glibc/sysdeps/unix/sysv/linux/ftruncate64.c

/* Copyright (C) 1997,1998,1999,2000,2001,2003,2005,2006,2011
	 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 <sys/types.h>
#include <errno.h>
#include <endian.h>
#include <unistd.h>

#include <sysdep.h>
#include <sys/syscall.h>

#include <kernel-features.h>

#ifdef __NR_ftruncate64
#ifndef __ASSUME_TRUNCATE64_SYSCALL
/* The variable is shared between all wrappers around *truncate64 calls.  */
extern int __have_no_truncate64;
#endif


/* Truncate the file referenced by FD to LENGTH bytes.  */
int
__ftruncate64 (int fd, off64_t length)
{
#ifndef __ASSUME_TRUNCATE64_SYSCALL
  if (! __have_no_truncate64)
#endif
    {
      unsigned int low = length & 0xffffffff;
      unsigned int high = length >> 32;
#ifndef __ASSUME_TRUNCATE64_SYSCALL
      int saved_errno = errno;
#endif
      int result = INLINE_SYSCALL (ftruncate64, 3, fd,
				   __LONG_LONG_PAIR (high, low));
#ifndef __ASSUME_TRUNCATE64_SYSCALL
      if (result != -1 || errno != ENOSYS)
#endif
	return result;

#ifndef __ASSUME_TRUNCATE64_SYSCALL
      __set_errno (saved_errno);
      __have_no_truncate64 = 1;
#endif
    }

#ifndef __ASSUME_TRUNCATE64_SYSCALL
  if ((off_t) length != length)
    {
      __set_errno (EINVAL);
      return -1;
    }
  return __ftruncate (fd, (off_t) length);
#endif
}
weak_alias (__ftruncate64, ftruncate64)

#else
/* Use the generic implementation.  */
# include <misc/ftruncate64.c>
#endif