// Copyright 2012 The Chromium Authors // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. // Defining IPC Messages // // Your IPC messages will be defined by macros inside of an XXX_messages.h // header file. Most of the time, the system can automatically generate all // of messaging mechanism from these definitions, but sometimes some manual // coding is required. In these cases, you will also have an XXX_messages.cc // implementation file as well. // // The senders of your messages will include your XXX_messages.h file to // get the full set of definitions they need to send your messages. // // Each XXX_messages.h file must be registered with the IPC system. This // requires adding two things: // - An XXXMsgStart value to the IPCMessageStart enum in ipc_message_start.h // - An inclusion of XXX_messages.h file in a message generator .h file // // The XXXMsgStart value is an enumeration that ensures uniqueness for // each different message file. Later, you will use this inside your // XXX_messages.h file before invoking message declaration macros: // #define IPC_MESSAGE_START XXXMsgStart // ( ... your macro invocations go here ... ) // // Message Generator Files // // A message generator .h header file pulls in all other message-declaring // headers for a given component. It is included by a message generator // .cc file, which is where all the generated code will wind up. Typically, // you will use an existing generator (e.g. common_message_generator.cc // in /chrome/common), but there are circumstances where you may add a // new one. // // In the rare circumstances where you can't re-use an existing file, // your YYY_message_generator.cc file for a component YYY would contain // the following code: // // Get basic type definitions. // #define IPC_MESSAGE_IMPL // #include "path/to/YYY_message_generator.h" // // Generate constructors. // #include "ipc/struct_constructor_macros.h" // #include "path/to/YYY_message_generator.h" // // Generate param traits write methods. // #include "ipc/param_traits_write_macros.h" // namespace IPC { // #include "path/to/YYY_message_generator.h" // } // namespace IPC // // Generate param traits read methods. // #include "ipc/param_traits_read_macros.h" // namespace IPC { // #include "path/to/YYY_message_generator.h" // } // namespace IPC // // Generate param traits log methods. // #include "ipc/param_traits_log_macros.h" // namespace IPC { // #include "path/to/YYY_message_generator.h" // } // namespace IPC // // In cases where manual generation is required, in your XXX_messages.cc // file, put the following after all the includes for param types: // #define IPC_MESSAGE_IMPL // #include "XXX_messages.h" // (... implementation of traits not auto-generated ...) // // Multiple Inclusion // // The XXX_messages.h file will be multiply-included by the // YYY_message_generator.cc file, so your XXX_messages file can't be // guarded in the usual manner. Ideally, there will be no need for any // inclusion guard, since the XXX_messages.h file should consist solely // of inclusions of other headers (which are self-guarding) and IPC // macros (which are multiply evaluating). // // Note that #pragma once cannot be used here; doing so would mark the whole // file as being singly-included. Since your XXX_messages.h file is only // partially-guarded, care must be taken to ensure that it is only included // by other .cc files (and the YYY_message_generator.h file). Including an // XXX_messages.h file in some other .h file may result in duplicate // declarations and a compilation failure. // // Type Declarations // // It is generally a bad idea to have type definitions in a XXX_messages.h // file; most likely the typedef will then be used in the message, as opposed // to the struct itself. Later, an IPC message dispatcher will need to call // a function taking that type, and that function is declared in some other // header. Thus, in order to get the type definition, the other header // would have to include the XXX_messages.h file, violating the rule above // about not including XXX_messages.h file in other .h files. // // One approach here is to move these type definitions to another (guarded) // .h file and include this second .h in your XXX_messages.h file. This // is still less than ideal, because the dispatched function would have to // redeclare the typedef or include this second header. This may be // reasonable in a few cases. // // Failing all of the above, then you will want to bracket the smallest // possible