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 {
  38       kNone = 0,
  39       kUrlFetcher,
  40       kBits
  41     };
  42
  43     DownloadMetrics();
  44
  45     GURL url;
  46
  47     Downloader downloader;
  48
  49     int error;
  50
  51     int64 bytes_downloaded;   // -1 means that the byte count is unknown.
  52     int64 bytes_total;
  53
  54     uint64 download_time_ms;
  55   };
  56
  57   // Contains the outcome of the download.
  58   struct Result {
  59     Result();
  60
  61     // Download error: 0 indicates success.
  62     int error;
  63
  64     // Path of the downloaded file if the download was successful.
  65     base::FilePath response;
  66   };
  67
  68   // The callback fires only once, regardless of how many urls are tried, and
  69   // how many successors in the chain of downloaders have handled the
  70   // download. The callback interface can be extended if needed to provide
  71   // more visibility into how the download has been handled, including
  72   // specific error codes and download metrics.
  73   typedef base::Callback<void (const Result& result)> DownloadCallback;
  74
  75   // Factory method to create an instance of this class and build the
  76   // chain of responsibility. |is_background_download| specifies that a
  77   // background downloader be used, if the platform supports it.
  78   static CrxDownloader* Create(
  79       bool is_background_download,
  80       net::URLRequestContextGetter* context_getter,
  81       scoped_refptr<base::SequencedTaskRunner> task_runner,
  82       const DownloadCallback& download_callback);
  83   virtual ~CrxDownloader();
  84
  85   // Starts the download. One instance of the class handles one download only.
  86   // One instance of CrxDownloader can only be started once, otherwise the
  87   // behavior is undefined. The callback gets invoked if the download can't
  88   // be started.
  89   void StartDownloadFromUrl(const GURL& url);
  90   void StartDownload(const std::vector<GURL>& urls);
  91
  92   const std::vector<DownloadMetrics> download_metrics() const;
  93
  94  protected:
  95   CrxDownloader(scoped_ptr<CrxDownloader> successor,
  96                 const DownloadCallback& download_callback);
  97
  98   // Handles the fallback in the case of multiple urls and routing of the
  99   // download to the following successor in the chain. Derived classes must call
 100   // this function after each attempt at downloading the urls provided
 101   // in the StartDownload function.
 102   // In case of errors, |is_handled| indicates that a server side error has
 103   // occured for the current url and the url should not be retried down
 104   // the chain to avoid DDOS of the server. This url will be removed from the
 105   // list of url and never tried again.
 106   void OnDownloadComplete(bool is_handled,
 107                           const Result& result,
 108                           const DownloadMetrics& download_metrics);
 109
 110   // Returns the url which is currently downloaded from.
 111   GURL url() const;
 112
 113  private:
 114   virtual void DoStartDownload(const GURL& url) = 0;
 115
 116   std::vector<GURL> urls_;
 117   scoped_ptr<CrxDownloader> successor_;
 118   DownloadCallback download_callback_;
 119
 120   std::vector<GURL>::iterator current_url_;
 121
 122   std::vector<DownloadMetrics> download_metrics_;
 123
 124   DISALLOW_COPY_AND_ASSIGN(CrxDownloader);
 125 };
 126
 127 }  // namespace component_updater
 128
 129 #endif  // CHROME_BROWSER_COMPONENT_UPDATER_CRX_DOWNLOADER_H_
 130