usr/src/share/doc/papers/fsinterface/fs/uio.h

/*
 * Copyright (c) 1982 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *      @(#)uio.h       6.4 (Berkeley) 2/23/86
 */

#ifndef _UIO_
#define _UIO_

/*
 * Description of an I/O operation which potentially
 * involves scatter-gather, with individual sections
 * described by iovec, below.  uio_resid is initially
 * set to the total size of the operation, and is
 * decremented as the operation proceeds.  uio_offset
 * is incremented by the amount of each operation.
 * uio_iov is incremented and uio_iovcnt is decremented
 * after each vector is processed.
 */
struct uio {
        struct  iovec *uio_iov;
        int     uio_iovcnt;
        off_t   uio_offset;
        int     uio_resid;
        enum    uio_rw uio_rw;
};

enum    uio_rw { UIO_READ, UIO_WRITE };

/*
 * Description of a contiguous section of an I/O operation.
 * If iov_op is non-null, it is called to implement the copy
 * operation, possibly by remapping, with the call
 *      (*iov_op)(from, to, count);
 * where from and to are caddr_t and count is int.
 * Otherwise, the copy is done in the normal way,
 * treating base as a user or kernel virtual address
 * according to iov_segflg.
 */
struct iovec {
        caddr_t iov_base;
        int     iov_len;
        enum    uio_seg iov_segflg;
        int     (*iov_op)();
};

/*
 * Segment flag values.
 */
enum    uio_seg {
        UIO_USERSPACE,          /* from user data space */
        UIO_SYSSPACE,           /* from system space */
        UIO_USERISPACE          /* from user I space */
};
#endif