14 files changed, 893 insertions, 0 deletions
diff --git a/dom/fs/shared/FileSystemHelpers.cpp b/dom/fs/shared/FileSystemHelpers.cpp
new file mode 100644
index 0000000000..24f1fc7fb8
--- /dev/null
+++ b/dom/fs/shared/FileSystemHelpers.cpp
@@ -0,0 +1,22 @@
+/* -*- 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 "FileSystemHelpers.h"
+
+#include "nsString.h"
+
+namespace mozilla::dom::fs {
+
+bool IsValidName(const mozilla::dom::fs::Name& aName) {
+  return !(aName.IsVoid() || aName.Length() == 0 ||
+#ifdef XP_WIN
+           aName.FindChar('\\') != kNotFound ||
+#endif
+           aName.FindChar('/') != kNotFound || aName.EqualsLiteral(".") ||
+           aName.EqualsLiteral(".."));
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/shared/FileSystemHelpers.h b/dom/fs/shared/FileSystemHelpers.h
new file mode 100644
index 0000000000..26a820f343
--- /dev/null
+++ b/dom/fs/shared/FileSystemHelpers.h
@@ -0,0 +1,147 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_SHARED_FILESYSTEMHELPERS_H_
+#define DOM_FS_SHARED_FILESYSTEMHELPERS_H_
+
+#include "FileSystemTypes.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla::dom::fs {
+
+// XXX Consider moving this class template to MFBT.
+
+// A wrapper class template on top of the RefPtr. The RefPtr provides us the
+// automatic reference counting of objects with AddRef() and Release() methods.
+// `Registered` provides automatic registration counting of objects with
+// Register() and Unregister() methods. Registration counting works similarly
+// as reference counting, but objects are not deleted when the number of
+// registrations drops to zero (that's managed by reference counting). Instead,
+// an object can trigger an asynchronous close operation which still needs to
+// hold and use the referenced object. Example:
+//
+// using BoolPromise = MozPromise<bool, nsresult, false>;
+//
+// class MyObject {
+//  public:
+//   NS_INLINE_DECL_REFCOUNTING(MyObject)
+//
+//   void Register() {
+//     mRegCnt++;
+//   }
+//
+//   void Unregister() {
+//     mRegCnt--;
+//     if (mRegCnt == 0) {
+//       BeginClose();
+//     }
+//   }
+//
+//  private:
+//   RefPtr<BoolPromise> BeginClose() {
+//     return InvokeAsync(mIOTaskQueue, __func__,
+//                []() {
+//                  return BoolPromise::CreateAndResolve(true, __func__);
+//                })
+//         ->Then(GetCurrentSerialEventTarget(), __func__,
+//                [self = RefPtr<MyObject>(this)](
+//                    const BoolPromise::ResolveOrRejectValue&) {
+//                  return self->mIOTaskQueue->BeginShutdown();
+//                })
+//         ->Then(GetCurrentSerialEventTarget(), __func__,
+//                [self = RefPtr<MyObject>(this)](
+//                    const ShutdownPromise::ResolveOrRejectValue&) {
+//                  return BoolPromise::CreateAndResolve(true, __func__);
+//                });
+//   }
+//
+//   RefPtr<TaskQueue> mIOTaskQueue;
+//   uint32_t mRegCnt = 0;
+// };
+
+template <class T>
+class Registered {
+ private:
+  RefPtr<T> mObject;
+
+ public:
+  ~Registered() {
+    if (mObject) {
+      mObject->Unregister();
+    }
+  }
+
+  Registered() = default;
+
+  Registered(const Registered& aOther) : mObject(aOther.mObject) {
+    mObject->Register();
+  }
+
+  Registered(Registered&& aOther) noexcept = default;
+
