1/* gethrxtime -- get high resolution real time
2
3   Copyright (C) 2005, 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
4
5   This program is free software: you can redistribute it and/or modify
6   it under the terms of the GNU General Public License as published by
7   the Free Software Foundation; either version 3 of the License, or
8   (at your option) any later version.
9
10   This program is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   GNU General Public License for more details.
14
15   You should have received a copy of the GNU General Public License
16   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
17
18/* Written by Paul Eggert.  */
19
20#include <config.h>
21
22#include "gethrxtime.h"
23
24#include <sys/time.h>
25#include "timespec.h"
26
27/* Get the current time, as a count of the number of nanoseconds since
28   an arbitrary epoch (e.g., the system boot time).  Prefer a
29   high-resolution clock that is not subject to resetting or
30   drifting.  */
31
32xtime_t
33gethrxtime (void)
34{
35#if HAVE_NANOUPTIME
36  {
37    struct timespec ts;
38    nanouptime (&ts);
39    return xtime_make (ts.tv_sec, ts.tv_nsec);
40  }
41#else
42
43# if defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME
44  {
45    struct timespec ts;
46    if (clock_gettime (CLOCK_MONOTONIC, &ts) == 0)
47      return xtime_make (ts.tv_sec, ts.tv_nsec);
48  }
49# endif
50
51# if HAVE_MICROUPTIME
52  {
53    struct timeval tv;
54    microuptime (&tv);
55    return xtime_make (tv.tv_sec, 1000 * tv.tv_usec);
56  }
57
58# else
59  /* No monotonically increasing clocks are available; fall back on a
60     clock that might jump backwards, since it's the best we can do.  */
61  {
62    struct timespec ts;
63    gettime (&ts);
64    return xtime_make (ts.tv_sec, ts.tv_nsec);
65  }
66# endif
67#endif
68}
69