1 files changed, 960 insertions, 0 deletions
diff --git a/dom/file/ipc/RemoteLazyInputStream.cpp b/dom/file/ipc/RemoteLazyInputStream.cpp
new file mode 100644
index 0000000000..10e2e41633
--- /dev/null
+++ b/dom/file/ipc/RemoteLazyInputStream.cpp
@@ -0,0 +1,960 @@
+/* -*- 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 "RemoteLazyInputStream.h"
+#include "RemoteLazyInputStreamChild.h"
+#include "RemoteLazyInputStreamParent.h"
+#include "mozilla/ipc/InputStreamParams.h"
+#include "mozilla/net/SocketProcessParent.h"
+#include "mozilla/SlicedInputStream.h"
+#include "mozilla/NonBlockingAsyncInputStream.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIAsyncOutputStream.h"
+#include "nsIPipe.h"
+#include "nsNetUtil.h"
+#include "nsStreamUtils.h"
+#include "nsStringStream.h"
+#include "RemoteLazyInputStreamStorage.h"
+#include "RemoteLazyInputStreamThread.h"
+
+namespace mozilla {
+
+using namespace dom;
+using net::SocketProcessParent;
+
+class RemoteLazyInputStream;
+
+namespace {
+
+class InputStreamCallbackRunnable final : public DiscardableRunnable {
+ public:
+  // Note that the execution can be synchronous in case the event target is
+  // null.
+  static void Execute(nsIInputStreamCallback* aCallback,
+                      nsIEventTarget* aEventTarget,
+                      RemoteLazyInputStream* aStream) {
+    MOZ_ASSERT(aCallback);
+
+    RefPtr<InputStreamCallbackRunnable> runnable =
+        new InputStreamCallbackRunnable(aCallback, aStream);
+
+    nsCOMPtr<nsIEventTarget> target = aEventTarget;
+    if (aEventTarget) {
+      target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+    } else {
+      runnable->Run();
+    }
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnInputStreamReady(mStream);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  InputStreamCallbackRunnable(nsIInputStreamCallback* aCallback,
+                              RemoteLazyInputStream* aStream)
+      : DiscardableRunnable("dom::InputStreamCallbackRunnable"),
+        mCallback(aCallback),
+        mStream(aStream) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  nsCOMPtr<nsIInputStreamCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+};
+
+class FileMetadataCallbackRunnable final : public DiscardableRunnable {
+ public:
+  static void Execute(nsIFileMetadataCallback* aCallback,
+                      nsIEventTarget* aEventTarget,
+                      RemoteLazyInputStream* aStream) {
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT(aEventTarget);
+
+    RefPtr<FileMetadataCallbackRunnable> runnable =
+        new FileMetadataCallbackRunnable(aCallback, aStream);
+
+    nsCOMPtr<nsIEventTarget> target = aEventTarget;
+    target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnFileMetadataReady(mStream);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  FileMetadataCallbackRunnable(nsIFileMetadataCallback* aCallback,
+                               RemoteLazyInputStream* aStream)
+      : DiscardableRunnable("dom::FileMetadataCallbackRunnable"),
+        mCallback(aCallback),
+        mStream(aStream) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  nsCOMPtr<nsIFileMetadataCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+};
+
+}  // namespace
+
+NS_IMPL_ADDREF(RemoteLazyInputStream);
+NS_IMPL_RELEASE(RemoteLazyInputStream);
+
+NS_INTERFACE_MAP_BEGIN(RemoteLazyInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamCallback)
+  NS_INTERFACE_MAP_ENTRY(nsICloneableInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsICloneableInputStreamWithRange)
+  NS_INTERFACE_MAP_ENTRY(nsIIPCSerializableInputStream)
+  NS_INTERFACE_MAP_ENTRY(nsIFileMetadata)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncFileMetadata)
+  NS_INTERFACE_MAP_ENTRY(nsIInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(nsIAsyncInputStreamLength)
+  NS_INTERFACE_MAP_ENTRY(mozIRemoteLazyInputStream)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIInputStream)
+NS_INTERFACE_MAP_END
+
+RemoteLazyInputStream::RemoteLazyInputStream(RemoteLazyInputStreamChild* aActor)
+    : mActor(aActor),
+      mState(eInit),
+      mStart(0),
+      mLength(0),
+      mConsumed(false),
+      mMutex("RemoteLazyInputStream::mMutex") {
+  MOZ_ASSERT(aActor);
+
+  mLength = aActor->Size();
+
+  if (XRE_IsParentProcess()) {
+    nsCOMPtr<nsIInputStream> stream;
+    auto storage = RemoteLazyInputStreamStorage::Get().unwrapOr(nullptr);
+    if (storage) {
+      storage->GetStream(mActor->ID(), 0, mLength, getter_AddRefs(stream));
+      if (stream) {
+        mState = eRunning;
+        mRemoteStream = stream;
+      }
+    }
+  }
+}
+
+RemoteLazyInputStream::~RemoteLazyInputStream() { Close(); }
+
+// nsIInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Available(uint64_t* aLength) {
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // We don't have a remoteStream yet: let's return 0.