+  MOZ_IMPLICIT Registered(RefPtr<T> aObject) : mObject(std::move(aObject)) {
+    if (mObject) {
+      mObject->Register();
+    }
+  }
+
+  Registered<T>& operator=(decltype(nullptr)) {
+    RefPtr<T> oldObject = std::move(mObject);
+    mObject = nullptr;
+    if (oldObject) {
+      oldObject->Unregister();
+    }
+    return *this;
+  }
+
+  Registered<T>& operator=(const Registered<T>& aRhs) {
+    if (aRhs.mObject) {
+      aRhs.mObject->Register();
+    }
+    RefPtr<T> oldObject = std::move(mObject);
+    mObject = aRhs.mObject;
+    if (oldObject) {
+      oldObject->Unregister();
+    }
+    return *this;
+  }
+
+  Registered<T>& operator=(Registered<T>&& aRhs) noexcept {
+    RefPtr<T> oldObject = std::move(mObject);
+    mObject = std::move(aRhs.mObject);
+    aRhs.mObject = nullptr;
+    if (oldObject) {
+      oldObject->Unregister();
+    }
+    return *this;
+  }
+
+  const RefPtr<T>& inspect() const { return mObject; }
+
+  RefPtr<T> unwrap() {
+    RefPtr<T> oldObject = std::move(mObject);
+    mObject = nullptr;
+    if (oldObject) {
+      oldObject->Unregister();
+    }
+    return oldObject;
+  }
+
+  T* get() const { return mObject; }
+
+  operator T*() const& { return get(); }
+
+  T* operator->() const { return get(); }
+};
+
+// Spec says valid names don't include (os-dependent) path separators,
+// and is not equal to a dot . or two dots ..
+// We want to use the same validator from both child and parent.
+bool IsValidName(const fs::Name& aName);
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_SHARED_FILESYSTEMHELPERS_H_
diff --git a/dom/fs/shared/FileSystemLog.cpp b/dom/fs/shared/FileSystemLog.cpp
new file mode 100644
index 0000000000..91afb3fc8f
--- /dev/null
+++ b/dom/fs/shared/FileSystemLog.cpp
@@ -0,0 +1,13 @@
+/* -*- 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 "FileSystemLog.h"
+
+namespace mozilla {
+
+LazyLogModule gOPFSLog("OPFS");
+
+}
diff --git a/dom/fs/shared/FileSystemLog.h b/dom/fs/shared/FileSystemLog.h
new file mode 100644
index 0000000000..6ea6d4ae77
--- /dev/null
+++ b/dom/fs/shared/FileSystemLog.h
@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_SHARED_FILESYSTEMLOG_H_
+#define DOM_FS_SHARED_FILESYSTEMLOG_H_
+
+#include "mozilla/Logging.h"
+
+namespace mozilla {
+extern LazyLogModule gOPFSLog;
+}
+
+#define LOG(args) MOZ_LOG(mozilla::gOPFSLog, mozilla::LogLevel::Debug, args)
+
+#define LOG_VERBOSE(args) \
+  MOZ_LOG(mozilla::gOPFSLog, mozilla::LogLevel::Verbose, args)
+
+#define LOG_ENABLED() MOZ_LOG_TEST(mozilla::gOPFSLog, mozilla::LogLevel::Debug)
+
+#endif  // DOM_FS_SHARED_FILESYSTEMLOG_H
diff --git a/dom/fs/shared/FileSystemTypes.h b/dom/fs/shared/FileSystemTypes.h
new file mode 100644
index 0000000000..3841698c71
--- /dev/null
+++ b/dom/fs/shared/FileSystemTypes.h
@@ -0,0 +1,29 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_FILESYSTEMTYPES_H_
+#define DOM_FS_FILESYSTEMTYPES_H_
+
+#include "nsStringFwd.h"
+
+template <class T>
+class nsTArray;
+
+namespace mozilla::dom::fs {
+
+using ContentType = nsCString;
+using DatabaseVersion = int32_t;
+using EntryId = nsCString;
+using Name = nsString;
+using Origin = nsCString;
+using PageNumber = int32_t;
+using Path = nsTArray<Name>;
+using TimeStamp = int64_t;
+using Usage = int64_t;
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_FILESYSTEMTYPES_H_
