[ON HOLD] Implement pull-based design for content decoding

net/filter/sdch_stream_source_delegate.h

Index: net/filter/sdch_stream_source_delegate.h
diff --git a/net/filter/sdch_stream_source_delegate.h b/net/filter/sdch_stream_source_delegate.h
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+++ b/net/filter/sdch_stream_source_delegate.h
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+// Copyright 2016 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_FILTER_SDCH_STREAM_SOURCE_DELEGATE_H_
+#define NET_FILTER_SDCH_STREAM_SOURCE_DELEGATE_H_
+
+#include <string>
+
+namespace net {
+
+class SdchStreamSource;
+
+// The |SdchStreamSourceDelegate| class acts as a delegate for
+// |SdchStreamSource| and
+// is responsible for error recovery and stats gathering. See the methods below
+// for descriptions of which errors the delegate is expected to handle and what
+// it can do to repair them.
+class SdchStreamSourceDelegate {
+ public:
+  virtual ~SdchStreamSourceDelegate(){};
+
+  // Called by the SdchStreamSource if an error occurs while parsing the
+  // server-sent dictionary ID, or if the specified dictionary can't be loaded
+  // (i.e., GetDictionary returned false). This method is expected to correct
+  // the error condition by either:
+  //   a) returning true and calling ReplaceOutput or Passthrough, or
+  //   b) returning false, in which case the StreamSource will return an error
+  //      to its caller
+  // Conceptually, the return value is true if the error has been
+  // handled/recovered from and false if not.
+  // This method must not retain a reference to |source| after returning.
+  virtual bool HandleDictionaryError(SdchStreamSource* source) = 0;
+
+  // Called by the SdchStreamSource if an error occurs while decoding the
+  // vcdiff-compressed data stream. Semantics are similar to
+  // HandleDictionaryError above. This method must not retain a reference to
+  // |source| after returning.
+  virtual bool HandleDecodingError(SdchStreamSource* source) = 0;
+
+  // Called by the SdchStreamSource to request the text of the specified
+  // dictionary. This method must either:
+  //   * Fill in |*text| and return true, or
+  //   * Leave |*text| untouched and return false.
+  // The return value is true if the named dictionary could be found and false
+  // otherwise.
+  //
+  // The |server_id| string is guaranteed to be a syntactically valid SDCH
+  // server-id.
+  virtual bool GetDictionary(const std::string& server_id,
+                             const std::string** text) = 0;
+
+  // Called by the SdchStreamSource to notify the delegate that the stream
+  // finished successfully. This method is purely advisory for statistics
+  // gathering.
+  virtual void NotifyStreamDone() = 0;
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_SDCH_STREAM_SOURCE_DELEGATE_H_