Add interfaces for most major Blimp net components.

blimp/net/blimp_message_output_buffer.h

Index: blimp/net/blimp_message_output_buffer.h
diff --git a/blimp/net/blimp_message_output_buffer.h b/blimp/net/blimp_message_output_buffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..0fff67eedcbc5538e0606213eb32ef5a8cec1d15
--- /dev/null
+++ b/blimp/net/blimp_message_output_buffer.h
@@ -0,0 +1,52 @@
+// 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 BLIMP_NET_BLIMP_MESSAGE_OUTPUT_BUFFER_H_
+#define BLIMP_NET_BLIMP_MESSAGE_OUTPUT_BUFFER_H_
+
+#include "base/macros.h"
+#include "blimp/net/blimp_message_ack_observer.h"
+#include "blimp/net/blimp_message_processor.h"
+#include "blimp/net/blimp_net_export.h"
+
+namespace blimp {
+
+class BlimpConnection;
+
+// Provides a FIFO buffer for reliable, ordered message delivery.
+// Messages are available for redelivery until they are acknowledged by the

[Wez, 2015/11/12 00:12:54]

nit: Class doesn't yet do re-delivery, so suggest "are retained..." and then a
separate comment at the end "This will be used in a future CL to implement Fast
Recovery of dropped connections."

[Kevin M, 2015/11/12 01:53:16]

Done.

+//    receiving end (via BlimpMessageAckObserver).

[Wez, 2015/11/12 00:12:54]

nit: Indentation.

[Kevin M, 2015/11/12 01:53:16]

Done.

+class BLIMP_NET_EXPORT BlimpMessageOutputBuffer
+    : public BlimpMessageProcessor,
+      public BlimpMessageAckObserver {
+ public:
+  BlimpMessageOutputBuffer();
+  ~BlimpMessageOutputBuffer() override;
+
+  // Sets the processor to receive messages from this buffer.
+  void SetOutgoingMessageProcessor(scoped_ptr<BlimpMessageProcessor> processor);

[Wez, 2015/11/12 00:12:54]

nit: The other CLs all seem to use bare pointers for this - let's be consistent.
I think bare pointers are fine for now, w/ callers owning the pipeline, and we
can change our minds later if need be.

nit: Could this become a simple setter?

[Kevin M, 2015/11/12 01:53:16]

Done.

+
+  // BlimpMessageProcessor implementation.
+  // |callback|, if set, will be called once the remote end has acknowledged the
+  //     receipt of |message|.
+  // A sequence of N dependent writes with one acknowledgement can be had by
+  //     calling ProcessMessage() N-1 times with an empty |callback|, then
+  //     calling the final (Nth) message with |callback| set.

[Wez, 2015/11/12 00:12:54]

This is too complicated - that |callback| can be null, if no callback is
desired, should be documented on the interface, not the implementation, and then
implementations have to cope with that constraint.

Documenting _when_ |callback| gets notified, specific to this impl, is valid,
though.

[Kevin M, 2015/11/12 01:53:16]

Done.

+  void ProcessMessage(const BlimpMessage& message,
+                      const net::CompletionCallback& callback) override;
+
+  // MessageAckObserver implementation.
+  // Removes BlimpMessages from the buffer whose ID is less than or equal to
+  // |message_id|.
+  // Invokes outstanding CompletionCallbacks for previously unacknowledged
+  // messages which have an ID less than or equal to |message_id|.

[Wez, 2015/11/12 00:12:54]

nit: Suggest reducing to "Flushes acknowledged messages from the buffer and
invokes their |callbacks|, if any."

Bear in mind that in principle a callback could delete this object, so we'll
need to think about the semantics in that case - or simply disallow that!

[Kevin M, 2015/11/12 01:53:16]

Done.

+  void OnMessageAck(int64 message_id) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BlimpMessageOutputBuffer);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLIMP_MESSAGE_OUTPUT_BUFFER_H_