Blimp: create MessageDispatcher class.

blimp/net/blimp_message_dispatcher.cc

Index: blimp/net/blimp_message_dispatcher.cc
diff --git a/blimp/net/blimp_message_dispatcher.cc b/blimp/net/blimp_message_dispatcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..864284fe7b6abbd08d7ac73d643bdcf82aec83d6
--- /dev/null
+++ b/blimp/net/blimp_message_dispatcher.cc
@@ -0,0 +1,48 @@
+// 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.
+
+#include "blimp/net/blimp_message_dispatcher.h"
+
+#include <string>
+
+#include "base/strings/stringprintf.h"
+
+namespace blimp {
+namespace {
+
+std::string BlimpMessageToDebugString(const BlimpMessage& message) {
+  return base::StringPrintf("<message type=%d>", message.type());
+}
+
+}  // namespace
+
+BlimpMessageDispatcher::BlimpMessageDispatcher() {}
+
+BlimpMessageDispatcher::~BlimpMessageDispatcher() {}
+
+void BlimpMessageDispatcher::AddReceiver(BlimpMessage::Type type,
+                                         BlimpMessageReceiver* receiver) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(receiver);
+  if (feature_receiver_map_.find(type) == feature_receiver_map_.end()) {
+    feature_receiver_map_.insert(std::make_pair(type, receiver));
+  } else {
+    DCHECK(false) << "Handler already registered for type=" << type << ".";

[Wez, 2015/10/09 23:15:34]

DLOG(FATAL)

[Kevin M, 2015/10/10 00:42:34]

Done.

+  }
+}
+
+bool BlimpMessageDispatcher::OnMessage(const BlimpMessage& message) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  auto receiver_iter = feature_receiver_map_.find(message.type());
+  if (receiver_iter == feature_receiver_map_.end()) {
+    VLOG(0) << "No registered receiver for "
+            << BlimpMessageToDebugString(message) << ".";

[Wez, 2015/10/09 23:15:34]

As previously noted, this indicates a coding error somewhere, or malicious
client, so it's not clear that logging anything here, at least in release
builds, is useful.  I think it'd be better to just have the OnMessage()
return-code be a net::Error and try to return something sensible - WDYT? 
Otherwise, maybe make this a DVLOG or DLOG(FATAL)

[Kevin M, 2015/10/10 00:42:34]

Done.

+    return false;
+  }
+
+  return receiver_iter->second->OnMessage(message);
+}
+
+}  // namespace blimp