root/include/linux/uio.h

INCLUDED FROM

DEFINITIONS

1. iov_length

#ifndef __LINUX_UIO_H
#define __LINUX_UIO_H

#include <linux/compiler.h>
#include <linux/types.h>

/*
 *      Berkeley style UIO structures   -       Alan Cox 1994.
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 */

struct iovec
{
        void __user *iov_base;  /* BSD uses caddr_t (1003.1g requires void *) */
        __kernel_size_t iov_len; /* Must be size_t (1003.1g) */
};

#ifdef __KERNEL__

struct kvec {
        void *iov_base; /* and that should *never* hold a userland pointer */
        size_t iov_len;
};

#endif

/*
 *      UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
 */
 
#define UIO_FASTIOV     8
#define UIO_MAXIOV      1024

/*
 * Total number of bytes covered by an iovec.
 *
 * NOTE that it is not safe to use this function until all the iovec's
 * segment lengths have been validated.  Because the individual lengths can
 * overflow a size_t when added together.
 */
static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
{
        unsigned long seg;
        size_t ret = 0;

        for (seg = 0; seg < nr_segs; seg++)
                ret += iov[seg].iov_len;
        return ret;
}

unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);

#endif