/*
 * Copyright 2016 Garrett D'Amore <garrett@damore.org>
 *
 * This software is supplied under the terms of the MIT License, a
 * copy of which should be located in the distribution where this
 * file was obtained (LICENSE.txt).  A copy of the license may also be
 * found online at https://opensource.org/licenses/MIT.
 */

/*
 * This is more of a direct #include of a .c rather than .h file.
 * But having it be a .h makes compiler rules work out properly.  Do
 * not include this more than once into your program, or you will
 * get multiple symbols defined.
 */

/*
 * POSIX clock stuff.
 */
#include "core/nng_impl.h"

#ifdef PLATFORM_POSIX_CLOCK

#include <time.h>
#include <errno.h>
#include <string.h>

#ifndef NNG_USE_GETTIMEOFDAY

/*
 * Use POSIX realtime stuff.
 */
uint64_t
nni_clock(void)
{
	struct timespec ts;
	uint64_t usec;

	if (clock_gettime(NNG_USE_CLOCKID, &ts) != 0) {
		/* This should never ever occur. */
		nni_panic("clock_gettime failed: %s", strerror(errno));
	}

	usec = ts.tv_sec;
	usec *= 1000000;
	usec += (ts.tv_nsec / 1000);
	return (usec);
}


void
nni_usleep(uint64_t usec)
{
	struct timespec ts;

	ts.tv_sec = usec / 1000000;
	ts.tv_nsec = (usec % 1000000) * 1000;

	/* Do this in a loop, so that interrupts don't actually wake us. */
	while (ts.tv_sec || ts.tv_nsec) {
		(void) nanosleep(&ts, &ts);
	}
}


#else   /* NNG_USE_GETTIMEOFDAY */

/*
 * If you're here, its because you don't have a modern clock_gettime with
 * monotonic clocks, or the necessary pthread_condattr_settclock().  In
 * this case, you should be advised that *bad* things can happen if your
 * system clock changes time while programs using this library are running.
 * (Basically, timeouts can take longer or shorter, leading to either hangs
 * or apparent spurious errors.  Eventually it should all sort itself out,
 * but if you change the clock by a large amount you might wonder what the
 * heck is happening until it does.)
 */

#include <pthread.h>
#include <sys/time.h>
#include <poll.h>

uint64_t
nni_clock(void)
{
	uint64_t usec;

	struct timeval tv;

	if (gettimeofday(&tv, NULL) != 0) {
		nni_panic("gettimeofday failed: %s", strerror(errno));
	}

	usec = tv.tv_sec;
	usec *= 1000000;
	usec += tv.tv_usec;
	return (usec);
}


void
nni_usleep(uint64_t usec)
{
	/*
	 * So probably there is no nanosleep.  We could in theory use
	 * pthread condition variables, but that means doing memory
	 * allocation, or forcing the use of pthreads where the platform
	 * might be preferring the use of another threading package.
	 * Additionally, use of pthreads means that we cannot use
	 * relative times in a clock_settime safe manner.
	 * So we can use poll() instead, which is rather coarse, but
	 * pretty much guaranteed to work.
	 */
	struct pollfd pfd;
	uint64_t now;
	uint64_t expire;

	/*
	 * Possibly we could pass NULL instead of pfd, but passing a valid
	 * pointer ensures that if the system dereferences the pointer it
	 * won't come back with EFAULT.
	 */
	pfd.fd = -1;
	pfd.events = 0;

	now = nni_clock();
	expire = now + usec;

	while (now < expire) {
		/*
		 * In theory we could round up to a whole number of msec,
		 * but under the covers poll already does some rounding up,
		 * and the loop above guarantees that we will not bail out
		 * early.  So this gives us a better chance to avoid adding
		 * nearly an extra unneeded millisecond to the wait.
		 */
		(void) poll(&pfd, 0, (int) ((expire - now) / 1000));
		now = nni_clock();
	}
}


#endif  /* NNG_USE_GETTIMEOFDAY */

#endif  /* PLATFORM_POSIX_CLOCK */