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谷歌浏览器的源码分析(11)   

2009-12-19 21:47:09|  分类: Chrome |  标签: |举报 |字号 订阅

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上一次介绍到怎么样从其它地方返回搜索到的超级连接,现在就来分析一下使用搜索引擎去查找的类SearchProvider,它是通过搜索引擎来查找出来的,在这里是通过GOOGLE搜索引擎来查找出来。它的声明如下:
#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.  When that data

#009  // comes back, the provider creates and returns matches for the best

#010  // suggestions.

 

SearchProvider类是继承AutocompleteProvider和URLFetcher类,AutocompleteProvider提供一个自动完成的结果,URLFetcher主要提供从URL获取数据和状态。

#011  class SearchProvider : public AutocompleteProvider,

#012                         public URLFetcher::Delegate {

#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 

 

 

开始获取。

#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 

 

当获取到数据回来时响应。

#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 

 

保存返回的结果。

#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 

 

运行获取搜索引擎数据。

#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 

 

在这个类里先调用函数SearchProvider::Start来获取缺省的搜索引擎,然后停止以前的搜索,接着SearchProvider::Run()函数里使用URLFetcher获取数据回来,它的代码如下:

#001   void SearchProvider::Run() {

#002    // Start a new request with the current input.

#003    DCHECK(!done_);

 

获取搜索的URL。

#004    const TemplateURLRef* const suggestions_url =

#005        default_provider_.suggestions_url();

 

建议代替的字符。

#006    DCHECK(suggestions_url->SupportsReplacement());

 

开始新的搜索。

#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  }

 

当前上面的搜索完成时,就会通知SearchProvider::OnURLFetchComplete函数来分析返回的结果,最后调用SearchProvider::ConvertResultsToAutocompleteMatches()函数来把结果转换自动完成的列表项。

 

通过上面的分析,就了解通过GOOGLE搜索引擎自动完成功能的实现。

 

本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/caimouse/archive/2008/09/22/2958960.aspx

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