr<IDBTransaction>& aTransaction, T& aPtr,
    RefPtr<Event> aEvent = nullptr);

namespace detail {
void DispatchSuccessEvent(const NotNull<RefPtr<IDBRequest>>& aRequest,
                          const SafeRefPtr<IDBTransaction>& aTransaction,
                          const RefPtr<Event>& aEvent);

template <class T>
std::enable_if_t<std::is_same_v<T, IDBDatabase> || std::is_same_v<T, IDBCursor>,
                 nsresult>
GetResult(JSContext* aCx, T* aDOMObject, JS::MutableHandle<JS::Value> aResult) {
  if (!aDOMObject) {
    aResult.setNull();
    return NS_OK;
  }

  const bool ok = GetOrCreateDOMReflector(aCx, aDOMObject, aResult);
  if (NS_WARN_IF(!ok)) {
    IDB_REPORT_INTERNAL_ERR();
    return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
  }

  return NS_OK;
}

nsresult GetResult(JSContext* aCx, const JS::Handle<JS::Value>* aValue,
                   JS::MutableHandle<JS::Value> aResult) {
  aResult.set(*aValue);
  return NS_OK;
}

nsresult GetResult(JSContext* aCx, const uint64_t* aValue,
                   JS::MutableHandle<JS::Value> aResult) {
  aResult.set(JS::NumberValue(*aValue));
  return NS_OK;
}

nsresult GetResult(JSContext* aCx, StructuredCloneReadInfoChild&& aCloneInfo,
                   JS::MutableHandle<JS::Value> aResult) {
  const bool ok =
      IDBObjectStore::DeserializeValue(aCx, std::move(aCloneInfo), aResult);

  if (NS_WARN_IF(!ok)) {
    return NS_ERROR_DOM_DATA_CLONE_ERR;
  }

  return NS_OK;
}

nsresult GetResult(JSContext* aCx, StructuredCloneReadInfoChild* aCloneInfo,
                   JS::MutableHandle<JS::Value> aResult) {
  return GetResult(aCx, std::move(*aCloneInfo), aResult);
}

nsresult GetResult(JSContext* aCx,
                   nsTArray<StructuredCloneReadInfoChild>* aCloneInfos,
                   JS::MutableHandle<JS::Value> aResult) {
  JS::Rooted<JSObject*> array(aCx, JS::NewArrayObject(aCx, 0));
  if (NS_WARN_IF(!array)) {
    IDB_REPORT_INTERNAL_ERR();
    return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
  }

  if (!aCloneInfos->IsEmpty()) {
    const uint32_t count = aCloneInfos->Length();

    if (NS_WARN_IF(!JS::SetArrayLength(aCx, array, count))) {
      IDB_REPORT_INTERNAL_ERR();
      return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
    }

    for (uint32_t index = 0; index < count; index++) {
      auto& cloneInfo = aCloneInfos->ElementAt(index);

      JS::Rooted<JS::Value> value(aCx);

      const nsresult rv = GetResult(aCx, std::move(cloneInfo), &value);
      if (NS_WARN_IF(NS_FAILED(rv))) {
        return rv;
      }

      if (NS_WARN_IF(
              !JS_DefineElement(aCx, array, index, value, JSPROP_ENUMERATE))) {
        IDB_REPORT_INTERNAL_ERR();
        return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
      }
    }
  }

  aResult.setObject(*array);
  return NS_OK;
}

nsresult GetResult(JSContext* aCx, const Key* aKey,
                   JS::MutableHandle<JS::Value> aResult) {
  const nsresult rv = aKey->ToJSVal(aCx, aResult);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }
  return NS_OK;
}

nsresult GetResult(JSContext* aCx, const nsTArray<Key>* aKeys,
                   JS::MutableHandle<JS::Value> aResult) {
  JS::Rooted<JSObject*> array(aCx, JS::NewArrayObject(aCx, 0));
  if (NS_WARN_IF(!array)) {
    IDB_REPORT_INTERNAL_ERR();
    return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
  }

  if (!aKeys->IsEmpty()) {
    const uint32_t count = aKeys->Length();

    if (NS_WARN_IF(!JS::SetArrayLength(aCx, array, count))) {
      IDB_REPORT_INTERNAL_ERR();
      return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
    }

    for (uint32_t index = 0; index < count; index++) {
      const Key& key = aKeys->ElementAt(index);
      MOZ_ASSERT(!key.IsUnset());

      JS::Rooted<JS::Value> value(aCx);

      const nsresult rv = GetResult(aCx, &key, &value);
      if (NS_WARN_IF(NS_FAILED(rv))) {
        return rv;
      }

      if (NS_WARN_IF(
              !JS_DefineElement(aCx, array, index, value, JSPROP_ENUMERATE))) {
        IDB_REPORT_INTERNAL_ERR();
        return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
      }
    }
  }

  aResult.setObject(*array);
  return NS_OK;
}
}  // namespace detail

auto DeserializeStructuredCloneFiles(
    IDBDatabase* aDatabase,
    const nsTArray<SerializedStructuredCloneFile>& aSerializedFiles,
    bool aForPreprocess) {
  MOZ_ASSERT_IF(aForPreprocess, aSerializedFiles.Length() == 1);

  return TransformIntoNewArray(
      aSerializedFiles,
      [aForPreprocess, &database = *aDatabase](
          const auto& serializedFile) -> StructuredCloneFileChild {
        MOZ_ASSERT_IF(
            aForPreprocess,
            serializedFile.type() == StructuredCloneFileBase::eStructuredClone);

        const NullableBlob& blob = serializedFile.file();

        switch (serializedFile.type()) {
          case StructuredCloneFileBase::eBlob: {
            MOZ_ASSERT(blob.type() == NullableBlob::TIPCBlob);

            const IPCBlob& ipcBlob = blob.get_IPCBlob();

            const RefPtr<BlobImpl> blobImpl =
                IPCBlobUtils::Deserialize(ipcBlob);
            MOZ_ASSERT(blobImpl);

            RefPtr<Blob> blob =
                Blob::Create(database.GetOwnerGlobal(), blobImpl);
            MOZ_ASSERT(blob);

            return {StructuredCloneFileBase::eBlob, std::move(blob)};
          }

          case StructuredCloneFileBase::eStructuredClone: {
            if (aForPreprocess) {
              MOZ_ASSERT(blob.type() == NullableBlob::TIPCBlob);

              const IPCBlob& ipcBlob = blob.get_IPCBlob();

              const RefPtr<BlobImpl> blobImpl =
                  IPCBlobUtils::Deserialize(ipcBlob);
              MOZ_ASSERT(blobImpl);

              RefPtr<Blob> blob =
                  Blob::Create(database.GetOwnerGlobal(), blobImpl);
              MOZ_ASSERT(blob);

              return {StructuredCloneFileBase::eStructuredClone,
                      std::move(blob)};
            }
            MOZ_ASSERT(blob.type() == NullableBlob::Tnull_t);

            return StructuredCloneFileChild{
                StructuredCloneFileBase::eStructuredClone};
          }

          case StructuredCloneFileBase::eMutableFile:
          case StructuredCloneFileBase::eWasmBytecode:
          case StructuredCloneFileBase::eWasmCompiled: {
            MOZ_ASSERT(blob.type() == NullableBlob::Tnull_t);

            return StructuredCloneFileChild{serializedFile.type()};

            // Don't set mBlob, support for storing WebAssembly.Modules has been
            // removed in bug 1469395. Support for de-serialization of
            // WebAssembly.Modules has been removed in bug 1561876. Support for
            // MutableFile has been removed in bug 1500343. Full removal is
            // tracked in bug 1487479.
          }

          default:
            MOZ_CRASH("Should never get here!");
        }
      });
}

JSStructuredCloneData PreprocessingNotSupported() {
  MOZ_CRASH("Preprocessing not (yet) supported!");
}

template <typename PreprocessInfoAccessor>
StructuredCloneReadInfoChild DeserializeStructuredCloneReadInfo(
    SerializedStructuredCloneReadInfo&& aSerialized,
    IDBDatabase* const aDatabase,
    PreprocessInfoAccessor preprocessInfoAccessor) {
  // XXX Make this a class invariant of SerializedStructuredCloneReadInfo.
  MOZ_ASSERT_IF(aSerialized.hasPreprocessInfo(),
                0 == aSerialized.data().data.Size());
  return {aSerialized.hasPreprocessInfo() ? preprocessInfoAccessor()
                                          : std::move(aSerialized.data().data),
          DeserializeStructuredCloneFiles(aDatabase, aSerialized.files(),
                                          /* aForPreprocess */ false),
          aDatabase};
}