section of your XXX_messages.h file containing these types // with an include guard macro. Be aware that providing an incomplete // class type declaration to avoid pulling in a long chain of headers is // acceptable when your XXX_messages.h header is being included by the // message sending caller's code, but not when the YYY_message_generator.c // is building the messages. In addition, due to the multiple inclusion // restriction, these type ought to be guarded. Follow a convention like: // #ifndef SOME_GUARD_MACRO // #define SOME_GUARD_MACRO // class some_class; // One incomplete class declaration // class_some_other_class; // Another incomplete class declaration // #endif // SOME_GUARD_MACRO // #ifdef IPC_MESSAGE_IMPL // #include "path/to/some_class.h" // Full class declaration // #include "path/to/some_other_class.h" // Full class declaration // #endif // IPC_MESSAGE_IMPL // (.. IPC macros using some_class and some_other_class ...) // // Macro Invocations // // You will use IPC message macro invocations for three things: // - New struct definitions for IPC // - Registering existing struct and enum definitions with IPC // - Defining the messages themselves // // New structs are defined with IPC_STRUCT_BEGIN(), IPC_STRUCT_MEMBER(), // IPC_STRUCT_END() family of macros. These cause the XXX_messages.h // to proclaim equivalent struct declarations for use by callers, as well // as later registering the type with the message generation. Note that // IPC_STRUCT_MEMBER() is only permitted inside matching calls to // IPC_STRUCT_BEGIN() / IPC_STRUCT_END(). There is also an // IPC_STRUCT_BEGIN_WITH_PARENT(), which behaves like IPC_STRUCT_BEGIN(), // but also accommodates structs that inherit from other structs. // // Externally-defined structs are registered with IPC_STRUCT_TRAITS_BEGIN(), // IPC_STRUCT_TRAITS_MEMBER(), and IPC_STRUCT_TRAITS_END() macros. These // cause registration of the types with message generation only. // There's also IPC_STRUCT_TRAITS_PARENT, which is used to register a parent // class (whose own traits are already defined). Note that // IPC_STRUCT_TRAITS_MEMBER() and IPC_STRUCT_TRAITS_PARENT are only permitted // inside matching calls to IPC_STRUCT_TRAITS_BEGIN() / // IPC_STRUCT_TRAITS_END(). // // Enum types are registered with a single IPC_ENUM_TRAITS_VALIDATE() macro. // There is no need to enumerate each value to the IPC mechanism. Instead, // pass an expression in terms of the parameter |value| to provide // range-checking. For convenience, the IPC_ENUM_TRAITS() is provided which // performs no checking, passing everything including out-of-range values. // Its use is discouraged. The IPC_ENUM_TRAITS_MAX_VALUE() macro can be used // for the typical case where the enum must be in the range 0..maxvalue // inclusive. The IPC_ENUM_TRAITS_MIN_MAX_VALUE() macro can be used for the // less typical case where the enum must be in the range minvalue..maxvalue // inclusive. // // Do not place semicolons following these IPC_ macro invocations. There // is no reason to expect that their expansion corresponds one-to-one with // C++ statements. // // Once the types have been declared / registered, message definitions follow. // "Sync" messages are just synchronous calls, the Send() call doesn't return // until a reply comes back. To declare a sync message, use the IPC_SYNC_ // macros. The numbers at the end show how many input/output parameters there // are (i.e. 1_2 is 1 in, 2 out). Input parameters are first, followed by // output parameters. The caller uses Send([route id, ], in1, &out1, &out2). // The receiver's handler function will be // void OnSyncMessageName(const type1& in1, type2* out1, type3* out2) // // A caller can also send a synchronous message, while the receiver can respond // at a later time. This is transparent from the sender's side. The receiver // needs to use a different handler that takes in a IPC::Message* as the output // type, stash the message, and when it has the data it can Send the message. // // Use the IPC_MESSAGE_HANDLER_DELAY_REPLY macro instead of IPC_MESSAGE_HANDLER // IPC_MESSAGE_HANDLER_DELAY_REPLY(ViewHostMsg_SyncMessageName, // OnSyncMessageName) // Unlike IPC_MESSAGE_HANDLER which works with IPC_BEGIN_MESSAGE_MAP as well as // IPC_BEGIN_MESSAGE_MAP_WITH_PARAM, one needs to use // IPC_MESSAGE_HANDLER_WITH_PARAM_DELAY_REPLY to properly handle the param. // // The handler function will look like: // void OnSyncMessageName(const type1& in1, IPC::Message* reply_msg); // // Receiver stashes the