Add a wrapper for fsync() function

Closes issue #35

docs/reference/glib/glib-sections.txt

@@ -1626,6 +1626,7 @@ g_remove
 g_rmdir
 g_fopen
 g_freopen
+g_fsync
 g_chmod
 g_access
 g_creat

glib/gstdio.c

@@ -1641,6 +1641,31 @@ g_freopen (const gchar *filename,
 #endif
 }
 
+/**
+ * g_fsync:
+ * @fd: a file descriptor
+ *
+ * A wrapper for the POSIX fsync() function (_commit() on Windows).
+ * The fsync() function is used to synchronize a file's in-core
+ * state with that of the disk.
+ *
+ * See the C library manual for more details about fsync().
+ *
+ * Returns: 0 on success, or -1 if an error occurred.
+ * The return value can be used exactly like the return value from fsync().
+ *
+ * Since: 2.64
+ */
+gint
+g_fsync (gint fd)
+{
+#ifdef G_OS_WIN32
+  return _commit (fd);
+#else
+  return fsync (fd);
+#endif
+}
+
 /**
  * g_utime:
  * @filename: (type filename): a pathname in the GLib file name encoding

glib/gstdio.h

@@ -76,6 +76,7 @@ typedef struct stat GStatBuf;
 #define g_remove  remove
 #define g_fopen   fopen
 #define g_freopen freopen
+#define g_fsync   fsync
 #define g_utime   utime
 #endif
 
@@ -158,6 +159,9 @@ FILE *g_freopen (const gchar *filename,
                  const gchar *mode,
                  FILE        *stream);
 
+GLIB_AVAILABLE_IN_2_64
+gint g_fsync    (gint fd);
+
 struct utimbuf;			/* Don't need the real definition of struct utimbuf when just
 				 * including this header.
 				 */

glib/tests/fileutils.c

@@ -866,6 +866,7 @@ test_set_contents (void)
   fd = g_file_open_tmp (NULL, &name, &error);
   g_assert_no_error (error);
   write (fd, "a", 1);
+  g_assert_cmpint (g_fsync (fd), ==, 0);
   close (fd);
 
   ret = g_file_get_contents (name, &buf, &len, &error);