sd_event_source_set_userdata, sd_event_source_get_userdata — Set or retrieve user data pointer of event sources
#include <systemd/sd-event.h>
void* sd_event_source_set_userdata( | sd_event_source *source, |
void *userdata); |
void* sd_event_source_get_userdata( | sd_event_source *source); |
sd_event_source_set_userdata() may be
used to set an arbitrary user data pointer for the event source
object specified as source. The user data
pointer is usually specified when creating an event source object
with calls such as
sd_event_add_io(3)
or
sd_event_add_time(3),
and may be updated with this call. The user data pointer is also
passed to all handler callback functions associated with the event
source. The userdata parameter specifies
the new user data pointer to set, the function returns the
previous user data pointer. Note that NULL is
a valid user data pointer.
sd_event_source_get_userdata() may be
used to query the current user data pointer assigned to the event
source object source.
On success,
sd_event_source_set_userdata() and
sd_event_source_get_userdata() return the
previously set user data pointer. On failure, they return
NULL.
Functions described here are available as a shared
library, which can be compiled against and linked to with the
libsystemd pkg-config(1)
file.
The code described here uses
getenv(3),
which is declared to be not multi-thread-safe. This means that the code calling the functions described
here must not call
setenv(3)
from a parallel thread. It is recommended to only do calls to setenv()
from an early phase of the program when no other threads have been started.
sd_event_source_set_userdata() and
sd_event_source_get_userdata() were added in version 229.