[AiS] ImageService

chrome/browser/bitmap_fetcher/bitmap_fetcher_service.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#ifndef CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_
+#define CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_
+
+#include "base/compiler_specific.h"
+#include "base/containers/mru_cache.h"
+#include "base/containers/scoped_ptr_hash_map.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "chrome/browser/bitmap_fetcher_delegate.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+namespace content {
+class BrowserContext;
+}  // namespace content
+
+namespace chrome {
+class BitmapFetcher;
+}  // namespace chrome
+
+class BitmapFetcherRequest;
+class GURL;
+class SkBitmap;
+
+// Service to retrieve images for Answers in Suggest.
+class BitmapFetcherService : public KeyedService,
+                             public chrome::BitmapFetcherDelegate {
+ public:
+  typedef int RequestId;
+  static const RequestId REQUEST_ID_INVALID = 0;
+
+  class Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Called whenever the image changes. Called with an empty image if the
+    // fetch failed or the request ended for any reason.
+    virtual void OnImageChanged(RequestId request_id,
+                                const SkBitmap& answers_image) = 0;
+  };
+
+  explicit BitmapFetcherService(content::BrowserContext* context);
+  virtual ~BitmapFetcherService();
+
+  // Cancels a request, if it is still in-flight.
+  void CancelRequest(RequestId requestId);
+
+  // Requests a new image. Will either trigger download or satisfy from cache.
+  // Takes ownership of |observer|. If there are too many outstanding requests,
+  // the request will fail and |observer| will be called to signal failure.
+  // Otherwise, |observer| will be called with either the cached image or the
+  // downloaded one.
+  // NOTE: The observer might be called back synchronously from RequestImage if
+  // the image is already in the cache.
+  RequestId RequestImage(const GURL& url, Observer* observer);
+
+  // Start fetching the image at the given |url|.
+  void Prefetch(const GURL& url);
+
+ protected:
+  // Create a bitmap fetcher for the given |url| and start it. Virtual method
+  // so tests can override this for different behavior.
+  virtual chrome::BitmapFetcher* CreateFetcher(const GURL& url);
+
+ private:
+  friend class BitmapFetcherServiceTest;
+
+  typedef ScopedVector<chrome::BitmapFetcher> BitmapFetchers;
+
+  // Gets the existing fetcher for |url| or constructs a new one if it doesn't
+  // exist.
+  const chrome::BitmapFetcher* EnsureFetcherForUrl(const GURL& url);
+
+  // Find a fetcher with a given |url|. Return NULL if none is found.
+  const chrome::BitmapFetcher* FindFetcherForUrl(const GURL& url);
+
+  // Remove |fetcher| from list of active fetchers. |fetcher| MUST be part of
+  // the list.
+  void RemoveFetcher(const chrome::BitmapFetcher* fetcher);
+
+  // BitmapFetcherDelegate implementation.
+  virtual void OnFetchComplete(const GURL url, const SkBitmap* bitmap) OVERRIDE;
+
+  // Currently active image fetchers.
+  BitmapFetchers active_fetchers_;
+
+  // Currently active requests.
+  ScopedVector<BitmapFetcherRequest> requests_;
+
+  // Cache of retrieved images.
+  struct CacheEntry {
+    CacheEntry();
+    ~CacheEntry();
+
+    scoped_ptr<const SkBitmap> bitmap;
+  };
+  base::OwningMRUCache<GURL, CacheEntry*> cache_;
+
+  // Current request ID to be used.
+  int current_request_id_;
+
+  // Browser context this service is active for.
+  content::BrowserContext* context_;
+
+  DISALLOW_COPY_AND_ASSIGN(BitmapFetcherService);
+};
+
+#endif  // CHROME_BROWSER_BITMAP_FETCHER_BITMAP_FETCHER_SERVICE_H_