/* Copyright (C) 2000-2018 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 <errno.h>

#include <fcntl.h>

#include <unistd.h>

#include <stdint.h>

#include <sys/fcntl.h>

#include <sys/stat.h>

#include <sys/statfs.h>

/* Reserve storage for the data of the file associated with FD.  This

   emulation is far from perfect, but the kernel cannot do not much

   better for network file systems, either.  */

int

__posix_fallocate64_l64 (int fd, __off64_t offset, __off64_t len)

{

  struct stat64 st;

  if (offset < 0 || len < 0)

    return EINVAL;

  /* Perform overflow check.  The outer cast relies on a GCC

     extension.  */

  if ((__off64_t) ((uint64_t) offset + (uint64_t) len) < 0)

    return EFBIG;

  /* pwrite64 below will not do the right thing in O_APPEND mode.  */

  {

    int flags = __fcntl (fd, F_GETFL, 0);

    if (flags < 0 || (flags & O_APPEND) != 0)

      return EBADF;

  }

  /* We have to make sure that this is really a regular file.  */

  if (__fxstat64 (_STAT_VER, fd, &st) != 0)

    return EBADF;

  if (S_ISFIFO (st.st_mode))

    return ESPIPE;

  if (! S_ISREG (st.st_mode))

    return ENODEV;

  if (len == 0)

    {

      /* This is racy, but there is no good way to satisfy a

	 zero-length allocation request.  */

      if (st.st_size < offset)

	{

	  int ret = __ftruncate64 (fd, offset);

	  if (ret != 0)

	    ret = errno;

	  return ret;

	}

      return 0;

    }

  /* Minimize data transfer for network file systems, by issuing

     single-byte write requests spaced by the file system block size.

     (Most local file systems have fallocate support, so this fallback

     code is not used there.)  */

  unsigned increment;

  {

    struct statfs64 f;

    if (__fstatfs64 (fd, &f) != 0)

      return errno;

    if (f.f_bsize == 0)

      increment = 512;

    else if (f.f_bsize < 4096)

      increment = f.f_bsize;

    else

      /* NFS clients do not propagate the block size of the underlying

	 storage and may report a much larger value which would still

	 leave holes after the loop below, so we cap the increment at

	 4096.  */

      increment = 4096;

  }

  /* Write a null byte to every block.  This is racy; we currently

     lack a better option.  Compare-and-swap against a file mapping

     might address local races, but requires interposition of a signal

     handler to catch SIGBUS.  */

  for (offset += (len - 1) % increment; len > 0; offset += increment)

    {

      len -= increment;

      if (offset < st.st_size)

	{

	  unsigned char c;

	  ssize_t rsize = __libc_pread64 (fd, &c, 1, offset);

	  if (rsize < 0)

	    return errno;

	  /* If there is a non-zero byte, the block must have been

	     allocated already.  */

	  else if (rsize == 1 && c != 0)

	    continue;

	}

      if (__libc_pwrite64 (fd, "", 1, offset) != 1)

	return errno;

    }

  return 0;

}

#undef __posix_fallocate64_l64

#include <shlib-compat.h>

#include <bits/wordsize.h>

#if __WORDSIZE == 32 && SHLIB_COMPAT(libc, GLIBC_2_2, GLIBC_2_3_3)

int

attribute_compat_text_section

__posix_fallocate64_l32 (int fd, off64_t offset, size_t len)

{

  return __posix_fallocate64_l64 (fd, offset, len);

}

versioned_symbol (libc, __posix_fallocate64_l64, posix_fallocate64,

		  GLIBC_2_3_3);

compat_symbol (libc, __posix_fallocate64_l32, posix_fallocate64, GLIBC_2_2);

#else

strong_alias (__posix_fallocate64_l64, posix_fallocate64);

#endif