uiomove(9) - NetBSD Manual Pages

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UIOMOVE(9)             NetBSD Kernel Developer's Manual             UIOMOVE(9)


NAME

     uiomove - move data described by a struct uio


SYNOPSIS

     #include <sys/systm.h>

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


DESCRIPTION

     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 space described by the structure; notionally,
                 the amount of data remaining to be transferred.

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

     uio_rw      A flag indicating whether date 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 kernel-space.

     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

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


SEE ALSO

     copy(9), fetch(9), store(9)

NetBSD 2.1                     February 12, 1999                    NetBSD 2.1