// TODO: Remove duplication between DispatchErrorEvent and DispatchSucessEvent.

void DispatchErrorEvent(
    MovingNotNull<RefPtr<IDBRequest>> aRequest, nsresult aErrorCode,
    const SafeRefPtr<IDBTransaction>& aTransaction = nullptr,
    RefPtr<Event> aEvent = nullptr) {
  const RefPtr<IDBRequest> request = std::move(aRequest);

  request->AssertIsOnOwningThread();
  MOZ_ASSERT(NS_FAILED(aErrorCode));
  MOZ_ASSERT(NS_ERROR_GET_MODULE(aErrorCode) == NS_ERROR_MODULE_DOM_INDEXEDDB);

  AUTO_PROFILER_LABEL("IndexedDB:DispatchErrorEvent", DOM);

  request->SetError(aErrorCode);

  if (!aEvent) {
    // Make an error event and fire it at the target.
    aEvent = CreateGenericEvent(request, nsDependentString(kErrorEventType),
                                eDoesBubble, eCancelable);
  }
  MOZ_ASSERT(aEvent);

  // XXX This is redundant if we are called from
  // DispatchSuccessEvent.
  Maybe<AutoSetCurrentTransaction> asct;
  if (aTransaction) {
    asct.emplace(SomeRef(*aTransaction));
  }

  if (aTransaction && aTransaction->IsInactive()) {
    aTransaction->TransitionToActive();
  }

  if (aTransaction) {
    IDB_LOG_MARK_CHILD_TRANSACTION_REQUEST(
        "Firing %s event with error 0x%x", "%s (0x%" PRIx32 ")",
        aTransaction->LoggingSerialNumber(), request->LoggingSerialNumber(),
        IDB_LOG_STRINGIFY(aEvent, kErrorEventType),
        static_cast<uint32_t>(aErrorCode));
  } else {
    IDB_LOG_MARK_CHILD_REQUEST("Firing %s event with error 0x%x",
                               "%s (0x%" PRIx32 ")",
                               request->LoggingSerialNumber(),
                               IDB_LOG_STRINGIFY(aEvent, kErrorEventType),
                               static_cast<uint32_t>(aErrorCode));
  }

  IgnoredErrorResult rv;
  const bool doDefault =
      request->DispatchEvent(*aEvent, CallerType::System, rv);
  if (NS_WARN_IF(rv.Failed())) {
    return;
  }

  MOZ_ASSERT(!aTransaction || aTransaction->IsActive() ||
             aTransaction->IsAborted() ||
             aTransaction->WasExplicitlyCommitted());

  if (aTransaction && aTransaction->IsActive()) {
    aTransaction->TransitionToInactive();

    // Do not abort the transaction here if this request is failed due to the
    // abortion of its transaction to ensure that the correct error cause of
    // the abort event be set in IDBTransaction::FireCompleteOrAbortEvents()
    // later.
    if (aErrorCode != NS_ERROR_DOM_INDEXEDDB_ABORT_ERR) {
      WidgetEvent* const internalEvent = aEvent->WidgetEventPtr();
      MOZ_ASSERT(internalEvent);

      if (internalEvent->mFlags.mExceptionWasRaised) {
        aTransaction->Abort(NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
      } else if (doDefault) {
        aTransaction->Abort(request);
      }
    }
  }
}

template <typename T>
void SetResultAndDispatchSuccessEvent(
    const NotNull<RefPtr<IDBRequest>>& aRequest,
    const SafeRefPtr<IDBTransaction>& aTransaction, T& aPtr,
    RefPtr<Event> aEvent) {
  const auto autoTransaction =
      AutoSetCurrentTransaction{aTransaction.maybeDeref()};

  AUTO_PROFILER_LABEL("IndexedDB:SetResultAndDispatchSuccessEvent", DOM);

  aRequest->AssertIsOnOwningThread();

  if (aTransaction && aTransaction->IsAborted()) {
    DispatchErrorEvent(aRequest, aTransaction->AbortCode(), aTransaction);
    return;
  }

  if (!aEvent) {
    aEvent =
        CreateGenericEvent(aRequest.get(), nsDependentString(kSuccessEventType),
                           eDoesNotBubble, eNotCancelable);
  }
  MOZ_ASSERT(aEvent);

  aRequest->SetResult(
      [&aPtr](JSContext* aCx, JS::MutableHandle<JS::Value> aResult) {
        MOZ_ASSERT(aCx);
        return detail::GetResult(aCx, &aPtr, aResult);
      });

  detail::DispatchSuccessEvent(aRequest, aTransaction, aEvent);
}

namespace detail {
void DispatchSuccessEvent(const NotNull<RefPtr<IDBRequest>>& aRequest,
                          const SafeRefPtr<IDBTransaction>& aTransaction,
                          const RefPtr<Event>& aEvent) {
  if (aTransaction && aTransaction->IsInactive()) {
    aTransaction->TransitionToActive();
  }

  if (aTransaction) {
    IDB_LOG_MARK_CHILD_TRANSACTION_REQUEST(
        "Firing %s event", "%s", aTransaction->LoggingSerialNumber(),
        aRequest->LoggingSerialNumber(),
        IDB_LOG_STRINGIFY(aEvent, kSuccessEventType));
  } else {
    IDB_LOG_MARK_CHILD_REQUEST("Firing %s event", "%s",
                               aRequest->LoggingSerialNumber(),
                               IDB_LOG_STRINGIFY(aEvent, kSuccessEventType));
  }

  MOZ_ASSERT_IF(aTransaction && !aTransaction->WasExplicitlyCommitted(),
                aTransaction->IsActive() && !aTransaction->IsAborted());

  IgnoredErrorResult rv;
  aRequest->DispatchEvent(*aEvent, rv);
  if (NS_WARN_IF(rv.Failed())) {
    return;
  }

  WidgetEvent* const internalEvent = aEvent->WidgetEventPtr();
  MOZ_ASSERT(internalEvent);

  if (aTransaction && aTransaction->IsActive()) {
    aTransaction->TransitionToInactive();

    if (internalEvent->mFlags.mExceptionWasRaised) {
      aTransaction->Abort(NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
    } else {
      // To handle upgrade transaction.
      aTransaction->CommitIfNotStarted();
    }
  }
}
}  // namespace detail

PRFileDesc* GetFileDescriptorFromStream(nsIInputStream* aStream) {
  MOZ_ASSERT(aStream);

  const nsCOMPtr<nsIFileMetadata> fileMetadata = do_QueryInterface(aStream);
  if (NS_WARN_IF(!fileMetadata)) {
    return nullptr;
  }

  PRFileDesc* fileDesc;
  const nsresult rv = fileMetadata->GetFileDescriptor(&fileDesc);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return nullptr;
  }

  MOZ_ASSERT(fileDesc);

  return fileDesc;
}

auto GetKeyOperator(const IDBCursorDirection aDirection) {
  switch (aDirection) {
    case IDBCursorDirection::Next:
    case IDBCursorDirection::Nextunique:
      return &Key::operator>=;
    case IDBCursorDirection::Prev:
    case IDBCursorDirection::Prevunique:
      return &Key::operator<=;
    default:
      MOZ_CRASH("Should never get here.");
  }
}

// Does not need to be threadsafe since this only runs on one thread, but
// inheriting from CancelableRunnable is easy.
template <typename T>
class DelayedActionRunnable final : public CancelableRunnable {
  using ActionFunc = void (T::*)();

  SafeRefPtr<T> mActor;
  RefPtr<IDBRequest> mRequest;
  ActionFunc mActionFunc;

 public:
  explicit DelayedActionRunnable(SafeRefPtr<T> aActor, ActionFunc aActionFunc)
      : CancelableRunnable("indexedDB::DelayedActionRunnable"),
        mActor(std::move(aActor)),
        mRequest(mActor->GetRequest()),
        mActionFunc(aActionFunc) {
    MOZ_ASSERT(mActor);
    mActor->AssertIsOnOwningThread();
    MOZ_ASSERT(mRequest);
    MOZ_ASSERT(mActionFunc);
  }

 private:
  ~DelayedActionRunnable() = default;

  NS_DECL_NSIRUNNABLE
  nsresult Cancel() override;
};

}  // namespace

/*******************************************************************************
 * Actor class declarations
 ******************************************************************************/

