NkKosTransport
NkKosTransport is a convenient wrapper for the Call, Recv and Reply system calls. It lets you work separately with messages' constant parts and arenas.
The NkKosTransport structure and methods for working with it are declared in the transport-kos.h file.
To initialize the transport, it is sufficient to call the NkKosTransport_Init() function by specifying the IPC handle of the channel that should be used to transmit messages (handle):
…
NkKosTransport transport;
NkKosTransport_Init(&transport, handle, NK_NULL, 0);
A channel has two IPC handles: client and server. Therefore, when initializing the transport, you need to specify the client handle for the utilized channel on the client side and the server handle on the server side.
The functions nk_transport_call(), nk_transport_recv() and nk_transport_reply() declared in transport.h (included in the transport-kos.h file) are used to call the transport.
The nk_transport_call() function is intended for sending a request and receiving a response:
/* The constant part (req) and arena of the request (req_arena) must be initialized
* with the actual input arguments of the method being called. The constant part (req)
* must also contain the RIID and MID values.
* The nk_transport_call() function generates a request and executes the Call system call.
* The response received from the server is inserted into res (constant part of the response) and
* res_arena (response arena). */
nk_transport_call(&transport.base, (struct nk_message *)&req, &req_arena, (struct nk_message *)&res, &res_arena);
When using a generated interface method (for example, the IPing_Ping method from the echo example) on the client side, the corresponding values of the RIID and MID are automatically inserted into the request, after which the nk_transport_call() function is called.
The nk_transport_recv() function is intended for receiving a request:
/* The nk_transport_recv () function executes the Recv system call.
* The request received from the client is inserted into req (constant part of the response) and
* req_arena (response arena). */
nk_transport_recv(&transport.base, (struct nk_message *)&req, &req_arena);
The nk_transport_reply() function is intended for sending a response:
/* The constant part (res) and request arena (res_arena) must be initialized
* with the actual output arguments of the server method being called.
* The nk_transport_reply() function generates a response and executes a Reply system call. */
nk_transport_reply(&transport.base, (struct nk_message *)&res, &res_arena);