Introduce WebSocketDeflatePredictor.

net/websockets/websocket_deflate_predictor.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_PREDICTOR_H_
+#define NET_WEBSOCKETS_WEBSOCKET_DEFLATE_PREDICTOR_H_
+
+#include <deque>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+
+namespace net {
+
+class WebSocketFrame;
+
+class NET_EXPORT_PRIVATE WebSocketDeflatePredictor {
+ public:
+  enum Result {
+    // Deflate and send the message.
+    DEFLATE,
+    // Do not deflate and send the original message.
+    DO_NOT_DEFLATE,
+    // Try compressing the message and send the smaller one of the original
+    // and the compressed message.
+    // Returning this result implies that the deflater is running on
+    // DoNotTakeOverContext mode and the entire message is visible.
+    TRY_DEFLATE,
+  };
+
+  virtual ~WebSocketDeflatePredictor() {}
+
+  // Predicts and returns whether the deflater should deflate |target_frame|
+  // or not. |frames[next_frame_index:]| consists of future frames.
+  // |target_frame| must be a data frame, but future frames can contain control
+  // frames.

[Adam Rice, 2013/10/24 07:59:23]

Maybe |target_frame| should also be passed as an index? I am not sure because it
depends on the implementation.

+  virtual Result predict(const WebSocketFrame* target_frame,
+                         const ScopedVector<WebSocketFrame>& frames,
+                         size_t next_frame_index) = 0;
+
+  // Records processed frame data for future prediction.
+  // Only data frames should be recorded. Do not pass control frames' data.
+  virtual void RecordProcessedFrame(bool was_compressed,
+                                    size_t original_size,
+                                    size_t compressed_size,
+                                    bool fin) = 0;
+};
+
+class NET_EXPORT_PRIVATE WebSocketAlwaysDeflatePredictor
+    : public WeSocketDeflatePredictor {
+ public:
+  virtual ~WebSocketAlwaysDeflatePredictor() {}
+
+  virtual Result predict(const WebSocketFrame* target_frame,
+                         const ScopedVector<WebSocketFrame>& frames,
+                         size_t next_frame_index) OVERRIDE {
+    return Deflate;
+  }
+
+  virtual void RecordProcessedFrame(bool was_compressed,
+                                    size_t original_size,
+                                    size_t compressed_size,
+                                    bool fin) OVERRIDE {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WebSocketAlwaysDeflatePredictor);
+};
+
+class NET_EXPORT_PRIVATE WebSocketNeverDeflatePredictor
+    : public WeSocketDeflatePredictor {
+ public:
+  virtual ~WebSocketNeverDeflatePredictor() {}
+
+  virtual Result predict(const WebSocketFrame* target_frame,
+                         const ScopedVector<WebSocketFrame>& frames,
+                         size_t next_frame_index) OVERRIDE {
+    return DoNotDeflate;

[Adam Rice, 2013/10/24 07:59:23]

DO_NOT_DEFLATE ?

+  }
+
+  virtual void RecordProcessedFrame(bool was_compressed,
+                                    size_t original_size,
+                                    size_t compressed_size,
+                                    bool fin) OVERRIDE {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WebSocketNeverDeflatePredictor);
+};
+
+}  // namespace net
+
+#endif  // NET_WEBSOCKETS_WEBSOCKET_DEFLATE_PREDICTOR_H_