lib/gettimeofday.c

   1 /* Provide gettimeofday for systems that don't have it or for which it's broken.
   2
   3    Copyright (C) 2001-2003, 2005-2007, 2009-2017 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, or (at your option)
   8    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 Jim Meyering */
  19
  20 #include <config.h>
  21
  22 /* Specification.  */
  23 #include <sys/time.h>
  24
  25 #include <time.h>
  26
  27 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  28 # define WINDOWS_NATIVE
  29 # include <windows.h>
  30 #endif
  31
  32 #include "localtime-buffer.h"
  33
  34 #ifdef WINDOWS_NATIVE
  35
  36 /* GetSystemTimePreciseAsFileTime was introduced only in Windows 8.  */
  37 typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
  38 static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
  39 static BOOL initialized = FALSE;
  40
  41 static void
  42 initialize (void)
  43 {
  44   HMODULE kernel32 = LoadLibrary ("kernel32.dll");
  45   if (kernel32 != NULL)
  46     {
  47       GetSystemTimePreciseAsFileTimeFunc =
  48         (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
  49     }
  50   initialized = TRUE;
  51 }
  52
  53 #endif
  54
  55 /* This is a wrapper for gettimeofday.  It is used only on systems
  56    that lack this function, or whose implementation of this function
  57    causes problems.
  58    Work around the bug in some systems whereby gettimeofday clobbers
  59    the static buffer that localtime uses for its return value.  The
  60    gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
  61    this problem.  */
  62
  63 int
  64 gettimeofday (struct timeval *restrict tv, void *restrict tz)
  65 {
  66 #undef gettimeofday
  67 #if HAVE_GETTIMEOFDAY
  68 # if GETTIMEOFDAY_CLOBBERS_LOCALTIME
  69   /* Save and restore the contents of the buffer used for localtime's
  70      result around the call to gettimeofday.  */
  71   struct tm save = *localtime_buffer_addr;
  72 # endif
  73
  74 # if defined timeval /* 'struct timeval' overridden by gnulib?  */
  75 #  undef timeval
  76   struct timeval otv;
  77   int result = gettimeofday (&otv, (struct timezone *) tz);
  78   if (result == 0)
  79     {
  80       tv->tv_sec = otv.tv_sec;
  81       tv->tv_usec = otv.tv_usec;
  82     }
  83 # else
  84   int result = gettimeofday (tv, (struct timezone *) tz);
  85 # endif
  86
  87 # if GETTIMEOFDAY_CLOBBERS_LOCALTIME
  88   *localtime_buffer_addr = save;
  89 # endif
  90
  91   return result;
  92
  93 #else
  94
  95 # ifdef WINDOWS_NATIVE
  96
  97   /* On native Windows, there are two ways to get the current time:
  98      GetSystemTimeAsFileTime
  99      <https://msdn.microsoft.com/en-us/library/ms724397.aspx>
 100      or
 101      GetSystemTimePreciseAsFileTime
 102      <https://msdn.microsoft.com/en-us/library/hh706895.aspx>.  */
 103   FILETIME current_time;
 104
 105   if (!initialized)
 106     initialize ();
 107   if (GetSystemTimePreciseAsFileTimeFunc != NULL)
 108     GetSystemTimePreciseAsFileTimeFunc (&current_time);
 109   else
 110     GetSystemTimeAsFileTime (&current_time);
 111
 112   /* Convert from FILETIME to 'struct timeval'.  */
 113   /* FILETIME: <https://msdn.microsoft.com/en-us/library/ms724284.aspx> */
 114   ULONGLONG since_1601 =
 115     ((ULONGLONG) current_time.dwHighDateTime << 32)
 116     | (ULONGLONG) current_time.dwLowDateTime;
 117   /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
 118      years, in total 134774 days.  */
 119   ULONGLONG since_1970 =
 120     since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
 121   ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
 122   tv->tv_sec = microseconds_since_1970 / (ULONGLONG) 1000000;
 123   tv->tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000;
 124
 125 # else
 126
 127 #  if !defined OK_TO_USE_1S_CLOCK
 128 #   error "Only 1-second nominal clock resolution found.  Is that intended?" \
 129           "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
 130 #  endif
 131   tv->tv_sec = time (NULL);
 132   tv->tv_usec = 0;
 133
 134 # endif
 135
 136   return 0;
 137
 138 #endif
 139 }