diff --git a/dom/fs/shared/IPCRejectReporter.cpp b/dom/fs/shared/IPCRejectReporter.cpp
new file mode 100644
index 0000000000..6f5f40b95c
--- /dev/null
+++ b/dom/fs/shared/IPCRejectReporter.cpp
@@ -0,0 +1,36 @@
+/* -*- 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 "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/ipc/MessageChannel.h"
+
+namespace mozilla::dom::fs {
+
+// TODO: Find a better way to deal with these errors
+void IPCRejectReporter(mozilla::ipc::ResponseRejectReason aReason) {
+  switch (aReason) {
+    case mozilla::ipc::ResponseRejectReason::ActorDestroyed:
+      // This is ok
+      break;
+    case mozilla::ipc::ResponseRejectReason::HandlerRejected:
+      QM_TRY(OkIf(false), QM_VOID);
+      break;
+    case mozilla::ipc::ResponseRejectReason::ChannelClosed:
+      QM_TRY(OkIf(false), QM_VOID);
+      break;
+    case mozilla::ipc::ResponseRejectReason::ResolverDestroyed:
+      QM_TRY(OkIf(false), QM_VOID);
+      break;
+    case mozilla::ipc::ResponseRejectReason::SendError:
+      QM_TRY(OkIf(false), QM_VOID);
+      break;
+    default:
+      QM_TRY(OkIf(false), QM_VOID);
+      break;
+  }
+}
+
+}  // namespace mozilla::dom::fs
diff --git a/dom/fs/shared/IPCRejectReporter.h b/dom/fs/shared/IPCRejectReporter.h
new file mode 100644
index 0000000000..db98ac917c
--- /dev/null
+++ b/dom/fs/shared/IPCRejectReporter.h
@@ -0,0 +1,20 @@
+/* -*- 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/. */
+
+namespace mozilla {
+
+namespace ipc {
+
+enum class ResponseRejectReason;
+
+}  // namespace ipc
+
+namespace dom::fs {
+
+void IPCRejectReporter(mozilla::ipc::ResponseRejectReason aReason);
+
+}  // namespace dom::fs
+}  // namespace mozilla
diff --git a/dom/fs/shared/ManagedMozPromiseRequestHolder.h b/dom/fs/shared/ManagedMozPromiseRequestHolder.h
new file mode 100644
index 0000000000..1b039577a3
--- /dev/null
+++ b/dom/fs/shared/ManagedMozPromiseRequestHolder.h
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_SHARED_MANAGEDMOZPROMISEREQUESTHOLDER_H_
+#define DOM_FS_SHARED_MANAGEDMOZPROMISEREQUESTHOLDER_H_
+
+#include "mozilla/MozPromise.h"
+#include "mozilla/RefPtr.h"
+#include "nsISupportsImpl.h"
+
+namespace mozilla::dom::fs {
+
+template <typename Manager, typename PromiseType>
+class ManagedMozPromiseRequestHolder final
+    : public MozPromiseRequestHolder<PromiseType> {
+ public:
+  explicit ManagedMozPromiseRequestHolder(Manager* aManager)
+      : mManager(aManager) {
+    mManager->RegisterPromiseRequestHolder(this);
+  }
+
+  NS_INLINE_DECL_REFCOUNTING(ManagedMozPromiseRequestHolder)
+
+ private:
+  ~ManagedMozPromiseRequestHolder() {
+    mManager->UnregisterPromiseRequestHolder(this);
+  }
+
+  RefPtr<Manager> mManager;
+};
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_SHARED_MANAGEDMOZPROMISEREQUESTHOLDER_H_
diff --git a/dom/fs/shared/PFileSystemAccessHandle.ipdl b/dom/fs/shared/PFileSystemAccessHandle.ipdl
new file mode 100644
index 0000000000..164f5f9062
--- /dev/null
+++ b/dom/fs/shared/PFileSystemAccessHandle.ipdl
@@ -0,0 +1,21 @@
+/* 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 protocol PFileSystemManager;
+
+namespace mozilla {
+namespace dom {
+
+async protocol PFileSystemAccessHandle
+{
+  manager PFileSystemManager;
+
+ parent:
+  async Close();
+
+  async __delete__();
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/fs/shared/PFileSystemAccessHandleControl.ipdl b/dom/fs/shared/PFileSystemAccessHandleControl.ipdl
