diff -r 000000000000 -r 6474c204b198 dom/file/FileHelper.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/file/FileHelper.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_file_filehelper_h__
+#define mozilla_dom_file_filehelper_h__
+
+#include "FileCommon.h"
+
+#include "nsIRequestObserver.h"
+
+class nsIFileStorage;
+
+BEGIN_FILE_NAMESPACE
+
+class FileHelper;
+class FileRequest;
+class FileOutputStreamWrapper;
+class LockedFile;
+
+class FileHelperListener
+{
+public:
+  NS_IMETHOD_(MozExternalRefCountType)
+  AddRef() = 0;
+
+  NS_IMETHOD_(MozExternalRefCountType)
+  Release() = 0;
+
+  virtual void
+  OnFileHelperComplete(FileHelper* aFileHelper) = 0;
+};
+
+/**
+ * Must be subclassed. The subclass must implement DoAsyncRun. It may then
+ * choose to implement GetSuccessResult to properly set the result of the
+ * success event. Call Enqueue to start the file operation.
+ */
+class FileHelper : public nsIRequestObserver
+{
+  friend class FileRequest;
+  friend class FileOutputStreamWrapper;
+
+public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIREQUESTOBSERVER
+
+  nsresult
+  Enqueue();
+
+  nsresult
+  AsyncRun(FileHelperListener* aListener);
+
+  void
+  OnStreamProgress(uint64_t aProgress, uint64_t aProgressMax);
+
+  void
+  OnStreamClose();
+
+  void
+  OnStreamDestroy();
+
+  static LockedFile*
+  GetCurrentLockedFile();
+
+protected:
+  FileHelper(LockedFile* aLockedFile, FileRequest* aRequest);
+
+  virtual ~FileHelper();
+
+  virtual nsresult
+  DoAsyncRun(nsISupports* aStream) = 0;
+
+  virtual nsresult
+  GetSuccessResult(JSContext* aCx, JS::MutableHandle<JS::Value> aVal);
+
+  virtual void
+  ReleaseObjects();
+
+  void
+  Finish();
+
+  nsCOMPtr<nsIFileStorage> mFileStorage;
+  nsRefPtr<LockedFile> mLockedFile;
+  nsRefPtr<FileRequest> mFileRequest;
+
+  nsRefPtr<FileHelperListener> mListener;
+  nsCOMPtr<nsIRequest> mRequest;
+
+private:
+  nsresult mResultCode;
+  bool mFinished;
+};
+
+END_FILE_NAMESPACE
+
+#endif // mozilla_dom_file_filehelper_h__