[fsp] Add FileStreamReader for the reading operation.

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/weak_ptr.h"
+#include "webkit/browser/blob/file_stream_reader.h"
+#include "webkit/browser/fileapi/file_system_url.h"
+
+namespace fileapi {
+class AsyncFileUtil;
+}  // namespace fileapi
+
+namespace chromeos {
+namespace file_system_provider {
+
+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)> InitializeCompletedCallback;
+
+  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:
+  // 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 initializing is completed with either a success or an error.
+  void OnInitializeCompleted(
+      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 a file system provider returns chunk of read data. Note, that
+  // this may be called multiple times per single Read() call, as long as
+  // |has_next| is set to true. |result| is set to success only if reading is
+  // successful, and the file has not changed while reading.
+  void OnReadChunkReceived(const net::CompletionCallback& callback,
+                           int chunk_length,
+                           bool has_next,
+                           base::File::Error result);
+
+  // Called when fetching length of the file is completed with either a success
+  // or an error.
+  void OnGetMetadataForGetLengthReceived(
+      const net::Int64CompletionCallback& callback,
+      base::File::Error result,
+      const base::File::Info& file_info);
+
+  // Same as Read(), but called after initializing is completed.
+  void ReadAfterInitialized(net::IOBuffer* buffer,
+                            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_;
+
+  // 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_