gnulib/import/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, 2009-2019 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 <https://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 __CYGWIN__
  28 # define WINDOWS_NATIVE
  29 # include <windows.h>
  30 #endif
  31
  32 #include "localtime-buffer.h"
  33
  34 #ifdef WINDOWS_NATIVE
  35
  36 /* Avoid warnings from gcc -Wcast-function-type.  */
  37 # define GetProcAddress \
  38    (void *) GetProcAddress
  39
  40 /* GetSystemTimePreciseAsFileTime was introduced only in Windows 8.  */
  41 typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
  42 static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
  43 static BOOL initialized = FALSE;
  44
  45 static void
  46 initialize (void)
  47 {
  48   HMODULE kernel32 = LoadLibrary ("kernel32.dll");
  49   if (kernel32 != NULL)
  50     {
  51       GetSystemTimePreciseAsFileTimeFunc =
  52         (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
  53     }
  54   initialized = TRUE;
  55 }
  56
  57 #endif
  58
  59 /* This is a wrapper for gettimeofday.  It is used only on systems
  60    that lack this function, or whose implementation of this function
  61    causes problems.
  62    Work around the bug in some systems whereby gettimeofday clobbers
  63    the static buffer that localtime uses for its return value.  The
  64    gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
  65    this problem.  */
  66
  67 int
  68 gettimeofday (struct timeval *restrict tv, void *restrict tz)
  69 {
  70 #undef gettimeofday
  71 #ifdef WINDOWS_NATIVE
  72
  73   /* On native Windows, there are two ways to get the current time:
  74      GetSystemTimeAsFileTime
  75      <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime>
  76      or
  77      GetSystemTimePreciseAsFileTime
  78      <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime>.
  79      GetSystemTimeAsFileTime produces values that jump by increments of
  80      15.627 milliseconds (!) on average.
  81      Whereas GetSystemTimePreciseAsFileTime values usually jump by 1 or 2
  82      microseconds.
  83      More discussion on this topic:
  84      <http://www.windowstimestamp.com/description>.  */
  85   FILETIME current_time;
  86
  87   if (!initialized)
  88     initialize ();
  89   if (GetSystemTimePreciseAsFileTimeFunc != NULL)
  90     GetSystemTimePreciseAsFileTimeFunc (&current_time);
  91   else
  92     GetSystemTimeAsFileTime (&current_time);
  93
  94   /* Convert from FILETIME to 'struct timeval'.  */
  95   /* FILETIME: <https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-filetime> */
  96   ULONGLONG since_1601 =
  97     ((ULONGLONG) current_time.dwHighDateTime << 32)
  98     | (ULONGLONG) current_time.dwLowDateTime;
  99   /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
 100      years, in total 134774 days.  */
 101   ULONGLONG since_1970 =
 102     since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
 103   ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
 104   tv->tv_sec = microseconds_since_1970 / (ULONGLONG) 1000000;
 105   tv->tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000;
 106
 107   return 0;
 108
 109 #else
 110
 111 # if HAVE_GETTIMEOFDAY
 112 #  if GETTIMEOFDAY_CLOBBERS_LOCALTIME
 113   /* Save and restore the contents of the buffer used for localtime's
 114      result around the call to gettimeofday.  */
 115   struct tm save = *localtime_buffer_addr;
 116 #  endif
 117
 118 #  if defined timeval /* 'struct timeval' overridden by gnulib?  */
 119 #   undef timeval
 120   struct timeval otv;
 121   int result = gettimeofday (&otv, (struct timezone *) tz);
 122   if (result == 0)
 123     {
 124       tv->tv_sec = otv.tv_sec;
 125       tv->tv_usec = otv.tv_usec;
 126     }
 127 #  else
 128   int result = gettimeofday (tv, (struct timezone *) tz);
 129 #  endif
 130
 131 #  if GETTIMEOFDAY_CLOBBERS_LOCALTIME
 132   *localtime_buffer_addr = save;
 133 #  endif
 134
 135   return result;
 136
 137 # else
 138
 139 #  if !defined OK_TO_USE_1S_CLOCK
 140 #   error "Only 1-second nominal clock resolution found.  Is that intended?" \
 141           "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
 142 #  endif
 143   tv->tv_sec = time (NULL);
 144   tv->tv_usec = 0;
 145
 146   return 0;
 147
 148 # endif
 149 #endif
 150 }