Add ChildPortServer, a MachMessageServer::Interface implementation for the child_port subsystem

util/mach/mach_message_util.cc

Index: util/mach/mach_message_util.cc
diff --git a/util/mach/mach_message_util.cc b/util/mach/mach_message_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a1392fe01886f9bf7bb0b2d9b15a54bb6bb36b10
--- /dev/null
+++ b/util/mach/mach_message_util.cc
@@ -0,0 +1,37 @@
+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/mach/mach_message_util.h"
+
+namespace crashpad {
+
+void PrepareMIGReplyFromRequest(const mach_msg_header_t* in_header,
+                                mach_msg_header_t* out_header) {
+  out_header->msgh_bits =
+      MACH_MSGH_BITS(MACH_MSGH_BITS_REMOTE(in_header->msgh_bits), 0);
+  out_header->msgh_remote_port = in_header->msgh_remote_port;
+  out_header->msgh_size = sizeof(mig_reply_error_t);
+  out_header->msgh_local_port = MACH_PORT_NULL;
+  out_header->msgh_id = in_header->msgh_id + 100;
+  reinterpret_cast<mig_reply_error_t*>(out_header)->NDR = NDR_record;
+
+  // MIG-generated dispatch routines don’t do this, but they should.
+  out_header->msgh_reserved = 0;
+}
+
+void SetMIGReplyError(mach_msg_header_t* out_header, kern_return_t error) {
+  reinterpret_cast<mig_reply_error_t*>(out_header)->RetCode = error;
+}
+
+}  // namespace crashpad