win32: import fsync(2) implementation from gnulib

2 files changed, 76 insertions, 0 deletions

diff --git a/win32/Kbuild b/win32/Kbuild
index b2b43b290..8248c994f 100644
--- a/win32/Kbuild
+++ b/win32/Kbuild
@@ -6,6 +6,7 @@ lib-y:=
 
 lib-$(CONFIG_PLATFORM_MINGW32) += env.o
 lib-$(CONFIG_PLATFORM_MINGW32) += fnmatch.o
+lib-$(CONFIG_PLATFORM_MINGW32) += fsync.o
 lib-$(CONFIG_PLATFORM_MINGW32) += ioctl.o
 lib-$(CONFIG_PLATFORM_MINGW32) += mingw.o
 lib-$(CONFIG_PLATFORM_MINGW32) += process.o
diff --git a/win32/fsync.c b/win32/fsync.c
new file mode 100644
index 000000000..6ab44d434
--- /dev/null
+++ b/win32/fsync.c
@@ -0,0 +1,75 @@
+/* Emulate fsync on platforms that lack it, primarily Windows and
+   cross-compilers like MinGW.
+
+   This is derived from sqlite3 sources.
+   https://www.sqlite.org/src/finfo?name=src/os_win.c
+   https://www.sqlite.org/copyright.html
+
+   Written by Richard W.M. Jones <rjones.at.redhat.com>
+
+   Copyright (C) 2008-2018 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include "libbb.h"
+#include <unistd.h>
+
+/* FlushFileBuffers */
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+
+# include <errno.h>
+
+/* Get _get_osfhandle.  */
+# include <io.h>
+
+int
+fsync (int fd)
+{
+  HANDLE h = (HANDLE) _get_osfhandle (fd);
+  DWORD err;
+
+  if (h == INVALID_HANDLE_VALUE)
+    {
+      errno = EBADF;
+      return -1;
+    }
+
+  if (!FlushFileBuffers (h))
+    {
+      /* Translate some Windows errors into rough approximations of Unix
+       * errors.  MSDN is useless as usual - in this case it doesn't
+       * document the full range of errors.
+       */
+      err = GetLastError ();
+      switch (err)
+        {
+        case ERROR_ACCESS_DENIED:
+          /* For a read-only handle, fsync should succeed, even though we have
+             no way to sync the access-time changes.  */
+          return 0;
+
+          /* eg. Trying to fsync a tty. */
+        case ERROR_INVALID_HANDLE:
+          errno = EINVAL;
+          break;
+
+        default:
+          errno = EIO;
+        }
+      return -1;
+    }
+
+  return 0;
+}