Tribblix: manual page: port

PORT_GET(3C) Standard C Library Functions PORT_GET(3C)

NAME

port_get, port_getn - retrieve event information from a port

SYNOPSIS

#include <port.h>

int port_get(int port, port_event_t *pe,
const timespec_t *timeout);

int port_getn(int port, port_event_t list[], uint_t max,
uint_t *nget, const timespec_t *timeout);

DESCRIPTION

The port_get() and port_getn() functions retrieve events from a port.
The port_get() function retrieves at most a single event. The
port_getn() function can retrieve multiple events.

The pe argument points to an uninitialized port_event_t structure
that is filled in by the system when the port_get() function returns
successfully.

The port_event_t structure contains the following members:

int portev_events; /* detected events */
ushort_t portev_source; /* event source */
uintptr_t portev_object; /* specific to event source */
void *portev_user; /* user defined cookie */

The portev_events and portev_object members are specific to the event
source. The portev_events denotes the delivered events. The
portev_object refers to the associated object (see port_create(3C)).
The portev_source member specifies the source of the event. The
portev_user member is a user-specified value.

If the timeout pointer is NULL, the port_get() function blocks until
an event is available. To poll for an event without waiting, timeout
should point to a zeroed timespec. A non-zeroed timespec specifies
the desired time to wait for events. The port_get() function returns
before the timeout elapses if an event is available, a signal occurs,
a port is closed by another thread, or the port is in or enters alert
mode. See port_alert(3C) for details on alert mode.

The port_getn() function can retrieve multiple events from a port.
The list argument is an array of uninitialized port_event_t
structures that is filled in by the system when the port_getn()
function returns successfully. The nget argument points to the
desired number of events to be retrieved. The max parameter specifies
the maximum number of events that can be returned in list[]. If max
is 0, the value pointed to by nget is set to the number of events
available on the port. The port_getn() function returns immediately
but no events are retrieved.

The port_getn() function block until the desired number of events are
available, the timeout elapses, a signal occurs, a port is closed by
another thread, or the port is in or enters alert mode.

On return, the value pointed to by nget is updated to the actual
number of events retrieved in list.

Threads calling the port_get() function might starve threads waiting
in the port_getn() function for more than one event. Similarly,
threads calling the port_getn() function for n events might starve
threads waiting in the port_getn() function for more than n events.

The port_get() and the port_getn() functions ignore non-shareable
events (see port_create(3C)) generated by other processes.

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned
and errno is set to indicate the error.

ERRORS

The port_get() and port_getn() functions will fail if:

EBADF
The port identifier is not valid.

EBADFD
The port argument is not an event port file descriptor.

EFAULT
Event or event list can not be delivered (list[] pointer
and/or user space reserved to accommodate the list of
events is not reasonable), or the timeout argument is not
reasonable.

EINTR
A signal was caught during the execution of the function.

EINVAL
The timeout element tv_sec is < 0 or the timeout element
tv_nsec is < 0 or > 1000000000.

ETIME
The time interval expired before the expected number of
events have been posted to the port.

The port_getn() function will fail if:

EINVAL
The list[] argument is NULL, the nget argument is NULL, or
the content of nget is > max and max is > 0.

EFAULT
The timeout argument is not reasonable.

ETIME
The time interval expired before the expected number of
events have been posted to the port (original value in
nget), or nget is updated with the number of returned
port_event_t structures in list[].

EXAMPLES

Example 1: Send a user event (PORT_SOURCE_USER) to a port and retrieve

it with port_get().

The following example sends a user event (PORT_SOURCE_USER) to a port
and retrieves it with port_get(). The portev_user and portev_events
members of the port_event_t structure are the same as the
corresponding user and events arguments of the port_send(3C)
function.

#include <port.h>

int myport;
port_event_t pe;
struct timespec timeout;
int ret;
void *user;
uintptr_t object;

myport = port_create();
if (myport < 0) {
/* port creation failed ... */
...
return(...);
}
...
events = 0x01; /* own event definition(s) */
object = <myobject>;
user = <my_own_value>;
ret = port_send(myport, events, user);
if (ret == -1) {
/* error detected ... */
...
close(myport);
return (...);
}

/*
* The following code could also be executed in another thread or
* process.
*/
timeout.tv_sec = 1; /* user defined */
timeout.tv_nsec = 0;
ret = port_get(myport, &pe, &timeout);
if (ret == -1) {
/*
* error detected :
* - EINTR or ETIME : log error code and try again ...
* - Other kind of errors : may have to close the port ...
*/
return(...);
}

/*
* After port_get() returns successfully, the port_event_t
* structure will be filled with:
* pe.portev_source = PORT_SOURCE_USER
* pe.portev_events = 0x01
* pe.portev_object = <myobject>
* pe.portev_user = <my_own_value>
*/
...
close(myport);

ATTRIBUTES