// DiscardableRunnable is used to make workers happy.
class BackgroundRequestChild::PreprocessHelper final
    : public DiscardableRunnable,
      public nsIInputStreamCallback,
      public nsIFileMetadataCallback {
  enum class State {
    // Just created on the owning thread, dispatched to the thread pool. Next
    // step is either Finishing if stream was ready to be read or
    // WaitingForStreamReady if the stream is not ready.
    Initial,

    // Waiting for stream to be ready on a thread pool thread. Next state is
    // Finishing.
    WaitingForStreamReady,

    // Waiting to finish/finishing on the owning thread. Next step is Completed.
    Finishing,

    // All done.
    Completed
  };

  const nsCOMPtr<nsIEventTarget> mOwningEventTarget;
  RefPtr<TaskQueue> mTaskQueue;
  nsCOMPtr<nsIInputStream> mStream;
  UniquePtr<JSStructuredCloneData> mCloneData;
  BackgroundRequestChild* mActor;
  const uint32_t mCloneDataIndex;
  nsresult mResultCode;
  State mState;

 public:
  PreprocessHelper(uint32_t aCloneDataIndex, BackgroundRequestChild* aActor)
      : DiscardableRunnable(
            "indexedDB::BackgroundRequestChild::PreprocessHelper"),
        mOwningEventTarget(aActor->GetActorEventTarget()),
        mActor(aActor),
        mCloneDataIndex(aCloneDataIndex),
        mResultCode(NS_OK),
        mState(State::Initial) {
    AssertIsOnOwningThread();
    MOZ_ASSERT(aActor);
    aActor->AssertIsOnOwningThread();
  }

  bool IsOnOwningThread() const {
    MOZ_ASSERT(mOwningEventTarget);

    bool current;
    return NS_SUCCEEDED(mOwningEventTarget->IsOnCurrentThread(¤t)) &&
           current;
  }

  void AssertIsOnOwningThread() const { MOZ_ASSERT(IsOnOwningThread()); }

  void ClearActor() {
    AssertIsOnOwningThread();

    mActor = nullptr;
  }

  nsresult Init(const StructuredCloneFileChild& aFile);

  nsresult Dispatch();

 private:
  ~PreprocessHelper() {
    MOZ_ASSERT(mState == State::Initial || mState == State::Completed);

    if (mTaskQueue) {
      mTaskQueue->BeginShutdown();
    }
  }

  nsresult Start();

  nsresult ProcessStream();

  void Finish();

  NS_DECL_ISUPPORTS_INHERITED
  NS_DECL_NSIRUNNABLE
  NS_DECL_NSIINPUTSTREAMCALLBACK
  NS_DECL_NSIFILEMETADATACALLBACK
};

/*******************************************************************************
 * BackgroundRequestChildBase
 ******************************************************************************/

BackgroundRequestChildBase::BackgroundRequestChildBase(
    MovingNotNull<RefPtr<IDBRequest>> aRequest)
    : mRequest(std::move(aRequest)) {
  mRequest->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundRequestChildBase);
}

BackgroundRequestChildBase::~BackgroundRequestChildBase() {
  AssertIsOnOwningThread();

  MOZ_COUNT_DTOR(indexedDB::BackgroundRequestChildBase);
}

#ifdef DEBUG

void BackgroundRequestChildBase::AssertIsOnOwningThread() const {
  mRequest->AssertIsOnOwningThread();
}

#endif  // DEBUG

/*******************************************************************************
 * BackgroundFactoryChild
 ******************************************************************************/

BackgroundFactoryChild::BackgroundFactoryChild(IDBFactory& aFactory)
    : mFactory(&aFactory) {
  AssertIsOnOwningThread();
  mFactory->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundFactoryChild);
}

BackgroundFactoryChild::~BackgroundFactoryChild() {
  MOZ_COUNT_DTOR(indexedDB::BackgroundFactoryChild);
}

void BackgroundFactoryChild::SendDeleteMeInternal() {
  AssertIsOnOwningThread();

  if (mFactory) {
    mFactory->ClearBackgroundActor();
    mFactory = nullptr;

    MOZ_ALWAYS_TRUE(PBackgroundIDBFactoryChild::SendDeleteMe());
  }
}

void BackgroundFactoryChild::ActorDestroy(ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (mFactory) {
    mFactory->ClearBackgroundActor();
#ifdef DEBUG
    mFactory = nullptr;
#endif
  }
}

PBackgroundIDBFactoryRequestChild*
BackgroundFactoryChild::AllocPBackgroundIDBFactoryRequestChild(
    const FactoryRequestParams& aParams) {
  MOZ_CRASH(
      "PBackgroundIDBFactoryRequestChild actors should be manually "
      "constructed!");
}

bool BackgroundFactoryChild::DeallocPBackgroundIDBFactoryRequestChild(
    PBackgroundIDBFactoryRequestChild* aActor) {
  MOZ_ASSERT(aActor);

  delete static_cast<BackgroundFactoryRequestChild*>(aActor);
  return true;
}

already_AddRefed<PBackgroundIDBDatabaseChild>
BackgroundFactoryChild::AllocPBackgroundIDBDatabaseChild(
    const DatabaseSpec& aSpec,
    PBackgroundIDBFactoryRequestChild* aRequest) const {
  AssertIsOnOwningThread();

  auto* const request = static_cast<BackgroundFactoryRequestChild*>(aRequest);
  MOZ_ASSERT(request);

  RefPtr<BackgroundDatabaseChild> actor =
      new BackgroundDatabaseChild(aSpec, request);
  return actor.forget();
}

mozilla::ipc::IPCResult
BackgroundFactoryChild::RecvPBackgroundIDBDatabaseConstructor(
    PBackgroundIDBDatabaseChild* aActor, const DatabaseSpec& aSpec,
    NotNull<PBackgroundIDBFactoryRequestChild*> aRequest) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aActor);

  return IPC_OK();
}

/*******************************************************************************
 * BackgroundFactoryRequestChild
 ******************************************************************************/

BackgroundFactoryRequestChild::BackgroundFactoryRequestChild(
    SafeRefPtr<IDBFactory> aFactory,
    MovingNotNull<RefPtr<IDBOpenDBRequest>> aOpenRequest, bool aIsDeleteOp,
    uint64_t aRequestedVersion)
    : BackgroundRequestChildBase(std::move(aOpenRequest)),
      mFactory(std::move(aFactory)),
      mDatabaseActor(nullptr),
      mRequestedVersion(aRequestedVersion),
      mIsDeleteOp(aIsDeleteOp) {
  // Can't assert owning thread here because IPDL has not yet set our manager!
  MOZ_ASSERT(mFactory);
  mFactory->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundFactoryRequestChild);
}

BackgroundFactoryRequestChild::~BackgroundFactoryRequestChild() {
  MOZ_COUNT_DTOR(indexedDB::BackgroundFactoryRequestChild);
}

NotNull<IDBOpenDBRequest*> BackgroundFactoryRequestChild::GetOpenDBRequest()
    const {
  AssertIsOnOwningThread();

  // XXX NotNull might provide something to encapsulate this
  return WrapNotNullUnchecked(
      static_cast<IDBOpenDBRequest*>(mRequest.get().get()));
}

void BackgroundFactoryRequestChild::SetDatabaseActor(
    BackgroundDatabaseChild* aActor) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(!aActor || !mDatabaseActor);

  mDatabaseActor = aActor;
}

void BackgroundFactoryRequestChild::HandleResponse(nsresult aResponse) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(NS_FAILED(aResponse));
  MOZ_ASSERT(NS_ERROR_GET_MODULE(aResponse) == NS_ERROR_MODULE_DOM_INDEXEDDB);

  mRequest->Reset();

  DispatchErrorEvent(mRequest, aResponse);

  if (mDatabaseActor) {
    mDatabaseActor->ReleaseDOMObject();
    MOZ_ASSERT(!mDatabaseActor);
  }
}

void BackgroundFactoryRequestChild::HandleResponse(
    const OpenDatabaseRequestResponse& aResponse) {
  AssertIsOnOwningThread();

  mRequest->Reset();

  auto* databaseActor = static_cast<BackgroundDatabaseChild*>(
      aResponse.database().AsChild().get());
  MOZ_ASSERT(databaseActor);

