[systemd-devel] Sending complex structures over sd-bus

[Lennart Poettering]

On Do, 25.10.18 03:06, guhan balasubramanian (guhan.sac at gmail.com) wrote:

> Hi,
> 
> I am trying to use the sd-bus to send structures that are a bit complex in
> nature.
> 
> For example, consider the following:
> 
> struct complex_struct {
>     int some_integers[10];
>     char *str;
> } cs;
> 
> cs property_to_send[10];
> 
> This d-bus property would be something like "a(ais)".
> 
> Assuming I want to send the above array, I am trying to right the
> property's function handler in the sd_bus_server for the same.
> 
> I know the open and close container can be used for simple arrays. I am
> finding it hard to make it work for the nested array case. Can some one
> please help point me to any example or references for the same?

You open the outer container first, and then the inner one.

When creating the message:

sd_bus_message_open_container(m, 'a', "(ais)"); /* open outer array */
for (i = 0; i < 10; i++) {
        sd_bus_message_open_container(m, 'r', "ais"); /* open array item structure */
        sd_bus_message_open_container(m, 'a', "i"); /* open inner array */
        for (j = 0; j < 10; j++) 
                sd_bus_message_append(m, "i", 4711);
        sd_bus_message_close_container(m); /* close inner array */
        sd_bus_message_append(m, "s", "test string");
        sd_bus_message_close_container(m); /* close array item structre */
}
sd_bus_message_close_container(m); /* close outer array */
        
And when processing a message it's kinda the same, you just use
enter/exit rather than open/close for the containers...

Lennart

-- 
Lennart Poettering, Red Hat