[Media Gallery] Added code to support mtp device media file system on Windows.

chrome/browser/media_gallery/win/mtp_device_delegate_impl_win.h

+// Copyright (c) 2012 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.
+//
+// This class supports media transfer protocol (MTP) device file system
+// operations. This class communicates with the portable device and completes
+// the requested file system operation. A portable device can have multiple
+// data partitions. A user can register each partition as a media file system.
+// This class is instantiated per MTP device partition.

[Ryan Sleevi, 2013/01/05 03:00:58]

STYLE: You should be describing these comments as Class comments, as per

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Class_...

This applies to every new header in this CL.

[kmadhusu, 2013/01/08 03:19:40]

rsleevi@: Moved some class detail comments from the file header to the class
header section. Do you want me to add some code samples on how these classes are
instantiated? (It seems pretty straightforward to me).

[Ryan Sleevi, 2013/01/09 00:20:36]

My main concern was comments like "This class" reasonably belong located with
the class itself.

You've currently separated out descriptions of this class between the file level
comments and the class level comments, but both are needed to understand how the
class works - so they arguably belong there.

My particular point was the (old) line 9, which you removed, but I think it's
generally inconsistent with expectations and style to have both file-level and
class-level comments both describing a class and how it is used.

[kmadhusu, 2013/01/09 18:11:14]

As we discussed, moved these class details to the class comments section and
also rephrased the comemnt.

+
+#ifndef CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_DELEGATE_IMPL_WIN_H_
+#define CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_DELEGATE_IMPL_WIN_H_
+
+#include <portabledeviceapi.h>
+#include <string>
+
+#include "base/platform_file.h"
+#include "base/sequenced_task_runner_helpers.h"
+#include "base/string16.h"
+#include "base/synchronization/lock.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/win/scoped_comptr.h"
+#include "chrome/browser/media_gallery/mtp_device_delegate_impl.h"
+#include "webkit/fileapi/file_system_file_util.h"
+#include "webkit/fileapi/media/mtp_device_delegate.h"
+
+class FilePath;
+
+namespace base {
+class SequencedTaskRunner;
+}
+
+namespace chrome {
+
+// This class communicates with the MTP device to complete isolated file system
+// operations. This class contains platform specific code to communicate with
+// the attached MTP device. Instantiate this class per MTP device storage
+// partition using CreateMTPDeviceDelegate(). This object lives on a sequenced
+// task runner thread, except for CancelPendingTasksAndDeleteDelegate() which
+// happens on the UI thread.
+class MTPDeviceDelegateImplWin : public fileapi::MTPDeviceDelegate {
+ public:
+  // Returns true to cancel the pending tasks if |this| object is scheduled to
+  // be deleted.
+  bool IsCancelTasksFlagSet();
+
+ private:
+  friend void CreateMTPDeviceDelegate(const string16&,
+                                      base::SequencedTaskRunner*,
+                                      const CreateMTPDeviceDelegateCallback&);
+  friend class base::DeleteHelper<MTPDeviceDelegateImplWin>;
+
+  // Defer the device initializations until the first file operation request.
+  // Do all the initializations in LazyInit() function.
+  MTPDeviceDelegateImplWin(const string16& pnp_device_id,
+                           base::SequencedTaskRunner* media_task_runner);
+
+  // Destructed via CancelPendingTasksAndDeleteDelegate().
+  virtual ~MTPDeviceDelegateImplWin();
+
+  // MTPDeviceDelegate:
+  virtual base::PlatformFileError GetFileInfo(
+      const FilePath& file_path,
+      base::PlatformFileInfo* file_info) OVERRIDE;
+  virtual scoped_ptr<fileapi::FileSystemFileUtil::AbstractFileEnumerator>
+      CreateFileEnumerator(const FilePath& root,
+                           bool recursive) OVERRIDE;
+  virtual base::PlatformFileError CreateSnapshotFile(
+      const FilePath& device_file_path,
+      const FilePath& local_path,
+      base::PlatformFileInfo* file_info) OVERRIDE;
+  virtual void CancelPendingTasksAndDeleteDelegate() OVERRIDE;
+
+  // Returns whether the device is ready for communication.
+  bool LazyInit();
+
+  // Returns the object id of the file object specified by the |file_path|,
+  // e.g. if the |file_path| is "\\MTP:StorageSerial:SID-{1001,,192}:125\DCIM"
+  // and |registered_device_path_| is "\\MTP:StorageSerial:SID-{1001,,192}:125",
+  // this function returns the identifier of the "DCIM" folder object.
+  //
+  // Returns an empty string if the device is detached while the request is in
+  // progress.
+  string16 GetFileObjectIdFromPath(const string16& file_path);
+
+  // The Pnp Device Id, used to open the device for communication,
+  // e.g. "\\?\usb#vid_04a9&pid_3073#12#{6ac27878-a6fa-4155-ba85-f1d4f33}".
+  string16 pnp_device_id_;
+
+  // The media file system root path, which is obtained during the registration
+  // of MTP device storage partition as a file system,
+  // e.g. "\\MTP:StorageSerial:SID-{10001,E,9823}:237483".
+  const string16 registered_device_path_;
+
+  // The MTP device storage partition object identifier, used to enumerate the
+  // storage contents, e.g. "s10001".
+  string16 storage_object_id_;
+
+  // The task runner where most of the class lives and runs (save for
+  // CancelPendingTasksAndDeleteDelegate).
+  scoped_refptr<base::SequencedTaskRunner> media_task_runner_;
+
+  // The portable device.
+  base::win::ScopedComPtr<IPortableDevice> device_;
+
+  // The lock to protect |cancel_pending_tasks_|. |cancel_pending_tasks_| is
+  // set on the UI thread when the
+  // (1) Browser application is in shutdown mode (or)
+  // (2) Last extension using this MTP device is destroyed (or)
+  // (3) Attached MTP device is removed (or)
+  // (4) User revoked the MTP device gallery permission.
+  base::Lock cancel_tasks_lock_;
+  bool cancel_pending_tasks_;
+
+  // The task runner can wait on this event until the device storage details
+  // are fetched.
+  base::WaitableEvent task_completed_event_;
+
+  DISALLOW_COPY_AND_ASSIGN(MTPDeviceDelegateImplWin);
+};
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_MEDIA_GALLERY_WIN_MTP_DEVICE_DELEGATE_IMPL_WIN_H_