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

net/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_STREAM_SOURCE_H
+#define NET_FILTER_STREAM_SOURCE_H
+
+#include "base/callback.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/filter/block_buffer.h"
+
+namespace net {
+
+class SdchStreamSourceDelegate;
+
+// The StreamSource class implements a producer of bytes. Sources often
+// incorporate a previous source from which they read undecoded input. Those
+// which incorporate a previous source take ownership of the previous source
+// when they are created.
+class StreamSource {
+ public:
+  enum SourceType {
+#define STREAM_SOURCE_TYPE(label) TYPE_##label,
+#include "net/filter/stream_source_type_list.h"
+#undef STREAM_SOURCE_TYPE
+    // Used for UMA.
+    TYPE_MAX,
+  };
+
+  // |type| is the type of the StreamSource. |previous| is the previous
+  // StreamSource in the chain. If |previous| is null, |this| is the start of
+  // the StreamSource chain.
+  StreamSource(SourceType type, std::unique_ptr<StreamSource> previous);
+
+  virtual ~StreamSource();
+
+  typedef base::Callback<void(net::Error, size_t)> OnReadCompleteCallback;
+
+  // Initiaties a read from the filter chain starting at this stream source.
+  // If it completes synchronously, it:
+  //   - Returns an Error other than ERR_IO_PENDING

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

nit: or OK.

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

Done.

+  //   - Writes |*bytes_read| with the count of bytes read
+  //   - Writes bytes into |*dest_buffer|

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

nit: Presumably only if it did return OK for both of these.

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

Done.

+  //   - Does not call |callback|
+  // If it completes asynchronously, it:
+  //   - Returns ERR_IO_PENDING
+  //   - Does not write |*bytes_read|
+  //   - Calls |callback| when it does complete, with an error code and a count
+  //     of bytes read, which are them placed into |*dest_buffer|.

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

nit, typo: "them" -> "then".

Presuming that's what you meant to type, I think it implies that the bytes are
placed after the callback is called, when I think they should be placed before
the callback is called.  Maybe "... and a count of bytes read and written into
|*dest_buffer|."?

[xunjieli, 2016/07/20 21:00:48]

Done.

+  // This method takes a reference to |*dest_buffer| if it completes
+  // asynchronously to ensure it does not get freed mid-read.
+  virtual net::Error Read(IOBuffer* dest_buffer,
+                          size_t buffer_size,
+                          size_t* bytes_read,
+                          const OnReadCompleteCallback& callback) = 0;
+
+  SourceType type() const { return type_; }
+
+  StreamSource* previous() const { return previous_.get(); }
+
+ protected:

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

protected fields aren't allowed.

[xunjieli, 2016/07/20 21:00:48]

Done.

+  SourceType type_;
+  // Previous StreamSource in the chain.
+  std::unique_ptr<StreamSource> previous_;
+  // Non-null when there is a read outstanding.
+  // scoped_refptr<IOBuffer> pending_read_buffer_;

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

nit: Should these lines be removed?

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

Done.

+  // Buffer for reading data out of |previous_| and then for use by |this|
+  // before the filtered data is returned through Read().
+  std::unique_ptr<BlockBuffer> buffer_;
+
+ private:

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

DISALLOW_COPY_AND_ASSIGN

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

Done.

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