+    if (mState == eInit || mState == ePending) {
+      *aLength = 0;
+      return NS_OK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mRemoteStream || mAsyncRemoteStream);
+
+    nsresult rv = EnsureAsyncRemoteStream(lock);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    asyncRemoteStream = mAsyncRemoteStream;
+  }
+
+  MOZ_ASSERT(asyncRemoteStream);
+  return asyncRemoteStream->Available(aLength);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Read(char* aBuffer, uint32_t aCount,
+                            uint32_t* aReadCount) {
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // Read is not available is we don't have a remoteStream.
+    if (mState == eInit || mState == ePending) {
+      return NS_BASE_STREAM_WOULD_BLOCK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mRemoteStream || mAsyncRemoteStream);
+
+    nsresult rv = EnsureAsyncRemoteStream(lock);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    asyncRemoteStream = mAsyncRemoteStream;
+  }
+
+  MOZ_ASSERT(asyncRemoteStream);
+  nsresult rv = asyncRemoteStream->Read(aBuffer, aCount, aReadCount);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  {
+    MutexAutoLock lock(mMutex);
+    mConsumed = true;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
+                                    uint32_t aCount, uint32_t* aResult) {
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // ReadSegments is not available is we don't have a remoteStream.
+    if (mState == eInit || mState == ePending) {
+      return NS_BASE_STREAM_WOULD_BLOCK;
+    }
+
+    if (mState == eClosed) {
+      return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mRemoteStream || mAsyncRemoteStream);
+
+    nsresult rv = EnsureAsyncRemoteStream(lock);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    asyncRemoteStream = mAsyncRemoteStream;
+  }
+
+  MOZ_ASSERT(asyncRemoteStream);
+  nsresult rv =
+      asyncRemoteStream->ReadSegments(aWriter, aClosure, aCount, aResult);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // If some data has been read, we mark the stream as consumed.
+  if (*aResult != 0) {
+    MutexAutoLock lock(mMutex);
+    mConsumed = true;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::IsNonBlocking(bool* aNonBlocking) {
+  *aNonBlocking = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Close() {
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  nsCOMPtr<nsIInputStream> remoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    if (mActor) {
+      mActor->ForgetStream(this);
+      mActor = nullptr;
+    }
+
+    asyncRemoteStream.swap(mAsyncRemoteStream);
+    remoteStream.swap(mRemoteStream);
+
+    mInputStreamCallback = nullptr;
+    mInputStreamCallbackEventTarget = nullptr;
+
+    mFileMetadataCallback = nullptr;
+    mFileMetadataCallbackEventTarget = nullptr;
+
+    mState = eClosed;
+  }
+
+  if (asyncRemoteStream) {
+    asyncRemoteStream->CloseWithStatus(NS_BASE_STREAM_CLOSED);
+  }
+
+  if (remoteStream) {
+    remoteStream->Close();
+  }
+
+  return NS_OK;
+}
+
+// nsICloneableInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetCloneable(bool* aCloneable) {
+  MutexAutoLock lock(mMutex);
+  *aCloneable = mState != eClosed;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Clone(nsIInputStream** aResult) {
+  MutexAutoLock lock(mMutex);
+
+  if (mState == eClosed) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  MOZ_ASSERT(mActor);
+
+  RefPtr<RemoteLazyInputStream> stream = mActor->CreateStream();
+  if (!stream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  stream->InitWithExistingRange(mStart, mLength, lock);
+
+  stream.forget(aResult);
+  return NS_OK;
+}
+
+// nsICloneableInputStreamWithRange interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::CloneWithRange(uint64_t aStart, uint64_t aLength,
+                                      nsIInputStream** aResult) {
+  MutexAutoLock lock(mMutex);
+
+  if (mState == eClosed) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  // Too short or out of range.
