[mojo] Implement pipe fusion API

mojo/edk/system/ports/node.h

 // 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 MOJO_EDK_SYSTEM_PORTS_NODE_H_
 #define MOJO_EDK_SYSTEM_PORTS_NODE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 119 matching lines @@
   // merged (B or C above) has ever been read from or written to directly, and
   // this must ONLY be called on one side of the merge, though it doesn't matter
   // which side.
   //
   // It is safe for the non-merged peers (A and D above) to be transferred,
   // closed, and/or written to before, during, or after the merge.
   int MergePorts(const PortRef& port_ref,
                  const NodeName& destination_node_name,
                  const PortName& destination_port_name);
 
+  // Like above but merges two ports local to this node. Because both ports are
+  // local this can also verify that neither port has been written to before the
+  // merge. If this fails for any reason, both ports are closed. Otherwise OK
+  // is returned and the ports' receiving peers are connected to each other.
+  int MergeLocalPorts(const PortRef& port0_ref, const PortRef& port1_ref);
+
   // Called to inform this node that communication with another node is lost
   // indefinitely. This triggers cleanup of ports bound to this node.
   int LostConnectionToNode(const NodeName& node_name);
 
  private:
   int OnUserMessage(ScopedMessage message);
   int OnPortAccepted(const PortName& port_name);
   int OnObserveProxy(const PortName& port_name,
                      const ObserveProxyEventData& event);
   int OnObserveProxyAck(const PortName& port_name, uint64_t last_sequence_num);
   int OnObserveClosure(const PortName& port_name, uint64_t last_sequence_num);
   int OnMergePort(const PortName& port_name, const MergePortEventData& event);
 
   int AddPortWithName(const PortName& port_name,
                       const scoped_refptr<Port>& port);
   void ErasePort(const PortName& port_name);
   void ErasePort_Locked(const PortName& port_name);
   scoped_refptr<Port> GetPort(const PortName& port_name);
   scoped_refptr<Port> GetPort_Locked(const PortName& port_name);
 
+  int MergePorts_Locked(const PortRef& port0_ref, const PortRef& port1_ref);
   void WillSendPort_Locked(Port* port,
                            const NodeName& to_node_name,
                            PortName* port_name,
                            PortDescriptor* port_descriptor);
   int AcceptPort(const PortName& port_name,
                  const PortDescriptor& port_descriptor);
 
   int WillSendMessage_Locked(Port* port,
                              const PortName& port_name,
                              Message* message);
@@ skipping 30 matching lines @@
   std::unordered_map<PortName, scoped_refptr<Port>> ports_;
 
   DISALLOW_COPY_AND_ASSIGN(Node);
 };
 
 }  // namespace ports
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_PORTS_NODE_H_