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/*
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* Copyright (c) 2002,2016 Mario de Sousa (msousa@fe.up.pt)
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*
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* This file is part of the Modbus library for Beremiz and matiec.
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*
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* This Modbus library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
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* General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this Modbus library. If not, see <http://www.gnu.org/licenses/>.
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*
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* This code is made available on the understanding that it will not be
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* used in safety-critical situations without a full and competent review.
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*/
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/* Time handling functions used by the modbus protocols... */
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#ifndef __MODBUS_TIME_UTIL_H
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#define __MODBUS_TIME_UTIL_H
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/************************************/
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/** **/
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/** Time format conversion **/
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/** **/
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/************************************/
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/* Function to load a struct timeval correctly from a double. */
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static inline struct timeval d_to_timeval(double time) {
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struct timeval tmp;
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tmp.tv_sec = time;
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tmp.tv_usec = 1e6*(time - tmp.tv_sec);
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return tmp;
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}
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/* Function to load a struct timespec correctly from a double. */
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static inline struct timespec d_to_timespec(double time) {
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struct timespec tmp;
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tmp.tv_sec = time;
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tmp.tv_nsec = 1e9*(time - tmp.tv_sec);
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return tmp;
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}
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/* Function to ... */
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static inline struct timespec timespec_dif(struct timespec ts1, struct timespec ts2) {
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struct timespec ts;
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ts.tv_sec = ts1.tv_sec - ts2.tv_sec;
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if(ts1.tv_nsec > ts2.tv_nsec) {
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ts.tv_nsec = ts1.tv_nsec - ts2.tv_nsec;
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} else {
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ts.tv_nsec = 1000000000 + ts1.tv_nsec - ts2.tv_nsec;
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ts.tv_sec--;
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}
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if (ts.tv_sec < 0)
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ts.tv_sec = ts.tv_nsec = 0;
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return ts;
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}
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/* Function to ... */
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static inline struct timespec timespec_add(struct timespec ts1, struct timespec ts2) {
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struct timespec ts;
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ts.tv_sec = ts1.tv_sec + ts2.tv_sec;
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ts.tv_nsec = ts1.tv_nsec + ts2.tv_nsec;
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ts.tv_sec += ts.tv_nsec / 1000000000;
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ts.tv_nsec = ts.tv_nsec % 1000000000;
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return ts;
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}
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/* Function to convert a struct timespec to a struct timeval. */
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static inline struct timeval timespec_to_timeval(struct timespec ts) {
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struct timeval tv;
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tv.tv_sec = ts.tv_sec;
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tv.tv_usec = ts.tv_nsec/1000;
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return tv;
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}
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/*
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* NOTE: clock_gettime() is rather expensive, between 7000 and 7500 clock
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* cycles (measured with rdtsc on an Intel Pentium)
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* gettimeofday() is half as expensive (3000 to 3500 clock cycles),
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* but is not POSIX compliant... :-(
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* Nevertheless this is peanuts (20 us on a 350 MHz cpu) compared to
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* the timescales required to read a modbus frame over a serial bus
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* (aprox. 10 ms for a 10 byte frame on a 9600 baud bus!)
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*/
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static inline struct timespec timespec_add_curtime(struct timespec ts) {
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struct timespec res = {.tv_sec = 0, .tv_nsec = 0};
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/* is ts = 0 also return 0 !! */
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if ((ts.tv_sec != 0) || (ts.tv_nsec != 0))
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if (clock_gettime(CLOCK_MONOTONIC, &res) >= 0)
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res = timespec_add(res, ts);
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return res;
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}
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/************************************/
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/** **/
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/** select() with absolute timeout **/
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/** **/
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/************************************/
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/* My private version of select using an absolute timeout, instead of the
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* usual relative timeout.
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*
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* NOTE: Ususal select semantics for (a: end_time == NULL) and
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* (b: *end_time == 0) also apply.
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*
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* (a) Indefinite timeout
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* (b) Try once, and and quit if no data available.
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*/
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/* Returns: -1 on error
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* 0 on timeout
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* >0 on success
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*/
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static int my_select(int fd, fd_set *rfds, fd_set *wfds, const struct timespec *end_time) {
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int res;
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struct timespec cur_time;
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struct timeval timeout, *tv_ptr;
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fd_set tmp_rfds, *tmp_rfds_ptr, tmp_wfds, *tmp_wfds_ptr;
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tmp_rfds_ptr = NULL;
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tmp_wfds_ptr = NULL;
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if (rfds != NULL) tmp_rfds_ptr = &tmp_rfds;
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if (wfds != NULL) tmp_wfds_ptr = &tmp_wfds;
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/*============================*
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* wait for data availability *
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*============================*/
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do {
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if (rfds != NULL) tmp_rfds = *rfds;
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if (wfds != NULL) tmp_wfds = *wfds;
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/* NOTE: To do the timeout correctly we would have to revert to timers
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* and asociated signals. That is not very thread friendly, and is
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* probably too much of a hassle trying to figure out which signal
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* to use. What if we don't have any free signals?
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*
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* The following solution is not correct, as it includes a race
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* condition. The following five lines of code should really
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* be atomic!
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*
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* NOTE: see also the timeout related comment in the
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* modbus_tcp_read() function!
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*/
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if (end_time == NULL) {
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tv_ptr = NULL;
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} else {
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tv_ptr = &timeout;
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if ((end_time->tv_sec == 0) && (end_time->tv_nsec == 0)) {
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timeout.tv_sec = timeout.tv_usec = 0;
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} else {
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/* ATOMIC - start */
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if (clock_gettime(CLOCK_MONOTONIC, &cur_time) < 0)
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return -1;
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timeout = timespec_to_timeval(timespec_dif(*end_time, cur_time));
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}
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}
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res = select(fd, tmp_rfds_ptr, tmp_wfds_ptr, NULL, tv_ptr);
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/* ATOMIC - end */
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#ifdef DEBUG
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{int i;
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if (tmp_rfds_ptr != NULL)
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for (i = 0; i < fd; i++)
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if (FD_ISSET(i, tmp_rfds_ptr))
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fprintf(stderr,"fd=%d is ready for reading\n", i);
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if (tmp_wfds_ptr != NULL)
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for (i = 0; i < fd; i++)
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if (FD_ISSET(i, tmp_wfds_ptr))
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fprintf(stderr,"fd=%d is ready for writing\n", i);
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}
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#endif
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if (res == 0) {
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#ifdef DEBUG
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printf("Comms time out\n");
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#endif
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return 0;
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}
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if ((res < 0) && (errno != EINTR)) {
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return -1;
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}
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} while (res <= 0);
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if (rfds != NULL) *rfds = tmp_rfds;
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if (wfds != NULL) *wfds = tmp_wfds;
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return res;
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}
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#endif /* __MODBUS_TIME_UTIL_H */
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