uio.h

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* Copyright (C) 1996, 1997 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _SYS_UIO_H
# error "Never include <bits/uio.h> directly; use <sys/uio.h> instead."
#endif


#include <sys/types.h>


/* We should normally use the Linux kernel header file to define this
   type and macros but this calls for trouble because of the header
   includes other kernel headers.  */

/* Size of object which can be written atomically.

   This macro has different values in different kernel versions.  The
   latest versions of ther kernel use 1024 and this is good choice.  Since
   the C library implementation of readv/writev is able to emulate the
   functionality even if the currently running kernel does not support
   this large value the readv/writev call will not fail because of this.  */
#define UIO_MAXIOV	1024


/* Structure for scatter/gather I/O.  */
struct iovec
  {
    void *iov_base;	/* Pointer to data.  */
    size_t iov_len;	/* Length of data.  */
  };