use variadic macros/templates in IPC message implementation

ipc/ipc_message_templates_impl.h

+// Copyright 2015 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 IPC_IPC_MESSAGE_TEMPLATES_IMPL_H_
+#define IPC_IPC_MESSAGE_TEMPLATES_IMPL_H_
+
+namespace IPC {
+
+template <typename... Ts>
+class ParamDeserializer : public MessageReplyDeserializer {
+ public:
+  explicit ParamDeserializer(const base::Tuple<Ts&...>& out) : out_(out) {}
+
+  bool SerializeOutputParameters(const IPC::Message& msg,
+                                 base::PickleIterator iter) override {
+    return ReadParam(&msg, &iter, &out_);
+  }
+
+  base::Tuple<Ts&...> out_;
+};
+
+template <typename Meta, typename... Ins>
+MessageT<Meta, base::Tuple<Ins...>, void>::MessageT(Routing routing,
+                                                    const Ins&... ins)
+    : Message(routing.id, ID, PRIORITY_NORMAL) {
+  WriteParam(this, base::MakeRefTuple(ins...));
+}
+
+template <typename Meta, typename... Ins>
+bool MessageT<Meta, base::Tuple<Ins...>, void>::Read(const Message* msg,
+                                                     Param* p) {
+  base::PickleIterator iter(*msg);
+  return ReadParam(msg, &iter, p);
+}
+
+template <typename Meta, typename... Ins>
+void MessageT<Meta, base::Tuple<Ins...>, void>::Log(std::string* name,
+                                                    const Message* msg,
+                                                    std::string* l) {
+  if (name)
+    *name = Meta::kName;
+  if (!msg || !l)
+    return;
+  Param p;
+  if (Read(msg, &p))
+    LogParam(p, l);
+}
+
+template <typename Meta, typename... Ins, typename... Outs>
+MessageT<Meta, base::Tuple<Ins...>, base::Tuple<Outs...>>::MessageT(
+    Routing routing,
+    const Ins&... ins,
+    Outs*... outs)
+    : SyncMessage(
+          routing.id,
+          ID,
+          PRIORITY_NORMAL,
+          new ParamDeserializer<Outs...>(base::MakeRefTuple(*outs...))) {
+  WriteParam(this, base::MakeRefTuple(ins...));
+}
+
+template <typename Meta, typename... Ins, typename... Outs>
+bool MessageT<Meta, base::Tuple<Ins...>, base::Tuple<Outs...>>::ReadSendParam(
+    const Message* msg,
+    SendParam* p) {
+  base::PickleIterator iter = SyncMessage::GetDataIterator(msg);
+  return ReadParam(msg, &iter, p);
+}
+
+template <typename Meta, typename... Ins, typename... Outs>
+bool MessageT<Meta, base::Tuple<Ins...>, base::Tuple<Outs...>>::ReadReplyParam(
+    const Message* msg,
+    ReplyParam* p) {
+  base::PickleIterator iter = SyncMessage::GetDataIterator(msg);
+  return ReadParam(msg, &iter, p);
+}
+
+template <typename Meta, typename... Ins, typename... Outs>
+void MessageT<Meta,
+              base::Tuple<Ins...>,
+              base::Tuple<Outs...>>::WriteReplyParams(Message* reply,
+                                                      const Outs&... outs) {
+  WriteParam(reply, base::MakeRefTuple(outs...));
+}
+
+template <typename Meta, typename... Ins, typename... Outs>
+void MessageT<Meta, base::Tuple<Ins...>, base::Tuple<Outs...>>::Log(
+    std::string* name,
+    const Message* msg,
+    std::string* l) {
+  if (name)
+    *name = Meta::kName;
+  if (!msg || !l)
+    return;
+  if (msg->is_sync()) {
+    SendParam p;
+    if (ReadSendParam(msg, &p))
+      LogParam(p, l);
+    AddOutputParamsToLog(msg, l);
+  } else {
+    ReplyParam p;
+    if (ReadReplyParam(msg, &p))
+      LogParam(p, l);
+  }
+}
+
+}  // namespace IPC
+
+#endif  // IPC_IPC_MESSAGE_TEMPLATES_IMPL_H_