[fsp] Make the reading operation abortable.

chrome/browser/chromeos/file_system_provider/fileapi/file_stream_reader.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_FILE_STREAM_READER_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_FILE_STREAM_READER_H_
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "webkit/browser/blob/file_stream_reader.h"
 #include "webkit/browser/fileapi/file_system_url.h"
 
 namespace chromeos {
 namespace file_system_provider {
 
 struct EntryMetadata;
 class ProvidedFileSystemInterface;
 
 // Implements a streamed file reader. It is lazily initialized by the first call
 // to Read().
 class FileStreamReader : public webkit_blob::FileStreamReader {
  public:
-  typedef base::Callback<
-      void(base::WeakPtr<ProvidedFileSystemInterface> file_system,
-           const base::FilePath& file_path,
-           int file_handle,
-           base::File::Error result)> OpenFileCompletedCallback;
-
   FileStreamReader(fileapi::FileSystemContext* context,
                    const fileapi::FileSystemURL& url,
                    int64 initial_offset,
                    const base::Time& expected_modification_time);
 
   virtual ~FileStreamReader();
 
   // webkit_blob::FileStreamReader overrides.
   virtual int Read(net::IOBuffer* buf,
                    int buf_len,
                    const net::CompletionCallback& callback) OVERRIDE;
   virtual int64 GetLength(
       const net::Int64CompletionCallback& callback) OVERRIDE;
 
  private:
+  // Helper class for executing operations on the provided file system. All
+  // of its methods must be called on UI thread. Callbacks are called on IO
+  // thread.
+  class OperationRunner;
+
   // State of the file stream reader.
   enum State { NOT_INITIALIZED, INITIALIZING, INITIALIZED, FAILED };
 
   // Called when Read() operation is completed with either a success of an
   // error.
   void OnReadCompleted(net::CompletionCallback callback, int result);
 
   // Initializes the reader by opening the file. When completed with success,
   // runs the |pending_closure|. Otherwise, calls the |error_callback|.
   void Initialize(const base::Closure& pending_closure,
                   const net::Int64CompletionCallback& error_callback);
 
   // Called when opening a file is completed with either a success or an error.
   void OnOpenFileCompleted(
       const base::Closure& pending_closure,
       const net::Int64CompletionCallback& error_callback,
-      base::WeakPtr<ProvidedFileSystemInterface> file_system,
-      const base::FilePath& file_path,
-      int file_handle,
       base::File::Error result);
 
   // Called when initialization is completed with either a success or an error.
   void OnInitializeCompleted(const base::Closure& pending_closure,
                              const net::Int64CompletionCallback& error_callback,
                              const EntryMetadata& metadata,
                              base::File::Error result);
 
   // Called when a file system provider returns chunk of read data. Note, that
   // this may be called multiple times per single Read() call, as long as
@@ skipping 16 matching lines @@
                             int buffer_length,
                             const net::CompletionCallback& callback);
 
   // Same as GetLength(), but called after initializing is completed.
   void GetLengthAfterInitialized(const net::Int64CompletionCallback& callback);
 
   fileapi::FileSystemURL url_;
   int64 current_offset_;
   int64 current_length_;
   base::Time expected_modification_time_;
+  scoped_refptr<OperationRunner> runner_;
   State state_;
 
-  // Set during initialization (in case of a success).
-  base::WeakPtr<ProvidedFileSystemInterface> file_system_;
-  base::FilePath file_path_;
-  int file_handle_;
-
   base::WeakPtrFactory<FileStreamReader> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(FileStreamReader);
 };
 
 }  // namespace file_system_provider
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_SYSTEM_PROVIDER_FILEAPI_FILE_STREAM_READER_H_