support/support_stat_nanoseconds.c

   1 /* Check if stat supports nanosecond resolution.
   2    Copyright (C) 2021-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <support/check.h>
  22 #include <support/support.h>
  23 #include <support/timespec.h>
  24 #include <stdbool.h>
  25 #include <sys/stat.h>
  26 #include <sys/types.h>
  27 #include <unistd.h>
  28
  29 bool
  30 support_stat_nanoseconds (const char *path)
  31 {
  32   bool support = true;
  33 #ifdef __linux__
  34   /* Obtain the original timestamp to restore at the end.  */
  35   struct stat ost;
  36   TEST_VERIFY_EXIT (stat (path, &ost) == 0);
  37
  38   const struct timespec tsp[] = { { 0, TIMESPEC_HZ - 1 },
  39                                   { 0, TIMESPEC_HZ / 2 } };
  40   TEST_VERIFY_EXIT (utimensat (AT_FDCWD, path, tsp, 0) == 0);
  41
  42   struct stat st;
  43   TEST_VERIFY_EXIT (stat (path, &st) == 0);
  44
  45   support = st.st_atim.tv_nsec == tsp[0].tv_nsec
  46             && st.st_mtim.tv_nsec == tsp[1].tv_nsec;
  47
  48   /* Reset to original timestamps.  */
  49   const struct timespec otsp[] =
  50   {
  51     { ost.st_atim.tv_sec, ost.st_atim.tv_nsec },
  52     { ost.st_mtim.tv_sec, ost.st_mtim.tv_nsec },
  53   };
  54   TEST_VERIFY_EXIT (utimensat (AT_FDCWD, path, otsp, 0) == 0);
  55 #endif
  56   return support;
  57 }