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

net/filter/sdch_stream_source.h

Index: net/filter/sdch_stream_source.h
diff --git a/net/filter/sdch_stream_source.h b/net/filter/sdch_stream_source.h
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+++ b/net/filter/sdch_stream_source.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_H
+#define NET_FILTER_SDCH_STREAM_SOURCE_H
+
+#include <memory>
+
+#include "net/base/sdch_dictionary.h"
+#include "net/base/sdch_manager.h"
+#include "net/filter/filter_stream_source.h"
+#include "net/filter/sdch_stream_source_delegate.h"
+
+namespace open_vcdiff {
+
+class VCDiffStreamingDecoder;
+
+}  // namespace open_vcdiff
+
+namespace net {
+
+class BlockBuffer;
+
+class SdchStreamSource : public FilterStreamSource {
+ public:
+  SdchStreamSource(std::unique_ptr<StreamSource> previous,
+                   SdchStreamSourceDelegate* delegate);
+  ~SdchStreamSource() override;
+
+  bool Init() override;
+
+  // For use by SdchStreamSourceDelegate. Switches this stream source into
+  // "passthrough" mode, where it will not decode any further output with
+  // vcdiff. This method can only be called during an invocation of the
+  // delegate's HandleDictionaryError or HandleDecodingError functions.
+  virtual void StopDecoding();
+
+  // For use by SdchStreamSourceDelegate. Replaces the entire output of this
+  // stream
+  // with the supplied |data|, which is of length |size|. Note that calling this
+  // method also stops vcdiff decoding as a side-effect - |data| should not
+  // point to vcdiff-encoded data. This method can only be called during an
+  // invocation of the delegate's HandleDictionaryError or HandleDecodingError
+  // functions.
+  virtual void ReplaceOutput(const char* data, size_t size);
+
+ private:
+  enum SdchStreamState {
+    SDCH_STREAM_ERROR,
+    SDCH_STREAM_MORE_INPUT,
+    SDCH_STREAM_MORE_OUTPUT_SPACE,
+  };
+
+  // StreamSource implementation:
+  Error ReadInternal(IOBuffer* dest,
+                     size_t buffer_size,
+                     size_t* bytes_read) override;
+
+  SdchStreamState Decompress(IOBuffer* dest_buffer,
+                             size_t buffer_size,
+                             size_t* bytes_read);
+  SdchStreamState Passthrough(IOBuffer* dest_buffer,
+                              size_t buffer_size,
+                              size_t* bytes_read);
+  SdchStreamState Flush(IOBuffer* dest_buffer,
+                        size_t buffer_size,
+                        size_t* bytes_read);
+
+  bool LoadDictionary();
+
+  // Returns whether |id| looks like a dictionary ID, meaning 8 characters of
+  // base64url followed by a null character.
+  bool CouldBeDictionaryId(const std::string& id) const;
+
+  bool AskDelegateToHandleDictionaryError();
+  bool AskDelegateToHandleDecodingError();
+
+  std::unique_ptr<open_vcdiff::VCDiffStreamingDecoder> decoder_;
+  SdchStreamSourceDelegate* delegate_;
+
+  // Buffer used to accumulate the dictionary ID.
+  std::string dictionary_id_;
+
+  // Since vcdiff may generate quite a bit of output at once, SdchStreamSource
+  // has to buffer excess output (more than requested by the caller) here to
+  // return later. This could maybe become quite large.
+  std::string buffered_output_;
+
+  bool output_replaced_;
+  bool passthrough_;
+  bool dictionary_tried_load_;
+
+  bool in_delegate_handler_;
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_SDCH_STREAM_SOURCE_H