Mojo: First stab at making MessagePipes work across OS pipes.

mojo/system/message_pipe.h

 // Copyright 2013 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_SYSTEM_MESSAGE_PIPE_H_
 #define MOJO_SYSTEM_MESSAGE_PIPE_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/lock.h"
 #include "mojo/public/system/core.h"
 #include "mojo/public/system/system_export.h"
+#include "mojo/system/message_in_transit.h"
 
 namespace mojo {
 namespace system {
 
+class Channel;
 class MessagePipeEndpoint;
 class Waiter;
 
 // |MessagePipe| is the secondary object implementing a message pipe (see the
 // explanatory comment in core_impl.cc). It is typically owned by the
 // dispatcher(s) corresponding to the local endpoints. This class is
 // thread-safe.
 class MOJO_SYSTEM_EXPORT MessagePipe :
     public base::RefCountedThreadSafe<MessagePipe> {
  public:
   MessagePipe(scoped_ptr<MessagePipeEndpoint> endpoint_0,
               scoped_ptr<MessagePipeEndpoint> endpoint_1);
 
   // Convenience constructor that constructs a |MessagePipe| with two new
   // |LocalMessagePipeEndpoint|s.
   MessagePipe();
 
+  // Gets the other port number (i.e., 0 -> 1, 1 -> 0).
+  static unsigned GetPeerPort(unsigned port);
+
   // These are called by the dispatcher to implement its methods of
   // corresponding names. In all cases, the port |port| must be open.
   void CancelAllWaiters(unsigned port);
   void Close(unsigned port);
   // Unlike |MessagePipeDispatcher::WriteMessage()|, this does not validate its
   // arguments. |bytes|/|num_bytes| and |handles|/|num_handles| must be valid.
   MojoResult WriteMessage(unsigned port,
                           const void* bytes, uint32_t num_bytes,
                           const MojoHandle* handles, uint32_t num_handles,
                           MojoWriteMessageFlags flags);
   // Unlike |MessagePipeDispatcher::ReadMessage()|, this does not validate its
   // arguments. |bytes|/|num_bytes| and |handles|/|num_handles| must be valid.
   MojoResult ReadMessage(unsigned port,
                          void* bytes, uint32_t* num_bytes,
                          MojoHandle* handles, uint32_t* num_handles,
                          MojoReadMessageFlags flags);
   MojoResult AddWaiter(unsigned port,
                        Waiter* waiter,
                        MojoWaitFlags flags,
                        MojoResult wake_result);
   void RemoveWaiter(unsigned port, Waiter* waiter);
 
+  // This is used internally by |WriteMessage()| and by |Channel| to enqueue
+  // messages (typically to a |LocalMessagePipeEndpoint|). Unlike
+  // |WriteMessage()|, |port| is the *destination* port. Takes ownership of
+  // |message|.
+  MojoResult EnqueueMessage(unsigned port, MessageInTransit* message);
+
+  // These are used by |Channel|.
+  void Attach(unsigned port,
+              scoped_refptr<Channel> channel,
+              MessageInTransit::EndpointId local_id);
+  void Run(unsigned port, MessageInTransit::EndpointId remote_id);
+
  private:
   friend class base::RefCountedThreadSafe<MessagePipe>;
   virtual ~MessagePipe();
 
+  // Used by |EnqueueMessage()| to handle control messages that are actually
+  // meant for us.
+  MojoResult HandleControlMessage(unsigned port, MessageInTransit* message);
+
   base::Lock lock_;  // Protects the following members.
   scoped_ptr<MessagePipeEndpoint> endpoints_[2];
 
   DISALLOW_COPY_AND_ASSIGN(MessagePipe);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_PIPE_H_