  IDBDatabase* const database = [this, databaseActor]() -> IDBDatabase* {
    IDBDatabase* database = databaseActor->GetDOMObject();
    if (!database) {
      Unused << this;

      if (NS_WARN_IF(!databaseActor->EnsureDOMObject())) {
        return nullptr;
      }
      MOZ_ASSERT(mDatabaseActor);

      database = databaseActor->GetDOMObject();
      MOZ_ASSERT(database);
    }

    return database;
  }();

  if (!database || database->IsClosed()) {
    // If the database was closed already, which is only possible if we fired an
    // "upgradeneeded" event, then we shouldn't fire a "success" event here.
    // Instead we fire an error event with AbortErr.
    DispatchErrorEvent(mRequest, NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
  } else {
    SetResultAndDispatchSuccessEvent(mRequest, nullptr, *database);
  }

  if (database) {
    MOZ_ASSERT(mDatabaseActor == databaseActor);

    databaseActor->ReleaseDOMObject();
  } else {
    databaseActor->SendDeleteMeInternal();
  }
  MOZ_ASSERT(!mDatabaseActor);
}

void BackgroundFactoryRequestChild::HandleResponse(
    const DeleteDatabaseRequestResponse& aResponse) {
  AssertIsOnOwningThread();

  RefPtr<Event> successEvent = IDBVersionChangeEvent::Create(
      mRequest.get(), nsDependentString(kSuccessEventType),
      aResponse.previousVersion());
  MOZ_ASSERT(successEvent);

  SetResultAndDispatchSuccessEvent(mRequest, nullptr, JS::UndefinedHandleValue,
                                   std::move(successEvent));

  MOZ_ASSERT(!mDatabaseActor);
}

void BackgroundFactoryRequestChild::ActorDestroy(ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (aWhy != Deletion) {
    GetOpenDBRequest()->NoteComplete();
  }
}

mozilla::ipc::IPCResult BackgroundFactoryRequestChild::Recv__delete__(
    const FactoryRequestResponse& aResponse) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  switch (aResponse.type()) {
    case FactoryRequestResponse::Tnsresult:
      HandleResponse(aResponse.get_nsresult());
      break;

    case FactoryRequestResponse::TOpenDatabaseRequestResponse:
      HandleResponse(aResponse.get_OpenDatabaseRequestResponse());
      break;

    case FactoryRequestResponse::TDeleteDatabaseRequestResponse:
      HandleResponse(aResponse.get_DeleteDatabaseRequestResponse());
      break;

    default:
      return IPC_FAIL(this, "Unknown response type!");
  }

  auto request = GetOpenDBRequest();
  request->NoteComplete();

  return IPC_OK();
}

mozilla::ipc::IPCResult BackgroundFactoryRequestChild::RecvBlocked(
    const uint64_t aCurrentVersion) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  const nsDependentString type(kBlockedEventType);

  RefPtr<Event> blockedEvent;
  if (mIsDeleteOp) {
    blockedEvent =
        IDBVersionChangeEvent::Create(mRequest.get(), type, aCurrentVersion);
    MOZ_ASSERT(blockedEvent);
  } else {
    blockedEvent = IDBVersionChangeEvent::Create(
        mRequest.get(), type, aCurrentVersion, mRequestedVersion);
    MOZ_ASSERT(blockedEvent);
  }

  RefPtr<IDBRequest> kungFuDeathGrip = mRequest;

  IDB_LOG_MARK_CHILD_REQUEST("Firing \"blocked\" event", "\"blocked\"",
                             kungFuDeathGrip->LoggingSerialNumber());

  IgnoredErrorResult rv;
  kungFuDeathGrip->DispatchEvent(*blockedEvent, rv);
  if (rv.Failed()) {
    NS_WARNING("Failed to dispatch event!");
  }

  return IPC_OK();
}

/*******************************************************************************
 * BackgroundDatabaseChild
 ******************************************************************************/

BackgroundDatabaseChild::BackgroundDatabaseChild(
    const DatabaseSpec& aSpec, BackgroundFactoryRequestChild* aOpenRequestActor)
    : mSpec(MakeUnique<DatabaseSpec>(aSpec)),
      mOpenRequestActor(aOpenRequestActor),
      mDatabase(nullptr),
      mPendingInvalidate(false) {
  // Can't assert owning thread here because IPDL has not yet set our manager!
  MOZ_ASSERT(aOpenRequestActor);

  MOZ_COUNT_CTOR(indexedDB::BackgroundDatabaseChild);
}

BackgroundDatabaseChild::~BackgroundDatabaseChild() {
  MOZ_COUNT_DTOR(indexedDB::BackgroundDatabaseChild);
}

#ifdef DEBUG

void BackgroundDatabaseChild::AssertIsOnOwningThread() const {
  static_cast<BackgroundFactoryChild*>(Manager())->AssertIsOnOwningThread();
}

#endif  // DEBUG

void BackgroundDatabaseChild::SendDeleteMeInternal() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(!mTemporaryStrongDatabase);
  MOZ_ASSERT(!mOpenRequestActor);

  if (mDatabase) {
    mDatabase->ClearBackgroundActor();
    mDatabase = nullptr;

    MOZ_ALWAYS_TRUE(PBackgroundIDBDatabaseChild::SendDeleteMe());
  }
}

bool BackgroundDatabaseChild::EnsureDOMObject() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mOpenRequestActor);

  if (mTemporaryStrongDatabase) {
    MOZ_ASSERT(!mSpec);
    MOZ_ASSERT(mDatabase == mTemporaryStrongDatabase);
    return true;
  }

  MOZ_ASSERT(mSpec);

  const auto request = mOpenRequestActor->GetOpenDBRequest();

  auto& factory =
      static_cast<BackgroundFactoryChild*>(Manager())->GetDOMObject();

  if (!factory.GetOwnerGlobal()) {
    // Already disconnected from global.

    // We need to clear mOpenRequestActor here, since that would otherwise be
    // done by ReleaseDOMObject, which cannot be called if EnsureDOMObject
    // failed.
    mOpenRequestActor = nullptr;

    return false;
  }

  // TODO: This AcquireStrongRefFromRawPtr looks suspicious. This should be
  // changed or at least well explained, see also comment on
  // BackgroundFactoryChild.
  mTemporaryStrongDatabase = IDBDatabase::Create(
      request, SafeRefPtr{&factory, AcquireStrongRefFromRawPtr{}}, this,
      std::move(mSpec));

  MOZ_ASSERT(mTemporaryStrongDatabase);
  mTemporaryStrongDatabase->AssertIsOnOwningThread();

  mDatabase = mTemporaryStrongDatabase;

  if (mPendingInvalidate) {
    mDatabase->Invalidate();
    mPendingInvalidate = false;
  }

  mOpenRequestActor->SetDatabaseActor(this);

  return true;
}

void BackgroundDatabaseChild::ReleaseDOMObject() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mTemporaryStrongDatabase);
  mTemporaryStrongDatabase->AssertIsOnOwningThread();
  MOZ_ASSERT(mOpenRequestActor);
  MOZ_ASSERT(mDatabase == mTemporaryStrongDatabase);

  mOpenRequestActor->SetDatabaseActor(nullptr);

  mOpenRequestActor = nullptr;

  // This may be the final reference to the IDBDatabase object so we may end up
  // calling SendDeleteMeInternal() here. Make sure everything is cleaned up
  // properly before proceeding.
  mTemporaryStrongDatabase = nullptr;

  // XXX Why isn't mDatabase set to nullptr here?
}

void BackgroundDatabaseChild::ActorDestroy(ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (mDatabase) {
    mDatabase->ClearBackgroundActor();
#ifdef DEBUG
    mDatabase = nullptr;
#endif
  }
}

PBackgroundIDBDatabaseFileChild*
BackgroundDatabaseChild::AllocPBackgroundIDBDatabaseFileChild(
    const IPCBlob& aIPCBlob) {
  MOZ_CRASH("PBackgroundIDBFileChild actors should be manually constructed!");
}

bool BackgroundDatabaseChild::DeallocPBackgroundIDBDatabaseFileChild(
    PBackgroundIDBDatabaseFileChild* aActor) const {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aActor);

  delete aActor;
  return true;
}

already_AddRefed<PBackgroundIDBVersionChangeTransactionChild>
BackgroundDatabaseChild::AllocPBackgroundIDBVersionChangeTransactionChild(
    const uint64_t aCurrentVersion, const uint64_t aRequestedVersion,
    const int64_t aNextObjectStoreId, const int64_t aNextIndexId) {
  AssertIsOnOwningThread();

  return RefPtr{new BackgroundVersionChangeTransactionChild(
                    mOpenRequestActor->GetOpenDBRequest())}
      .forget();
}

mozilla::ipc::IPCResult
BackgroundDatabaseChild::RecvPBackgroundIDBVersionChangeTransactionConstructor(
    PBackgroundIDBVersionChangeTransactionChild* aActor,
    const uint64_t& aCurrentVersion, const uint64_t& aRequestedVersion,
    const int64_t& aNextObjectStoreId, const int64_t& aNextIndexId) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aActor);
  MOZ_ASSERT(mOpenRequestActor);

