谷歌瀏覽器的源碼分析 11
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上一次介紹到怎麽樣從其它地方返回搜索到的超級連接，現在就來分析一下使用搜索引擎去查找的類SearchProvider，它是通過搜索引擎來查找出來的，在這裏是通過GOOGLE搜索引擎來查找出來。它的聲明如下：#001 // Autocomplete provider for searches and suggestions from a search engine.
#002 //
#003 // After construction, the autocomplete controller repeatedly calls Start()
#004 // with some user input, each time expecting to receive a small set of the best
#005 // matches (either synchronously or asynchronously).
#006 //
#007 // Initially the provider creates a match that searches for the current input
#008 // text. It also starts a task to query the Suggest servers.
#009 // comes back, the provider creates and returns matches for the best
#010 // suggestions.
SearchProvider類是繼承AutocompleteProvider和URLFetcher類，AutocompleteProvider提供一個自動完成的結果，URLFetcher主要提供從URL獲取數據和狀態。
#011 class SearchProvider : public AutocompleteProvider,
#012
#013 public:
#014 SearchProvider(ACProviderListener* listener, Profile* profile)
#015 : AutocompleteProvider(listener, profile, "Search"),
#016 last_default_provider_(NULL),
#017 fetcher_(NULL),
#018 history_request_pending_(false),
#019 have_history_results_(false),
#020 suggest_results_pending_(false),
#021 have_suggest_results_(false) {
#022 }
#023
開始獲取。
#024 // AutocompleteProvider
#025 virtual void Start(const AutocompleteInput& input,
#026 bool minimal_changes,
#027 bool synchronous_only);
停止查找。
#028 virtual void Stop();
#029
當獲取到數據回來時響應。
#030 // URLFetcher::Delegate
#031 virtual void OnURLFetchComplete(const URLFetcher* source,
#032 const GURL& url,
#033 const URLRequestStatus& status,
#034 int response_code,
#035 const ResponseCookies& cookies,
#036 const std::string& data);
#037
#038 private:
#039 struct NavigationResult {
#040 NavigationResult(const std::wstring& url, const std::wstring& site_name)
#041 : url(url),
#042 site_name(site_name) {
#043 }
#044
#045 // The URL.
#046 std::wstring url;
#047
#048 // Name for the site.
#049 std::wstring site_name;
#050 };
#051
保存返回的結果。
#052 typedef std::vector<std::wstring> SuggestResults;
#053 typedef std::vector<NavigationResult> NavigationResults;
#054 typedef std::vector<history::KeywordSearchTermVisit> HistoryResults;
#055 typedef std::map<std::wstring, AutocompleteMatch> MatchMap;
#056
運行獲取搜索引擎數據。
#057 // Called when timer_ expires.
#058 void Run();
#059
#060 // Determines whether an asynchronous subcomponent query should run for the
#061 // current input. If so, starts it if necessary; otherwise stops it.
#062 // NOTE: These functions do not update |done_|. Callers must do so.
#063 void StartOrStopHistoryQuery(bool minimal_changes, bool synchronous_only);
#064 void StartOrStopSuggestQuery(bool minimal_changes, bool synchronous_only);
#065
#066 // Functions to stop the separate asynchronous subcomponents.
#067 // NOTE: These functions do not update |done_|. Callers must do so.
#068 void StopHistory();
#069 void StopSuggest();
#070
#071 // Called back by the history system to return searches that begin with the
#072 // input text.
#073 void OnGotMostRecentKeywordSearchTerms(
#074 CancelableRequestProvider::Handle handle,
#075 HistoryResults* results);
#076
#077 // Parses the results from the Suggest server and stores up to kMaxMatches of
#078 // them in server_results_. Returns whether parsing succeeded.
#079 bool ParseSuggestResults(Value* root_val);
#080
#081 // Converts the parsed server results in server_results_ to a set of
#082 // AutocompleteMatches and adds them to |matches_|. This also sets |done_|
#083 // correctly.
#084 void ConvertResultsToAutocompleteMatches();
#085
#086 // Determines the relevance for a particular match. We use different scoring
#087 // algorithms for the different types of matches.
#088 int CalculateRelevanceForWhatYouTyped() const;
#089 // |time| is the time at which this query was last seen.
#090 int CalculateRelevanceForHistory(const Time& time) const;
#091 // |suggestion_value| is which suggestion this is in the list returned from
#092 // the server; the best suggestion is suggestion number 0.