IPC::Message* pointer, and when it's ready, it does: // ViewHostMsg_SyncMessageName::WriteReplyParams(reply_msg, out1, out2); // Send(reply_msg); // Files that want to export their ipc messages should do // #undef IPC_MESSAGE_EXPORT // #define IPC_MESSAGE_EXPORT VISIBILITY_MACRO // after including this header, but before using any of the macros below. // (This needs to be before the include guard.) #undef IPC_MESSAGE_EXPORT #define IPC_MESSAGE_EXPORT #ifndef IPC_IPC_MESSAGE_MACROS_H_ #define IPC_IPC_MESSAGE_MACROS_H_ #include <stdint.h> #include <tuple> #include "base/export_template.h" #include "base/hash/md5_constexpr.h" #include "base/notreached.h" #include "base/task/common/task_annotator.h" #include "ipc/ipc_message_templates.h" #include "ipc/ipc_message_utils.h" #include "ipc/param_traits_macros.h" // Convenience macro for defining structs without inheritance. Should not need // to be subsequently redefined. #define IPC_STRUCT_BEGIN(struct_name) … // Macros for defining structs. Will be subsequently redefined. #define IPC_STRUCT_BEGIN_WITH_PARENT(struct_name, parent) … // Optional variadic parameters specify the default value for this struct // member. They are passed through to the constructor for |type|. #define IPC_STRUCT_MEMBER(type, name, ...) … #define IPC_STRUCT_END() … // Message macros collect arguments and funnel them into the common message // generation macro. These should never be redefined. // Asynchronous messages have only in parameters and are declared like: // IPC_MESSAGE_CONTROL(FooMsg, int, float) #define IPC_MESSAGE_CONTROL(msg_class, ...) … #define IPC_MESSAGE_ROUTED(msg_class, ...) … // Synchronous messages have both in and out parameters, so the lists need to // be parenthesized to disambiguate: // IPC_SYNC_MESSAGE_CONTROL(BarMsg, (int, int), (bool)) // // Implementation detail: The parentheses supplied by the caller for // disambiguation are also used to trigger the IPC_TUPLE invocations below, // so "IPC_TUPLE in" and "IPC_TUPLE out" are intentional. #define IPC_SYNC_MESSAGE_CONTROL(msg_class, in, out) … #define IPC_SYNC_MESSAGE_ROUTED(msg_class, in, out) … #define IPC_TUPLE(...) … #define IPC_MESSAGE_DECL(msg_name, kind, in_tuple, out_tuple) … #if defined(IPC_MESSAGE_IMPL) // "Implementation" inclusion provides the explicit template definition // for msg_name. #define IPC_MESSAGE_EXTRA … #define IPC_MESSAGE_DEFINE_KIND … #elif defined(IPC_MESSAGE_MACROS_LOG_ENABLED) #ifndef IPC_LOG_TABLE_ADD_ENTRY #error You need to define IPC_LOG_TABLE_ADD_ENTRY(msg_id, logger) #endif // "Log table" inclusion produces extra logging registration code. #define IPC_MESSAGE_EXTRA … #else // Normal inclusion produces nothing extra. #define IPC_MESSAGE_EXTRA(msg_name) … #endif // defined(IPC_MESSAGE_IMPL) // Message IDs // Note: we currently use __LINE__ to give unique IDs to messages within // a file. They're globally unique since each file defines its own // IPC_MESSAGE_START. #define IPC_MESSAGE_ID() … #define IPC_MESSAGE_ID_CLASS(id) … #define IPC_MESSAGE_ID_LINE(id) … // Message crackers and handlers. Usage: // // bool MyClass::OnMessageReceived(const IPC::Message& msg) { // bool handled = true; // IPC_BEGIN_MESSAGE_MAP(MyClass, msg) // IPC_MESSAGE_HANDLER(MsgClassOne, OnMsgClassOne) // ...more handlers here ... // IPC_MESSAGE_HANDLER(MsgClassTen, OnMsgClassTen) // IPC_MESSAGE_UNHANDLED(handled = false) // IPC_END_MESSAGE_MAP() // return handled; // } #define IPC_TASK_ANNOTATOR_STRINGIFY(s) … // A macro to be used from within the IPC_MESSAGE_FORWARD macros, for providing // the IPC message context to the TaskAnnotator. This allows posted tasks to be // associated with the incoming IPC message that caused them to be posted. #define IPC_TASK_ANNOTATOR_CONTEXT(msg_class) … #define IPC_BEGIN_MESSAGE_MAP(class_name, msg) … #define IPC_BEGIN_MESSAGE_MAP_WITH_PARAM(class_name, msg, param) … #define IPC_MESSAGE_FORWARD(msg_class, obj, member_func) … #define IPC_MESSAGE_HANDLER(msg_class, member_func) … #define IPC_MESSAGE_FORWARD_DELAY_REPLY(msg_class, obj, member_func) … #define IPC_MESSAGE_HANDLER_DELAY_REPLY(msg_class, member_func) … #define IPC_MESSAGE_FORWARD_WITH_PARAM_DELAY_REPLY(msg_class, obj, \ member_func) … #define IPC_MESSAGE_HANDLER_WITH_PARAM_DELAY_REPLY(msg_class, member_func) … #define IPC_MESSAGE_HANDLER_GENERIC(msg_class, code) … #define IPC_REPLY_HANDLER(func) … #define IPC_MESSAGE_UNHANDLED(code) … #define IPC_MESSAGE_UNHANDLED_ERROR() … #define IPC_END_MESSAGE_MAP() … // This corresponds to an enum value from