/* Define at-style functions like fstatat, unlinkat, fchownat, etc.

   Copyright (C) 2006, 2009-2017 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