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/* read_wait.c - Wait for data to read on a fd.
*
* Copyright (C) 2011, Darren Besler (dbesler@beehive.mb.ca)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program - see the file COPYING.
*
* See `CHANGES' file for revision history.
*/
#include <sys/time.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <errno.h>
#include "tacplus.h"
#include "libtac.h"
static int delta_msecs(struct timeval *newer, struct timeval *older) {
long deltasecs, deltausecs;
struct timeval now;
if (newer == NULL) {
gettimeofday(&now, NULL);
newer = &now;
}
deltasecs = newer->tv_sec - older->tv_sec;
deltausecs = newer->tv_usec - older->tv_usec;
if ( newer->tv_usec < older->tv_usec ) {
deltasecs--;
deltausecs = (1000000+newer->tv_usec) - older->tv_usec;
} else {
deltausecs = newer->tv_usec - older->tv_usec;
}
return (deltasecs*1000)+(deltausecs/1000);
}
/*
* tac_read_wait
*
* Parms:
* fd - open fd to wait on till data avail, or timeout
* timeout - maximum time to wait in milliseconds
* size - amount of data to wait for
* 0 : any amount of data
* >0 : amount of data to wait for
* timeleft - return of time left from timeout
*
* Returns:
* 0 - data avail, no timeout
* -1 - timeout
* n - errno
*/
int tac_read_wait(int fd, int timeout, int size, int *time_left) {
int retval = 0;
int remaining;
struct pollfd fds[1];
struct timeval start;
gettimeofday(&start, NULL);
/* setup for read timeout.
* will use poll() as it provides greatest compatibility
* vs setsockopt(SO_RCVTIMEO) which isn't supported on Solaris
*/
remaining = timeout; /* in msecs */
fds[0].fd = fd;
fds[0].events = POLLIN;
while (remaining > 0) {
int rc;
int avail = 0;
rc = poll(fds, 1, remaining);
remaining -= delta_msecs(NULL, &start);
if ( time_left != NULL ) {
*time_left = remaining > 0 ? remaining : 0;
}
/* why did poll return */
if (rc == 0) { /* Receive timeout */
retval = -1;
break;
}
if (rc > 0) { /* there is data available */
if (size > 0 && /* check for enuf available? */
ioctl(fd,FIONREAD,(char*)&avail) == 0 && avail < size) {
continue; /* not enuf yet, wait for more */
} else {
break;
}
}
if (rc < 0 && errno == EINTR) { // interrupt
continue;
}
/* all other conditions is an error */
retval = errno;
break;
}
return retval;
} /* read_wait */
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