chrome/browser/component_updater/crx_downloader.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_
   6 #define CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "base/callback.h"
  12 #include "base/files/file_path.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "base/sequenced_task_runner.h"
  16 #include "url/gurl.h"
  17
  18 namespace net {
  19 class URLRequestContextGetter;
  20 }
  21
  22 namespace component_updater {
  23
  24 // Defines a download interface for downloading components, with retrying on
  25 // fallback urls in case of errors. This class implements a chain of
  26 // responsibility design pattern. It can give successors in the chain a chance
  27 // to handle a download request, until one of them succeeds, or there are no
  28 // more urls or successors to try. A callback is always called at the end of
  29 // the download, one time only.
  30 // When multiple urls and downloaders exists, first all the urls are tried, in
  31 // the order they are provided in the StartDownload function argument. After
  32 // that, the download request is routed to the next downloader in the chain.
  33 // The members of this class expect to be called from the UI thread only.
  34 class CrxDownloader {
  35  public:
  36   struct DownloadMetrics {
  37     enum Downloader { kNone = 0, kUrlFetcher, kBits };
  38
  39     DownloadMetrics();
  40
  41     GURL url;
  42
  43     Downloader downloader;
  44
  45     int error;
  46
  47     int64 downloaded_bytes;  // -1 means that the byte count is unknown.
  48     int64 total_bytes;
  49
  50     uint64 download_time_ms;
  51   };
  52
  53   // Contains the progress or the outcome of the download.
  54   struct Result {
  55     Result();
  56
  57     // Download error: 0 indicates success.
  58     int error;
  59
  60     // Path of the downloaded file if the download was successful.
  61     base::FilePath response;
  62
  63     // Number of bytes actually downloaded, not including the bytes downloaded
  64     // as a result of falling back on urls.
  65     int64 downloaded_bytes;
  66
  67     // Number of bytes expected to be downloaded.
  68     int64 total_bytes;
  69   };
  70
  71   // The callback fires only once, regardless of how many urls are tried, and
  72   // how many successors in the chain of downloaders have handled the
  73   // download. The callback interface can be extended if needed to provide
  74   // more visibility into how the download has been handled, including
  75   // specific error codes and download metrics.
  76   typedef base::Callback<void(const Result& result)> DownloadCallback;
  77
  78   // The callback may fire 0 or many times during a download. Since this
  79   // class implements a chain of responsibility, the callback can fire for
  80   // different urls and different downloaders. The number of actual downloaded
  81   // bytes is not guaranteed to monotonically increment over time.
  82   typedef base::Callback<void(const Result& result)> ProgressCallback;
  83
  84   // Factory method to create an instance of this class and build the
  85   // chain of responsibility. |is_background_download| specifies that a
  86   // background downloader be used, if the platform supports it.
  87   static CrxDownloader* Create(
  88       bool is_background_download,
  89       net::URLRequestContextGetter* context_getter,
  90       scoped_refptr<base::SequencedTaskRunner> task_runner);
  91   virtual ~CrxDownloader();
  92
  93   void set_progress_callback(const ProgressCallback& progress_callback);
  94
  95   // Starts the download. One instance of the class handles one download only.
  96   // One instance of CrxDownloader can only be started once, otherwise the
  97   // behavior is undefined. The callback gets invoked if the download can't
  98   // be started.
  99   void StartDownloadFromUrl(const GURL& url,
 100                             const DownloadCallback& download_callback);
 101   void StartDownload(const std::vector<GURL>& urls,
 102                      const DownloadCallback& download_callback);
 103
 104   const std::vector<DownloadMetrics> download_metrics() const;
 105
 106  protected:
 107   explicit CrxDownloader(scoped_ptr<CrxDownloader> successor);
 108
 109   // Handles the fallback in the case of multiple urls and routing of the
 110   // download to the following successor in the chain. Derived classes must call
 111   // this function after each attempt at downloading the urls provided
 112   // in the StartDownload function.
 113   // In case of errors, |is_handled| indicates that a server side error has
 114   // occured for the current url and the url should not be retried down
 115   // the chain to avoid DDOS of the server. This url will be removed from the
 116   // list of url and never tried again.
 117   void OnDownloadComplete(bool is_handled,
 118                           const Result& result,
 119                           const DownloadMetrics& download_metrics);
 120
 121   // Calls the callback when progress is made.
 122   void OnDownloadProgress(const Result& result);
 123
 124   // Returns the url which is currently being downloaded from.
 125   GURL url() const;
 126
 127  private:
 128   virtual void DoStartDownload(const GURL& url) = 0;
 129
 130   std::vector<GURL> urls_;
 131   scoped_ptr<CrxDownloader> successor_;
 132   DownloadCallback download_callback_;
 133   ProgressCallback progress_callback_;
 134
 135   std::vector<GURL>::iterator current_url_;
 136
 137   std::vector<DownloadMetrics> download_metrics_;
 138
 139   DISALLOW_COPY_AND_ASSIGN(CrxDownloader);
 140 };
 141
 142 }  // namespace component_updater
 143
 144 #endif  // CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_