new file mode 100644
index 0000000000..1380a50e02
--- /dev/null
+++ b/dom/fs/shared/PFileSystemAccessHandleControl.ipdl
@@ -0,0 +1,18 @@
+/* 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/. */
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+
+namespace mozilla {
+namespace dom {
+
+async protocol PFileSystemAccessHandleControl
+{
+ parent:
+  async Close()
+      returns(void_t ok);
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/fs/shared/PFileSystemManager.ipdl b/dom/fs/shared/PFileSystemManager.ipdl
new file mode 100644
index 0000000000..917e375aaa
--- /dev/null
+++ b/dom/fs/shared/PFileSystemManager.ipdl
@@ -0,0 +1,412 @@
+/* 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 protocol PFileSystemAccessHandle;
+include protocol PFileSystemAccessHandleControl;
+include protocol PFileSystemWritableFileStream;
+
+include IPCBlob;
+include RandomAccessStreamParams;
+
+using mozilla::dom::fs::ContentType from "mozilla/dom/FileSystemTypes.h";
+using mozilla::dom::fs::EntryId from "mozilla/dom/FileSystemTypes.h";
+using mozilla::dom::fs::Name from "mozilla/dom/FileSystemTypes.h";
+using mozilla::dom::fs::Origin from "mozilla/dom/FileSystemTypes.h";
+using mozilla::dom::fs::PageNumber from "mozilla/dom/FileSystemTypes.h";
+using mozilla::dom::fs::TimeStamp from "mozilla/dom/FileSystemTypes.h";
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+
+namespace mozilla {
+namespace dom {
+namespace fs {
+
+/**
+ * Identifies a file or a directory and contains its user provided name.
+ */
+struct FileSystemEntryMetadata
+{
+  EntryId entryId;
+  Name entryName;
+  bool directory;
+};
+
+/**
+ * Identifies a file or a directory with its parent identifier and
+ * user provided name.
+ */
+struct FileSystemChildMetadata
+{
+  EntryId parentId;
+  Name childName;
+};
+
+/**
+ * Identifies a file with its parent directory and name, and
+ * indicates whether the file may be created if it is missing.
+ */
+struct FileSystemGetHandleRequest
+{
+  FileSystemChildMetadata handle;
+  bool create;
+};
+
+/**
+ * Contains a file or directory or an error.
+ */
+union FileSystemGetHandleResponse
+{
+  nsresult;
+  EntryId;
+};
+
+/**
+ * Contains an identifier for a parent directory and a page number
+ * which is used to fetch the next set of entries when the directory
+ * contains so many items that communicating all of them in one message
+ * is an impractical.
+ */
+struct FileSystemGetEntriesRequest
+{
+  EntryId parentId;
+  PageNumber page;
+};
+
+/**
+ * Contains a set of directories and files
+ * under the same parent directory.
+ */
+struct FileSystemDirectoryListing
+{
+  FileSystemEntryMetadata[] directories;
+  FileSystemEntryMetadata[] files;
+};
+
+/**
+ * Contains a set of entries or an error.
+ */
+union FileSystemGetEntriesResponse
+{
+  nsresult;
+  FileSystemDirectoryListing;
+};
+
+/**
+ * Contains entry handle information.
+ */
+struct FileSystemGetFileRequest
+{
+  EntryId entryId;
+};
+
+/**
+ * Contains the properties of a file and a file descriptor.
+ * The properties may differ from the properties of the
+ * underlying object of the file descriptor.
+ */
+struct FileSystemFileProperties
+{
+  TimeStamp last_modified_ms;
+  IPCBlob file;
+  ContentType type;
+  Name[] path;
+};
+
+/**
+ * Contains file properties or an error.
