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

net/filter/filter_stream_source.h

+// 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_FILTER_STREAM_SOURCE_H
+#define NET_FILTER_FILTER_STREAM_SOURCE_H
+
+#include <memory>
+
+#include "net/base/net_errors.h"
+#include "net/filter/stream_source.h"
+
+namespace net {
+
+class IOBuffer;
+
+class FilterStreamSource : public StreamSource {

[Randy Smith (Not in Mondays), 2016/04/26 21:54:01]

nit: comment as to use.

[xunjieli, 2016/07/20 21:00:47]

Done.

+ public:
+  FilterStreamSource(SourceType type, std::unique_ptr<StreamSource> previous);

[mmenke, 2016/04/29 19:10:54]

Hrm...Wonder about "next" vs "previous".

We could say "data flows from the previous one to the next one", which is the
name scheme you're using.

Or we could say "the read command comes in the previous one, and is passed to
the next one", which is the actual way the logic works.

Maybe there's a clearer name?  I dunno.

[xunjieli, 2016/07/20 21:00:47]

Done. I have added a comment. I think |previous| is reasonable in the sense that
this is a pull-based design where data is requested from the previous source in
the filter chain. The read command actually comes from the next source in the
filter chain.

+
+  ~FilterStreamSource() override;
+
+  net::Error Read(IOBuffer* dest_buffer,
+                  size_t buffer_size,
+                  size_t* bytes_read,
+                  const OnReadCompleteCallback& callback) override;
+
+  // Subclass override this method to perform any initialization that needs to
+  // be completed before Read() can be called. Returns whether initialization
+  // has succeeded. If failed, filter chain will not be used.
+  virtual bool Init();
+
+ private:
+  // Asynchronous callback used in previous_->Read().
+  void OnReadComplete(const OnReadCompleteCallback& callback,
+                      IOBuffer* dest_buffer,
+                      size_t dest_buffer_size,
+                      Error error,
+                      size_t bytes_read);
+
+  // Also see Read(). Subclasses should implement this method to read data into
+  // |dest_buffer| until more input is needed from |previous_|.
+  // This method must complete synchronously (i.e. It cannot return
+  // ERR_IO_PENDING).
+  virtual net::Error ReadInternal(IOBuffer* dest_buffer,

[Randy Smith (Not in Mondays), 2016/04/26 21:54:01]

I think this would be cleaner if it took an input argument (buffer_, presumably)
so that buffer_ didn't need to be protected and used by all the derived classes.
 (Possibly buffer_ should be declared here, but I haven't looked at the
non-filter StreamSource yet, so I'm not sure.)

[xunjieli, 2016/07/20 21:00:47]

Done.

+                                  size_t buffer_size,
+                                  size_t* bytes_read) = 0;

[mmenke, 2016/04/29 19:10:54]

DISALLOW_COPY_AND_ASSIGN

[xunjieli, 2016/07/20 21:00:47]

Done.

+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_FILTER_STREAM_SOURCE_H