$NetBSD: uiomove.9,v 1.6 2001/12/26 00:16:30 wiz Exp $
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.Dd $Mdocdate: March 15 2016 $ .Dt UIOMOVE 9 .Os .Sh NAME .Nm uiomove .Nd move data described by a struct uio .Sh SYNOPSIS n sys/systm.h .Ft int .Fn uiomove "void *buf" "size_t n" "struct uio *uio" .Sh DESCRIPTION The .Nm function copies up to .Fa n bytes between the kernel-space address pointed to by .Fa buf and the addresses described by .Fa uio , which may be in user-space or kernel-space.
p The .Fa uio argument is a pointer to a .Fa struct uio as defined by n sys/uio.h : d -literal 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;/* associated process or NULL */ }; .Ed
p A .Fa struct uio typically describes data in motion. Several of the fields described below reflect that expectation. l -tag -width uio_xxxxxx t uio_iov Pointer to array of .Fa struct iovecs : d -literal struct iovec { void *iov_base; /* Base address. */ size_t iov_len; /* Length. */ }; .Ed t uio_iovcnt The number of iovecs in the array. t uio_offset An offset into the corresponding object. t uio_resid The amount of data remaining to be transferred. t uio_segflg A flag indicating whether the space described is in user-space (UIO_USERSPACE) or kernel-space (UIO_SYSSPACE). t uio_rw A flag indicating whether data should be read into the space (UIO_READ) or written from the space (UIO_WRITE). t uio_procp A pointer to a process whose data area is described by the structure, or which is having the I/O done on its behalf if the area is in kernel-space. .Nm uiomove itself does not use this field if the area is in kernel-space, but other functions that take a .Fa struct uio may depend on this information. .El
p The value of .Fa uio->uio_rw controls whether .Nm copies data from .Fa buf to .Fa uio or vice versa.
p The lesser of .Fa n or .Fa uio->uio_resid bytes are copied.
p .Nm changes fields of the structure pointed to by .Fa uio , such that .Fa uio->uio_resid is decremented by the amount of data moved, .Fa 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 .Nm to easily be used to fill or drain the region of data. .Sh RETURN VALUES .Nm returns 0 on success or EFAULT if a bad address is encountered. .Sh SEE ALSO .Xr copy 9