DLPI Programmer's Guide

Appendix A 157
Sample Programs
Connectionless Mode
AREA_SIZE, /* maxlen = AREA_SIZE */
0, /* len gets filled in for each message */
data_area /* buf = data area */
};
/**************************************************************************
get the next message from a stream; get_msg() returns one of the
following defines
**************************************************************************/
#define GOT_CTRL 1 /* message has only a control part */
#define GOT_DATA 2 /* message has only a data part */
#define GOT_BOTH 3 /* message has both control and data parts */
int
get_msg(fd)
int fd; /* file descriptor */
{
int flags = 0; /* 0 ---> get any available message */
int result = 0; /* return value */
/*
zero first byte of control area so the caller can call check_ctrl
without checking the get_msg return value; if there was only data
in the message and the user was expecting control or control + data,
then when he calls check_ctrl it will compare the expected primitive
zero and print information about the primitive that it got.
*/
ctrl_area[0] = 0;
/* call getmsg and check for an error */
if(getmsg(fd, &ctrl_buf, &data_buf, &flags) < 0) {
printf(”error: getmsg failed, errno = %d\n”, errno);
exit(1);
}
if(ctrl_buf.len > 0) {
result |= GOT_CTRL;
}
if(data_buf.len > 0) {
result |= GOT_DATA;
}
return(result);
}
/**************************************************************************
check that control message is the expected message
**************************************************************************/
void
check_ctrl(ex_prim)
int ex_prim; /* the expected primitive */
{
dl_error_ack_t *err_ack = (dl_error_ack_t *)ctrl_area;
/* did we get the expected primitive? */
if(err_ack->dl_primitive != ex_prim) {
/* did we get a control part */
if(ctrl_buf.len) {
/* yup; is it an ERROR_ACK? */