+  if (aLength == 0 || aStart >= mLength) {
+    return NS_NewCStringInputStream(aResult, ""_ns);
+  }
+
+  MOZ_ASSERT(mActor);
+
+  RefPtr<RemoteLazyInputStream> stream = mActor->CreateStream();
+  if (!stream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  CheckedInt<uint64_t> streamSize = mLength;
+  streamSize -= aStart;
+  if (!streamSize.isValid()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (aLength > streamSize.value()) {
+    aLength = streamSize.value();
+  }
+
+  stream->InitWithExistingRange(aStart + mStart, aLength, lock);
+
+  stream.forget(aResult);
+  return NS_OK;
+}
+
+// nsIAsyncInputStream interface
+
+NS_IMETHODIMP
+RemoteLazyInputStream::CloseWithStatus(nsresult aStatus) { return Close(); }
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncWait(nsIInputStreamCallback* aCallback,
+                                 uint32_t aFlags, uint32_t aRequestedCount,
+                                 nsIEventTarget* aEventTarget) {
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // See RemoteLazyInputStream.h for more information about this state
+    // machine.
+
+    switch (mState) {
+      // First call, we need to retrieve the stream from the parent actor.
+      case eInit:
+        MOZ_ASSERT(mActor);
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = aEventTarget;
+        mState = ePending;
+
+        mActor->StreamNeeded(this, aEventTarget);
+        return NS_OK;
+
+      // We are still waiting for the remote inputStream
+      case ePending: {
+        if (mInputStreamCallback && aCallback) {
+          return NS_ERROR_FAILURE;
+        }
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = aEventTarget;
+        return NS_OK;
+      }
+
+      // We have the remote inputStream, let's check if we can execute the
+      // callback.
+      case eRunning: {
+        if (mInputStreamCallback && aCallback) {
+          return NS_ERROR_FAILURE;
+        }
+
+        nsresult rv = EnsureAsyncRemoteStream(lock);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          return rv;
+        }
+
+        mInputStreamCallback = aCallback;
+        mInputStreamCallbackEventTarget = aEventTarget;
+
+        asyncRemoteStream = mAsyncRemoteStream;
+        break;
+      }
+
+      case eClosed:
+        [[fallthrough]];
+      default:
+        MOZ_ASSERT(mState == eClosed);
+        if (mInputStreamCallback && aCallback) {
+          return NS_ERROR_FAILURE;
+        }
+        break;
+    }
+  }
+
+  if (asyncRemoteStream) {
+    return asyncRemoteStream->AsyncWait(aCallback ? this : nullptr, 0, 0,
+                                        aEventTarget);
+  }
+
+  // if asyncRemoteStream is nullptr here, that probably means the stream has
+  // been closed and the callback can be executed immediately
+  InputStreamCallbackRunnable::Execute(aCallback, aEventTarget, this);
+  return NS_OK;
+}
+
+void RemoteLazyInputStream::StreamReady(
+    already_AddRefed<nsIInputStream> aInputStream) {
+  nsCOMPtr<nsIInputStream> inputStream = std::move(aInputStream);
+
+  // If inputStream is null, it means that the serialization went wrong or the
+  // stream is not available anymore. We keep the state as pending just to
+  // block any additional operation.
