Add CompositeMachMessageServer and its test

util/mach/composite_mach_message_server.cc

Index: util/mach/composite_mach_message_server.cc
diff --git a/util/mach/composite_mach_message_server.cc b/util/mach/composite_mach_message_server.cc
new file mode 100644
index 0000000000000000000000000000000000000000..abbe5bcf38858cc27934520b0140782701f902f6
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+++ b/util/mach/composite_mach_message_server.cc
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+// 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/composite_mach_message_server.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "base/logging.h"
+#include "util/mach/mach_message.h"
+
+namespace crashpad {
+
+CompositeMachMessageServer::CompositeMachMessageServer()
+    : MachMessageServer::Interface(),
+      handler_map_(),
+      request_size_(sizeof(mach_msg_header_t)),
+      reply_size_(sizeof(mig_reply_error_t)) {
+}
+
+CompositeMachMessageServer::~CompositeMachMessageServer() {
+}
+
+void CompositeMachMessageServer::AddHandler(
+    MachMessageServer::Interface* handler) {
+  // Other cycles would be invalid as well, but they aren’t currently checked.
+  DCHECK_NE(handler, this);
+
+  std::set<mach_msg_id_t> request_ids = handler->MachMessageServerRequestIDs();
+  for (mach_msg_id_t request_id : request_ids) {
+    std::pair<HandlerMap::const_iterator, bool> result =
+        handler_map_.insert(std::make_pair(request_id, handler));
+    CHECK(result.second) << "duplicate request ID " << request_id;
+  }
+
+  request_size_ =
+      std::max(request_size_, handler->MachMessageServerRequestSize());
+  reply_size_ = std::max(reply_size_, handler->MachMessageServerReplySize());
+}
+
+bool CompositeMachMessageServer::MachMessageServerFunction(
+    const mach_msg_header_t* in,
+    mach_msg_header_t* out,
+    bool* destroy_complex_request) {
+  HandlerMap::const_iterator iterator = handler_map_.find(in->msgh_id);
+  if (iterator == handler_map_.end()) {
+    // Do what MIG-generated server routines do when they can’t dispatch a
+    // message.
+    PrepareMIGReplyFromRequest(in, out);
+    SetMIGReplyError(out, MIG_BAD_ID);
+    return false;
+  }
+
+  MachMessageServer::Interface* handler = iterator->second;
+  return handler->MachMessageServerFunction(in, out, destroy_complex_request);
+}
+
+std::set<mach_msg_id_t>
+CompositeMachMessageServer::MachMessageServerRequestIDs() {
+  std::set<mach_msg_id_t> request_ids;
+  for (const auto& entry : handler_map_) {
+    request_ids.insert(entry.first);
+  }
+  return request_ids;
+}
+
+mach_msg_size_t CompositeMachMessageServer::MachMessageServerRequestSize() {
+  return request_size_;
+}
+
+mach_msg_size_t CompositeMachMessageServer::MachMessageServerReplySize() {
+  return reply_size_;
+}
+
+}  // namespace crashpad