Blimp: define HeliumTransport/HeliumStream interfaces.

blimp/net/helium/helium_transport.h

Index: blimp/net/helium/helium_transport.h
diff --git a/blimp/net/helium/helium_transport.h b/blimp/net/helium/helium_transport.h
new file mode 100644
index 0000000000000000000000000000000000000000..21157da8e5f850435bc93a9a1037b9380f3a699b
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+++ b/blimp/net/helium/helium_transport.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_TRANSPORT_H_
+#define BLIMP_NET_HELIUM_HELIUM_TRANSPORT_H_
+
+#include <memory>
+
+#include "base/callback.h"
+#include "base/cancelable_callback.h"
+#include "blimp/net/helium/helium_result.h"
+
+namespace blimp {
+
+// Pure virtual interface for a HeliumStream factory. Subclasses can use this
+// interface to encapsulate transport-specific stream connection semantics.
+class HeliumTransport {
+ public:
+  // Callback invoked with the stream and result code of a Connect or Accept
+  // attempt.
+  // The HeliumStream is assumed to be authenticated and ready to use.
+  // If the connection attempt failed, the value of |stream| will be null and
+  // |result| will be set to the relevant error code.
+  using StreamCreatedCallback =
+      base::CancelableCallback<void(std::unique_ptr<HeliumStream> stream,
+                                    HeliumResult result)>;
+
+  // Callback to be invoked when the underlying transport transitions
+  // between an offline/unusable state and an online/usable state.
+  using AvailabilityChangedCallback = base::Callback<void(bool)>;
+
+  virtual void SetAvailabilityChangedCallback(
+      const AvailabilityChangedCallback& callback);
+
+  // Asynchronously attempts to connect a new HeliumStream.
+  // Multiple overlapping connection attempts are permitted.
+  // The caller can cancel |cb| if it no longer needs the stream.
+  virtual void Connect(const StreamCreatedCallback& cb) = 0;
+
+  // Accepts an incoming connection from the peer.
+  virtual void Accept(const StreamCreatedCallback& cb) = 0;
+
+  // Returns true if the underlying transport has the necessary resources
+  // and connectivity for Connect and Accept operations.
+  virtual bool IsAvailable() = 0;
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_HELIUM_TRANSPORT_H_