text: // 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 COMPONENTS_COMPONENT_UPDATER_BACKGROUND_DOWNLOADER_WIN_H_
  #define COMPONENTS_COMPONENT_UPDATER_BACKGROUND_DOWNLOADER_WIN_H_
  
  #include <windows.h>
  #include <bits.h>
  
  #include "base/macros.h"
  #include "base/memory/ref_counted.h"
  #include "base/strings/string16.h"
  #include "base/threading/thread_checker.h"
  #include "base/time/time.h"
  #include "base/timer/timer.h"
  #include "base/win/scoped_comptr.h"
  #include "components/component_updater/crx_downloader.h"
  
  namespace base {
  class FilePath;
  class MessageLoopProxy;
  class SingleThreadTaskRunner;
  }
  
  namespace component_updater {
  
  // Implements a downloader in terms of the BITS service. The public interface
  // of this class and the CrxDownloader overrides are expected to be called
  // from the main thread. The rest of the class code runs on a single thread
  // task runner. This task runner must be initialized to work with COM objects.
  // Instances of this class are created and destroyed in the main thread.
  // See the implementation of the class destructor for details regarding the
  // clean up of resources acquired in this class.
  class BackgroundDownloader : public CrxDownloader {
   protected:
    friend class CrxDownloader;
    BackgroundDownloader(scoped_ptr<CrxDownloader> successor,
                         net::URLRequestContextGetter* context_getter,
                         scoped_refptr<base::SingleThreadTaskRunner> task_runner);
    virtual ~BackgroundDownloader();
  
   private:
    // Overrides for CrxDownloader.
    virtual void DoStartDownload(const GURL& url) OVERRIDE;
  
    // Called asynchronously on the |task_runner_| at different stages during
    // the download. |OnDownloading| can be called multiple times.
    // |EndDownload| switches the execution flow from the |task_runner_| to the
    // main thread. Accessing any data members of this object from the
    // |task_runner_|after calling |EndDownload| is unsafe.
    void BeginDownload(const GURL& url);
    void OnDownloading();
    void EndDownload(HRESULT hr);
  
    // Handles the job state transitions to a final state.
    void OnStateTransferred();
    void OnStateError();
    void OnStateCancelled();
    void OnStateAcknowledged();
  
    // Handles the transition to a transient state where the job is in the
    // queue but not actively transferring data.
    void OnStateQueued();
  
    // Handles the job state transition to a transient, non-final error state.
    void OnStateTransientError();
  
    // Handles the job state corresponding to transferring data.
    void OnStateTransferring();
  
    HRESULT QueueBitsJob(const GURL& url);
    HRESULT CreateOrOpenJob(const GURL& url);
    HRESULT InitializeNewJob(const GURL& url);
  
    // Returns true if at the time of the call, it appears that the job
    // has not been making progress toward completion.
    bool IsStuck();
  
    // Makes the downloaded file available to the caller by renaming the
    // temporary file to its destination and removing it from the BITS queue.
    HRESULT CompleteJob();
  
    // Ensures that we are running on the same thread we created the object on.
    base::ThreadChecker thread_checker_;
  
    // Used to post responses back to the main thread. Initialized on the main
    // loop but accessed from the task runner.
    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
  
    net::URLRequestContextGetter* context_getter_;
    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
  
    // The timer and the BITS interface pointers have thread affinity. These
    // members are initialized on the task runner and they must be destroyed
    // on the task runner.
    scoped_ptr<base::RepeatingTimer<BackgroundDownloader> > timer_;
  
    base::win::ScopedComPtr<IBackgroundCopyManager> bits_manager_;
    base::win::ScopedComPtr<IBackgroundCopyJob> job_;
  
    // Contains the time when the download of the current url has started.
    base::Time download_start_time_;
  
    // Contains the time when the BITS job is last seen making progress.
    base::Time job_stuck_begin_time_;
  
    // True if EndDownload was called.
    bool is_completed_;
  
    // Contains the path of the downloaded file if the download was successful.
    base::FilePath response_;
  
    DISALLOW_COPY_AND_ASSIGN(BackgroundDownloader);
  };
  
  }  // namespace component_updater
  
  #endif  // COMPONENTS_COMPONENT_UPDATER_BACKGROUND_DOWNLOADER_WIN_H_
  