ipc(5) - SerenityOS man pages

Name

IPC - Inter-Process Communication endpoint definition format (.ipc)

Synopsis

The IPC format of SerenityOS is a domain-specific language (DSL) used to define communication endpoints for IPC.

Description

Informally, IPC files - with the help of the IPC compiler - are used to generate message classes that will wrap messages for interprocess communication in the system. IPC syntax is loosely inspired by C++ headers. Generated IPC message classes support encode and decode functions to pass messages between the processes.

Every IPC pair in the system has a client endpoint and a server endpoint that are described in the IPC files. Each IPC endpoint should have a unique hashable name that will uniquely identify endpoints in the system.

There are 2 types of APIs that are supported by the IPC files: synchronous and asynchronous. Synchronous function calls always wait for a response from the other side, while the asynchronous counterparts do not. In other words, in case of the synchronous calls, the IPC library will not return until it has a response for a caller.

Ideally, all APIs for the server endpoint should be asynchronous.

Examples

To create a new connection, you first need to generate client and server endpoints. These endpoints should implement the communication logic using the IPC compiler-generated API messages.

Start from defining an endpoint in the IPC file in MyServer.ipc.

endpoint MyServer
{
    SyncAPI(String text) => (i32 status)
    AsyncAPI(i32 mode) =|
}

Part of the generated C++ messages:

class SyncAPI final : public IPC::Message {
public:
    using ResponseType = SyncAPIResponse;
    SyncAPI(const String& text) : m_text(text) {}
    virtual ~SyncAPI() override {}
    static OwnPtr<SyncAPI> decode(...);
    virtual IPC::MessageBuffer encode(...) const override;
};

Then, you need to inherit your connection class from IPC::ConnectionFromClient with created server and client endpoints as template parameters if it is a server connection. Otherwise, your class need to be inherited from IPC::ConnectionToServer with created server and client endpoints as template parameters and from the client endpoint class.

Part of the connection implementations:

// Server side.
namespace MyServer {

class ConnectionFromClient final
    : public IPC::ConnectionFromClient<MyClientEndpoint, MyServerEndpoint> {};

}

// Client side.
namespace MyClient {
    
    class Client final
        : public IPC::ConnectionToServer<MyClientEndpoint, MyServerEndpoint>
        , public MyClientEndpoint {};
    
}

Note, there are two types of functions for sending the messages: synchronous and asynchronous. The generated asynchronous functions are prefixed with async_ and the names of the synchronous functions are not changed.

See also