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      1 // Copyright (c) 2011 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 // This is the global interface for the dns prefetch services.  It centralizes
      6 // initialization, along with all the callbacks etc. to connect to the browser
      7 // process.  This allows the more standard DNS prefetching services, such as
      8 // provided by Predictor to be left as more generally usable code, and possibly
      9 // be shared across multiple client projects.
     10 
     11 #ifndef CHROME_BROWSER_NET_PREDICTOR_API_H_
     12 #define CHROME_BROWSER_NET_PREDICTOR_API_H_
     13 #pragma once
     14 
     15 
     16 #include <string>
     17 #include <vector>
     18 
     19 #include "base/memory/ref_counted.h"
     20 #include "chrome/browser/autocomplete/autocomplete.h"
     21 #include "chrome/browser/net/predictor.h"
     22 
     23 namespace base {
     24 class FieldTrial;
     25 }
     26 
     27 class PrefService;
     28 
     29 namespace chrome_browser_net {
     30 
     31 // Deletes |referral_list| when done.
     32 void FinalizePredictorInitialization(
     33     Predictor* global_predictor,
     34     const std::vector<GURL>& urls_to_prefetch,
     35     ListValue* referral_list);
     36 
     37 // Free all resources allocated by FinalizePredictorInitialization. After that
     38 // you must not call any function from this file.
     39 void FreePredictorResources();
     40 
     41 //------------------------------------------------------------------------------
     42 // Global APIs relating to predictions in browser.
     43 void EnablePredictor(bool enable);
     44 void DiscardInitialNavigationHistory();
     45 void RegisterUserPrefs(PrefService* user_prefs);
     46 
     47 // Renderer bundles up list and sends to this browser API via IPC.
     48 // TODO(jar): Use UrlList instead to include port and scheme.
     49 void DnsPrefetchList(const NameList& hostnames);
     50 
     51 // This API is used by the autocomplete popup box (as user types).
     52 // This will either preresolve the domain name, or possibly preconnect creating
     53 // an open TCP/IP connection to the host.
     54 void AnticipateOmniboxUrl(const GURL& url, bool preconnectable);
     55 
     56 // This API should only be called when we're absolutely certain that we will
     57 // be connecting to the URL.  It will preconnect the url and it's associated
     58 // subresource domains immediately.
     59 void PreconnectUrlAndSubresources(const GURL& url);
     60 
     61 // When displaying info in about:dns, the following API is called.
     62 void PredictorGetHtmlInfo(std::string* output);
     63 
     64 // Destroy the predictor's internal state: referrers and work queue.
     65 void ClearPredictorCache();
     66 
     67 //------------------------------------------------------------------------------
     68 // When we navigate to a frame that may contain embedded resources, we may know
     69 // in advance some other URLs that will need to be connected to (via TCP and
     70 // sometimes SSL).  This function initiates those connections
     71 void PredictFrameSubresources(const GURL& url);
     72 
     73 // During startup, we learn what the first N urls visited are, and then resolve
     74 // the associated hosts ASAP during our next startup.
     75 void LearnAboutInitialNavigation(const GURL& url);
     76 
     77 // Call when we should learn from a navigation about a relationship to a
     78 // subresource target, and its containing frame, which was loaded as a referring
     79 // URL.
     80 void LearnFromNavigation(const GURL& referring_url, const GURL& target_url);
     81 
     82 //------------------------------------------------------------------------------
     83 void SavePredictorStateForNextStartupAndTrim(PrefService* prefs);
     84 // Helper class to handle global init and shutdown.
     85 class PredictorInit {
     86  public:
     87   // Too many concurrent lookups performed in parallel may overload a resolver,
     88   // or may cause problems for a local router.  The following limits that count.
     89   static const size_t kMaxSpeculativeParallelResolves;
     90 
     91   // When prefetch requests are queued beyond some period of time, then the
     92   // system is congested, and we need to clear all queued requests to get out
     93   // of that state.  The following is the suggested default time limit.
     94   static const int kMaxSpeculativeResolveQueueDelayMs;
     95 
     96   PredictorInit(PrefService* user_prefs, PrefService* local_state,
     97                 bool preconnect_enabled);
     98   ~PredictorInit();
     99 
    100  private:
    101   // Maintain a field trial instance when we do A/B testing.
    102   scoped_refptr<base::FieldTrial> trial_;
    103 
    104   DISALLOW_COPY_AND_ASSIGN(PredictorInit);
    105 };
    106 
    107 }  // namespace chrome_browser_net
    108 
    109 #endif  // CHROME_BROWSER_NET_PREDICTOR_API_H_
    110