PROTOTYPE: PlzNavigate: use a Mojo data pipe to stream navigation data to the renderer.

content/child/mojo_pipe_received_data.h

+// Copyright 2015 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 CONTENT_CHILD_MOJO_PIPI_RECEIVED_DATA_
+#define CONTENT_CHILD_MOJO_PIPI_RECEIVED_DATA_
+
+#include "content/public/child/request_peer.h"
+#include "mojo/public/cpp/system/data_pipe.h"
+
+// This class implements a minimal RequestPeer::ReceivedData for consuming data
+// from a Mojo pipe.
+//
+// This is based off of:
+// * mojo/common/data_pipe_drainer.cc for consuming a Mojo data pipe.
+// * content/child/shared_memory_received_data_factory.h for ReceivedData
+// implementation.
+//
+// TODO(carlosk): We might need a factory model as well like it's done in
+// SharedMemoryReceivedDataFactory to handle the case of the pipe being closed
+// while there are results floating around. This is a problem similar to the one
+// with the buffer on the browser side.
+
+namespace content {
+
+class MojoPipeReceivedData final : public RequestPeer::ReceivedData {
+ public:
+  static scoped_ptr<RequestPeer::ReceivedData> Create(
+      mojo::DataPipeConsumerHandle source,
+      const void* buffer,
+      uint32_t num_bytes);
+
+  ~MojoPipeReceivedData() override;
+
+  // RequestPeer::ReceivedData implementation.
+  const char* payload() const override;
+  int length() const override;
+  int encoded_length() const override;
+
+ private:
+  MojoPipeReceivedData(mojo::DataPipeConsumerHandle source,
+                       const void* buffer,
+                       uint32_t num_bytes);
+
+  // TODO(carlosk): to be safer and simpler I'm making a copy of the data to a
+  // intermediary buffer. Final implementation should hold the internal Mojo
+  // buffer alive until being destroyed.
+  // TODO(carlosk): we need to hold a reference to the source pipe to be able to
+  // get then later release the internal Mojo buffer with the data (instead of
+  // having an extra step of copying it out into another buffer). This *might*
+  // also be required to stop the producer of sending more data while we haven't
+  // consumed the current bundle (otherwise how does Mojo know about this at
+  // all?).
+  // The problems is that we don't want its ownership. Maybe we should switch to
+  // using a linked_ptr  shared with the ResourceLoader (instead of
+  // ScopedDataPipeConsumerHandle). This might be enough to make so that we
+  // don't need a factory as described above.
+  // mojo::DataPipeConsumerHandle UNSAFEPTR_source_;
+  // const void* const buffer_;
+  const uint32_t num_bytes_;
+  scoped_ptr<char> real_contents_;
+
+  DISALLOW_COPY_AND_ASSIGN(MojoPipeReceivedData);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_MOJO_PIPI_RECEIVED_DATA_