Blimp: define HeliumTransport/HeliumStream interfaces.

blimp/net/helium/helium_stream.h

Index: blimp/net/helium/helium_stream.h
diff --git a/blimp/net/helium/helium_stream.h b/blimp/net/helium/helium_stream.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 BLIMP_NET_HELIUM_HELIUM_STREAM_H_
+#define BLIMP_NET_HELIUM_HELIUM_STREAM_H_
+
+#include <memory>
+
+#include "base/callback.h"
+#include "blimp/net/helium/helium_result.h"
+
+namespace blimp {
+
+class HeliumMessage;
+
+// Pure virtual interface for HeliumMessage-oriented transport streams.
+// Details about how the HeliumStream is bound to the network layer are handled
+// by subclasses of HeliumStream.
+class HeliumStream {
+ public:
+  using ReceiveMessageCallback =
+      base::Callback<void(std::unique_ptr<HeliumMessage>, HeliumResult)>;
+
+  virtual ~HeliumStream() = default;
+
+  // Sends |helium_message| over the Stream. |callback| is invoked when the
+  // message is sent (or otherwise moved to the low-level write buffers),
+  // which signals the caller that it is clear to send another message.
+  //
+  // The caller is responsible for ensuring that only one outstanding
+  // SendMessage() call is made at a time.
+  virtual void SendMessage(
+      std::unique_ptr<HeliumMessage> helium_message,
+      const base::Callback<void(HeliumResult)>& callback) = 0;
+
+  // Asynchronously reads a HeliumMessage from the stream.
+  // The caller is responsible for ensuring that only one outstanding
+  // ReceiveMessage() call is made at a time.
+  //
+  // In the event that an error occurred, a null pointer will be passed instead
+  // of a HeliumMessage, with a HeliumResult describing the failure reason.
+  // The HeliumStream object is considered inactive/unusable at this point and
+  // should be discarded by its owner.
+  virtual void ReceiveMessage(const ReceiveMessageCallback& on_receive_cb) = 0;
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_HELIUM_STREAM_H_