ipc/ipc_message_templates.h - chromium/src - Git at Google

 // 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_H_
 #define IPC_IPC_MESSAGE_TEMPLATES_H_

 #include <stdint.h>

 #include <tuple>
 #include <type_traits>
 #include <utility>

 #include "base/logging.h"
 #include "base/trace_event/trace_event.h"
 #include "base/tuple.h"
 #include "build/build_config.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_message_utils.h"

 namespace IPC {

 template <typename Tuple, size_t... Ns>
 auto TupleForwardImpl(Tuple&& tuple, std::index_sequence<Ns...>) -> decltype(
     std::forward_as_tuple(std::get<Ns>(std::forward<Tuple>(tuple))...)) {
   return std::forward_as_tuple(std::get<Ns>(std::forward<Tuple>(tuple))...);
 }

 // Transforms std::tuple contents to the forwarding form.
 // Example:
 //   std::tuple<int, int&, const int&, int&&>&&
 //     -> std::tuple<int&&, int&, const int&, int&&>.
 //   const std::tuple<int, const int&, int&&>&
 //     -> std::tuple<const int&, int&, const int&, int&>.
 //
 // TupleForward(std::make_tuple(a, b, c)) is equivalent to
 // std::forward_as_tuple(a, b, c).
 template <typename Tuple>
 auto TupleForward(Tuple&& tuple) -> decltype(TupleForwardImpl(
     std::forward<Tuple>(tuple),
     std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>())) {
   return TupleForwardImpl(
       std::forward<Tuple>(tuple),
       std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>());
 }

 // This function is for all the async IPCs that don't pass an extra parameter
 // using IPC_BEGIN_MESSAGE_MAP_WITH_PARAM.
 template <typename ObjT, typename Method, typename P, typename Tuple>
 void DispatchToMethod(ObjT* obj, Method method, P*, Tuple&& tuple) {
   base::DispatchToMethod(obj, method, std::forward<Tuple>(tuple));
 }

 template <typename ObjT,
           typename Method,
           typename P,
           typename Tuple,
           size_t... Ns>
 void DispatchToMethodImpl(ObjT* obj,
                           Method method,
                           P* parameter,
                           Tuple&& tuple,
                           std::index_sequence<Ns...>) {
   (obj->*method)(parameter, std::get<Ns>(std::forward<Tuple>(tuple))...);
 }

 // The following function is for async IPCs which have a dispatcher with an
 // extra parameter specified using IPC_BEGIN_MESSAGE_MAP_WITH_PARAM.
 template <typename ObjT, typename P, typename... Args, typename Tuple>
 std::enable_if_t<sizeof...(Args) == std::tuple_size<std::decay_t<Tuple>>::value>
 DispatchToMethod(ObjT* obj,
                  void (ObjT::*method)(P*, Args...),
                  P* parameter,
                  Tuple&& tuple) {
   constexpr size_t size = std::tuple_size<std::decay_t<Tuple>>::value;
   DispatchToMethodImpl(obj, method, parameter, std::forward<Tuple>(tuple),
                        std::make_index_sequence<size>());
 }

 enum class MessageKind {
   CONTROL,
   ROUTED,
 };

 // Routing is a helper struct so MessageT's private common constructor has a
 // different type signature than the public "int32_t routing_id" one.
 struct Routing {
   explicit Routing(int32_t id) : id(id) {}
   int32_t id;
 };

 // We want to restrict MessageT's constructors so that a routing_id is always
 // provided for ROUTED messages and never provided for CONTROL messages, so
 // use the SFINAE technique from N4387's "Implementation Hint" section.
 #if defined(COMPILER_MSVC)
 // MSVC 2013 doesn't support default arguments for template member functions
 // of templated classes, so there we have to rely on the DCHECKs instead.
 // TODO(mdempsky): Reevaluate once MSVC 2015.
 #define IPC_MESSAGET_SFINAE(x)
 #else
 #define IPC_MESSAGET_SFINAE(x) \
   template <bool X = (x), typename std::enable_if<X, bool>::type = false>
 #endif

