Implementing preload=metadata for video

webkit/glue/media/buffered_resource_loader.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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 WEBKIT_GLUE_MEDIA_BUFFERED_RESOURCE_LOADER_H_
 #define WEBKIT_GLUE_MEDIA_BUFFERED_RESOURCE_LOADER_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/scoped_ptr.h"
 #include "base/timer.h"
 #include "googleurl/src/gurl.h"
 #include "media/base/seekable_buffer.h"
 #include "net/base/file_stream.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebURLLoader.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebURLLoaderClient.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebURLRequest.h"
 #include "webkit/glue/media/web_data_source.h"
 #include "webkit/glue/webmediaplayer_impl.h"
 
 namespace webkit_glue {
 
 const int64 kPositionNotSpecified = -1;
 
 const char kHttpScheme[] = "http";
 const char kHttpsScheme[] = "https";
 const char kDataScheme[] = "data";
 
+class BufferedDataSource;
+class DeferStrategy;
 // This class works inside demuxer thread and render thread. It contains a
 // WebURLLoader and does the actual resource loading. This object does
 // buffering internally, it defers the resource loading if buffer is full
 // and un-defers the resource loading if it is under buffered.
 class BufferedResourceLoader :
     public base::RefCountedThreadSafe<BufferedResourceLoader>,
     public WebKit::WebURLLoaderClient {
  public:
   typedef Callback0::Type NetworkEventCallback;
 
@@ skipping 37 matching lines @@
   //   The read has failed because of an error with the network.
   // - net::ERR_CACHE_MISS
   //   The read was made too far away from the current buffered position.
   virtual void Read(int64 position, int read_size,
                     uint8* buffer, net::CompletionCallback* callback);
 
   // Returns the position of the last byte buffered. Returns
   // |kPositionNotSpecified| if such value is not available.
   virtual int64 GetBufferedPosition();
 
-  // Sets whether deferring data is allowed or disallowed.
-  virtual void SetAllowDefer(bool is_allowed);
+  // Changes the defer strategy based on the state of BufferedDataSource.
+  virtual void UpdateDeferStrategy(BufferedDataSource*);

[acolwell GONE FROM CHROMIUM, 2011/03/25 04:35:28]

missing parameter name. Shouldn't this take a DeferStrategy instead of a
BufferedDataSource?

[vrk (LEFT CHROMIUM), 2011/03/25 21:33:32]

Done.

 
   // Gets the content length in bytes of the instance after this loader has been
   // started. If this value is |kPositionNotSpecified|, then content length is
   // unknown.
   virtual int64 content_length();
 
   // Gets the original size of the file requested. If this value is
   // |kPositionNotSpecified|, then the size is unknown.
   virtual int64 instance_size();
 
@@ skipping 36 matching lines @@
       WebKit::WebURLLoader* loader,
       double finishTime);
   virtual void didFail(
       WebKit::WebURLLoader* loader,
       const WebKit::WebURLError&);
 
   bool HasSingleOrigin() const;
 
  protected:
   friend class base::RefCountedThreadSafe<BufferedResourceLoader>;
+  friend class DeferStrategy;
+  friend class NeverDeferStrategy;
+  friend class ThresholdDeferStrategy;
+  friend class ReadThenDeferStrategy;

[acolwell GONE FROM CHROMIUM, 2011/03/25 04:35:28]

Not thrilled by all this friending. It feels like something isn't encapsulated
correctly.

[vrk (LEFT CHROMIUM), 2011/03/25 21:33:32]

N/A now!

 
   virtual ~BufferedResourceLoader();
 
  private:
   friend class BufferedResourceLoaderTest;
 
   // Defer the resource loading if the buffer is full.
   void EnableDeferIfNeeded();
 
   // Disable defer loading if we are under-buffered.
@@ skipping 33 matching lines @@
   void NotifyNetworkEvent();
 
   bool HasPendingRead() { return read_callback_.get() != NULL; }
 
   // A sliding window of buffer.
   scoped_ptr<media::SeekableBuffer> buffer_;
 
   // True if resource loading was deferred.
   bool deferred_;
 
-  // True if resource loader is allowed to defer, false otherwise.
-  bool defer_allowed_;
+  // Strategy for deferring.
+  DeferStrategy* defer_strategy_;
 
   // True if resource loading has completed.
   bool completed_;
 
   // True if a range request was made.
   bool range_requested_;
 
   // True if response data received is a partial range.
   bool partial_response_;
 
@@ skipping 28 matching lines @@
 
   // Used to ensure mocks for unittests are used instead of reset in Start().
   bool keep_test_loader_;
 
   DISALLOW_COPY_AND_ASSIGN(BufferedResourceLoader);
 };
 
 }  // namespace webkit_glue
 
 #endif  // WEBKIT_GLUE_MEDIA_BUFFERED_RESOURCE_LOADER_H_