+
+  if (!inputStream) {
+    return;
+  }
+
+  nsCOMPtr<nsIFileMetadataCallback> fileMetadataCallback;
+  nsCOMPtr<nsIEventTarget> fileMetadataCallbackEventTarget;
+  nsCOMPtr<nsIInputStreamCallback> inputStreamCallback;
+  nsCOMPtr<nsIEventTarget> inputStreamCallbackEventTarget;
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // We have been closed in the meantime.
+    if (mState == eClosed) {
+      if (inputStream) {
+        MutexAutoUnlock unlock(mMutex);
+        inputStream->Close();
+      }
+      return;
+    }
+
+    // Now it's the right time to apply a slice if needed.
+    if (mStart > 0 || mLength < mActor->Size()) {
+      inputStream =
+          new SlicedInputStream(inputStream.forget(), mStart, mLength);
+    }
+
+    mRemoteStream = inputStream;
+
+    MOZ_ASSERT(mState == ePending);
+    mState = eRunning;
+
+    fileMetadataCallback.swap(mFileMetadataCallback);
+    fileMetadataCallbackEventTarget.swap(mFileMetadataCallbackEventTarget);
+
+    inputStreamCallback = mInputStreamCallback ? this : nullptr;
+    inputStreamCallbackEventTarget = mInputStreamCallbackEventTarget;
+
+    if (inputStreamCallback) {
+      nsresult rv = EnsureAsyncRemoteStream(lock);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return;
+      }
+
+      MOZ_ASSERT(mAsyncRemoteStream);
+      asyncRemoteStream = mAsyncRemoteStream;
+    }
+  }
+
+  if (fileMetadataCallback) {
+    FileMetadataCallbackRunnable::Execute(
+        fileMetadataCallback, fileMetadataCallbackEventTarget, this);
+  }
+
+  if (inputStreamCallback) {
+    MOZ_ASSERT(asyncRemoteStream);
+
+    nsresult rv = asyncRemoteStream->AsyncWait(inputStreamCallback, 0, 0,
+                                               inputStreamCallbackEventTarget);
+    Unused << NS_WARN_IF(NS_FAILED(rv));
+  }
+}
+
+void RemoteLazyInputStream::InitWithExistingRange(
+    uint64_t aStart, uint64_t aLength, const MutexAutoLock& aProofOfLock) {
+  MOZ_ASSERT(mActor->Size() >= aStart + aLength);
+  mStart = aStart;
+  mLength = aLength;
+
+  // In the child, we slice in StreamReady() when we set mState to eRunning.
+  // But in the parent, we start out eRunning, so it's necessary to slice the
+  // stream as soon as we have the information during the initialization phase
+  // because the stream is immediately consumable.
+  if (mState == eRunning && mRemoteStream && XRE_IsParentProcess() &&
+      (mStart > 0 || mLength < mActor->Size())) {
+    mRemoteStream =
+        new SlicedInputStream(mRemoteStream.forget(), mStart, mLength);
+  }
+}
+
+// nsIInputStreamCallback
+
+NS_IMETHODIMP
+RemoteLazyInputStream::OnInputStreamReady(nsIAsyncInputStream* aStream) {
+  nsCOMPtr<nsIInputStreamCallback> callback;
+  nsCOMPtr<nsIEventTarget> callbackEventTarget;
+  {
+    MutexAutoLock lock(mMutex);
+
+    // We have been closed in the meantime.
+    if (mState == eClosed) {
+      return NS_OK;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+    MOZ_ASSERT(mAsyncRemoteStream == aStream);
+
+    // The callback has been canceled in the meantime.
+    if (!mInputStreamCallback) {
+      return NS_OK;
+    }
+
+    callback.swap(mInputStreamCallback);
+    callbackEventTarget.swap(mInputStreamCallbackEventTarget);
+  }
+
+  // This must be the last operation because the execution of the callback can
+  // be synchronous.
