Introduce WebSocketDeflatePredictor.

net/websockets/websocket_deflate_stream.h

 // Copyright 2013 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 NET_WEBSOCKETS_WEBSOCKET_DEFLATE_STREAM_H_
 #define NET_WEBSOCKETS_WEBSOCKET_DEFLATE_STREAM_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
 #include "net/websockets/websocket_deflater.h"
 #include "net/websockets/websocket_frame.h"
 #include "net/websockets/websocket_inflater.h"
 #include "net/websockets/websocket_stream.h"
 
 class GURL;
 
 namespace net {
 
+class WebSocketDeflatePredictor;
+
 // WebSocketDeflateStream is a WebSocketStream subclass.
 // WebSocketDeflateStream is for permessage-deflate WebSocket extension[1].
 //
+// WebSocketDeflateStream::ReadFrames and WriteFrames may change frame
+// boundary. In particular, if a control frame is placed in the middle of
+// data message frames, the control frame can overtake data frames.
+// Say there are frames df1, df2 and cf, df1 and df2 are frames of a
+// data message and cf is a control message frame. cf may arrive first and
+// data frames may follow cf.
+// Note that message boundary will be preserved, i.e. if the last frame of
+// a message m1 is read / written before the last frame of a message m2,
+// WebSocketDeflateStream will respect the order.
+//
 // [1]: http://tools.ietf.org/html/draft-ietf-hybi-permessage-compression-12
 class NET_EXPORT_PRIVATE WebSocketDeflateStream : public WebSocketStream {
  public:
   WebSocketDeflateStream(scoped_ptr<WebSocketStream> stream,
-                         WebSocketDeflater::ContextTakeOverMode mode);
+                         WebSocketDeflater::ContextTakeOverMode mode,
+                         scoped_ptr<WebSocketDeflatePredictor> predictor);
   virtual ~WebSocketDeflateStream();
 
   // WebSocketStream functions.
   virtual int ReadFrames(ScopedVector<WebSocketFrame>* frames,
                          const CompletionCallback& callback) OVERRIDE;
   virtual int WriteFrames(ScopedVector<WebSocketFrame>* frames,
                           const CompletionCallback& callback) OVERRIDE;
   virtual void Close() OVERRIDE;
   virtual std::string GetSubProtocol() const OVERRIDE;
   virtual std::string GetExtensions() const OVERRIDE;
 
  private:
   enum ReadingState {
     READING_COMPRESSED_MESSAGE,
     READING_UNCOMPRESSED_MESSAGE,
     NOT_READING,
   };
 
   enum WritingState {
     WRITING_COMPRESSED_MESSAGE,
     WRITING_UNCOMPRESSED_MESSAGE,
+    WRITING_POSSIBLY_COMPRESSED_MESSAGE,
     NOT_WRITING,
   };
 
   void OnReadComplete(ScopedVector<WebSocketFrame>* frames,
                       const CompletionCallback& callback,
                       int result);
 
   // This function deflates |frames| and stores the result to |frames| itself.
   int Deflate(ScopedVector<WebSocketFrame>* frames);
+  void OnMessageStart(const ScopedVector<WebSocketFrame>& frames, size_t index);
+  int AppendCompressedFrame(const WebSocketFrameHeader& header,
+                            ScopedVector<WebSocketFrame>* frames_to_write);
+  int AppendPossiblyCompressedMessage(
+      ScopedVector<WebSocketFrame>* frames,
+      ScopedVector<WebSocketFrame>* frames_to_write);
 
   // This function inflates |frames| and stores the result to |frames| itself.
   int Inflate(ScopedVector<WebSocketFrame>* frames);
 
   int InflateAndReadIfNecessary(ScopedVector<WebSocketFrame>* frames,
                                 const CompletionCallback& callback);
 
   const scoped_ptr<WebSocketStream> stream_;
   WebSocketDeflater deflater_;
   WebSocketInflater inflater_;
   ReadingState reading_state_;
   WritingState writing_state_;
   WebSocketFrameHeader::OpCode current_reading_opcode_;
   WebSocketFrameHeader::OpCode current_writing_opcode_;
+  scoped_ptr<WebSocketDeflatePredictor> predictor_;
 
   DISALLOW_COPY_AND_ASSIGN(WebSocketDeflateStream);
 };
 
 }  // namespace net
 
 #endif  // NET_WEBSOCKETS_WEBSOCKET_DEFLATE_STREAM_H_