Mojo C++ bindings: introduce an optional array to store transferred interface IDs in messages.

mojo/public/cpp/bindings/lib/message_builder.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/public/cpp/bindings/lib/message_builder.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
-#include "mojo/public/cpp/bindings/lib/serialization_util.h"
-#include "mojo/public/cpp/bindings/message.h"
+#include "mojo/public/cpp/bindings/lib/array_internal.h"
+#include "mojo/public/cpp/bindings/lib/bindings_internal.h"
+#include "mojo/public/cpp/bindings/lib/buffer.h"
+#include "mojo/public/cpp/bindings/lib/message_internal.h"
 
 namespace mojo {
 namespace internal {
 
 template <typename Header>
 void Allocate(Buffer* buf, Header** header) {
   *header = static_cast<Header*>(buf->Allocate(sizeof(Header)));
   (*header)->num_bytes = sizeof(Header);
 }
 
-MessageBuilder::MessageBuilder(uint32_t name, size_t payload_size) {
-  InitializeMessage(sizeof(MessageHeader) + payload_size);
+MessageBuilder::MessageBuilder(uint32_t name,
+                               uint32_t flags,
+                               size_t payload_size,
+                               size_t payload_interface_id_count) {
+  if (payload_interface_id_count > 0) {
+    // Version 2
+    InitializeMessage(
+        sizeof(MessageHeaderV2) + Align(payload_size) +
+        ArrayDataTraits<uint32_t>::GetStorageSize(
+            static_cast<uint32_t>(payload_interface_id_count)));
 
-  MessageHeader* header;
-  Allocate(message_.buffer(), &header);
-  header->version = 0;
-  header->name = name;
+    MessageHeaderV2* header;
+    Allocate(message_.buffer(), &header);
+    header->version = 2;
+    header->name = name;
+    header->flags = flags;
+    // Set it to right after the message header.

[Ken Rockot(use gerrit already), 2017/01/31 18:33:42]

nit: Maybe clarify this comment -- something like "The payload immediately
follows the header"

[yzshen1, 2017/01/31 19:26:05]

Done.

+    header->payload.Set(header + 1);
+  } else if (flags &
+             (Message::kFlagExpectsResponse | Message::kFlagIsResponse)) {
+    // Version 1
+    InitializeMessage(sizeof(MessageHeaderV1) + payload_size);
+
+    MessageHeaderV1* header;
+    Allocate(message_.buffer(), &header);
+    header->version = 1;
+    header->name = name;
+    header->flags = flags;
+  } else {
+    InitializeMessage(sizeof(MessageHeader) + payload_size);
+
+    MessageHeader* header;
+    Allocate(message_.buffer(), &header);
+    header->version = 0;
+    header->name = name;
+    header->flags = flags;
+  }
 }
 
 MessageBuilder::~MessageBuilder() {
 }
 
-MessageBuilder::MessageBuilder() {}
-
 void MessageBuilder::InitializeMessage(size_t size) {
   message_.Initialize(static_cast<uint32_t>(Align(size)),
                       true /* zero_initialized */);
 }
 
-MessageWithRequestIDBuilder::MessageWithRequestIDBuilder(uint32_t name,
-                                                         size_t payload_size,
-                                                         uint32_t flags,
-                                                         uint64_t request_id) {
-  InitializeMessage(sizeof(MessageHeaderWithRequestID) + payload_size);
-
-  MessageHeaderWithRequestID* header;
-  Allocate(message_.buffer(), &header);
-  header->version = 1;
-  header->name = name;
-  header->flags = flags;
-  header->request_id = request_id;
-}
-
 }  // namespace internal
 }  // namespace mojo