1.\" $NetBSD: uiomove.9,v 1.14 2008/04/30 13:10:58 martin Exp $ 2.\" 3.\" Copyright (c) 1996 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 16.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 17.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 18.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 19.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25.\" POSSIBILITY OF SUCH DAMAGE. 26.\" 27.Dd March 7, 2007 28.Dt UIOMOVE 9 29.Os 30.Sh NAME 31.Nm uiomove 32.Nd move data described by a struct uio 33.Sh SYNOPSIS 34.In sys/systm.h 35.Ft int 36.Fn uiomove "void *buf" "size_t n" "struct uio *uio" 37.Sh DESCRIPTION 38The 39.Nm 40function copies up to 41.Fa n 42bytes between the kernel-space address pointed 43to by 44.Fa buf 45and the addresses described by 46.Fa uio , 47which may be in user-space or kernel-space. 48.Pp 49The 50.Fa uio 51argument is a pointer to a 52.Fa struct uio 53as defined by 54.Aq Pa sys/uio.h : 55.Bd -literal 56struct uio { 57 struct iovec *uio_iov; /* pointer to array of iovecs */ 58 int uio_iovcnt; /* number of iovecs in array */ 59 off_t uio_offset; /* offset into file this uio corresponds to */ 60 size_t uio_resid; /* residual i/o count */ 61 enum uio_rw uio_rw; 62 struct vmspace *uio_vmspace; 63}; 64.Ed 65.Pp 66A 67.Fa struct uio 68typically describes data in motion. 69Several of the fields described below reflect that expectation. 70.Pp 71.Bl -tag -width uio_xxxxxx 72.It uio_iov 73Pointer to array of 74.Fa struct iovecs : 75.Bd -literal 76struct iovec { 77 void *iov_base; /* Base address. */ 78 size_t iov_len; /* Length. */ 79}; 80.Ed 81.It uio_iovcnt 82The number of iovecs in the array. 83.It uio_offset 84An offset into the corresponding object. 85.It uio_resid 86The amount of space described by the structure; notionally, the amount 87of data remaining to be transferred. 88.It uio_rw 89A flag indicating whether data should be read into the space 90(UIO_READ) or written from the space (UIO_WRITE). 91.It uio_vmspace 92A pointer to the address space which is being transferred to or from. 93.El 94.Pp 95The value of 96.Fa uio-\*[Gt]uio_rw 97controls whether 98.Nm 99copies data from 100.Fa buf 101to 102.Fa uio 103or vice versa. 104.Pp 105The lesser of 106.Fa n 107or 108.Fa uio-\*[Gt]uio_resid 109bytes are copied. 110.Pp 111.Nm 112changes fields of the structure pointed to by 113.Fa uio , 114such that 115.Fa uio-\*[Gt]uio_resid 116is decremented by the amount of data moved, 117.Fa uio-\*[Gt]uio_offset 118is incremented by the same amount, and the array of iovecs is adjusted 119to point that much farther into the region described. 120This allows multiple calls to 121.Nm 122to easily be used to fill or drain the region of data. 123.Sh RETURN VALUES 124.Nm 125returns 0 on success or EFAULT if a bad address is encountered. 126.Sh SEE ALSO 127.Xr copy 9 , 128.Xr fetch 9 , 129.Xr store 9 130