+ */
+union FileSystemGetFileResponse
+{
+  nsresult;
+  FileSystemFileProperties;
+};
+
+/**
+ * Contains entry handle information.
+ */
+struct FileSystemGetAccessHandleRequest
+{
+  EntryId entryId;
+};
+
+struct FileSystemAccessHandleProperties
+{
+  RandomAccessStreamParams streamParams;
+  ManagedEndpoint<PFileSystemAccessHandleChild> accessHandleChildEndpoint;
+  Endpoint<PFileSystemAccessHandleControlChild> accessHandleControlChildEndpoint;
+};
+
+union FileSystemGetAccessHandleResponse
+{
+  nsresult;
+  FileSystemAccessHandleProperties;
+};
+
+/**
+ * Contains entry handle information.
+ */
+struct FileSystemGetWritableRequest
+{
+  EntryId entryId;
+  bool keepData;
+};
+
+struct FileSystemWritableFileStreamProperties
+{
+  RandomAccessStreamParams streamParams;
+  PFileSystemWritableFileStream writableFileStream;
+};
+
+union FileSystemGetWritableFileStreamResponse
+{
+  nsresult;
+  FileSystemWritableFileStreamProperties;
+};
+
+/**
+ * Represents a pair of file system entries which
+ * are not necessarily connected by a path.
+ */
+struct FileSystemEntryPair
+{
+  EntryId parentId;
+  EntryId childId;
+};
+
+/**
+ * Contains a pair of file system entries.
+ */
+struct FileSystemResolveRequest
+{
+  FileSystemEntryPair endpoints;
+};
+
+/**
+ * Contains a file system path.
+ */
+struct FileSystemPath
+{
+  Name[] path;
+};
+
+/**
+ * Contains a potentially empty path or an error.
+ */
+union FileSystemResolveResponse
+{
+  nsresult;
+  FileSystemPath?;
+};
+
+/**
+ * Identifies a file with its parent directory and name, and
+ * indicates whether all the children of a directory may be removed.
+ */
+struct FileSystemRemoveEntryRequest
+{
+  FileSystemChildMetadata handle;
+  bool recursive;
+};
+
+/**
+ * Contains an error or nothing.
+ */
+union FileSystemRemoveEntryResponse
+{
+  nsresult;
+  void_t;
+};
+
+/**
+ * Identifies a file/directory to be moved and the new name, and the
+ * destination directory
+ */
+struct FileSystemMoveEntryRequest
+{
+  FileSystemEntryMetadata handle;
+  FileSystemChildMetadata destHandle;
+};
+
+/**
+ * Identifies a file/directory to be renamed and the new name
+ */
+struct FileSystemRenameEntryRequest
+{
+  FileSystemEntryMetadata handle;
+  Name name;
+};
+
+/**
+ * Contains an error or the new entryId
+ */
+union FileSystemMoveEntryResponse
+{
+  nsresult;
+  void_t;
+};
+
+}  // namespace fs
+
+async protocol PFileSystemManager
+{
+  manages PFileSystemAccessHandle;
+  manages PFileSystemWritableFileStream;
+
+ parent:
+  /**
+   * TODO: documentation
+   */
+  [VirtualSendImpl]
+  async GetRootHandle()
+      returns(FileSystemGetHandleResponse response);
+
+  /**
+   * Initiates an asynchronous request for the handle of
+   * a subdirectory with a given name under the current directory.
+   *
+   * Invalid names are rejected with an appropriate error.
+   *
+   * If the subdirectory exists, a handle to it is always returned.
+   *
+   * If no child of any kind with the given name exists and
+   * the create-flag of the input is set, the subdirectory will be created,
+   * otherwise an appropriate error is returned.
+   *
+   * @param[in] handle request containing a create flag
+   *
+   * @returns error or entry handle
+   */
+  [VirtualSendImpl]
+  async GetDirectoryHandle(FileSystemGetHandleRequest request)
+      returns(FileSystemGetHandleResponse handle);
+
+  /**
+   * Initiates an asynchronous request for the handle to
+   * a file with a given name under the current directory.
