Mojo: Make MessageInTransit more opaque.

mojo/system/message_in_transit.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_IN_TRANSIT_H_
 #define MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 30 matching lines @@
 
   // Creates a |MessageInTransit| of the given |type| and |subtype|, with
   // message data given by |bytes|/|num_bytes|.
   // TODO(vtl): Add ability to tack on handle information.
   static MessageInTransit* Create(Type type,
                                   Subtype subtype,
                                   const void* bytes,
                                   uint32_t num_bytes,
                                   uint32_t num_handles);
 
-  // Destroys a |MessageInTransit| created using |Create()|.
+  MessageInTransit* Clone() const;
+
+  // Destroys a |MessageInTransit| created using |Create()| or |Clone()|.
   void Destroy();
 
+  // Gets the "main" buffer for a |MessageInTransit|. A |MessageInTransit| can
+  // be serialized by writing the main buffer. The returned pointer will be
+  // aligned to a multiple of |kMessageAlignment| bytes, and the size of the
+  // buffer (see below) will also be a multiple of |kMessageAlignment|.
+  // TODO(vtl): Add a "secondary" buffer, so that this makes more sense.
+  const void* main_buffer() const {
+    return static_cast<const void*>(this);
+  }
+
+  // Gets the size of the main buffer (in number of bytes).
+  size_t main_buffer_size() const {
+    return RoundUpMessageAlignment(sizeof(*this) + header()->data_size);
+  }
+
   // Gets the size of the data (in number of bytes). This is the full size of
   // the data that follows the header, and may include data other than the
   // message data. (See also |num_bytes()|.)
   uint32_t data_size() const {
     return header()->data_size;
   }
 
   // Gets the data (of size |data_size()| bytes).
   const void* data() const {
     return reinterpret_cast<const char*>(this) + sizeof(*this);
   }
 
   // Gets the size of the message data.
   uint32_t num_bytes() const {
     return header()->num_bytes;
   }
 
   // Gets the message data (of size |num_bytes()| bytes).
   const void* bytes() const {
     return reinterpret_cast<const char*>(this) + sizeof(*this);
   }
 
   uint32_t num_handles() const {
     return header()->num_handles;
   }
 
-  size_t size_with_header_and_padding() const {
-    return RoundUpMessageAlignment(sizeof(*this) + header()->data_size);
-  }
-
   Type type() const { return header()->type; }
   Subtype subtype() const { return header()->subtype; }
   EndpointId source_id() const { return header()->source_id; }
   EndpointId destination_id() const { return header()->destination_id; }
 
   void set_source_id(EndpointId source_id) { header()->source_id = source_id; }
   void set_destination_id(EndpointId destination_id) {
     header()->destination_id = destination_id;
   }
 
@@ skipping 50 matching lines @@
 
 // The size of |MessageInTransit| must be appropriate to maintain alignment of
 // the following data.
 COMPILE_ASSERT(sizeof(MessageInTransit) % MessageInTransit::kMessageAlignment ==
                    0, MessageInTransit_has_wrong_size);
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_MESSAGE_IN_TRANSIT_H_