illumos: manual page: vnd

VND_POLLFD(3VND) VND_POLLFD(3VND)

NAME

vnd_pollfd - get file descriptor for polling

SYNOPSIS

cc [ flag... ] file... -lvnd [ library... ]
#include <libvnd.h>

int vnd_pollfd(vnd_handle_t *vhp);

DESCRIPTION

The vnd_pollfd() function returns an integer id which corresponds to the
file descriptor that represents the underlying device that is associated
with the vnd handle vhp. This file descriptor is suitable for use with
port_associate(3C) and similar polling techniques such as poll(2). Use of
the file descriptor outside of these uses may cause undocumented behavior
from the rest of the library.

The file descriptor in question is still managed by libvnd. The caller
must not call close(2) on it. Once vnd_close(3VND) has been called, any
further use of the file descriptor is undefined behavior.

RETURN VALUES

The function returns the integer id of the file descriptor that
corresponds to the underlying vnd device.

EXAMPLES

Example 1 Use event ports for vnd notifications

The following sample C program shows how to use the vnd_pollfd function
with event ports to be notified whenever there is data available to be
read. This program assumes that a vnd device named "vnd0" exists in the
current zone. For an example of creating the device, see Example 1 in
vnd_create(3VND).

#include <libvnd.h>
#include <port.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>

int
main(void)
{
vnd_handle_t *vhp;
vnd_errno_t vnderr;
int port, syserr, vfd, ret;

port = port_create();
if (port < 0) {
perror("port_create");
return (1);
}

vhp = vnd_open(NULL, "vnd0", &vnderr, &syserr);
if (vhp == NULL) {
if (vnderr == VND_E_SYS)
(void) fprintf(stderr, "failed to open device: %s",
vnd_strsyserror(syserr));
else
(void) fprintf(stderr, "failed to open device: %s",
vnd_strerror(vnderr));
(void) close(port);
return (1);
}

vfd = vnd_pollfd(vhp);
if (fcntl(vfd, F_SETFL, O_NONBLOCK) != 0) {
perror("fcntl");
vnd_close(vhp);
(void) close(port);
return (1);
}

if (port_associate(port, PORT_SOURCE_FD, vfd, POLLIN, NULL) != 0) {
perror("port_associate");
vnd_close(vhp);
(void) close(port);
return (1);
}

for (;;) {
port_event_t pe;

if (port_get(port, &pe, NULL) != 0) {
if (errno == EINTR)
continue;
perror("port_get");
vnd_close(vhp);
(void) close(port);
return (1);
}

/*
* Read the data with vnd_frameio_read(3VND) and
* optionally break out of the loop or continue to the
* next iteration and reassociate vfd with the event
* port.
*/
}
}