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

/* writev supports all Linux kernels >= 2.0.
   Copyright (C) 1997,1998,2000,2002,2003,2009 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 <stddef.h>
#include <sys/param.h>
#include <sys/uio.h>

#include <sysdep-cancel.h>
#include <sys/syscall.h>
#include <bp-checks.h>
#include <kernel-features.h>

#ifndef __ASSUME_COMPLETE_READV_WRITEV
static ssize_t __atomic_writev_replacement (int, const struct iovec *,
					    int) internal_function;
#endif


/* Not all versions of the kernel support the large number of records.  */
#ifndef UIO_FASTIOV
# define UIO_FASTIOV	8	/* 8 is a safe number.  */
#endif


ssize_t
__libc_writev (fd, vector, count)
     int fd;
     const struct iovec *vector;
     int count;
{
  ssize_t result;

  if (SINGLE_THREAD_P)
    result = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count), count);
  else
    {
      int oldtype = LIBC_CANCEL_ASYNC ();

      result = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count), count);

      LIBC_CANCEL_RESET (oldtype);
    }

#ifdef __ASSUME_COMPLETE_READV_WRITEV
  return result;
#else
  if (result >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
    return result;

  return __atomic_writev_replacement (fd, vector, count);
#endif
}
strong_alias (__libc_writev, __writev)
weak_alias (__libc_writev, writev)

#ifndef __ASSUME_COMPLETE_READV_WRITEV
# define __libc_writev static internal_function __atomic_writev_replacement
# include <sysdeps/posix/writev.c>
#endif