/* Get directory entries.  Linux non-LFS version.

   Copyright (C) 1993-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library.  If not, see

   <http://www.gnu.org/licenses/>.  */

#include <dirent.h>

#if !_DIRENT_MATCHES_DIRENT64

# include <unistd.h>

# include <string.h>

# include <errno.h>

# ifndef DIRENT_SET_DP_INO

#  define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value)

# endif

/* Pack the dirent64 struct down into 32-bit offset/inode fields, and

   ensure that no overflow occurs.  */

ssize_t

__getdents (int fd, char *buf, size_t nbytes)

{

  union

  {

    /* For !_DIRENT_MATCHES_DIRENT64 kernel 'linux_dirent64' has the same

       layout of 'struct dirent64'.  */

    struct dirent64 k;

    struct dirent u;

    char b[1];

  } *kbuf = (void *) buf, *outp, *inp;

  size_t kbytes = nbytes;

  off64_t last_offset = -1;

  ssize_t retval;

# define size_diff (offsetof (struct dirent64, d_name) \

		    - offsetof (struct dirent, d_name))

  char kbuftmp[sizeof (struct dirent) + size_diff];

  if (nbytes <= sizeof (struct dirent))

    kbuf = (void*) kbuftmp;

  retval = INLINE_SYSCALL_CALL (getdents64, fd, kbuf, kbytes);

  if (retval == -1)

    return -1;

  /* These two pointers might alias the same memory buffer.

     Standard C requires that we always use the same type for them,

     so we must use the union type.  */

  inp = kbuf;

  outp = (void *) buf;

  while (&inp->b < &kbuf->b + retval)

    {

      const size_t alignment = _Alignof (struct dirent);

      /* Since inp->k.d_reclen is already aligned for the kernel

         structure this may compute a value that is bigger

         than necessary.  */

      size_t old_reclen = inp->k.d_reclen;

      size_t new_reclen = ((old_reclen - size_diff + alignment - 1)

                           & ~(alignment - 1));

      /* Copy the data out of the old structure into temporary space.

         Then copy the name, which may overlap if BUF == KBUF.  */

      const uint64_t d_ino = inp->k.d_ino;

      const int64_t d_off = inp->k.d_off;

      const uint8_t d_type = inp->k.d_type;

      memmove (outp->u.d_name, inp->k.d_name,

               old_reclen - offsetof (struct dirent64, d_name));

      /* Now we have copied the data from INP and access only OUTP.  */

      DIRENT_SET_DP_INO (&outp->u, d_ino);

      outp->u.d_off = d_off;

      if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)

           && outp->u.d_ino != d_ino)

          || (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)

              && outp->u.d_off != d_off))

        {

          /* Overflow.  If there was at least one entry before this one,

             return them without error, otherwise signal overflow.  */

          if (last_offset != -1)

            {

              __lseek64 (fd, last_offset, SEEK_SET);

              return outp->b - buf;

            }

	  return INLINE_SYSCALL_ERROR_RETURN_VALUE (EOVERFLOW);

        }

      last_offset = d_off;

      outp->u.d_reclen = new_reclen;

      outp->u.d_type = d_type;

      inp = (void *) inp + old_reclen;

      outp = (void *) outp + new_reclen;

    }

  return outp->b - buf;

}

# undef DIRENT_SET_DP_INO

#endif /* _DIRENT_MATCHES_DIRENT64  */