  MaybeCollectGarbageOnIPCMessage();

  auto* const actor =
      static_cast<BackgroundVersionChangeTransactionChild*>(aActor);

  if (!EnsureDOMObject()) {
    NS_WARNING("Factory is already disconnected from global");

    actor->SendDeleteMeInternal(true);

    // XXX This is a hack to ensure that transaction/request serial numbers stay
    // in sync between parent and child. Actually, it might be better to create
    // an IDBTransaction in the child and abort that.
    Unused
        << mozilla::ipc::BackgroundChildImpl::GetThreadLocalForCurrentThread()
               ->mIndexedDBThreadLocal->NextTransactionSN(
                   IDBTransaction::Mode::VersionChange);
    Unused << IDBRequest::NextSerialNumber();

    // No reason to IPC_FAIL here.
    return IPC_OK();
  }

  MOZ_ASSERT(!mDatabase->IsInvalidated());

  // XXX NotNull might encapsulate this
  const auto request =
      WrapNotNullUnchecked(RefPtr{mOpenRequestActor->GetOpenDBRequest().get()});

  SafeRefPtr<IDBTransaction> transaction = IDBTransaction::CreateVersionChange(
      mDatabase, actor, request, aNextObjectStoreId, aNextIndexId);
  MOZ_ASSERT(transaction);

  transaction->AssertIsOnOwningThread();

  actor->SetDOMTransaction(transaction.clonePtr());

  const auto database = WrapNotNull(mDatabase);

  database->EnterSetVersionTransaction(aRequestedVersion);

  request->SetTransaction(transaction.clonePtr());

  RefPtr<Event> upgradeNeededEvent = IDBVersionChangeEvent::Create(
      request.get(), nsDependentString(kUpgradeNeededEventType),
      aCurrentVersion, aRequestedVersion);
  MOZ_ASSERT(upgradeNeededEvent);

  SetResultAndDispatchSuccessEvent(
      WrapNotNullUnchecked<RefPtr<IDBRequest>>(request.get()), transaction,
      *database, std::move(upgradeNeededEvent));

  return IPC_OK();
}

mozilla::ipc::IPCResult BackgroundDatabaseChild::RecvVersionChange(
    const uint64_t aOldVersion, const Maybe<uint64_t> aNewVersion) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (!mDatabase || mDatabase->IsClosed()) {
    return IPC_OK();
  }

  RefPtr<IDBDatabase> kungFuDeathGrip = mDatabase;

  // Handle bfcache'd windows.
  if (nsGlobalWindowInner* owner = kungFuDeathGrip->GetOwnerWindow()) {
    // The database must be closed if the window is already frozen.
    bool shouldAbortAndClose = owner->IsFrozen();

    // Anything in the bfcache has to be evicted and then we have to close the
    // database also.
    if (owner->RemoveFromBFCacheSync()) {
      shouldAbortAndClose = true;
    }

    if (shouldAbortAndClose) {
      // Invalidate() doesn't close the database in the parent, so we have
      // to call Close() and AbortTransactions() manually.
      kungFuDeathGrip->AbortTransactions(/* aShouldWarn */ false);
      kungFuDeathGrip->Close();
      return IPC_OK();
    }
  }

  // Otherwise fire a versionchange event.
  const nsDependentString type(kVersionChangeEventType);

  RefPtr<Event> versionChangeEvent;

  if (aNewVersion.isNothing()) {
    versionChangeEvent =
        IDBVersionChangeEvent::Create(kungFuDeathGrip, type, aOldVersion);
    MOZ_ASSERT(versionChangeEvent);
  } else {
    versionChangeEvent = IDBVersionChangeEvent::Create(
        kungFuDeathGrip, type, aOldVersion, aNewVersion.value());
    MOZ_ASSERT(versionChangeEvent);
  }

  IDB_LOG_MARK("Child : Firing \"versionchange\" event",
               "C: IDBDatabase \"versionchange\" event", IDB_LOG_ID_STRING());

  IgnoredErrorResult rv;
  kungFuDeathGrip->DispatchEvent(*versionChangeEvent, rv);
  if (rv.Failed()) {
    NS_WARNING("Failed to dispatch event!");
  }

  if (!kungFuDeathGrip->IsClosed()) {
    SendBlocked();
  }

  return IPC_OK();
}

mozilla::ipc::IPCResult BackgroundDatabaseChild::RecvInvalidate() {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (mDatabase) {
    mDatabase->Invalidate();
  } else {
    mPendingInvalidate = true;
  }

  return IPC_OK();
}

mozilla::ipc::IPCResult
BackgroundDatabaseChild::RecvCloseAfterInvalidationComplete() {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (mDatabase) {
    mDatabase->DispatchTrustedEvent(nsDependentString(kCloseEventType));
  }

  return IPC_OK();
}

/*******************************************************************************
 * BackgroundTransactionBase
 ******************************************************************************/

BackgroundTransactionBase::BackgroundTransactionBase(
    SafeRefPtr<IDBTransaction> aTransaction)
    : mTemporaryStrongTransaction(std::move(aTransaction)),
      mTransaction(mTemporaryStrongTransaction.unsafeGetRawPtr()) {
  MOZ_ASSERT(mTransaction);
  mTransaction->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(BackgroundTransactionBase);
}

#ifdef DEBUG

void BackgroundTransactionBase::AssertIsOnOwningThread() const {
  MOZ_ASSERT(mTransaction);
  mTransaction->AssertIsOnOwningThread();
}

#endif  // DEBUG

void BackgroundTransactionBase::NoteActorDestroyed() {
  AssertIsOnOwningThread();
  MOZ_ASSERT_IF(mTemporaryStrongTransaction, mTransaction);

  if (mTransaction) {
    mTransaction->ClearBackgroundActor();

    // Normally this would be DEBUG-only but NoteActorDestroyed is also called
    // from SendDeleteMeInternal. In that case we're going to receive an actual
    // ActorDestroy call later and we don't want to touch a dead object.
    mTemporaryStrongTransaction = nullptr;
    mTransaction = nullptr;
  }
}

void BackgroundTransactionBase::SetDOMTransaction(
    SafeRefPtr<IDBTransaction> aTransaction) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aTransaction);
  aTransaction->AssertIsOnOwningThread();
  MOZ_ASSERT(!mTemporaryStrongTransaction);
  MOZ_ASSERT(!mTransaction);

  mTemporaryStrongTransaction = std::move(aTransaction);
  mTransaction = mTemporaryStrongTransaction.unsafeGetRawPtr();
}

void BackgroundTransactionBase::NoteComplete() {
  AssertIsOnOwningThread();
  MOZ_ASSERT_IF(mTransaction, mTemporaryStrongTransaction);

  mTemporaryStrongTransaction = nullptr;
}

/*******************************************************************************
 * BackgroundTransactionChild
 ******************************************************************************/

BackgroundTransactionChild::BackgroundTransactionChild(
    SafeRefPtr<IDBTransaction> aTransaction)
    : BackgroundTransactionBase(std::move(aTransaction)) {
  MOZ_COUNT_CTOR(indexedDB::BackgroundTransactionChild);
}

BackgroundTransactionChild::~BackgroundTransactionChild() {
  MOZ_COUNT_DTOR(indexedDB::BackgroundTransactionChild);
}

#ifdef DEBUG

void BackgroundTransactionChild::AssertIsOnOwningThread() const {
  static_cast<BackgroundDatabaseChild*>(Manager())->AssertIsOnOwningThread();
}

#endif  // DEBUG

void BackgroundTransactionChild::SendDeleteMeInternal() {
  AssertIsOnOwningThread();

  if (mTransaction) {
    NoteActorDestroyed();

    MOZ_ALWAYS_TRUE(PBackgroundIDBTransactionChild::SendDeleteMe());
  }
}

void BackgroundTransactionChild::ActorDestroy(ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  NoteActorDestroyed();
}

mozilla::ipc::IPCResult BackgroundTransactionChild::RecvComplete(
    const nsresult aResult) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mTransaction);

  MaybeCollectGarbageOnIPCMessage();

  mTransaction->FireCompleteOrAbortEvents(aResult);

