1  /* Provide gettimeofday for systems that don't have it or for which it's broken.
       2  
       3     Copyright (C) 2001-2003, 2005-2007, 2009-2023 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  }