+  MOZ_ASSERT(callback);
+  InputStreamCallbackRunnable::Execute(callback, callbackEventTarget, this);
+  return NS_OK;
+}
+
+// nsIIPCSerializableInputStream
+
+void RemoteLazyInputStream::Serialize(
+    mozilla::ipc::InputStreamParams& aParams,
+    FileDescriptorArray& aFileDescriptors, bool aDelayedStart,
+    uint32_t aMaxSize, uint32_t* aSizeUsed,
+    mozilla::ipc::ParentToChildStreamActorManager* aManager) {
+  MOZ_ASSERT(aSizeUsed);
+  *aSizeUsed = 0;
+
+  // So far we support only socket process serialization.
+  MOZ_DIAGNOSTIC_ASSERT(
+      aManager == SocketProcessParent::GetSingleton(),
+      "Serializing an RemoteLazyInputStream parent to child is "
+      "wrong! The caller must be fixed! See IPCBlobUtils.h.");
+  SocketProcessParent* socketActor = SocketProcessParent::GetSingleton();
+
+  nsresult rv;
+  nsCOMPtr<nsIAsyncInputStream> asyncRemoteStream;
+  RefPtr<RemoteLazyInputStreamParent> parentActor;
+  {
+    MutexAutoLock lock(mMutex);
+    rv = EnsureAsyncRemoteStream(lock);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+    asyncRemoteStream = mAsyncRemoteStream;
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+  }
+
+  MOZ_ASSERT(asyncRemoteStream);
+
+  parentActor = RemoteLazyInputStreamParent::Create(asyncRemoteStream, mLength,
+                                                    0, &rv, socketActor);
+  MOZ_ASSERT(parentActor);
+
+  if (!socketActor->SendPRemoteLazyInputStreamConstructor(
+          parentActor, parentActor->ID(), parentActor->Size())) {
+    MOZ_CRASH("The serialization is not supposed to fail");
+  }
+
+  aParams = mozilla::ipc::RemoteLazyInputStreamParams(parentActor);
+}
+
+void RemoteLazyInputStream::Serialize(
+    mozilla::ipc::InputStreamParams& aParams,
+    FileDescriptorArray& aFileDescriptors, bool aDelayedStart,
+    uint32_t aMaxSize, uint32_t* aSizeUsed,
+    mozilla::ipc::ChildToParentStreamActorManager* aManager) {
+  MOZ_ASSERT(aSizeUsed);
+  *aSizeUsed = 0;
+
+  MutexAutoLock lock(mMutex);
+
+  mozilla::ipc::RemoteLazyInputStreamRef params;
+  params.id() = mActor->ID();
+  params.start() = mStart;
+  params.length() = mLength;
+
+  aParams = params;
+}
+
+bool RemoteLazyInputStream::Deserialize(
+    const mozilla::ipc::InputStreamParams& aParams,
+    const FileDescriptorArray& aFileDescriptors) {
+  MOZ_CRASH("This should never be called.");
+  return false;
+}
+
+// nsIAsyncFileMetadata
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncFileMetadataWait(nsIFileMetadataCallback* aCallback,
+                                             nsIEventTarget* aEventTarget) {
+  MOZ_ASSERT(!!aCallback == !!aEventTarget);
+
+  // If we have the callback, we must have the event target.
+  if (NS_WARN_IF(!!aCallback != !!aEventTarget)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // See RemoteLazyInputStream.h for more information about this state
+  // machine.
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    switch (mState) {
+      // First call, we need to retrieve the stream from the parent actor.
+      case eInit:
+        MOZ_ASSERT(mActor);
+
+        mFileMetadataCallback = aCallback;
+        mFileMetadataCallbackEventTarget = aEventTarget;
+        mState = ePending;
+
+        mActor->StreamNeeded(this, aEventTarget);
+        return NS_OK;
+
+      // We are still waiting for the remote inputStream
+      case ePending:
+        if (mFileMetadataCallback && aCallback) {
+          return NS_ERROR_FAILURE;
+        }
+
+        mFileMetadataCallback = aCallback;
+        mFileMetadataCallbackEventTarget = aEventTarget;
+        return NS_OK;
+
+      // We have the remote inputStream, let's check if we can execute the
+      // callback.
