libevent/evutil_time.c

/*
 * Copyright (c) 2007-2012 Niels Provos and Nick Mathewson
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "event2/event-config.h"
#include "evconfig-private.h"

#ifdef _WIN32
#include <winsock2.h>
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#endif

#include <sys/types.h>
#ifdef EVENT__HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <errno.h>
#include <limits.h>
#ifndef EVENT__HAVE_GETTIMEOFDAY
#include <sys/timeb.h>
#endif
#if !defined(EVENT__HAVE_NANOSLEEP) && !defined(EVENT_HAVE_USLEEP) && \
	!defined(_WIN32)
#include <sys/select.h>
#endif
#include <time.h>
#include <sys/stat.h>
#include <string.h>

#include "event2/util.h"
#include "util-internal.h"
#include "log-internal.h"

#ifndef EVENT__HAVE_GETTIMEOFDAY
/* No gettimeofday; this must be windows. */
int
evutil_gettimeofday(struct timeval *tv, struct timezone *tz)
{
#ifdef _MSC_VER
#define U64_LITERAL(n) n##ui64
#else
#define U64_LITERAL(n) n##llu
#endif

	/* Conversion logic taken from Tor, which in turn took it
	 * from Perl.  GetSystemTimeAsFileTime returns its value as
	 * an unaligned (!) 64-bit value containing the number of
	 * 100-nanosecond intervals since 1 January 1601 UTC. */
#define EPOCH_BIAS U64_LITERAL(116444736000000000)
#define UNITS_PER_SEC U64_LITERAL(10000000)
#define USEC_PER_SEC U64_LITERAL(1000000)
#define UNITS_PER_USEC U64_LITERAL(10)
	union {
		FILETIME ft_ft;
		ev_uint64_t ft_64;
	} ft;

	if (tv == NULL)
		return -1;

	GetSystemTimeAsFileTime(&ft.ft_ft);

	if (EVUTIL_UNLIKELY(ft.ft_64 < EPOCH_BIAS)) {
		/* Time before the unix epoch. */
		return -1;
	}
	ft.ft_64 -= EPOCH_BIAS;
	tv->tv_sec = (long) (ft.ft_64 / UNITS_PER_SEC);
	tv->tv_usec = (long) ((ft.ft_64 / UNITS_PER_USEC) % USEC_PER_SEC);
	return 0;
}
#endif

#define MAX_SECONDS_IN_MSEC_LONG \
	(((LONG_MAX) - 999) / 1000)

long
evutil_tv_to_msec_(const struct timeval *tv)
{
	if (tv->tv_usec > 1000000 || tv->tv_sec > MAX_SECONDS_IN_MSEC_LONG)
		return -1;

	return (tv->tv_sec * 1000) + ((tv->tv_usec + 999) / 1000);
}

void
evutil_usleep_(const struct timeval *tv)
{
	if (!tv)
		return;
#if defined(_WIN32)
	{
		long msec = evutil_tv_to_msec_(tv);
		Sleep((DWORD)msec);
	}
#elif defined(EVENT__HAVE_NANOSLEEP)
	{
		struct timespec ts;
		ts.tv_sec = tv->tv_sec;
		ts.tv_nsec = tv->tv_usec*1000;
		nanosleep(&ts, NULL);
	}
#elif defined(EVENT__HAVE_USLEEP)
	/* Some systems don't like to usleep more than 999999 usec */
	sleep(tv->tv_sec);
	usleep(tv->tv_usec);
#else
	select(0, NULL, NULL, NULL, tv);
#endif
}


/*
   This function assumes it's called repeatedly with a
   not-actually-so-monotonic time source whose outputs are in 'tv'. It
   implements a trivial ratcheting mechanism so that the values never go
   backwards.
 */
static void
adjust_monotonic_time(struct evutil_monotonic_timer *base,
    struct timeval *tv)
{
	evutil_timeradd(tv, &base->adjust_monotonic_clock, tv);

	if (evutil_timercmp(tv, &base->last_time, <)) {
		/* Guess it wasn't monotonic after all. */
		struct timeval adjust;
		evutil_timersub(&base->last_time, tv, &adjust);
		evutil_timeradd(&adjust, &base->adjust_monotonic_clock,
		    &base->adjust_monotonic_clock);
		*tv = base->last_time;
	}
	base->last_time = *tv;
}

#if defined(HAVE_POSIX_MONOTONIC)
/* =====
   The POSIX clock_gettime() interface provides a few ways to get at a
   monotonic clock.  CLOCK_MONOTONIC is most widely supported.  Linux also
   provides a CLOCK_MONOTONIC_COARSE with accuracy of about 1-4 msec.

   On all platforms I'm aware of, CLOCK_MONOTONIC really is monotonic.
   Platforms don't agree about whether it should jump on a sleep/resume.
 */

int
evutil_configure_monotonic_time_(struct evutil_monotonic_timer *base,
    int precise)
{
	/* CLOCK_MONOTONIC exists on FreeBSD, Linux, and Solaris.  You need to
	 * check for it at runtime, because some older kernel versions won't
	 * have it working. */
	struct timespec	ts;
#ifdef CLOCK_MONOTONIC_COARSE
#if CLOCK_MONOTONIC_COARSE < 0
	/* Technically speaking, nothing keeps CLOCK_* from being negative (as
	 * far as I know). This check and the one below make sure that it's
	 * safe for us to use -1 as an "unset" value. */
#error "I didn't expect CLOCK_MONOTONIC_COARSE to be < 0"
#endif
	if (! precise) {
		if (clock_gettime(CLOCK_MONOTONIC_COARSE, &ts) == 0) {
			base->monotonic_clock = CLOCK_MONOTONIC_COARSE;
			return 0;
		}
	}
#endif
	if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
		base->monotonic_clock = CLOCK_MONOTONIC;
		return 0;
	}

