lib/fsync.c

   1 /* Emulate fsync on platforms that lack it, primarily Windows and
   2    cross-compilers like MinGW.
   3
   4    This is derived from sqlite3 sources.
   5    https://www.sqlite.org/src/finfo?name=src/os_win.c
   6    https://www.sqlite.org/copyright.html
   7
   8    Written by Richard W.M. Jones <rjones.at.redhat.com>
   9
  10    Copyright (C) 2008-2018 Free Software Foundation, Inc.
  11
  12    This library is free software; you can redistribute it and/or
  13    modify it under the terms of the GNU General Public
  14    License as published by the Free Software Foundation; either
  15    version 3 of the License, or (at your option) any later version.
  16
  17    This library is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20    General Public License for more details.
  21
  22    You should have received a copy of the GNU General Public License
  23    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  24
  25 #include <config.h>
  26 #include <unistd.h>
  27
  28 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  29
  30 /* FlushFileBuffers */
  31 # define WIN32_LEAN_AND_MEAN
  32 # include <windows.h>
  33
  34 # include <errno.h>
  35
  36 /* Get _get_osfhandle.  */
  37 # if GNULIB_MSVC_NOTHROW
  38 #  include "msvc-nothrow.h"
  39 # else
  40 #  include <io.h>
  41 # endif
  42
  43 int
  44 fsync (int fd)
  45 {
  46   HANDLE h = (HANDLE) _get_osfhandle (fd);
  47   DWORD err;
  48
  49   if (h == INVALID_HANDLE_VALUE)
  50     {
  51       errno = EBADF;
  52       return -1;
  53     }
  54
  55   if (!FlushFileBuffers (h))
  56     {
  57       /* Translate some Windows errors into rough approximations of Unix
  58        * errors.  MSDN is useless as usual - in this case it doesn't
  59        * document the full range of errors.
  60        */
  61       err = GetLastError ();
  62       switch (err)
  63         {
  64         case ERROR_ACCESS_DENIED:
  65           /* For a read-only handle, fsync should succeed, even though we have
  66              no way to sync the access-time changes.  */
  67           return 0;
  68
  69           /* eg. Trying to fsync a tty. */
  70         case ERROR_INVALID_HANDLE:
  71           errno = EINVAL;
  72           break;
  73
  74         default:
  75           errno = EIO;
  76         }
  77       return -1;
  78     }
  79
  80   return 0;
  81 }
  82
  83 #else /* !Windows */
  84
  85 # error "This platform lacks fsync function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib."
  86
  87 #endif /* !Windows */