+      case eRunning:
+        break;
+
+      // Stream is closed.
+      default:
+        MOZ_ASSERT(mState == eClosed);
+        return NS_BASE_STREAM_CLOSED;
+    }
+
+    MOZ_ASSERT(mState == eRunning);
+  }
+
+  FileMetadataCallbackRunnable::Execute(aCallback, aEventTarget, this);
+  return NS_OK;
+}
+
+// nsIFileMetadata
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetSize(int64_t* aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    fileMetadata = do_QueryInterface(mRemoteStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetSize(aRetval);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetLastModified(int64_t* aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    fileMetadata = do_QueryInterface(mRemoteStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetLastModified(aRetval);
+}
+
+NS_IMETHODIMP
+RemoteLazyInputStream::GetFileDescriptor(PRFileDesc** aRetval) {
+  nsCOMPtr<nsIFileMetadata> fileMetadata;
+  {
+    MutexAutoLock lock(mMutex);
+    fileMetadata = do_QueryInterface(mRemoteStream);
+    if (!fileMetadata) {
+      return mState == eClosed ? NS_BASE_STREAM_CLOSED : NS_ERROR_FAILURE;
+    }
+  }
+
+  return fileMetadata->GetFileDescriptor(aRetval);
+}
+
+nsresult RemoteLazyInputStream::EnsureAsyncRemoteStream(
+    const MutexAutoLock& aProofOfLock) {
+  // We already have an async remote stream.
+  if (mAsyncRemoteStream) {
+    return NS_OK;
+  }
+
+  if (!mRemoteStream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIInputStream> stream = mRemoteStream;
+  // We don't return NS_ERROR_NOT_IMPLEMENTED from ReadSegments,
+  // so it's possible that callers are expecting us to succeed in the future.
+  // We need to make sure the stream we return here supports ReadSegments,
+  // so wrap if in a buffered stream if necessary.
+  if (!NS_InputStreamIsBuffered(stream)) {
+    nsCOMPtr<nsIInputStream> bufferedStream;
+    nsresult rv = NS_NewBufferedInputStream(getter_AddRefs(bufferedStream),
+                                            stream.forget(), 4096);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    stream = bufferedStream;
+  }
+
+  // If the stream is blocking, we want to make it unblocking using a pipe.
+  bool nonBlocking = false;
+  nsresult rv = stream->IsNonBlocking(&nonBlocking);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIAsyncInputStream> asyncStream = do_QueryInterface(stream);
+
+  // If non-blocking and non-async, let's use NonBlockingAsyncInputStream.
+  if (nonBlocking && !asyncStream) {
+    rv = NonBlockingAsyncInputStream::Create(stream.forget(),
+                                             getter_AddRefs(asyncStream));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    MOZ_ASSERT(asyncStream);
+  }
+
+  if (!asyncStream) {
+    // Let's make the stream async using the DOMFile thread.