  NoteComplete();
  return IPC_OK();
}

PBackgroundIDBRequestChild*
BackgroundTransactionChild::AllocPBackgroundIDBRequestChild(
    const int64_t& aRequestId, const RequestParams& aParams) {
  MOZ_CRASH(
      "PBackgroundIDBRequestChild actors should be manually "
      "constructed!");
}

bool BackgroundTransactionChild::DeallocPBackgroundIDBRequestChild(
    PBackgroundIDBRequestChild* aActor) {
  MOZ_ASSERT(aActor);

  delete static_cast<BackgroundRequestChild*>(aActor);
  return true;
}

PBackgroundIDBCursorChild*
BackgroundTransactionChild::AllocPBackgroundIDBCursorChild(
    const int64_t& aRequestId, const OpenCursorParams& aParams) {
  AssertIsOnOwningThread();

  MOZ_CRASH("PBackgroundIDBCursorChild actors should be manually constructed!");
}

bool BackgroundTransactionChild::DeallocPBackgroundIDBCursorChild(
    PBackgroundIDBCursorChild* aActor) {
  MOZ_ASSERT(aActor);

  delete aActor;
  return true;
}

/*******************************************************************************
 * BackgroundVersionChangeTransactionChild
 ******************************************************************************/

BackgroundVersionChangeTransactionChild::
    BackgroundVersionChangeTransactionChild(IDBOpenDBRequest* aOpenDBRequest)
    : mOpenDBRequest(aOpenDBRequest) {
  MOZ_ASSERT(aOpenDBRequest);
  aOpenDBRequest->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundVersionChangeTransactionChild);
}

BackgroundVersionChangeTransactionChild::
    ~BackgroundVersionChangeTransactionChild() {
  AssertIsOnOwningThread();

  MOZ_COUNT_DTOR(indexedDB::BackgroundVersionChangeTransactionChild);
}

#ifdef DEBUG

void BackgroundVersionChangeTransactionChild::AssertIsOnOwningThread() const {
  static_cast<BackgroundDatabaseChild*>(Manager())->AssertIsOnOwningThread();
}

#endif  // DEBUG

void BackgroundVersionChangeTransactionChild::SendDeleteMeInternal(
    bool aFailedConstructor) {
  AssertIsOnOwningThread();

  if (mTransaction || aFailedConstructor) {
    NoteActorDestroyed();

    MOZ_ALWAYS_TRUE(
        PBackgroundIDBVersionChangeTransactionChild::SendDeleteMe());
  }
}

void BackgroundVersionChangeTransactionChild::ActorDestroy(
    ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  mOpenDBRequest = nullptr;

  NoteActorDestroyed();
}

mozilla::ipc::IPCResult BackgroundVersionChangeTransactionChild::RecvComplete(
    const nsresult aResult) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  if (!mTransaction) {
    return IPC_OK();
  }

  MOZ_ASSERT(mOpenDBRequest);

  IDBDatabase* database = mTransaction->Database();
  MOZ_ASSERT(database);

  database->ExitSetVersionTransaction();

  if (NS_FAILED(aResult)) {
    database->Close();
  }

  RefPtr<IDBOpenDBRequest> request = mOpenDBRequest;
  MOZ_ASSERT(request);

  mTransaction->FireCompleteOrAbortEvents(aResult);

  request->SetTransaction(nullptr);
  request = nullptr;

  mOpenDBRequest = nullptr;

  NoteComplete();
  return IPC_OK();
}

PBackgroundIDBRequestChild*
BackgroundVersionChangeTransactionChild::AllocPBackgroundIDBRequestChild(
    const int64_t& aRequestId, const RequestParams& aParams) {
  MOZ_CRASH(
      "PBackgroundIDBRequestChild actors should be manually "
      "constructed!");
}

bool BackgroundVersionChangeTransactionChild::DeallocPBackgroundIDBRequestChild(
    PBackgroundIDBRequestChild* aActor) {
  MOZ_ASSERT(aActor);

  delete static_cast<BackgroundRequestChild*>(aActor);
  return true;
}

PBackgroundIDBCursorChild*
BackgroundVersionChangeTransactionChild::AllocPBackgroundIDBCursorChild(
    const int64_t& aRequestId, const OpenCursorParams& aParams) {
  AssertIsOnOwningThread();

  MOZ_CRASH("PBackgroundIDBCursorChild actors should be manually constructed!");
}

bool BackgroundVersionChangeTransactionChild::DeallocPBackgroundIDBCursorChild(
    PBackgroundIDBCursorChild* aActor) {
  MOZ_ASSERT(aActor);

  delete aActor;
  return true;
}

/*******************************************************************************
 * BackgroundRequestChild
 ******************************************************************************/

BackgroundRequestChild::BackgroundRequestChild(
    MovingNotNull<RefPtr<IDBRequest>> aRequest)
    : BackgroundRequestChildBase(std::move(aRequest)),
      mTransaction(mRequest->AcquireTransaction()),
      mRunningPreprocessHelpers(0),
      mCurrentCloneDataIndex(0),
      mPreprocessResultCode(NS_OK),
      mGetAll(false) {
  MOZ_ASSERT(mTransaction);
  mTransaction->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundRequestChild);
}

BackgroundRequestChild::~BackgroundRequestChild() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(!mTransaction);

  MOZ_COUNT_DTOR(indexedDB::BackgroundRequestChild);
}

void BackgroundRequestChild::MaybeSendContinue() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mRunningPreprocessHelpers > 0);

  if (--mRunningPreprocessHelpers == 0) {
    PreprocessResponse response;

    if (NS_SUCCEEDED(mPreprocessResultCode)) {
      if (mGetAll) {
        response = ObjectStoreGetAllPreprocessResponse();
      } else {
        response = ObjectStoreGetPreprocessResponse();
      }
    } else {
      response = mPreprocessResultCode;
    }

    MOZ_ALWAYS_TRUE(SendContinue(response));
  }
}

void BackgroundRequestChild::OnPreprocessFinished(
    uint32_t aCloneDataIndex, UniquePtr<JSStructuredCloneData> aCloneData) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aCloneDataIndex < mCloneInfos.Length());
  MOZ_ASSERT(aCloneData);

  auto& cloneInfo = mCloneInfos[aCloneDataIndex];
  MOZ_ASSERT(cloneInfo.mPreprocessHelper);
  MOZ_ASSERT(!cloneInfo.mCloneData);

  cloneInfo.mCloneData = std::move(aCloneData);

  MaybeSendContinue();

  cloneInfo.mPreprocessHelper = nullptr;
}

void BackgroundRequestChild::OnPreprocessFailed(uint32_t aCloneDataIndex,
                                                nsresult aErrorCode) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aCloneDataIndex < mCloneInfos.Length());
  MOZ_ASSERT(NS_FAILED(aErrorCode));

  auto& cloneInfo = mCloneInfos[aCloneDataIndex];
  MOZ_ASSERT(cloneInfo.mPreprocessHelper);
  MOZ_ASSERT(!cloneInfo.mCloneData);

  if (NS_SUCCEEDED(mPreprocessResultCode)) {
    mPreprocessResultCode = aErrorCode;
  }

  MaybeSendContinue();

  cloneInfo.mPreprocessHelper = nullptr;
}

UniquePtr<JSStructuredCloneData> BackgroundRequestChild::GetNextCloneData() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mCurrentCloneDataIndex < mCloneInfos.Length());
  MOZ_ASSERT(mCloneInfos[mCurrentCloneDataIndex].mCloneData);

  return std::move(mCloneInfos[mCurrentCloneDataIndex++].mCloneData);
}

void BackgroundRequestChild::HandleResponse(nsresult aResponse) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(NS_FAILED(aResponse));
  MOZ_ASSERT(NS_ERROR_GET_MODULE(aResponse) == NS_ERROR_MODULE_DOM_INDEXEDDB);
  MOZ_ASSERT(mTransaction);

  DispatchErrorEvent(mRequest, aResponse, mTransaction.clonePtr());
}

void BackgroundRequestChild::HandleResponse(const Key& aResponse) {
  AssertIsOnOwningThread();

  SetResultAndDispatchSuccessEvent(mRequest, AcquireTransaction(), aResponse);
}

void BackgroundRequestChild::HandleResponse(const nsTArray<Key>& aResponse) {
  AssertIsOnOwningThread();

  SetResultAndDispatchSuccessEvent(mRequest, AcquireTransaction(), aResponse);
}

void BackgroundRequestChild::HandleResponse(
    SerializedStructuredCloneReadInfo&& aResponse) {
  AssertIsOnOwningThread();

  if (!mTransaction->Database()->GetOwnerGlobal()) {
    // Ignore the response, since we have already been disconnected from the
    // global.
    return;
  }

  auto cloneReadInfo = DeserializeStructuredCloneReadInfo(
      std::move(aResponse), mTransaction->Database(),
      [this] { return std::move(*GetNextCloneData()); });

