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

/* writev supports all Linux kernels >= 2.0.
   Copyright (C) 1997, 1998 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <stddef.h>
#include <sys/param.h>
#include <sys/uio.h>

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

extern ssize_t __syscall_writev __P ((int, const struct iovec *, int));
static ssize_t __atomic_writev_replacement __P ((int, const struct iovec *,
						 int)) internal_function;


/* 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


/* We should deal with kernel which have a smaller UIO_FASTIOV as well
   as a very big count.  */
ssize_t
__writev (fd, vector, count)
     int fd;
     const struct iovec *vector;
     int count;
{
  int errno_saved = errno;
  ssize_t bytes_written;

  bytes_written = INLINE_SYSCALL (writev, 3, fd, vector, count);

  if (bytes_written >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
    return bytes_written;

  /* Restore the old error value as if nothing happened.  */
  __set_errno (errno_saved);

  return __atomic_writev_replacement (fd, vector, count);
}
weak_alias (__writev, writev)

#define __writev static internal_function __atomic_writev_replacement
#include <sysdeps/posix/writev.c>