#if CLOCK_MONOTONIC < 0
#error "I didn't expect CLOCK_MONOTONIC to be < 0"
#endif

	base->monotonic_clock = -1;
	return 0;
}

int
evutil_gettime_monotonic_(struct evutil_monotonic_timer *base,
    struct timeval *tp)
{
	struct timespec ts;

	if (base->monotonic_clock < 0) {
		if (evutil_gettimeofday(tp, NULL) < 0)
			return -1;
		adjust_monotonic_time(base, tp);
		return 0;
	}

	if (clock_gettime(base->monotonic_clock, &ts) == -1)
		return -1;
	tp->tv_sec = ts.tv_sec;
	tp->tv_usec = ts.tv_nsec / 1000;

	return 0;
}
#endif

#if defined(HAVE_MACH_MONOTONIC)
/* ======
   Apple is a little late to the POSIX party.  And why not?  Instead of
   clock_gettime(), they provide mach_absolute_time().  Its units are not
   fixed; we need to use mach_timebase_info() to get the right functions to
   convert its units into nanoseconds.

   To all appearances, mach_absolute_time() seems to be honest-to-goodness
   monotonic.  Whether it stops during sleep or not is unspecified in
   principle, and dependent on CPU architecture in practice.
 */

int
evutil_configure_monotonic_time_(struct evutil_monotonic_timer *base,
    int precise)
{
	struct mach_timebase_info mi;
	memset(base, 0, sizeof(*base));
	/* OSX has mach_absolute_time() */
	if (mach_timebase_info(&mi) == 0 && mach_absolute_time() != 0) {
		/* mach_timebase_info tells us how to convert
		 * mach_absolute_time() into nanoseconds, but we
		 * want to use microseconds instead. */
		mi.denom *= 1000;
		memcpy(&base->mach_timebase_units, &mi, sizeof(mi));
	} else {
		base->mach_timebase_units.numer = 0;
	}
	return 0;
}

int
evutil_gettime_monotonic_(struct evutil_monotonic_timer *base,
    struct timeval *tp)
{
	ev_uint64_t abstime, usec;
	if (base->mach_timebase_units.numer == 0) {
		if (evutil_gettimeofday(tp, NULL) < 0)
			return -1;
		adjust_monotonic_time(base, tp);
		return 0;
	}

	abstime = mach_absolute_time();
	usec = (abstime * base->mach_timebase_units.numer)
	    / (base->mach_timebase_units.denom);
	tp->tv_sec = usec / 1000000;
	tp->tv_usec = usec % 1000000;

	return 0;
}
#endif

#if defined(HAVE_WIN32_MONOTONIC)
/* =====
   Turn we now to Windows.  Want monontonic time on Windows?

   Windows has QueryPerformanceCounter(), which gives time most high-
   resolution time.  It's a pity it's not so monotonic in practice; it's
   also got some fun bugs, especially with older Windowses, under
   virtualizations, with funny hardware, on multiprocessor systems, and so
   on.  PEP418 [1] has a nice roundup here.

   There's GetTickCount64(), which gives a number of 1-msec ticks since
   startup.  The accuracy here might be as bad as 10-20 msec, I hear.
   There's an undocumented function (NtSetTimerResolution) that allegedly
   increases the accuracy. Good luck!

   There's also GetTickCount(), which is only 32 bits, but seems to be
   supported on pre-Vista versions of Windows.

   The less said about timeGetTime() the better.

   "We don't care.  We don't have to.  We're the Phone Company."
            -- Lily Tomlin, SNL


   [1] http://www.python.org/dev/peps/pep-0418
 */
int
evutil_configure_monotonic_time_(struct evutil_monotonic_timer *base,
    int precise)
{
	memset(base, 0, sizeof(*base));
	base->last_tick_count = GetTickCount();

	return 0;
}

int
evutil_gettime_monotonic_(struct evutil_monotonic_timer *base,
    struct timeval *tp)
{
	/* TODO: Support GetTickCount64. */
	/* TODO: Support alternate timer backends if the user asked
	 * for a high-precision timer. QueryPerformanceCounter is
	 * possibly a good idea, but it is also supposed to have
	 * reliability issues under various circumstances. */
	DWORD ticks = GetTickCount();
	if (ticks < base->last_tick_count) {
		/* The 32-bit timer rolled over. Let's assume it only
		 * happened once.  Add 2**32 msec to adjust_tick_count. */
		const struct timeval tv_rollover = { 4294967, 296000 };
		evutil_timeradd(&tv_rollover, &base->adjust_tick_count, &base->adjust_tick_count);
	}
	base->last_tick_count = ticks;
	tp->tv_sec = ticks / 1000;
	tp->tv_usec = (ticks % 1000) * 1000;
	evutil_timeradd(tp, &base->adjust_tick_count, tp);

	adjust_monotonic_time(base, tp);

	return 0;
}
#endif

#if defined(HAVE_FALLBACK_MONOTONIC)
/* =====
   And if none of the other options work, let's just use gettimeofday(), and
   ratchet it forward so that it acts like a monotonic timer, whether it
   wants to or not.
 */

int
evutil_configure_monotonic_time_(struct evutil_monotonic_timer *base,
    int precise)
{
	memset(base, 0, sizeof(*base));
	return 0;
}

int
evutil_gettime_monotonic_(struct evutil_monotonic_timer *base,
    struct timeval *tp)
{
	if (evutil_gettimeofday(tp, NULL) < 0)
		return -1;
	adjust_monotonic_time(base, tp);
	return 0;

}
#endif