  SetResultAndDispatchSuccessEvent(mRequest, AcquireTransaction(),
                                   cloneReadInfo);
}

void BackgroundRequestChild::HandleResponse(
    nsTArray<SerializedStructuredCloneReadInfo>&& aResponse) {
  AssertIsOnOwningThread();

  if (!mTransaction->Database()->GetOwnerGlobal()) {
    // Ignore the response, since we have already been disconnected from the
    // global.
    return;
  }

  nsTArray<StructuredCloneReadInfoChild> cloneReadInfos;

  QM_TRY(OkIf(cloneReadInfos.SetCapacity(aResponse.Length(), fallible)),
         QM_VOID, ([&aResponse, this](const auto) {
           // Since we are under memory pressure, release aResponse early.
           aResponse.Clear();

           DispatchErrorEvent(mRequest, NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR,
                              AcquireTransaction());

           MOZ_ASSERT(mTransaction->IsAborted());
         }));

  std::transform(std::make_move_iterator(aResponse.begin()),
                 std::make_move_iterator(aResponse.end()),
                 MakeBackInserter(cloneReadInfos),
                 [database = mTransaction->Database(), this](
                     SerializedStructuredCloneReadInfo&& serializedCloneInfo) {
                   return DeserializeStructuredCloneReadInfo(
                       std::move(serializedCloneInfo), database,
                       [this] { return std::move(*GetNextCloneData()); });
                 });

  SetResultAndDispatchSuccessEvent(mRequest, AcquireTransaction(),
                                   cloneReadInfos);
}

void BackgroundRequestChild::HandleResponse(JS::Handle<JS::Value> aResponse) {
  AssertIsOnOwningThread();

  SetResultAndDispatchSuccessEvent(
      mRequest, AcquireTransaction(),
      const_cast<const JS::Handle<JS::Value>&>(aResponse));
}

void BackgroundRequestChild::HandleResponse(const uint64_t aResponse) {
  AssertIsOnOwningThread();

  SetResultAndDispatchSuccessEvent(mRequest, AcquireTransaction(), aResponse);
}

nsresult BackgroundRequestChild::HandlePreprocess(
    const PreprocessInfo& aPreprocessInfo) {
  return HandlePreprocessInternal(
      AutoTArray<PreprocessInfo, 1>{aPreprocessInfo});
}

nsresult BackgroundRequestChild::HandlePreprocess(
    const nsTArray<PreprocessInfo>& aPreprocessInfos) {
  AssertIsOnOwningThread();
  mGetAll = true;

  return HandlePreprocessInternal(aPreprocessInfos);
}

nsresult BackgroundRequestChild::HandlePreprocessInternal(
    const nsTArray<PreprocessInfo>& aPreprocessInfos) {
  AssertIsOnOwningThread();

  IDBDatabase* database = mTransaction->Database();

  const uint32_t count = aPreprocessInfos.Length();

  mCloneInfos.SetLength(count);

  // TODO: Since we use the stream transport service, this can spawn 25 threads
  //       and has the potential to cause some annoying browser hiccups.
  //       Consider using a single thread or a very small threadpool.
  for (uint32_t index = 0; index < count; index++) {
    const PreprocessInfo& preprocessInfo = aPreprocessInfos[index];

    const auto files =
        DeserializeStructuredCloneFiles(database, preprocessInfo.files(),
                                        /* aForPreprocess */ true);

    MOZ_ASSERT(files.Length() == 1);

    auto& preprocessHelper = mCloneInfos[index].mPreprocessHelper;
    preprocessHelper = MakeRefPtr<PreprocessHelper>(index, this);

    nsresult rv = preprocessHelper->Init(files[0]);
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    rv = preprocessHelper->Dispatch();
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    mRunningPreprocessHelpers++;
  }

  return NS_OK;
}

void BackgroundRequestChild::ActorDestroy(ActorDestroyReason aWhy) {
  AssertIsOnOwningThread();

  MaybeCollectGarbageOnIPCMessage();

  for (auto& cloneInfo : mCloneInfos) {
    const auto& preprocessHelper = cloneInfo.mPreprocessHelper;

    if (preprocessHelper) {
      preprocessHelper->ClearActor();
    }
  }
  mCloneInfos.Clear();

  if (mTransaction) {
    mTransaction->AssertIsOnOwningThread();

    mTransaction->OnRequestFinished(/* aRequestCompletedSuccessfully */
                                    aWhy == Deletion);
#ifdef DEBUG
    mTransaction = nullptr;
#endif
  }
}

mozilla::ipc::IPCResult BackgroundRequestChild::Recv__delete__(
    RequestResponse&& aResponse) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mTransaction);

  MaybeCollectGarbageOnIPCMessage();

  if (mTransaction->IsAborted()) {
    // Always fire an "error" event with ABORT_ERR if the transaction was
    // aborted, even if the request succeeded or failed with another error.
    HandleResponse(NS_ERROR_DOM_INDEXEDDB_ABORT_ERR);
  } else {
    switch (aResponse.type()) {
      case RequestResponse::Tnsresult:
        HandleResponse(aResponse.get_nsresult());
        break;

      case RequestResponse::TObjectStoreAddResponse:
        HandleResponse(aResponse.get_ObjectStoreAddResponse().key());
        break;

      case RequestResponse::TObjectStorePutResponse:
        HandleResponse(aResponse.get_ObjectStorePutResponse().key());
        break;

      case RequestResponse::TObjectStoreGetResponse:
        HandleResponse(
            std::move(aResponse.get_ObjectStoreGetResponse().cloneInfo()));
        break;

      case RequestResponse::TObjectStoreGetKeyResponse:
        HandleResponse(aResponse.get_ObjectStoreGetKeyResponse().key());
        break;

      case RequestResponse::TObjectStoreGetAllResponse:
        HandleResponse(
            std::move(aResponse.get_ObjectStoreGetAllResponse().cloneInfos()));
        break;

      case RequestResponse::TObjectStoreGetAllKeysResponse:
        HandleResponse(aResponse.get_ObjectStoreGetAllKeysResponse().keys());
        break;

      case RequestResponse::TObjectStoreDeleteResponse:
      case RequestResponse::TObjectStoreClearResponse:
        HandleResponse(JS::UndefinedHandleValue);
        break;

      case RequestResponse::TObjectStoreCountResponse:
        HandleResponse(aResponse.get_ObjectStoreCountResponse().count());
        break;

      case RequestResponse::TIndexGetResponse:
        HandleResponse(std::move(aResponse.get_IndexGetResponse().cloneInfo()));
        break;

      case RequestResponse::TIndexGetKeyResponse:
        HandleResponse(aResponse.get_IndexGetKeyResponse().key());
        break;

      case RequestResponse::TIndexGetAllResponse:
        HandleResponse(
            std::move(aResponse.get_IndexGetAllResponse().cloneInfos()));
        break;

      case RequestResponse::TIndexGetAllKeysResponse:
        HandleResponse(aResponse.get_IndexGetAllKeysResponse().keys());
        break;

      case RequestResponse::TIndexCountResponse:
        HandleResponse(aResponse.get_IndexCountResponse().count());
        break;

      default:
        return IPC_FAIL(this, "Unknown response type!");
    }
  }

  mTransaction->OnRequestFinished(/* aRequestCompletedSuccessfully */ true);

  // Null this out so that we don't try to call OnRequestFinished() again in
  // ActorDestroy.
  mTransaction = nullptr;

  return IPC_OK();
}

mozilla::ipc::IPCResult BackgroundRequestChild::RecvPreprocess(
    const PreprocessParams& aParams) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mTransaction);

  MaybeCollectGarbageOnIPCMessage();

  nsresult rv;

  switch (aParams.type()) {
    case PreprocessParams::TObjectStoreGetPreprocessParams: {
      const auto& params = aParams.get_ObjectStoreGetPreprocessParams();

      rv = HandlePreprocess(params.preprocessInfo());

      break;
    }

    case PreprocessParams::TObjectStoreGetAllPreprocessParams: {
      const auto& params = aParams.get_ObjectStoreGetAllPreprocessParams();

      rv = HandlePreprocess(params.preprocessInfos());

      break;
    }

    default:
      return IPC_FAIL(this, "Unknown params type!");
  }

  if (NS_WARN_IF(NS_FAILED(rv))) {
    QM_WARNONLY_TRY(OkIf(SendContinue(rv)));
  }

  return IPC_OK();
}

nsresult BackgroundRequestChild::PreprocessHelper::Init(
    const StructuredCloneFileChild& aFile) {
  AssertIsOnOwningThread();
  MOZ_ASSERT(aFile.HasBlob());
  MOZ_ASSERT(aFile.Type() == StructuredCloneFileBase::eStructuredClone);
  MOZ_ASSERT(mState == State::Initial);