 // MessageT is the common template used for all user-defined message types.
 // It's intended to be used via the macros defined in ipc_message_macros.h.
 template <typename Meta,
           typename InTuple = typename Meta::InTuple,
           typename OutTuple = typename Meta::OutTuple>
 class MessageT;

 // Asynchronous message partial specialization.
 template <typename Meta, typename... Ins>
 class MessageT<Meta, std::tuple<Ins...>, void> : public Message {
  public:
   using Param = std::tuple<Ins...>;
   enum { ID = Meta::ID };

   // TODO(mdempsky): Remove.  Uses of MyMessage::Schema::Param can be replaced
   // with just MyMessage::Param.
   using Schema = MessageT;

   IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::CONTROL)
   MessageT(const Ins&... ins) : MessageT(Routing(MSG_ROUTING_CONTROL), ins...) {
     DCHECK(Meta::kKind == MessageKind::CONTROL) << Meta::kName;
   }

   IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::ROUTED)
   MessageT(int32_t routing_id, const Ins&... ins)
       : MessageT(Routing(routing_id), ins...) {
     DCHECK(Meta::kKind == MessageKind::ROUTED) << Meta::kName;
   }

   static bool Read(const Message* msg, Param* p);
   static void Log(std::string* name, const Message* msg, std::string* l);

   template <class T, class S, class P, class Method>
   static bool Dispatch(const Message* msg,
                        T* obj,
                        S* sender,
                        P* parameter,
                        Method func) {
     TRACE_EVENT0("ipc", Meta::kName);
     Param p;
     if (Read(msg, &p)) {
       DispatchToMethod(obj, func, parameter, std::move(p));
       return true;
     }
     return false;
   }

  private:
   MessageT(Routing routing, const Ins&... ins);
 };

 // Synchronous message partial specialization.
 template <typename Meta, typename... Ins, typename... Outs>
 class MessageT<Meta, std::tuple<Ins...>, std::tuple<Outs...>>
     : public SyncMessage {
  public:
   using SendParam = std::tuple<Ins...>;
   using ReplyParam = std::tuple<Outs...>;
   enum { ID = Meta::ID };

   // TODO(mdempsky): Remove.  Uses of MyMessage::Schema::{Send,Reply}Param can
   // be replaced with just MyMessage::{Send,Reply}Param.
   using Schema = MessageT;

   IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::CONTROL)
   MessageT(const Ins&... ins, Outs*... outs)
       : MessageT(Routing(MSG_ROUTING_CONTROL), ins..., outs...) {
     DCHECK(Meta::kKind == MessageKind::CONTROL) << Meta::kName;
   }

   IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::ROUTED)
   MessageT(int32_t routing_id, const Ins&... ins, Outs*... outs)
       : MessageT(Routing(routing_id), ins..., outs...) {
     DCHECK(Meta::kKind == MessageKind::ROUTED) << Meta::kName;
   }

   static bool ReadSendParam(const Message* msg, SendParam* p);
   static bool ReadReplyParam(const Message* msg, ReplyParam* p);
   static void WriteReplyParams(Message* reply, const Outs&... outs);
   static void Log(std::string* name, const Message* msg, std::string* l);

   template <class T, class S, class P, class Method>
   static bool Dispatch(const Message* msg,
                        T* obj,
                        S* sender,
                        P* /* parameter */,
                        Method func) {
     TRACE_EVENT0("ipc", Meta::kName);
     SendParam send_params;
     bool ok = ReadSendParam(msg, &send_params);
     Message* reply = SyncMessage::GenerateReply(msg);
     if (!ok) {
       NOTREACHED() << "Error deserializing message " << msg->type();
       reply->set_reply_error();
       sender->Send(reply);
       return false;
     }

