components/precache/core/precache_fetcher.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 COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
   6 #define COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
   7
   8 #include <list>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "url/gurl.h"
  16
  17 namespace net {
  18 class URLFetcher;
  19 class URLRequestContextGetter;
  20 }
  21
  22 namespace precache {
  23
  24 // Public interface to code that fetches resources that the user is likely to
  25 // want to fetch in the future, putting them in the network stack disk cache.
  26 // Precaching is intended to be done when Chrome is not actively in use, likely
  27 // hours ahead of the time when the resources are actually needed.
  28 //
  29 // This class takes as input a prioritized list of URL domains that the user
  30 // commonly visits, referred to as starting hosts. This class interacts with a
  31 // server, sending it the list of starting hosts sequentially. For each starting
  32 // host, the server returns a manifest of resource URLs that are good candidates
  33 // for precaching. Every resource returned is fetched, and responses are cached
  34 // as they are received. Destroying the PrecacheFetcher while it is precaching
  35 // will cancel any fetch in progress and cancel precaching.
  36 //
  37 // The URLs of the server-side component must be specified in order for the
  38 // PrecacheFetcher to work. This includes the URL that the precache
  39 // configuration settings are fetched from and the prefix of URLs where precache
  40 // manifests are fetched from. These can be set by using command line switches
  41 // or by providing default values.
  42 //
  43 // Sample interaction:
  44 //
  45 // class MyPrecacheFetcherDelegate : public PrecacheFetcher::PrecacheDelegate {
  46 //  public:
  47 //   void PrecacheResourcesForTopURLs(
  48 //       net::URLRequestContextGetter* request_context,
  49 //       const std::list<GURL>& top_urls) {
  50 //     fetcher_.reset(new PrecacheFetcher(request_context, top_urls, this));
  51 //     fetcher_->Start();
  52 //   }
  53 //
  54 //   virtual void OnDone() {
  55 //     // Do something when precaching is done.
  56 //   }
  57 //
  58 //  private:
  59 //   scoped_ptr<PrecacheFetcher> fetcher_;
  60 // };
  61 class PrecacheFetcher {
  62  public:
  63   class PrecacheDelegate {
  64    public:
  65     // Called when the fetching of resources has finished, whether the resources
  66     // were fetched or not. If the PrecacheFetcher is destroyed before OnDone is
  67     // called, then precaching will be canceled and OnDone will not be called.
  68     virtual void OnDone() = 0;
  69   };
  70
  71   // Constructs a new PrecacheFetcher. The |starting_hosts| parameter is a
  72   // prioritized list of hosts that the user commonly visits. These hosts are
  73   // used by a server side component to construct a list of resource URLs that
  74   // the user is likely to fetch.
  75   PrecacheFetcher(const std::vector<std::string>& starting_hosts,
  76                   net::URLRequestContextGetter* request_context,
  77                   PrecacheDelegate* precache_delegate);
  78
  79   virtual ~PrecacheFetcher();
  80
  81   // Starts fetching resources to precache. URLs are fetched sequentially. Can
  82   // be called from any thread. Start should only be called once on a
  83   // PrecacheFetcher instance.
  84   void Start();
  85
  86  private:
  87   class Fetcher;
  88
  89   // Fetches the next resource or manifest URL, if any remain. Fetching is done
  90   // sequentially and depth-first: all resources are fetched for a manifest
  91   // before the next manifest is fetched. This is done to limit the length of
  92   // the |resource_urls_to_fetch_| list, reducing the memory usage.
  93   void StartNextFetch();
  94
  95   // Called when the precache configuration settings have been fetched.
  96   // Determines the list of manifest URLs to fetch according to the list of
  97   // |starting_hosts_| and information from the precache configuration settings.
  98   // If the fetch of the configuration settings fails, then precaching ends.
  99   void OnConfigFetchComplete(const net::URLFetcher& source);
 100
 101   // Called when a precache manifest has been fetched. Builds the list of
 102   // resource URLs to fetch according to the URLs in the manifest. If the fetch
 103   // of a manifest fails, then it skips to the next manifest.
 104   void OnManifestFetchComplete(const net::URLFetcher& source);
 105
 106   // Called when a resource has been fetched.
 107   void OnResourceFetchComplete(const net::URLFetcher& source);
 108
 109   // The prioritized list of starting hosts that the server will pick resource
 110   // URLs to be precached for.
 111   const std::vector<std::string> starting_hosts_;
 112
 113   // The request context used when fetching URLs.
 114   scoped_refptr<net::URLRequestContextGetter> request_context_;
 115
 116   // Non-owning pointer. Should not be NULL.
 117   PrecacheDelegate* precache_delegate_;
 118
 119   scoped_ptr<Fetcher> fetcher_;
 120
 121   std::list<GURL> manifest_urls_to_fetch_;
 122   std::list<GURL> resource_urls_to_fetch_;
 123
 124   DISALLOW_COPY_AND_ASSIGN(PrecacheFetcher);
 125 };
 126
 127 }  // namespace precache
 128
 129 #endif  // COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_