1 files changed, 146 insertions, 0 deletions

diff --git a/lib/at-func.c b/lib/at-func.c
new file mode 100644
index 00000000000..481eea475a1
--- /dev/null
+++ b/lib/at-func.c
@@ -0,0 +1,146 @@
+/* Define at-style functions like fstatat, unlinkat, fchownat, etc.
+   Copyright (C) 2006, 2009-2012 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 3 of the License, 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, see <http://www.gnu.org/licenses/>.  */
+
+/* written by Jim Meyering */
+
+#include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
+
+#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
+# include <errno.h>
+# ifndef ENOTSUP
+#  define ENOTSUP EINVAL
+# endif
+#else
+# include "openat.h"
+# include "openat-priv.h"
+# include "save-cwd.h"
+#endif
+
+#ifdef AT_FUNC_USE_F1_COND
+# define CALL_FUNC(F)                           \
+  (flag == AT_FUNC_USE_F1_COND                  \
+    ? AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS)     \
+    : AT_FUNC_F2 (F AT_FUNC_POST_FILE_ARGS))
+# define VALIDATE_FLAG(F)                       \
+  if (flag & ~AT_FUNC_USE_F1_COND)              \
+    {                                           \
+      errno = EINVAL;                           \
+      return FUNC_FAIL;                         \
+    }
+#else
+# define CALL_FUNC(F) (AT_FUNC_F1 (F AT_FUNC_POST_FILE_ARGS))
+# define VALIDATE_FLAG(F) /* empty */
+#endif
+
+#ifdef AT_FUNC_RESULT
+# define FUNC_RESULT AT_FUNC_RESULT
+#else
+# define FUNC_RESULT int
+#endif
+
+#ifdef AT_FUNC_FAIL
+# define FUNC_FAIL AT_FUNC_FAIL
+#else
+# define FUNC_FAIL -1
+#endif
+
+/* Call AT_FUNC_F1 to operate on FILE, which is in the directory
+   open on descriptor FD.  If AT_FUNC_USE_F1_COND is defined to a value,
+   AT_FUNC_POST_FILE_PARAM_DECLS must include a parameter named flag;
+   call AT_FUNC_F2 if FLAG is 0 or fail if FLAG contains more bits than
+   AT_FUNC_USE_F1_COND.  Return int and fail with -1 unless AT_FUNC_RESULT
+   or AT_FUNC_FAIL are defined.  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.  */
+FUNC_RESULT
+AT_FUNC_NAME (int fd, char const *file AT_FUNC_POST_FILE_PARAM_DECLS)
+{
+  VALIDATE_FLAG (flag);
+
+  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
+    return CALL_FUNC (file);
+
+#ifdef GNULIB_SUPPORT_ONLY_AT_FDCWD
+  errno = ENOTSUP;
+  return FUNC_FAIL;
+#else
+  {
+  /* Be careful to choose names unlikely to conflict with
+     AT_FUNC_POST_FILE_PARAM_DECLS.  */
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  FUNC_RESULT err;
+
+  {
+    char proc_buf[OPENAT_BUFFER_SIZE];
+    char *proc_file = openat_proc_name (proc_buf, fd, file);
+    if (proc_file)
+      {
+        FUNC_RESULT proc_result = CALL_FUNC (proc_file);
+        int proc_errno = errno;
+        if (proc_file != proc_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 (FUNC_FAIL != 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 (0 <= fd && fd == saved_cwd.desc)
+    {
+      /* If saving the working directory collides with the user's
+         requested fd, then the user's fd must have been closed to
+         begin with.  */
+      free_cwd (&saved_cwd);
+      errno = EBADF;
+      return FUNC_FAIL;
+    }
+
+  if (fchdir (fd) != 0)
+    {
+      saved_errno = errno;
+      free_cwd (&saved_cwd);
+      errno = saved_errno;
+      return FUNC_FAIL;
+    }
+
+  err = CALL_FUNC (file);
+  saved_errno = (err == FUNC_FAIL ? errno : 0);
+
+  if (restore_cwd (&saved_cwd) != 0)
+    openat_restore_fail (errno);
+
+  free_cwd (&saved_cwd);
+
+  if (saved_errno)
+    errno = saved_errno;
+  return err;
+  }
+#endif
+}
+#undef CALL_FUNC
+#undef FUNC_RESULT
+#undef FUNC_FAIL