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 // Support modularity by calling to load a new SDCH filter dictionary. 6 // Note that this sort of calling can't be done in the /net directory, as it has 7 // no concept of the HTTP cache (which is only visible at the browser level). 8 9 #ifndef CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_ 10 #define CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_ 11 #pragma once 12 13 #include <queue> 14 #include <set> 15 #include <string> 16 17 #include "base/memory/scoped_ptr.h" 18 #include "base/task.h" 19 #include "chrome/common/net/url_fetcher.h" 20 #include "net/base/sdch_manager.h" 21 22 class SdchDictionaryFetcher : public URLFetcher::Delegate, 23 public net::SdchFetcher { 24 public: 25 SdchDictionaryFetcher(); 26 virtual ~SdchDictionaryFetcher(); 27 28 // Stop fetching dictionaries, and abandon any current URLFetcheer operations 29 // so that the IO thread can be stopped. 30 static void Shutdown(); 31 32 // Implementation of SdchFetcher class. 33 // This method gets the requested dictionary, and then calls back into the 34 // SdchManager class with the dictionary's text. 35 virtual void Schedule(const GURL& dictionary_url); 36 37 private: 38 // Delay in ms between Schedule and actual download. 39 // This leaves the URL in a queue, which is de-duped, so that there is less 40 // chance we'll try to load the same URL multiple times when a pile of 41 // page subresources (or tabs opened in parallel) all suggest the dictionary. 42 static const int kMsDelayFromRequestTillDownload = 100; 43 44 // Ensure the download after the above delay. 45 void ScheduleDelayedRun(); 46 47 // Make sure we're processing (or waiting for) the the arrival of the next URL 48 // in the |fetch_queue_|. 49 void StartFetching(); 50 51 // Implementation of URLFetcher::Delegate. Called after transmission 52 // completes (either successfully or with failure). 53 virtual void OnURLFetchComplete(const URLFetcher* source, 54 const GURL& url, 55 const net::URLRequestStatus& status, 56 int response_code, 57 const ResponseCookies& cookies, 58 const std::string& data); 59 60 // A queue of URLs that are being used to download dictionaries. 61 std::queue<GURL> fetch_queue_; 62 // The currently outstanding URL fetch of a dicitonary. 63 // If this is null, then there is no outstanding request. 64 scoped_ptr<URLFetcher> current_fetch_; 65 66 // Always spread out the dictionary fetches, so that they don't steal 67 // bandwidth from the actual page load. Create delayed tasks to spread out 68 // the download. 69 ScopedRunnableMethodFactory<SdchDictionaryFetcher> method_factory_; 70 bool task_is_pending_; 71 72 // Althought the SDCH spec does not preclude a server from using a single URL 73 // to load several distinct dictionaries (by telling a client to load a 74 // dictionary from an URL several times), current implementations seem to have 75 // that 1-1 relationship (i.e., each URL points at a single dictionary, and 76 // the dictionary content does not change over time, and hence is not worth 77 // trying to load more than once). In addition, some dictionaries prove 78 // unloadable only after downloading them (because they are too large? ...or 79 // malformed?). As a protective element, Chromium will *only* load a 80 // dictionary at most once from a given URL (so that it doesn't waste 81 // bandwidth trying repeatedly). 82 // The following set lists all the dictionary URLs that we've tried to load, 83 // so that we won't try to load from an URL more than once. 84 // TODO(jar): Try to augment the SDCH proposal to include this restiction. 85 std::set<GURL> attempted_load_; 86 87 DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher); 88 }; 89 90 #endif // CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_ 91