+    nsCOMPtr<nsIAsyncInputStream> pipeIn;
+    nsCOMPtr<nsIAsyncOutputStream> pipeOut;
+    rv = NS_NewPipe2(getter_AddRefs(pipeIn), getter_AddRefs(pipeOut), true,
+                     true);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    RefPtr<RemoteLazyInputStreamThread> thread =
+        RemoteLazyInputStreamThread::GetOrCreate();
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    rv = NS_AsyncCopy(stream, pipeOut, thread, NS_ASYNCCOPY_VIA_WRITESEGMENTS);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return rv;
+    }
+
+    asyncStream = pipeIn;
+  }
+
+  MOZ_ASSERT(asyncStream);
+  mAsyncRemoteStream = asyncStream;
+  mRemoteStream = nullptr;
+
+  return NS_OK;
+}
+
+// nsIInputStreamLength
+
+NS_IMETHODIMP
+RemoteLazyInputStream::Length(int64_t* aLength) {
+  MutexAutoLock lock(mMutex);
+
+  if (mState == eClosed) {
+    return NS_BASE_STREAM_CLOSED;
+  }
+
+  if (mConsumed) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return NS_BASE_STREAM_WOULD_BLOCK;
+}
+
+namespace {
+
+class InputStreamLengthCallbackRunnable final : public DiscardableRunnable {
+ public:
+  static void Execute(nsIInputStreamLengthCallback* aCallback,
+                      nsIEventTarget* aEventTarget,
+                      RemoteLazyInputStream* aStream, int64_t aLength) {
+    MOZ_ASSERT(aCallback);
+    MOZ_ASSERT(aEventTarget);
+
+    RefPtr<InputStreamLengthCallbackRunnable> runnable =
+        new InputStreamLengthCallbackRunnable(aCallback, aStream, aLength);
+
+    nsCOMPtr<nsIEventTarget> target = aEventTarget;
+    target->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  }
+
+  NS_IMETHOD
+  Run() override {
+    mCallback->OnInputStreamLengthReady(mStream, mLength);
+    mCallback = nullptr;
+    mStream = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  InputStreamLengthCallbackRunnable(nsIInputStreamLengthCallback* aCallback,
+                                    RemoteLazyInputStream* aStream,
+                                    int64_t aLength)
+      : DiscardableRunnable("dom::InputStreamLengthCallbackRunnable"),
+        mCallback(aCallback),
+        mStream(aStream),
+        mLength(aLength) {
+    MOZ_ASSERT(mCallback);
+    MOZ_ASSERT(mStream);
+  }
+
+  nsCOMPtr<nsIInputStreamLengthCallback> mCallback;
+  RefPtr<RemoteLazyInputStream> mStream;
+  const int64_t mLength;
+};
+
+}  // namespace
+
+// nsIAsyncInputStreamLength
+
+NS_IMETHODIMP
+RemoteLazyInputStream::AsyncLengthWait(nsIInputStreamLengthCallback* aCallback,
+                                       nsIEventTarget* aEventTarget) {
+  // If we have the callback, we must have the event target.
+  if (NS_WARN_IF(!!aCallback != !!aEventTarget)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    mLengthCallback = aCallback;
+    mLengthCallbackEventTarget = aEventTarget;
+
+    if (mState != eClosed && !mConsumed) {
+      MOZ_ASSERT(mActor);
+
+      if (aCallback) {
+        mActor->LengthNeeded(this, aEventTarget);
+      }
+
+      return NS_OK;
+    }
+  }
+
+  // If execution has reached here, it means the stream is either closed or
+  // consumed, and therefore the callback can be executed immediately
+  InputStreamLengthCallbackRunnable::Execute(aCallback, aEventTarget, this, -1);
+  return NS_OK;
+}
+
+void RemoteLazyInputStream::LengthReady(int64_t aLength) {
+  nsCOMPtr<nsIInputStreamLengthCallback> lengthCallback;
+  nsCOMPtr<nsIEventTarget> lengthCallbackEventTarget;
+
+  {
+    MutexAutoLock lock(mMutex);
+
+    // Stream has been closed in the meantime. Callback can be executed
+    // immediately
+    if (mState == eClosed || mConsumed) {
+      aLength = -1;
+    } else {
+      if (mStart > 0) {
+        aLength -= mStart;
+      }
+
+      if (mLength < mActor->Size()) {
+        // If the remote stream must be sliced, we must return here the
+        // correct value.
+        aLength = XPCOM_MIN(aLength, (int64_t)mLength);
+      }
+    }
+
+    lengthCallback.swap(mLengthCallback);
+    lengthCallbackEventTarget.swap(mLengthCallbackEventTarget);
+  }
+
+  if (lengthCallback) {
+    InputStreamLengthCallbackRunnable::Execute(
+        lengthCallback, lengthCallbackEventTarget, this, aLength);
+  }
+}
+
+}  // namespace mozilla