     ReplyParam reply_params;
     base::DispatchToMethod(obj, func, std::move(send_params), &reply_params);
     WriteParam(reply, reply_params);
     LogReplyParamsToMessage(reply_params, msg);
     sender->Send(reply);
     return true;
   }

   template <class T, class P, class Method>
   static bool DispatchDelayReply(const Message* msg,
                                  T* obj,
                                  P* /* parameter */,
                                  Method func) {
     TRACE_EVENT0("ipc", Meta::kName);
     SendParam send_params;
     bool ok = ReadSendParam(msg, &send_params);
     Message* reply = SyncMessage::GenerateReply(msg);
     if (!ok) {
       NOTREACHED() << "Error deserializing message " << msg->type();
       reply->set_reply_error();
       obj->Send(reply);
       return false;
     }

     std::tuple<Message&> t = std::tie(*reply);
     ConnectMessageAndReply(msg, reply);
     base::DispatchToMethod(obj, func, std::move(send_params), &t);
     return true;
   }

   template <class T, class P, class Method>
   static bool DispatchWithParamDelayReply(const Message* msg,
                                           T* obj,
                                           P* parameter,
                                           Method func) {
     TRACE_EVENT0("ipc", Meta::kName);
     SendParam send_params;
     bool ok = ReadSendParam(msg, &send_params);
     Message* reply = SyncMessage::GenerateReply(msg);
     if (!ok) {
       NOTREACHED() << "Error deserializing message " << msg->type();
       reply->set_reply_error();
       obj->Send(reply);
       return false;
     }

     std::tuple<Message&> t = std::tie(*reply);
     ConnectMessageAndReply(msg, reply);
     std::tuple<P*> parameter_tuple(parameter);
     base::DispatchToMethod(
         obj, func,
         std::tuple_cat(std::move(parameter_tuple), TupleForward(send_params)),
         &t);
     return true;
   }

  private:
   MessageT(Routing routing, const Ins&... ins, Outs*... outs);
 };

 }  // namespace IPC

 #if defined(IPC_MESSAGE_IMPL)
 #include "ipc/ipc_message_templates_impl.h"
 #endif

 #endif  // IPC_IPC_MESSAGE_TEMPLATES_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_H_
	#define IPC_IPC_MESSAGE_TEMPLATES_H_

	#include <stdint.h>

	#include <tuple>
	#include <type_traits>
	#include <utility>

	#include "base/logging.h"
	#include "base/trace_event/trace_event.h"
	#include "base/tuple.h"
	#include "build/build_config.h"
	#include "ipc/ipc_message.h"
	#include "ipc/ipc_message_utils.h"

	namespace IPC {

	template <typename Tuple, size_t... Ns>
	auto TupleForwardImpl(Tuple&& tuple, std::index_sequence<Ns...>) -> decltype(
	std::forward_as_tuple(std::get<Ns>(std::forward<Tuple>(tuple))...)) {
	return std::forward_as_tuple(std::get<Ns>(std::forward<Tuple>(tuple))...);
	}

	// Transforms std::tuple contents to the forwarding form.
	// Example:
	// std::tuple<int, int&, const int&, int&&>&&
	// -> std::tuple<int&&, int&, const int&, int&&>.
	// const std::tuple<int, const int&, int&&>&
	// -> std::tuple<const int&, int&, const int&, int&>.
	//
	// TupleForward(std::make_tuple(a, b, c)) is equivalent to
	// std::forward_as_tuple(a, b, c).
	template <typename Tuple>
	auto TupleForward(Tuple&& tuple) -> decltype(TupleForwardImpl(
	std::forward<Tuple>(tuple),
	std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>())) {
	return TupleForwardImpl(
	std::forward<Tuple>(tuple),
	std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>());
	}

	// This function is for all the async IPCs that don't pass an extra parameter
	// using IPC_BEGIN_MESSAGE_MAP_WITH_PARAM.
	template <typename ObjT, typename Method, typename P, typename Tuple>
	void DispatchToMethod(ObjT* obj, Method method, P*, Tuple&& tuple) {
	base::DispatchToMethod(obj, method, std::forward<Tuple>(tuple));
	}

	template <typename ObjT,
	typename Method,
	typename P,
	typename Tuple,
	size_t... Ns>
	void DispatchToMethodImpl(ObjT* obj,
	Method method,
	P* parameter,
	Tuple&& tuple,
	std::index_sequence<Ns...>) {
	(obj->*method)(parameter, std::get<Ns>(std::forward<Tuple>(tuple))...);
	}

