chrome/browser/bitmap_fetcher/bitmap_fetcher_service.h

   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/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     // TODO(dschuyler) The comment differs from what the code does, follow-up.
  41     virtual void OnImageChanged(RequestId request_id,
  42                                 const SkBitmap& answers_image) = 0;
  43   };
  44
  45   explicit BitmapFetcherService(content::BrowserContext* context);
  46   ~BitmapFetcherService() override;
  47
  48   // Cancels a request, if it is still in-flight.
  49   void CancelRequest(RequestId requestId);
  50
  51   // Requests a new image. Will either trigger download or satisfy from cache.
  52   // Takes ownership of |observer|. If there are too many outstanding requests,
  53   // the request will fail and |observer| will be called to signal failure.
  54   // Otherwise, |observer| will be called with either the cached image or the
  55   // downloaded one.
  56   // NOTE: The observer might be called back synchronously from RequestImage if
  57   // the image is already in the cache.
  58   RequestId RequestImage(const GURL& url, Observer* observer);
  59
  60   // Start fetching the image at the given |url|.
  61   void Prefetch(const GURL& url);
  62
  63  protected:
  64   // Create a bitmap fetcher for the given |url| and start it. Virtual method
  65   // so tests can override this for different behavior.
  66   virtual chrome::BitmapFetcher* CreateFetcher(const GURL& url);
  67
  68  private:
  69   friend class BitmapFetcherServiceTest;
  70
  71   typedef ScopedVector<chrome::BitmapFetcher> BitmapFetchers;
  72
  73   // Gets the existing fetcher for |url| or constructs a new one if it doesn't
  74   // exist.
  75   const chrome::BitmapFetcher* EnsureFetcherForUrl(const GURL& url);
  76
  77   // Find a fetcher with a given |url|. Return NULL if none is found.
  78   const chrome::BitmapFetcher* FindFetcherForUrl(const GURL& url);
  79
  80   // Remove |fetcher| from list of active fetchers. |fetcher| MUST be part of
  81   // the list.
  82   void RemoveFetcher(const chrome::BitmapFetcher* fetcher);
  83
  84   // BitmapFetcherDelegate implementation.
  85   void OnFetchComplete(const GURL& url, const SkBitmap* bitmap) override;
  86
  87   // Currently active image fetchers.
  88   BitmapFetchers active_fetchers_;
  89
  90   // Currently active requests.
  91   ScopedVector<BitmapFetcherRequest> requests_;
  92
  93   // Cache of retrieved images.
  94   struct CacheEntry {
  95     CacheEntry();
  96     ~CacheEntry();
  97
  98     scoped_ptr<const SkBitmap> bitmap;
  99   };
 100   base::OwningMRUCache<GURL, CacheEntry*> cache_;
 101
 102   // Current request ID to be used.
 103   int current_request_id_;
 104
 105   // Browser context this service is active for.
 106   content::BrowserContext* context_;
 107
 108   DISALLOW_COPY_AND_ASSIGN(BitmapFetcherService);
 109 };
 110
 111 #endif  // CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_