+   *
+   * Invalid names are rejected with an appropriate error.
+   *
+   * If the file exists, a handle to it is always returned.
+   *
+   * If no child of any kind with the given name exists and
+   * the create-flag of the input is set, the file will be created,
+   * otherwise an appropriate error is returned.
+   *
+   * @param[in] handle request containing a create flag
+   *
+   * @returns error or entry handle
+   */
+  [VirtualSendImpl]
+  async GetFileHandle(FileSystemGetHandleRequest request)
+      returns(FileSystemGetHandleResponse handle);
+
+  /**
+   * Initiates an asynchronous request for a read-only object representing the
+   * file corresponding to the current file handle.
+   *
+   * The returned object provides read-only access.
+   *
+   * If the underlying file object is modified through a mutable interface,
+   * the returned value is considered stale. Concurrent changes are not
+   * guaranteed to be visible or invisible. Using a stale object
+   * returns appropriate errors when the results are unpredictable.
+   *
+   * @param[in] request for a file object
+   *
+   * @returns error or file object
+   */
+  [VirtualSendImpl]
+  async GetFile(FileSystemGetFileRequest request)
+      returns(FileSystemGetFileResponse response);
+
+  /**
+   * TODO: documentation
+   */
+  [VirtualSendImpl]
+  async GetAccessHandle(FileSystemGetAccessHandleRequest request)
+      returns(FileSystemGetAccessHandleResponse response);
+
+  /**
+   * TODO: documentation
+   */
+  [VirtualSendImpl]
+  async GetWritable(FileSystemGetWritableRequest request)
+      returns(FileSystemGetWritableFileStreamResponse fileData);
+
+  /**
+   * Initiates an asynchronous request for the file system path
+   * associated with a file system entry.
+   *
+   * @param[in] request identifying a file object
+   *
+   * @returns error or file system path
+   */
+  [VirtualSendImpl]
+  async Resolve(FileSystemResolveRequest request)
+      returns(FileSystemResolveResponse response);
+
+  /**
+   * Initiates an asynchronous request for an iterator to the child entries
+   * under the calling directory handle.
+   *
+   * If the directory item names or the directory structure is modified while
+   * the iterator is in use, the iterator remains safe to use but no guarantees
+   * are made regarding the visibility of the concurrent changes.
+   * It is possible that a file which is added after the iteration has begun
+   * will not be returned, or that among the values there are invalid file
+   * handles whose underlying objects have been removed after the iteration
+   * started.
+   *
+   * @param[in] request for a iterator
+   *
+   * @returns error or iterator
+   */
+  [VirtualSendImpl]
+  async GetEntries(FileSystemGetEntriesRequest request)
+      returns(FileSystemGetEntriesResponse entries);
+
+  /**
+   * Initiates an asynchronous request to delete a directory or file with a
+   * given name under the calling directory handle.
+   *
+   * If recursive flag of the request is not set, a request to remove a
+   * non-empty directory returns an appropriate error, otherwise all the child
+   * files and directories are made to vanish.
+   *
+   * The recursive flag has no impact on files.
+   *
+   * @param[in] request containing a recursive flag
+   *
+   * @returns error information
+   */
+  [VirtualSendImpl]
+  async RemoveEntry(FileSystemRemoveEntryRequest request)
+      returns(FileSystemRemoveEntryResponse response);
+
+  /**
+   * Initiates an asynchronous request to move a directory or file with a
+   * given name to a given destination and new name.