	// The following function is for async IPCs which have a dispatcher with an
	// extra parameter specified using IPC_BEGIN_MESSAGE_MAP_WITH_PARAM.
	template <typename ObjT, typename P, typename... Args, typename Tuple>
	std::enable_if_t<sizeof...(Args) == std::tuple_size<std::decay_t<Tuple>>::value>
	DispatchToMethod(ObjT* obj,
	void (ObjT::method)(P, Args...),
	P* parameter,
	Tuple&& tuple) {
	constexpr size_t size = std::tuple_size<std::decay_t<Tuple>>::value;
	DispatchToMethodImpl(obj, method, parameter, std::forward<Tuple>(tuple),
	std::make_index_sequence<size>());
	}

	enum class MessageKind {
	CONTROL,
	ROUTED,
	};

	// Routing is a helper struct so MessageT's private common constructor has a
	// different type signature than the public "int32_t routing_id" one.
	struct Routing {
	explicit Routing(int32_t id) : id(id) {}
	int32_t id;
	};

	// We want to restrict MessageT's constructors so that a routing_id is always
	// provided for ROUTED messages and never provided for CONTROL messages, so
	// use the SFINAE technique from N4387's "Implementation Hint" section.
	#if defined(COMPILER_MSVC)
	// MSVC 2013 doesn't support default arguments for template member functions
	// of templated classes, so there we have to rely on the DCHECKs instead.
	// TODO(mdempsky): Reevaluate once MSVC 2015.
	#define IPC_MESSAGET_SFINAE(x)
	#else
	#define IPC_MESSAGET_SFINAE(x) \
	template <bool X = (x), typename std::enable_if<X, bool>::type = false>
	#endif

	// MessageT is the common template used for all user-defined message types.
	// It's intended to be used via the macros defined in ipc_message_macros.h.
	template <typename Meta,
	typename InTuple = typename Meta::InTuple,
	typename OutTuple = typename Meta::OutTuple>
	class MessageT;

	// Asynchronous message partial specialization.
	template <typename Meta, typename... Ins>
	class MessageT<Meta, std::tuple<Ins...>, void> : public Message {
	public:
	using Param = std::tuple<Ins...>;
	enum { ID = Meta::ID };

	// TODO(mdempsky): Remove. Uses of MyMessage::Schema::Param can be replaced
	// with just MyMessage::Param.
	using Schema = MessageT;

	IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::CONTROL)
	MessageT(const Ins&... ins) : MessageT(Routing(MSG_ROUTING_CONTROL), ins...) {
	DCHECK(Meta::kKind == MessageKind::CONTROL) << Meta::kName;
	}

	IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::ROUTED)
	MessageT(int32_t routing_id, const Ins&... ins)
	: MessageT(Routing(routing_id), ins...) {
	DCHECK(Meta::kKind == MessageKind::ROUTED) << Meta::kName;
	}

	static bool Read(const Message* msg, Param* p);
	static void Log(std::string* name, const Message* msg, std::string* l);

	template <class T, class S, class P, class Method>
	static bool Dispatch(const Message* msg,
	T* obj,
	S* sender,
	P* parameter,
	Method func) {
	TRACE_EVENT0("ipc", Meta::kName);
	Param p;
	if (Read(msg, &p)) {
	DispatchToMethod(obj, func, parameter, std::move(p));
	return true;
	}
	return false;
	}

	private:
	MessageT(Routing routing, const Ins&... ins);
	};

	// Synchronous message partial specialization.
	template <typename Meta, typename... Ins, typename... Outs>
	class MessageT<Meta, std::tuple<Ins...>, std::tuple<Outs...>>
	: public SyncMessage {
	public:
	using SendParam = std::tuple<Ins...>;
	using ReplyParam = std::tuple<Outs...>;
	enum { ID = Meta::ID };

