Mojo: Make MessageInTransit more opaque still.

mojo/system/message_in_transit.cc

 // 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.
 
 #include "mojo/system/message_in_transit.h"
 
 #include <string.h>
 
 #include <new>
 
@@ skipping 59 matching lines @@
                                                        kMessageAlignment));
   memcpy(buffer, main_buffer(), buffer_size);
   return reinterpret_cast<MessageInTransit*>(buffer);
 }
 
 void MessageInTransit::Destroy() {
   // No need to call the destructor, since we're POD.
   base::AlignedFree(this);
 }
 
+// static
+bool MessageInTransit::GetNextMessageSize(const void* buffer,
+                                          size_t buffer_size,
+                                          size_t* next_message_size) {
+  DCHECK(buffer);
+  DCHECK_EQ(reinterpret_cast<uintptr_t>(buffer) %
+                MessageInTransit::kMessageAlignment, 0u);
+  DCHECK(next_message_size);
+
+  if (buffer_size < sizeof(Header))
+    return false;
+
+  const Header* header = static_cast<const Header*>(buffer);
+  *next_message_size =
+      RoundUpMessageAlignment(sizeof(MessageInTransit) + header->data_size);
+  return true;
+}
+
+// static
+const MessageInTransit* MessageInTransit::CreateReadOnlyFromBuffer(
+    const void* buffer) {
+  DCHECK(buffer);
+  DCHECK_EQ(reinterpret_cast<uintptr_t>(buffer) %
+                MessageInTransit::kMessageAlignment, 0u);
+  return static_cast<const MessageInTransit*>(buffer);
+}
+
 MessageInTransit::MessageInTransit(uint32_t data_size,
                                    Type type,
                                    Subtype subtype,
                                    uint32_t num_bytes,
                                    uint32_t num_handles)
     : header_(data_size, type, subtype, kInvalidEndpointId, kInvalidEndpointId,
               num_bytes, num_handles) {
   DCHECK_GE(header()->data_size, header()->num_bytes);
 }
 
 }  // namespace system
 }  // namespace mojo