/* Duplicate an open file descriptor to a specified file descriptor.

   Copyright (C) 1999, 2004-2007, 2009-2020 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 <https://www.gnu.org/licenses/>.  */

/* written by Paul Eggert */

#include <config.h>

/* Specification.  */

#include <unistd.h>

#include <errno.h>

#include <fcntl.h>

#if HAVE_DUP2

# undef dup2

# if defined _WIN32 && ! defined __CYGWIN__

/* Get declarations of the native Windows API functions.  */

#  define WIN32_LEAN_AND_MEAN

#  include <windows.h>

#  if HAVE_MSVC_INVALID_PARAMETER_HANDLER

#   include "msvc-inval.h"

#  endif

/* Get _get_osfhandle.  */

#  if GNULIB_MSVC_NOTHROW

#   include "msvc-nothrow.h"

#  else

#   include <io.h>

#  endif

#  if HAVE_MSVC_INVALID_PARAMETER_HANDLER

static int

dup2_nothrow (int fd, int desired_fd)

{

  int result;

  TRY_MSVC_INVAL

    {

      result = dup2 (fd, desired_fd);

    }

  CATCH_MSVC_INVAL

    {

      errno = EBADF;

      result = -1;

    }

  DONE_MSVC_INVAL;

  return result;

}

#  else

#   define dup2_nothrow dup2

#  endif

static int

ms_windows_dup2 (int fd, int desired_fd)

{

  int result;

  /* If fd is closed, mingw hangs on dup2 (fd, fd).  If fd is open,

     dup2 (fd, fd) returns 0, but all further attempts to use fd in

     future dup2 calls will hang.  */

  if (fd == desired_fd)

    {

      if ((HANDLE) _get_osfhandle (fd) == INVALID_HANDLE_VALUE)

        {

          errno = EBADF;

          return -1;

        }

      return fd;

    }

  /* Wine 1.0.1 return 0 when desired_fd is negative but not -1:

     https://bugs.winehq.org/show_bug.cgi?id=21289 */

  if (desired_fd < 0)

    {

      errno = EBADF;

      return -1;

    }

  result = dup2_nothrow (fd, desired_fd);

  if (result == 0)

    result = desired_fd;

  return result;

}

#  define dup2 ms_windows_dup2

# elif defined __KLIBC__

#  include <InnoTekLIBC/backend.h>

static int

klibc_dup2dirfd (int fd, int desired_fd)

{

  int tempfd;

  int dupfd;

  tempfd = open ("NUL", O_RDONLY);

  if (tempfd == -1)

    return -1;

  if (tempfd == desired_fd)

    {

      close (tempfd);

      char path[_MAX_PATH];

      if (__libc_Back_ioFHToPath (fd, path, sizeof (path)))

        return -1;

      return open(path, O_RDONLY);

    }

  dupfd = klibc_dup2dirfd (fd, desired_fd);

  close (tempfd);

  return dupfd;

}

static int

klibc_dup2 (int fd, int desired_fd)

{

  int dupfd;

  struct stat sbuf;

  dupfd = dup2 (fd, desired_fd);

  if (dupfd == -1 && errno == ENOTSUP \

      && !fstat (fd, &sbuf) && S_ISDIR (sbuf.st_mode))

    {

      close (desired_fd);

      return klibc_dup2dirfd (fd, desired_fd);

    }

  return dupfd;

}

#  define dup2 klibc_dup2

# endif

int

rpl_dup2 (int fd, int desired_fd)

{

  int result;

# ifdef F_GETFL

  /* On Linux kernels 2.6.26-2.6.29, dup2 (fd, fd) returns -EBADF.

     On Cygwin 1.5.x, dup2 (1, 1) returns 0.

     On Cygwin 1.7.17, dup2 (1, -1) dumps core.

     On Cygwin 1.7.25, dup2 (1, 256) can dump core.

     On Haiku, dup2 (fd, fd) mistakenly clears FD_CLOEXEC.  */

#  if HAVE_SETDTABLESIZE

  setdtablesize (desired_fd + 1);

#  endif

  if (desired_fd < 0)

    fd = desired_fd;

  if (fd == desired_fd)

    return fcntl (fd, F_GETFL) == -1 ? -1 : fd;

# endif

  result = dup2 (fd, desired_fd);

  /* Correct an errno value on FreeBSD 6.1 and Cygwin 1.5.x.  */

  if (result == -1 && errno == EMFILE)

    errno = EBADF;

# if REPLACE_FCHDIR

  if (fd != desired_fd && result != -1)

    result = _gl_register_dup (fd, result);

# endif

  return result;

}

#else /* !HAVE_DUP2 */

/* On older platforms, dup2 did not exist.  */

# ifndef F_DUPFD

static int

dupfd (int fd, int desired_fd)

{

  int duplicated_fd = dup (fd);

  if (duplicated_fd < 0 || duplicated_fd == desired_fd)

    return duplicated_fd;

  else

    {

      int r = dupfd (fd, desired_fd);

      int e = errno;

      close (duplicated_fd);

      errno = e;

      return r;

    }

}

# endif

int

dup2 (int fd, int desired_fd)

{

  int result = fcntl (fd, F_GETFL) < 0 ? -1 : fd;

  if (result == -1 || fd == desired_fd)

    return result;

  close (desired_fd);

# ifdef F_DUPFD

  result = fcntl (fd, F_DUPFD, desired_fd);

#  if REPLACE_FCHDIR

  if (0 <= result)

    result = _gl_register_dup (fd, result);

#  endif

# else

  result = dupfd (fd, desired_fd);

# endif

  if (result == -1 && (errno == EMFILE || errno == EINVAL))

    errno = EBADF;

  return result;

}

#endif /* !HAVE_DUP2 */