[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"
+
+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:
+  virtual ~StreamSource(){};

[mmenke, 2016/02/18 22:58:28]

Remove semi-colon

[xunjieli, 2016/03/03 23:00:09]

Done.

+  typedef base::Callback<void(net::Error, size_t)> OnReadCompleteCallback;
+
+  // Reads bytes from this source. This method can either complete synchronously
+  // or asynchronously. If it completes synchronously, it:
+  //   - Returns an Error other than ERR_IO_PENDING
+  //   - Writes |*bytes_read| with the count of bytes read
+  //   - Writes bytes into |*dest_buffer|
+  //   - 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|.
+  // 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;
+
+  // Returns how many bytes total have been returned by Read() of |this|.
+  virtual size_t GetBytesOutput() const = 0;

[mmenke, 2016/02/18 22:58:28]

Is this method really needed?  Can't the URLRequestJob just track how many bytes
its read both before and after all filers have been applied?  Seems simpler than
having near identical byte tracking code in all filter implementations, and
testing them all seems like a pain.

+
+  // This method constructs a chain of StreamSources from a vector of
+  // Content-Type values and an SdchStreamSourceDelegate. If any of the
+  // constructed
+  // StreamSources are SdchStreamSources, they will be constructed with
+  // |delegate|.
+  static scoped_ptr<StreamSource> BuildSourceChain(
+      scoped_ptr<StreamSource> previous,
+      const std::vector<std::string>& type,
+      SdchStreamSourceDelegate* delegate);
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_STREAM_SOURCE_H