IPCMessageStart. #define IPC_MESSAGE_CLASS(message) … // Deprecated legacy macro names. // TODO(mdempsky): Replace uses with generic names. #define IPC_MESSAGE_CONTROL0(msg) … #define IPC_MESSAGE_CONTROL1(msg, a) … #define IPC_MESSAGE_CONTROL2(msg, a, b) … #define IPC_MESSAGE_CONTROL3(msg, a, b, c) … #define IPC_MESSAGE_CONTROL4(msg, a, b, c, d) … #define IPC_MESSAGE_CONTROL5(msg, a, b, c, d, e) … #define IPC_MESSAGE_ROUTED0(msg) … #define IPC_MESSAGE_ROUTED1(msg, a) … #define IPC_MESSAGE_ROUTED2(msg, a, b) … #define IPC_MESSAGE_ROUTED3(msg, a, b, c) … #define IPC_MESSAGE_ROUTED4(msg, a, b, c, d) … #define IPC_MESSAGE_ROUTED5(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL0_0(msg) … #define IPC_SYNC_MESSAGE_CONTROL0_1(msg, a) … #define IPC_SYNC_MESSAGE_CONTROL0_2(msg, a, b) … #define IPC_SYNC_MESSAGE_CONTROL0_3(msg, a, b, c) … #define IPC_SYNC_MESSAGE_CONTROL0_4(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_CONTROL1_0(msg, a) … #define IPC_SYNC_MESSAGE_CONTROL1_1(msg, a, b) … #define IPC_SYNC_MESSAGE_CONTROL1_2(msg, a, b, c) … #define IPC_SYNC_MESSAGE_CONTROL1_3(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_CONTROL1_4(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL2_0(msg, a, b) … #define IPC_SYNC_MESSAGE_CONTROL2_1(msg, a, b, c) … #define IPC_SYNC_MESSAGE_CONTROL2_2(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_CONTROL2_3(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL2_4(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_CONTROL3_0(msg, a, b, c) … #define IPC_SYNC_MESSAGE_CONTROL3_1(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_CONTROL3_2(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL3_3(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_CONTROL3_4(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_CONTROL4_0(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_CONTROL4_1(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL4_2(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_CONTROL4_3(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_CONTROL4_4(msg, a, b, c, d, e, f, g, h) … #define IPC_SYNC_MESSAGE_CONTROL5_0(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_CONTROL5_1(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_CONTROL5_2(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_CONTROL5_3(msg, a, b, c, d, e, f, g, h) … #define IPC_SYNC_MESSAGE_CONTROL5_4(msg, a, b, c, d, e, f, g, h, i) … #define IPC_SYNC_MESSAGE_ROUTED0_0(msg) … #define IPC_SYNC_MESSAGE_ROUTED0_1(msg, a) … #define IPC_SYNC_MESSAGE_ROUTED0_2(msg, a, b) … #define IPC_SYNC_MESSAGE_ROUTED0_3(msg, a, b, c) … #define IPC_SYNC_MESSAGE_ROUTED0_4(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_ROUTED1_0(msg, a) … #define IPC_SYNC_MESSAGE_ROUTED1_1(msg, a, b) … #define IPC_SYNC_MESSAGE_ROUTED1_2(msg, a, b, c) … #define IPC_SYNC_MESSAGE_ROUTED1_3(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_ROUTED1_4(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_ROUTED2_0(msg, a, b) … #define IPC_SYNC_MESSAGE_ROUTED2_1(msg, a, b, c) … #define IPC_SYNC_MESSAGE_ROUTED2_2(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_ROUTED2_3(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_ROUTED2_4(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_ROUTED3_0(msg, a, b, c) … #define IPC_SYNC_MESSAGE_ROUTED3_1(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_ROUTED3_2(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_ROUTED3_3(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_ROUTED3_4(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_ROUTED3_5(msg, a, b, c, d, e, f, g, h) … #define IPC_SYNC_MESSAGE_ROUTED4_0(msg, a, b, c, d) … #define IPC_SYNC_MESSAGE_ROUTED4_1(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_ROUTED4_2(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_ROUTED4_3(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_ROUTED4_4(msg, a, b, c, d, e, f, g, h) … #define IPC_SYNC_MESSAGE_ROUTED5_0(msg, a, b, c, d, e) … #define IPC_SYNC_MESSAGE_ROUTED5_1(msg, a, b, c, d, e, f) … #define IPC_SYNC_MESSAGE_ROUTED5_2(msg, a, b, c, d, e, f, g) … #define IPC_SYNC_MESSAGE_ROUTED5_3(msg, a, b, c, d, e, f, g, h) … #define IPC_SYNC_MESSAGE_ROUTED5_4(msg, a, b, c, d, e, f, g, h, i) … #endif // IPC_IPC_MESSAGE_MACROS_H_ // Clean up IPC_MESSAGE_START in this unguarded section so that the // XXX_messages.h files need not do so themselves. This makes the // XXX_messages.h files easier to write. #undef IPC_MESSAGE_START
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