#093 int CalculateRelevanceForSuggestion(size_t suggestion_value) const;
#094 // |suggestion_value| is same as above.
#095 int CalculateRelevanceForNavigation(size_t suggestion_value) const;
#096
#097 // Creates an AutocompleteMatch for "Search <engine> for |query_string|" with
#098 // the supplied relevance. Adds this match to |map|; if such a match already
#099 // exists, whichever one has lower relevance is eliminated.
#100 void AddMatchToMap(const std::wstring& query_string,
#101 int relevance,
#102 int accepted_suggestion,
#103 MatchMap* map);
#104 // Returns an AutocompleteMatch for a navigational suggestion.
#105 AutocompleteMatch NavigationToMatch(const NavigationResult& query_string,
#106 int relevance);
#107
#108 // Trims "http:" and up to two subsequent slashes from |url|. Returns the
#109 // number of characters that were trimmed.
#110 // TODO(kochi): this is duplicate from history_autocomplete
#111 static size_t TrimHttpPrefix(std::wstring* url);
#112
#113 // Don‘t send any queries to the server until some time has elapsed after
#114 // the last keypress, to avoid flooding the server with requests we are
#115 // likely to end up throwing away anyway.
#116 static const int kQueryDelayMs;
#117
#118 // The user‘s input.
#119 AutocompleteInput input_;
#120
#121 TemplateURL default_provider_; // Cached across the life of a query so we
#122 // behave consistently even if the user
#123 // changes their default while the query is
#124 // running.
#125 const TemplateURL* last_default_provider_;
#126 // TODO(pkasting): http://b/1162970 We
#127 // shouldn‘t need this.
#128
#129 // An object we can use to cancel history requests.
#130 CancelableRequestConsumer history_request_consumer_;
#131
#132 // Searches in the user‘s history that begin with the input text.
#133 HistoryResults history_results_;
#134
#135 // Whether history_results_ is valid (so we can tell invalid apart from
#136 // empty).
#137 bool have_history_results_;
#138
#139 // Whether we are waiting for a history request to finish.
#140 bool history_request_pending_;
#141
#142 // True if we‘re expecting suggest results that haven‘t yet arrived. This
#143 // could be because either |timer_| or |fetcher| is still running (see below).
#144 bool suggest_results_pending_;
#145
#146 // A timer to start a query to the suggest server after the user has stopped
#147 // typing for long enough.
#148 base::OneShotTimer<SearchProvider> timer_;
#149
#150 // The fetcher that retrieves suggest results from the server.
#151 scoped_ptr<URLFetcher> fetcher_;
#152
#153 // Suggestions returned by the Suggest server for the input text.
#154 SuggestResults suggest_results_;
#155
#156 // Navigational suggestions returned by the server.
#157 NavigationResults navigation_results_;
#158
#159 // Whether suggest_results_ is valid.
#160 bool have_suggest_results_;
#161
#162 DISALLOW_EVIL_CONSTRUCTORS(SearchProvider);
#163 };
#164
在這個類裏先調用函數SearchProvider::Start來獲取缺省的搜索引擎，然後停止以前的搜索，接著SearchProvider::Run()函數裏使用URLFetcher獲取數據回來，它的代碼如下：
#001 void SearchProvider::Run() {
#002 // Start a new request with the current input.
#003 DCHECK(!done_);
獲取搜索的URL。
#004 const TemplateURLRef* const suggestions_url =
#005 default_provider_.suggestions_url();
建議代替的字符。
#006 DCHECK(suggestions_url->SupportsReplacement());
開始新的搜索。
#007 fetcher_.reset(new URLFetcher(GURL(suggestions_url->ReplaceSearchTerms(
#008 default_provider_, input_.text(),
#009 TemplateURLRef::NO_SUGGESTIONS_AVAILABLE, std::wstring())),
#010 URLFetcher::GET, this));
#011 fetcher_->set_request_context(profile_->GetRequestContext());
#012 fetcher_->Start();
#013 }
當前上面的搜索完成時，就會通知SearchProvider::OnURLFetchComplete函數來分析返回的結果，最後調用SearchProvider::ConvertResultsToAutocompleteMatches()函數來把結果轉換自動完成的列表項。
通過上面的分析，就了解通過GOOGLE搜索引擎自動完成功能的實現。
再分享一下我老師大神的人工智能教程吧。零基礎！通俗易懂！風趣幽默！還帶黃段子！希望你也加入到我們人工智能的隊伍中來！http://www.captainbed.net
谷歌瀏覽器的源碼分析 11