NAME    [Toc]    [Back]

     uiomove - move data described by a struct uio

SYNOPSIS    [Toc]    [Back]

     #include <sys/systm.h>

     int
     uiomove(void *buf, int n, struct uio *uio);

DESCRIPTION    [Toc]    [Back]

     The uiomove function copies up to n bytes between  the  kernel-space address
  pointed to by buf and the addresses described by uio,
which may be
     in user-space or kernel-space.

     The uio argument is a pointer to a struct uio as defined  by
<sys/uio.h>:

     struct uio {
             struct   iovec  *uio_iov;  /*  pointer  to  array of
iovecs */
             int     uio_iovcnt;     /* number of iovecs in array
*/
             off_t   uio_offset;     /* offset into file this uio
corresponds to */
             size_t  uio_resid;      /* residual i/o count */
             enum    uio_seg uio_segflg;
             enum    uio_rw uio_rw;
             struct  proc *uio_procp;/* process if  UIO_USERSPACE
*/
     };

     A struct uio typically describes data in motion.  Several of
the fields
     described below reflect that expectation.

     uio_iov     Pointer to array of struct iovecs:

                 struct iovec {
                         void    *iov_base;      /* Base address.
*/
                         size_t   iov_len;       /* Length. */
                 };

     uio_iovcnt  The number of iovecs in the array.

     uio_offset  An offset into the corresponding object.

     uio_resid    The amount of data remaining to be transferred.

     uio_segflg  A flag indicating whether the space described is
in userspace
     (UIO_USERSPACE)     or    kernel-space
(UIO_SYSSPACE).

     uio_rw      A flag indicating whether data  should  be  read
into the space
                 (UIO_READ)    or    written   from   the   space
(UIO_WRITE).

     uio_procp   A pointer to the process whose data area is  described by the
                 structure,  or  NULL  if  the area is in kernelspace.

     The value of uio->uio_rw controls whether uiomove copies data from buf to
     uio or vice versa.

     The lesser of n or uio->resid bytes are copied.

     uiomove  changes  fields of the structure pointed to by uio,
such that
     uio->uio_resid is decremented by the amount of data moved,
     uio->uio_offset is incremented by the same amount,  and  the
array of
     iovecs  is  adjusted to point that much farther into the region described.
     This allows multiple calls to uiomove to easily be  used  to
fill or drain
     the region of data.

RETURN VALUES    [Toc]    [Back]

     uiomove  returns  0 on success or EFAULT if a bad address is
encountered.

SEE ALSO    [Toc]    [Back]

     copy(9)

OpenBSD     3.6                        February     12,      1999