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, 2009-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser 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 #ifdef WINDOWS_NATIVE
  33
  34 /* Don't assume that UNICODE is not defined.  */
  35 # undef LoadLibrary
  36 # define LoadLibrary LoadLibraryA
  37
  38 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
  39
  40 /* Avoid warnings from gcc -Wcast-function-type.  */
  41 #  define GetProcAddress \
  42     (void *) GetProcAddress
  43
  44 /* GetSystemTimePreciseAsFileTime was introduced only in Windows 8.  */
  45 typedef void (WINAPI * GetSystemTimePreciseAsFileTimeFuncType) (FILETIME *lpTime);
  46 static GetSystemTimePreciseAsFileTimeFuncType GetSystemTimePreciseAsFileTimeFunc = NULL;
  47 static BOOL initialized = FALSE;
  48
  49 static void
  50 initialize (void)
  51 {
  52   HMODULE kernel32 = LoadLibrary ("kernel32.dll");
  53   if (kernel32 != NULL)
  54     {
  55       GetSystemTimePreciseAsFileTimeFunc =
  56         (GetSystemTimePreciseAsFileTimeFuncType) GetProcAddress (kernel32, "GetSystemTimePreciseAsFileTime");
  57     }
  58   initialized = TRUE;
  59 }
  60
  61 # else
  62
  63 #  define GetSystemTimePreciseAsFileTimeFunc GetSystemTimePreciseAsFileTime
  64
  65 # endif
  66
  67 #endif
  68
  69 /* This is a wrapper for gettimeofday.  It is used only on systems
  70    that lack this function, or whose implementation of this function
  71    causes problems.
  72    Work around the bug in some systems whereby gettimeofday clobbers
  73    the static buffer that localtime uses for its return value.  The
  74    gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
  75    this problem.  */
  76
  77 int
  78 gettimeofday (struct timeval *restrict tv, void *restrict tz)
  79 {
  80 #undef gettimeofday
  81 #ifdef WINDOWS_NATIVE
  82
  83   /* On native Windows, there are two ways to get the current time:
  84      GetSystemTimeAsFileTime
  85      <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime>
  86      or
  87      GetSystemTimePreciseAsFileTime
  88      <https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime>.
  89      GetSystemTimeAsFileTime produces values that jump by increments of
  90      15.627 milliseconds (!) on average.
  91      Whereas GetSystemTimePreciseAsFileTime values usually jump by 1 or 2
  92      microseconds.
  93      More discussion on this topic:
  94      <http://www.windowstimestamp.com/description>.  */
  95   FILETIME current_time;
  96
  97 # if !(_WIN32_WINNT >= _WIN32_WINNT_WIN8)
  98   if (!initialized)
  99     initialize ();
 100 # endif
 101   if (GetSystemTimePreciseAsFileTimeFunc != NULL)
 102     GetSystemTimePreciseAsFileTimeFunc (&current_time);
 103   else
 104     GetSystemTimeAsFileTime (&current_time);
 105
 106   /* Convert from FILETIME to 'struct timeval'.  */
 107   /* FILETIME: <https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-filetime> */
 108   ULONGLONG since_1601 =
 109     ((ULONGLONG) current_time.dwHighDateTime << 32)
 110     | (ULONGLONG) current_time.dwLowDateTime;
 111   /* Between 1601-01-01 and 1970-01-01 there were 280 normal years and 89 leap
 112      years, in total 134774 days.  */
 113   ULONGLONG since_1970 =
 114     since_1601 - (ULONGLONG) 134774 * (ULONGLONG) 86400 * (ULONGLONG) 10000000;
 115   ULONGLONG microseconds_since_1970 = since_1970 / (ULONGLONG) 10;
 116   *tv = (struct timeval) {
 117     .tv_sec  = microseconds_since_1970 / (ULONGLONG) 1000000,
 118     .tv_usec = microseconds_since_1970 % (ULONGLONG) 1000000
 119   };
 120
 121   return 0;
 122
 123 #else
 124
 125 # if HAVE_GETTIMEOFDAY
 126
 127 #  if defined timeval /* 'struct timeval' overridden by gnulib?  */
 128 #   undef timeval
 129   struct timeval otv;
 130   int result = gettimeofday (&otv, (struct timezone *) tz);
 131   if (result == 0)
 132     *tv = otv;
 133 #  else
 134   int result = gettimeofday (tv, (struct timezone *) tz);
 135 #  endif
 136
 137   return result;
 138
 139 # else
 140
 141 #  if !defined OK_TO_USE_1S_CLOCK
 142 #   error "Only 1-second nominal clock resolution found.  Is that intended?" \
 143           "If so, compile with the -DOK_TO_USE_1S_CLOCK option."
 144 #  endif
 145   *tv = (struct timeval) { .tv_sec = time (NULL), .tv_usec = 0 };
 146
 147   return 0;
 148
 149 # endif
 150 #endif
 151 }