  // The stream transport service is used for asynchronous processing. It has a
  // threadpool with a high cap of 25 threads. Fortunately, the service can be
  // used on workers too.
  nsCOMPtr<nsIEventTarget> target =
      do_GetService(NS_STREAMTRANSPORTSERVICE_CONTRACTID);
  MOZ_ASSERT(target);

  // We use a TaskQueue here in order to be sure that the events are dispatched
  // in the correct order. This is not guaranteed in case we use the I/O thread
  // directly.
  mTaskQueue = TaskQueue::Create(target.forget(), "BackgroundRequestChild");

  ErrorResult errorResult;

  nsCOMPtr<nsIInputStream> stream;
  // XXX After Bug 1620560, MutableBlob is not needed here anymore.
  aFile.MutableBlob().CreateInputStream(getter_AddRefs(stream), errorResult);
  if (NS_WARN_IF(errorResult.Failed())) {
    return errorResult.StealNSResult();
  }

  mStream = std::move(stream);

  mCloneData = MakeUnique<JSStructuredCloneData>(
      JS::StructuredCloneScope::DifferentProcessForIndexedDB);

  return NS_OK;
}

nsresult BackgroundRequestChild::PreprocessHelper::Dispatch() {
  AssertIsOnOwningThread();
  MOZ_ASSERT(mState == State::Initial);

  nsresult rv = mTaskQueue->Dispatch(this, NS_DISPATCH_NORMAL);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  return NS_OK;
}

nsresult BackgroundRequestChild::PreprocessHelper::Start() {
  MOZ_ASSERT(!IsOnOwningThread());
  MOZ_ASSERT(mStream);
  MOZ_ASSERT(mState == State::Initial);

  nsresult rv;

  PRFileDesc* fileDesc = GetFileDescriptorFromStream(mStream);
  if (fileDesc) {
    rv = ProcessStream();
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    return NS_OK;
  }

  mState = State::WaitingForStreamReady;

  nsCOMPtr<nsIAsyncFileMetadata> asyncFileMetadata = do_QueryInterface(mStream);
  if (asyncFileMetadata) {
    rv = asyncFileMetadata->AsyncFileMetadataWait(this, mTaskQueue);
    if (NS_WARN_IF(NS_FAILED(rv))) {
      return rv;
    }

    return NS_OK;
  }

  nsCOMPtr<nsIAsyncInputStream> asyncStream = do_QueryInterface(mStream);
  if (!asyncStream) {
    return NS_ERROR_NO_INTERFACE;
  }

  rv = asyncStream->AsyncWait(this, 0, 0, mTaskQueue);
  if (NS_WARN_IF(NS_FAILED(rv))) {
    return rv;
  }

  return NS_OK;
}

nsresult BackgroundRequestChild::PreprocessHelper::ProcessStream() {
  MOZ_ASSERT(!IsOnOwningThread());
  MOZ_ASSERT(mStream);
  MOZ_ASSERT(mState == State::Initial ||
             mState == State::WaitingForStreamReady);

  // We need to get the internal stream (which is an nsFileInputStream) because
  // SnappyUncompressInputStream doesn't support reading from async input
  // streams.

  nsCOMPtr<mozIRemoteLazyInputStream> blobInputStream =
      do_QueryInterface(mStream);
  MOZ_ASSERT(blobInputStream);

  nsCOMPtr<nsIInputStream> internalInputStream;
  MOZ_ALWAYS_SUCCEEDS(
      blobInputStream->TakeInternalStream(getter_AddRefs(internalInputStream)));
  MOZ_ASSERT(internalInputStream);

  QM_TRY(MOZ_TO_RESULT(
      SnappyUncompressStructuredCloneData(*internalInputStream, *mCloneData)));

  mState = State::Finishing;

  QM_TRY(MOZ_TO_RESULT(mOwningEventTarget->Dispatch(this, NS_DISPATCH_NORMAL)));

  return NS_OK;
}

void BackgroundRequestChild::PreprocessHelper::Finish() {
  AssertIsOnOwningThread();

  if (mActor) {
    if (NS_SUCCEEDED(mResultCode)) {
      mActor->OnPreprocessFinished(mCloneDataIndex, std::move(mCloneData));

      MOZ_ASSERT(!mCloneData);
    } else {
      mActor->OnPreprocessFailed(mCloneDataIndex, mResultCode);
    }
  }

  mState = State::Completed;
}

NS_IMPL_ISUPPORTS_INHERITED(BackgroundRequestChild::PreprocessHelper,
                            DiscardableRunnable, nsIInputStreamCallback,
                            nsIFileMetadataCallback)

NS_IMETHODIMP
BackgroundRequestChild::PreprocessHelper::Run() {
  nsresult rv;

  switch (mState) {
    case State::Initial:
      rv = Start();
      break;

    case State::WaitingForStreamReady:
      rv = ProcessStream();
      break;

    case State::Finishing:
      Finish();
      return NS_OK;

    default:
      MOZ_CRASH("Bad state!");
  }

  if (NS_WARN_IF(NS_FAILED(rv)) && mState != State::Finishing) {
    if (NS_SUCCEEDED(mResultCode)) {
      mResultCode = rv;
    }

    // Must set mState before dispatching otherwise we will race with the owning
    // thread.
    mState = State::Finishing;

    if (IsOnOwningThread()) {
      Finish();
    } else {
      MOZ_ALWAYS_SUCCEEDS(
          mOwningEventTarget->Dispatch(this, NS_DISPATCH_NORMAL));
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
BackgroundRequestChild::PreprocessHelper::OnInputStreamReady(
    nsIAsyncInputStream* aStream) {
  MOZ_ASSERT(!IsOnOwningThread());
  MOZ_ASSERT(mState == State::WaitingForStreamReady);

  MOZ_ALWAYS_SUCCEEDS(this->Run());

  return NS_OK;
}

NS_IMETHODIMP
BackgroundRequestChild::PreprocessHelper::OnFileMetadataReady(
    nsIAsyncFileMetadata* aObject) {
  MOZ_ASSERT(!IsOnOwningThread());
  MOZ_ASSERT(mState == State::WaitingForStreamReady);

  MOZ_ALWAYS_SUCCEEDS(this->Run());

  return NS_OK;
}

/*******************************************************************************
 * BackgroundCursorChild
 ******************************************************************************/

BackgroundCursorChildBase::BackgroundCursorChildBase(
    const NotNull<IDBRequest*> aRequest, const Direction aDirection)
    : mRequest(aRequest),
      mTransaction(aRequest->MaybeTransactionRef()),
      mStrongRequest(aRequest),
      mDirection(aDirection) {
  MOZ_ASSERT(mTransaction);
}

MovingNotNull<RefPtr<IDBRequest>> BackgroundCursorChildBase::AcquireRequest()
    const {
  AssertIsOnOwningThread();

  // XXX This could be encapsulated by NotNull
  return WrapNotNullUnchecked(RefPtr{mRequest->get()});
}

template <IDBCursorType CursorType>
BackgroundCursorChild<CursorType>::BackgroundCursorChild(
    const NotNull<IDBRequest*> aRequest, SourceType* aSource,
    Direction aDirection)
    : BackgroundCursorChildBase(aRequest, aDirection),
      mSource(WrapNotNull(aSource)),
      mCursor(nullptr),
      mInFlightResponseInvalidationNeeded(false) {
  aSource->AssertIsOnOwningThread();

  MOZ_COUNT_CTOR(indexedDB::BackgroundCursorChild<CursorType>);
}

template <IDBCursorType CursorType>
BackgroundCursorChild<CursorType>::~BackgroundCursorChild() {
  MOZ_COUNT_DTOR(indexedDB::BackgroundCursorChild<CursorType>);
}

template <IDBCursorType CursorType>
SafeRefPtr<BackgroundCursorChild<CursorType>>
BackgroundCursorChild<CursorType>::SafeRefPtrFromThis() {
  return BackgroundCursorChildBase::SafeRefPtrFromThis()
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