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

mojo/system/proxy_message_pipe_endpoint.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_PROXY_MESSAGE_PIPE_ENDPOINT_H_
+#define MOJO_SYSTEM_PROXY_MESSAGE_PIPE_ENDPOINT_H_
+
+#include <stdint.h>
+
+#include <deque>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "mojo/public/system/core.h"
+#include "mojo/system/message_in_transit.h"
+#include "mojo/system/message_pipe_endpoint.h"
+
+namespace mojo {
+namespace system {
+
+class Channel;
+
+// A |ProxyMessagePipeEndpoint| connects an end of a |MessagePipe| to a
+// |Channel|, over which it transmits and receives data (to/from another
+// |ProxyMessagePipeEndpoint|). So a |MessagePipe| with one endpoint local and
+// the other endpoint remote consists of a |LocalMessagePipeEndpoint| and a
+// |ProxyMessagePipeEndpoint|, with only the local endpoint being accessible via
+// a |MessagePipeDispatcher|.
+//
+// Like any |MessagePipeEndpoint|, a |ProxyMessagePipeEndpoint| is owned by a
+// |MessagePipe|.
+//  - A |ProxyMessagePipeEndpoint| starts out *detached*, i.e., not associated
+//    to any |Channel|. When *attached*, it gets a reference to a |Channel| and
+//    is assigned a local ID. A |ProxyMessagePipeEndpoint| must be detached
+//    before destruction; this is done inside |Close()|.
+//  - When attached, a |ProxyMessagePipeEndpoint| starts out not running. When
+//    run, it gets a remote ID.
+class ProxyMessagePipeEndpoint : public MessagePipeEndpoint {
+ public:
+  ProxyMessagePipeEndpoint();
+  virtual ~ProxyMessagePipeEndpoint();
+
+  // |MessagePipeEndpoint| implementation:
+  virtual void Close() OVERRIDE;
+  virtual bool OnPeerClose() OVERRIDE;
+  virtual MojoResult EnqueueMessage(MessageInTransit* message) OVERRIDE;
+  virtual void Attach(scoped_refptr<Channel> channel,
+                      MessageInTransit::EndpointId local_id) OVERRIDE;
+  virtual bool Run(MessageInTransit::EndpointId remote_id) OVERRIDE;
+
+ private:
+  bool is_attached() const {
+    return !!channel_.get();
+  }
+
+  bool is_running() const {
+    return remote_id_ != MessageInTransit::kInvalidEndpointId;
+  }
+
+#ifdef NDEBUG
+  void AssertConsistentState() const {}
+#else
+  void AssertConsistentState() const;
+#endif
+
+  // This should only be set if we're attached.
+  scoped_refptr<Channel> channel_;
+
+  // |local_id_| should be set to something other than
+  // |MessageInTransit::kInvalidEndpointId| when we're attached.
+  MessageInTransit::EndpointId local_id_;
+
+  // |remote_id_| being set to anything other than
+  // |MessageInTransit::kInvalidEndpointId| indicates that we're "running",
+  // i.e., actively able to send messages. We should only ever be running if
+  // we're attached.
+  MessageInTransit::EndpointId remote_id_;
+
+  bool is_open_;
+  bool is_peer_open_;
+
+  // This queue is only used while we're detached, to store messages while we're
+  // not ready to send them yet.
+  std::deque<MessageInTransit*> paused_message_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProxyMessagePipeEndpoint);
+};
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_SYSTEM_PROXY_MESSAGE_PIPE_ENDPOINT_H_