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uio(9s) [osf1 man page]

uio(9s) 																   uio(9s)

uio - General: Describes I/O, either single vector or multiple vectors SYNOPSIS
----------------------------- Member Name Data Type ----------------------------- uio_iov struct iovec * uio_iovcnt int uio_offset off_t uio_segflg enum uio_seg uio_resid int uio_rw enum uio_rw ----------------------------- MEMBERS
Specifies a pointer to the first iovec structure. The iovec structure has two members: one that specifies the address of the segment and another that specifies the size of the segment. The system allocates contiguous iovec structures for a given transfer. Specifies the num- ber of iovec structures for this transfer. Specifies the offset within the file. Specifies the segment type. This member can be set to one of the following values: UIO_USERSPACE (the segment is from the user data space), UIO_SYSSPACE (the segment is from the system space), or UIO_USERISPACE (the segment is from the user I space). Specifies the number of bytes that still need to be transferred. Specifies whether the transfer is a read or a write. This member is set by read and write system calls according to the corresponding field in the file descriptor. This member can be set to one of the following values: UIO_READ (read transfer), UIO_WRITE (write transfer), or UIO_AIORW (Alpha I/O read/write transfer). DESCRIPTION
The uio data structure describes, either singler-vector or multiple-vector I/O. Typically, kernel modules do not manipulate the members of this data structure. However, the data structure is presented here for the purpose of understanding the uiomove routine, which operates on the members of the uio structure. FILES
Routines: uiomove(9r) uio(9s)

Check Out this Related Man Page

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

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; int uio_iovcnt; off_t uio_offset; size_t uio_resid; enum uio_rw uio_rw; struct vmspace *uio_vmspace; }; A struct uio typically describes data in motion. Several of the fields described below reflect that expectation. uio_iov Pointer to array of I/O vectors to be processed. The struct iovec is defined to be: struct iovec { void *iov_base; size_t iov_len; }; The members in the struct iovec should only be initialized. These are: iov_base The address for a range of memory to or from which data is transferred. iov_len The number of bytes of data to be transferred to or from the range of memory starting at iov_base. uio_iovcnt The number of I/O vectors in the uio_iov 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_rw A flag indicating whether data should be read into the space (UIO_READ) or written from the space (UIO_WRITE). uio_vmspace A pointer to the address space which is being transferred to or from. The value of uio->uio_rw controls whether uiomove() copies data from buf to uio or vice versa. The lesser of n or uio->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
Upon successful completion, uiomove() returns 0. If a bad address is encountered, EFAULT is returned. SEE ALSO
copy(9), fetch(9), store(9) BSD
April 26, 2010 BSD
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