+   *
+   * @returns error information
+   */
+  async MoveEntry(FileSystemMoveEntryRequest request)
+      returns(FileSystemMoveEntryResponse response);
+
+  /**
+   * Initiates an asynchronous request to rename a directory or file
+   *
+   * @returns error information
+   */
+  async RenameEntry(FileSystemRenameEntryRequest request)
+      returns(FileSystemMoveEntryResponse response);
+
+ child:
+  async PFileSystemWritableFileStream();
+
+  async CloseAll()
+      returns(nsresult rv);
+};
+
+} // namespace dom
+} // namespace mozilla
+
diff --git a/dom/fs/shared/PFileSystemWritableFileStream.ipdl b/dom/fs/shared/PFileSystemWritableFileStream.ipdl
new file mode 100644
index 0000000000..c71e4cbf43
--- /dev/null
+++ b/dom/fs/shared/PFileSystemWritableFileStream.ipdl
@@ -0,0 +1,23 @@
+/* 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 protocol PFileSystemManager;
+
+using struct mozilla::void_t from "mozilla/ipc/IPCCore.h";
+
+namespace mozilla {
+namespace dom {
+
+async protocol PFileSystemWritableFileStream
+{
+  manager PFileSystemManager;
+
+ parent:
+  async Close() returns(void_t ok);
+
+  async __delete__();
+};
+
+} // namespace dom
+} // namespace mozilla
diff --git a/dom/fs/shared/TargetPtrHolder.h b/dom/fs/shared/TargetPtrHolder.h
new file mode 100644
index 0000000000..952fc075b9
--- /dev/null
+++ b/dom/fs/shared/TargetPtrHolder.h
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DOM_FS_SHARED_TARGETPTRHOLDER_H_
+#define DOM_FS_SHARED_TARGETPTRHOLDER_H_
+
+#include "mozilla/RefPtr.h"
+#include "nsCOMPtr.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::dom::fs {
+
+// TODO: Remove this ad hoc class when bug 1805830 is fixed.
+template <typename T>
+class TargetPtrHolder {
+ public:
+  MOZ_IMPLICIT TargetPtrHolder(T* aRawPtr)
+      : mTarget(GetCurrentSerialEventTarget()), mPtr(aRawPtr) {
+    MOZ_ASSERT(mPtr);
+  }
+
+  TargetPtrHolder(const TargetPtrHolder&) = default;
+
+  TargetPtrHolder& operator=(const TargetPtrHolder&) = default;
+
+  TargetPtrHolder(TargetPtrHolder&&) = default;
+
+  TargetPtrHolder& operator=(TargetPtrHolder&&) = default;
+
+  ~TargetPtrHolder() {
+    if (!mPtr) {
+      return;
+    }
+
+    NS_ProxyRelease("TargetPtrHolder::mPtr", mTarget, mPtr.forget());
+  }
+
+  T* get() const {
+    MOZ_ASSERT(mPtr);
+
+    return mPtr.get();
+  }
+
+  T* operator->() const MOZ_NO_ADDREF_RELEASE_ON_RETURN { return get(); }
+
+  bool operator!() { return !mPtr.get(); }
+
+ private:
+  nsCOMPtr<nsISerialEventTarget> mTarget;
+  RefPtr<T> mPtr;
+};
+
+}  // namespace mozilla::dom::fs
+
+#endif  // DOM_FS_SHARED_TARGETPTRHOLDER_H_
diff --git a/dom/fs/shared/moz.build b/dom/fs/shared/moz.build
new file mode 100644
index 0000000000..1aaa2574ae
--- /dev/null
+++ b/dom/fs/shared/moz.build
@@ -0,0 +1,34 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+EXPORTS.mozilla.dom += [
+    "FileSystemHelpers.h",
+    "FileSystemLog.h",
+    "FileSystemTypes.h",
+]
+
+EXPORTS.mozilla.dom.fs += [
+    "IPCRejectReporter.h",
+    "ManagedMozPromiseRequestHolder.h",
+    "TargetPtrHolder.h",
+]
+
+UNIFIED_SOURCES += [
+    "FileSystemHelpers.cpp",
+    "FileSystemLog.cpp",
+    "IPCRejectReporter.cpp",
+]
+
+FINAL_LIBRARY = "xul"
+
+IPDL_SOURCES += [
+    "PFileSystemAccessHandle.ipdl",
+    "PFileSystemAccessHandleControl.ipdl",
+    "PFileSystemManager.ipdl",
+    "PFileSystemWritableFileStream.ipdl",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")