1.\" $NetBSD: dofileread.9,v 1.2 2002/10/20 10:46:57 wiz Exp $ 2.\" 3.\" Copyright (c) 2002 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Gregory McGarry. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd October 20, 2002 38.Dt DOFILEREAD 9 39.Os 40.Sh NAME 41.Nm dofileread , 42.Nm dofilewrite , 43.Nm dofilereadv , 44.Nm dofilewritev , 45.Nd high-level file operations 46.Sh SYNOPSIS 47.Fd #include \*[Lt]sys/file.h\*[Gt] 48.Ft int 49.Fn dofileread "struct proc *p" "int fd" "struct file *fp" "void *buf" \ 50"size_t nbyte" "off_t *offset" "int flags" "register_t *retval" 51.Ft int 52.Fn dofilewrite "struct proc *p" "int fd" "struct file *fp" \ 53"const void *buf" "size_t nbyte" "off_t *offset" "int flags" \ 54"register_t *retval" 55.Ft int 56.Fn dofilereadv "struct proc *p" "int fd" "struct file *fp" \ 57"const struct iovec *iovp" "int iovcnt" "off_t *offset" "int flags" \ 58"register_t *retval" 59.Ft int 60.Fn dofilewritev "struct proc *p" "int fd" "struct file *fp" \ 61"const struct iovec *iovp" "int iovcnt" "off_t *offset" "int flags" \ 62"register_t *retval" 63.Sh DESCRIPTION 64The function implement the underlying functionality of the 65.Xr read 2 , 66.Xr write 2 , 67.Xr readv 2 , 68and 69.Xr writev 2 70system calls. They are also used throughout the kernel as high-level 71access routines for file I/O. 72.Pp 73The 74.Fn dofileread 75function 76attempts to read 77.Fa nbytes 78of data from the object referenced by file entry 79.Fa fp 80into the buffer pointed to by 81.Fa buf . 82The 83.Fn dofilewrite 84function 85attempts to write 86.Fa nbytes 87of data to the object referenced by file entry 88.Fa fp 89from the buffer pointed to by 90.Fa buf . 91.Pp 92The 93.Fn dofilereadv 94and 95.Fn dofilewritev 96functions perform the same operations, but scatters the data with the 97.Fa iovcnt 98buffers specified by the members of the 99.Fa iov 100array. 101.Pp 102The offset of the file operations is explicitly specified by 103.Fa *offset . 104The new file offset after the file operation is returned in 105.Fa *offset . 106If the FOF_UPDATE_OFFSET flag is specified in the 107.Fa flags 108argument, the file offset in the file entry 109.Fa fp 110is updated to reflect the new file offset, otherwise it remains 111unchanged after the operation. 112.Pp 113The file descriptor 114.Fa fd 115is largely unused except for use by the ktrace framework for reporting 116to userlevel the process's file descriptor. 117.Pp 118Upon successful completion the number of bytes which were transferred 119is returned in 120.Fa *retval . 121.Sh RETURN VALUES 122Upon successful complete zero is returned, otherwise and appropriate 123error is returned. 124.Sh CODE REFERENCES 125This section describes places within the 126.Nx 127source tree where actual code implementing or utilising these file 128operations can be found. All pathnames are relative to 129.Pa /usr/src . 130.Pp 131The framework for these file operations is implemented within the file 132.Pa sys/kern/sys_generic.c . 133.Sh SEE ALSO 134.Xr file 9 135