linux/include/linux/uio.h
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   1#ifndef __LINUX_UIO_H
   2#define __LINUX_UIO_H
   3
   4#include <linux/compiler.h>
   5#include <linux/types.h>
   6
   7/*
   8 *      Berkeley style UIO structures   -       Alan Cox 1994.
   9 *
  10 *              This program is free software; you can redistribute it and/or
  11 *              modify it under the terms of the GNU General Public License
  12 *              as published by the Free Software Foundation; either version
  13 *              2 of the License, or (at your option) any later version.
  14 */
  15
  16struct iovec
  17{
  18        void __user *iov_base;  /* BSD uses caddr_t (1003.1g requires void *) */
  19        __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
  20};
  21
  22/*
  23 *      UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
  24 */
  25 
  26#define UIO_FASTIOV     8
  27#define UIO_MAXIOV      1024
  28
  29#ifdef __KERNEL__
  30
  31struct kvec {
  32        void *iov_base; /* and that should *never* hold a userland pointer */
  33        size_t iov_len;
  34};
  35
  36/*
  37 * Total number of bytes covered by an iovec.
  38 *
  39 * NOTE that it is not safe to use this function until all the iovec's
  40 * segment lengths have been validated.  Because the individual lengths can
  41 * overflow a size_t when added together.
  42 */
  43static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
  44{
  45        unsigned long seg;
  46        size_t ret = 0;
  47
  48        for (seg = 0; seg < nr_segs; seg++)
  49                ret += iov[seg].iov_len;
  50        return ret;
  51}
  52
  53unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
  54#endif
  55
  56#endif
  57
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