1 files changed, 86 insertions, 0 deletions
diff --git a/lib/at-func.c b/lib/at-func.c
new file mode 100644
index 0000000..f98c207
--- /dev/null
+++ b/lib/at-func.c
@@ -0,0 +1,86 @@
+/* Define an at-style functions like fstatat, unlinkat, fchownat, etc.
+   Copyright (C) 2006 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#define CALL_FUNC(F)				\
+  (AT_FUNC_USE_F1_COND				\
+    ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS)	\
+    : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS))
+
+/* Call AT_FUNC_F1 or AT_FUNC_F2 (testing AT_FUNC_USE_F1_COND to
+   determine which) to operate on FILE, which is in the directory
+   open on descriptor FD.  If possible, do it without changing the
+   working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then AT_FUNC_F?/restore_cwd.  If either the save_cwd or the restore_cwd
+   fails, then give a diagnostic and exit nonzero.  */
+int
+AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS)
+{
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  int err;
+
+  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
+    return CALL_FUNC (file);
+
+  {
+    char buf[OPENAT_BUFFER_SIZE];
+    char *proc_file = openat_proc_name (buf, fd, file);
+    if (proc_file)
+      {
+	int proc_result = CALL_FUNC (proc_file);
+	int proc_errno = errno;
+	if (proc_file != buf)
+	  free (proc_file);
+	/* If the syscall succeeds, or if it fails with an unexpected
+	   errno value, then return right away.  Otherwise, fall through
+	   and resort to using save_cwd/restore_cwd.  */
+	if (0 <= proc_result)
+	  return proc_result;
+	if (! EXPECTED_ERRNO (proc_errno))
+	  {
+	    errno = proc_errno;
+	    return proc_result;
+	  }
+      }
+  }
+
+  if (save_cwd (&saved_cwd) != 0)
+    openat_save_fail (errno);
+
+  if (fchdir (fd) != 0)
+    {
+      saved_errno = errno;
+      free_cwd (&saved_cwd);
+      errno = saved_errno;
+      return -1;
+    }
+
+  err = CALL_FUNC (file);
+  saved_errno = (err < 0 ? errno : 0);
+
+  if (restore_cwd (&saved_cwd) != 0)
+    openat_restore_fail (errno);
+
+  free_cwd (&saved_cwd);
+
+  if (saved_errno)
+    errno = saved_errno;
+  return err;
+}
+#undef CALL_FUNC