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      1 // Copyright 2014 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 #ifndef CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_
      5 #define CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_
      6 
      7 #include "base/compiler_specific.h"
      8 #include "base/containers/mru_cache.h"
      9 #include "base/containers/scoped_ptr_hash_map.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "base/memory/scoped_vector.h"
     12 #include "chrome/browser/bitmap_fetcher_delegate.h"
     13 #include "components/keyed_service/core/keyed_service.h"
     14 
     15 namespace content {
     16 class BrowserContext;
     17 }  // namespace content
     18 
     19 namespace chrome {
     20 class BitmapFetcher;
     21 }  // namespace chrome
     22 
     23 class BitmapFetcherRequest;
     24 class GURL;
     25 class SkBitmap;
     26 
     27 // Service to retrieve images for Answers in Suggest.
     28 class BitmapFetcherService : public KeyedService,
     29                              public chrome::BitmapFetcherDelegate {
     30  public:
     31   typedef int RequestId;
     32   static const RequestId REQUEST_ID_INVALID = 0;
     33 
     34   class Observer {
     35    public:
     36     virtual ~Observer() {}
     37 
     38     // Called whenever the image changes. Called with an empty image if the
     39     // fetch failed or the request ended for any reason.
     40     virtual void OnImageChanged(RequestId request_id,
     41                                 const SkBitmap& answers_image) = 0;
     42   };
     43 
     44   explicit BitmapFetcherService(content::BrowserContext* context);
     45   virtual ~BitmapFetcherService();
     46 
     47   // Cancels a request, if it is still in-flight.
     48   void CancelRequest(RequestId requestId);
     49 
     50   // Requests a new image. Will either trigger download or satisfy from cache.
     51   // Takes ownership of |observer|. If there are too many outstanding requests,
     52   // the request will fail and |observer| will be called to signal failure.
     53   // Otherwise, |observer| will be called with either the cached image or the
     54   // downloaded one.
     55   // NOTE: The observer might be called back synchronously from RequestImage if
     56   // the image is already in the cache.
     57   RequestId RequestImage(const GURL& url, Observer* observer);
     58 
     59   // Start fetching the image at the given |url|.
     60   void Prefetch(const GURL& url);
     61 
     62  protected:
     63   // Create a bitmap fetcher for the given |url| and start it. Virtual method
     64   // so tests can override this for different behavior.
     65   virtual chrome::BitmapFetcher* CreateFetcher(const GURL& url);
     66 
     67  private:
     68   friend class BitmapFetcherServiceTest;
     69 
     70   typedef ScopedVector<chrome::BitmapFetcher> BitmapFetchers;
     71 
     72   // Gets the existing fetcher for |url| or constructs a new one if it doesn't
     73   // exist.
     74   const chrome::BitmapFetcher* EnsureFetcherForUrl(const GURL& url);
     75 
     76   // Find a fetcher with a given |url|. Return NULL if none is found.
     77   const chrome::BitmapFetcher* FindFetcherForUrl(const GURL& url);
     78 
     79   // Remove |fetcher| from list of active fetchers. |fetcher| MUST be part of
     80   // the list.
     81   void RemoveFetcher(const chrome::BitmapFetcher* fetcher);
     82 
     83   // BitmapFetcherDelegate implementation.
     84   virtual void OnFetchComplete(const GURL url, const SkBitmap* bitmap) OVERRIDE;
     85 
     86   // Currently active image fetchers.
     87   BitmapFetchers active_fetchers_;
     88 
     89   // Currently active requests.
     90   ScopedVector<BitmapFetcherRequest> requests_;
     91 
     92   // Cache of retrieved images.
     93   struct CacheEntry {
     94     CacheEntry();
     95     ~CacheEntry();
     96 
     97     scoped_ptr<const SkBitmap> bitmap;
     98   };
     99   base::OwningMRUCache<GURL, CacheEntry*> cache_;
    100 
    101   // Current request ID to be used.
    102   int current_request_id_;
    103 
    104   // Browser context this service is active for.
    105   content::BrowserContext* context_;
    106 
    107   DISALLOW_COPY_AND_ASSIGN(BitmapFetcherService);
    108 };
    109 
    110 #endif  // CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_
    111