	// TODO(mdempsky): Remove. Uses of MyMessage::Schema::{Send,Reply}Param can
	// be replaced with just MyMessage::{Send,Reply}Param.
	using Schema = MessageT;

	IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::CONTROL)
	MessageT(const Ins&... ins, Outs*... outs)
	: MessageT(Routing(MSG_ROUTING_CONTROL), ins..., outs...) {
	DCHECK(Meta::kKind == MessageKind::CONTROL) << Meta::kName;
	}

	IPC_MESSAGET_SFINAE(Meta::kKind == MessageKind::ROUTED)
	MessageT(int32_t routing_id, const Ins&... ins, Outs*... outs)
	: MessageT(Routing(routing_id), ins..., outs...) {
	DCHECK(Meta::kKind == MessageKind::ROUTED) << Meta::kName;
	}

	static bool ReadSendParam(const Message* msg, SendParam* p);
	static bool ReadReplyParam(const Message* msg, ReplyParam* p);
	static void WriteReplyParams(Message* reply, const Outs&... outs);
	static void Log(std::string* name, const Message* msg, std::string* l);

	template <class T, class S, class P, class Method>
	static bool Dispatch(const Message* msg,
	T* obj,
	S* sender,
	P* /* parameter */,
	Method func) {
	TRACE_EVENT0("ipc", Meta::kName);
	SendParam send_params;
	bool ok = ReadSendParam(msg, &send_params);
	Message* reply = SyncMessage::GenerateReply(msg);
	if (!ok) {
	NOTREACHED() << "Error deserializing message " << msg->type();
	reply->set_reply_error();
	sender->Send(reply);
	return false;
	}

	ReplyParam reply_params;
	base::DispatchToMethod(obj, func, std::move(send_params), &reply_params);
	WriteParam(reply, reply_params);
	LogReplyParamsToMessage(reply_params, msg);
	sender->Send(reply);
	return true;
	}

	template <class T, class P, class Method>
	static bool DispatchDelayReply(const Message* msg,
	T* obj,
	P* /* parameter */,
	Method func) {
	TRACE_EVENT0("ipc", Meta::kName);
	SendParam send_params;
	bool ok = ReadSendParam(msg, &send_params);
	Message* reply = SyncMessage::GenerateReply(msg);
	if (!ok) {
	NOTREACHED() << "Error deserializing message " << msg->type();
	reply->set_reply_error();
	obj->Send(reply);
	return false;
	}

	std::tuple<Message&> t = std::tie(*reply);
	ConnectMessageAndReply(msg, reply);
	base::DispatchToMethod(obj, func, std::move(send_params), &t);
	return true;
	}

	template <class T, class P, class Method>
	static bool DispatchWithParamDelayReply(const Message* msg,
	T* obj,
	P* parameter,
	Method func) {
	TRACE_EVENT0("ipc", Meta::kName);
	SendParam send_params;
	bool ok = ReadSendParam(msg, &send_params);
	Message* reply = SyncMessage::GenerateReply(msg);
	if (!ok) {
	NOTREACHED() << "Error deserializing message " << msg->type();
	reply->set_reply_error();
	obj->Send(reply);
	return false;
	}

	std::tuple<Message&> t = std::tie(*reply);
	ConnectMessageAndReply(msg, reply);
	std::tuple<P*> parameter_tuple(parameter);
	base::DispatchToMethod(
	obj, func,
	std::tuple_cat(std::move(parameter_tuple), TupleForward(send_params)),
	&t);
	return true;
	}

	private:
	MessageT(Routing routing, const Ins&... ins, Outs*... outs);
	};

	} // namespace IPC

	#if defined(IPC_MESSAGE_IMPL)
	#include "ipc/ipc_message_templates_impl.h"
	#endif

	#endif // IPC_IPC_MESSAGE_TEMPLATES_H_