gettimeofday.c 4.56 KB
Newer Older
1 2
/* Provide gettimeofday for systems that don't have it or for which it's broken.

Paul Eggert's avatar
Paul Eggert committed
3
   Copyright (C) 2001-2003, 2005-2007, 2009-2019 Free Software Foundation, Inc.
4 5 6 7 8 9 10 11 12 13 14 15

   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 3, 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
Paul Eggert's avatar
Paul Eggert committed
16
   along with this program; if not, see <https://www.gnu.org/licenses/>.  */
17 18 19 20 21 22 23 24 25 26

/* written by Jim Meyering */

#include <config.h>

/* Specification.  */
#include <sys/time.h>

#include <time.h>

Paul Eggert's avatar
Paul Eggert committed
27
#if defined _WIN32 && ! defined __CYGWIN__
Paul Eggert's avatar
Paul Eggert committed
28 29
# define WINDOWS_NATIVE
# include <windows.h>
30 31
#endif

Paul Eggert's avatar
Paul Eggert committed
32
#include "localtime-buffer.h"
Paul Eggert's avatar
Paul Eggert committed
33 34 35

#ifdef WINDOWS_NATIVE

Paul Eggert's avatar
Paul Eggert committed
36 37 38 39
/* Avoid warnings from gcc -Wcast-function-type.  */
# define GetProcAddress \
   (void *) GetProcAddress

Paul Eggert's avatar
Paul Eggert committed
40 41 42 43 44 45 46 47 48 49 50 51
/* GetSystemTimePreciseAsFileTime was introduced only in Windows 8.  */
typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
static BOOL initialized = FALSE;

static void
initialize (void)
{
  HMODULE kernel32 = LoadLibrary ("kernel32.dll");
  if (kernel32 != NULL)
    {
      GetSystemTimePreciseAsFileTimeFunc =
Paul Eggert's avatar
Paul Eggert committed
52
        (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
Paul Eggert's avatar
Paul Eggert committed
53 54 55 56
    }
  initialized = TRUE;
}

57 58 59 60
#endif

/* This is a wrapper for gettimeofday.  It is used only on systems
   that lack this function, or whose implementation of this function
Paul Eggert's avatar
Paul Eggert committed
61 62 63 64 65
   causes problems.
   Work around the bug in some systems whereby gettimeofday clobbers
   the static buffer that localtime uses for its return value.  The
   gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
   this problem.  */
66 67 68 69 70

int
gettimeofday (struct timeval *restrict tv, void *restrict tz)
{
#undef gettimeofday
Paul Eggert's avatar
Paul Eggert committed
71
#ifdef WINDOWS_NATIVE
Paul Eggert's avatar
Paul Eggert committed
72 73 74 75 76 77

  /* On native Windows, there are two ways to get the current time:
     GetSystemTimeAsFileTime
     <https://msdn.microsoft.com/en-us/library/ms724397.aspx>
     or
     GetSystemTimePreciseAsFileTime
Paul Eggert's avatar
Paul Eggert committed
78 79 80 81 82 83 84
     <https://msdn.microsoft.com/en-us/library/hh706895.aspx>.
     GetSystemTimeAsFileTime produces values that jump by increments of
     15.627 milliseconds (!) on average.
     Whereas GetSystemTimePreciseAsFileTime values usually jump by 1 or 2
     microseconds.
     More discussion on this topic:
     <http://www.windowstimestamp.com/description>.  */
Paul Eggert's avatar
Paul Eggert committed
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
  FILETIME current_time;

  if (!initialized)
    initialize ();
  if (GetSystemTimePreciseAsFileTimeFunc != NULL)
    GetSystemTimePreciseAsFileTimeFunc (&current_time);
  else
    GetSystemTimeAsFileTime (&current_time);

  /* Convert from FILETIME to 'struct timeval'.  */
  /* FILETIME: <https://msdn.microsoft.com/en-us/library/ms724284.aspx> */
  ULONGLONG since_1601 =
    ((ULONGLONG) current_time.dwHighDateTime << 32)
    | (ULONGLONG) current_time.dwLowDateTime;
  /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
     years, in total 134774 days.  */
  ULONGLONG since_1970 =
    since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
  ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
  tv->tv_sec = microseconds_since_1970 / (ULONGLONG) 1000000;
  tv->tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000;
106

Paul Eggert's avatar
Paul Eggert committed
107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136
  return 0;

#else

# if HAVE_GETTIMEOFDAY
#  if GETTIMEOFDAY_CLOBBERS_LOCALTIME
  /* Save and restore the contents of the buffer used for localtime's
     result around the call to gettimeofday.  */
  struct tm save = *localtime_buffer_addr;
#  endif

#  if defined timeval /* 'struct timeval' overridden by gnulib?  */
#   undef timeval
  struct timeval otv;
  int result = gettimeofday (&otv, (struct timezone *) tz);
  if (result == 0)
    {
      tv->tv_sec = otv.tv_sec;
      tv->tv_usec = otv.tv_usec;
    }
#  else
  int result = gettimeofday (tv, (struct timezone *) tz);
#  endif

#  if GETTIMEOFDAY_CLOBBERS_LOCALTIME
  *localtime_buffer_addr = save;
#  endif

  return result;

137 138 139 140 141 142 143 144 145 146 147
# else

#  if !defined OK_TO_USE_1S_CLOCK
#   error "Only 1-second nominal clock resolution found.  Is that intended?" \
          "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
#  endif
  tv->tv_sec = time (NULL);
  tv->tv_usec = 0;

  return 0;

Paul Eggert's avatar
Paul Eggert committed
148
# endif
149 150
#endif
}