root/lib/gettimeofday.c

DEFINITIONS

1. initialize
2. gettimeofday

     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 }