138451Smsmith/* $NetBSD: lseek.c,v 1.4 1997/01/22 00:38:10 cgd Exp $ */ 238451Smsmith 338451Smsmith/*- 438451Smsmith * Copyright (c) 1993 538451Smsmith * The Regents of the University of California. All rights reserved. 638451Smsmith * 738451Smsmith * This code is derived from software contributed to Berkeley by 838451Smsmith * The Mach Operating System project at Carnegie-Mellon University. 938451Smsmith * 1038451Smsmith * Redistribution and use in source and binary forms, with or without 1138451Smsmith * modification, are permitted provided that the following conditions 1238451Smsmith * are met: 1338451Smsmith * 1. Redistributions of source code must retain the above copyright 1438451Smsmith * notice, this list of conditions and the following disclaimer. 1538451Smsmith * 2. Redistributions in binary form must reproduce the above copyright 1638451Smsmith * notice, this list of conditions and the following disclaimer in the 1738451Smsmith * documentation and/or other materials provided with the distribution. 1838451Smsmith * 4. Neither the name of the University nor the names of its contributors 1938451Smsmith * may be used to endorse or promote products derived from this software 2038451Smsmith * without specific prior written permission. 2138451Smsmith * 2238451Smsmith * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 2338451Smsmith * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 2438451Smsmith * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 2538451Smsmith * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 2638451Smsmith * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 2738451Smsmith * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 2838451Smsmith * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 2938451Smsmith * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 3038451Smsmith * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 3138451Smsmith * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 3238451Smsmith * SUCH DAMAGE. 3338451Smsmith * 3438451Smsmith * @(#)lseek.c 8.1 (Berkeley) 6/11/93 3538451Smsmith * 3638451Smsmith * 3738451Smsmith * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University 3838451Smsmith * All Rights Reserved. 3938451Smsmith * 4038451Smsmith * Author: Alessandro Forin 4138451Smsmith * 4238451Smsmith * Permission to use, copy, modify and distribute this software and its 4338451Smsmith * documentation is hereby granted, provided that both the copyright 4438451Smsmith * notice and this permission notice appear in all copies of the 4538451Smsmith * software, derivative works or modified versions, and any portions 4638451Smsmith * thereof, and that both notices appear in supporting documentation. 4738451Smsmith * 4838451Smsmith * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 4938451Smsmith * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR 5038451Smsmith * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 5138451Smsmith * 5238451Smsmith * Carnegie Mellon requests users of this software to return to 5338451Smsmith * 5438451Smsmith * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 5538451Smsmith * School of Computer Science 5638451Smsmith * Carnegie Mellon University 5738451Smsmith * Pittsburgh PA 15213-3890 5838451Smsmith * 5938451Smsmith * any improvements or extensions that they make and grant Carnegie the 6038451Smsmith * rights to redistribute these changes. 6138451Smsmith */ 6238451Smsmith 6384221Sdillon#include <sys/cdefs.h> 6484221Sdillon__FBSDID("$FreeBSD: stable/10/lib/libstand/lseek.c 321071 2017-07-17 06:46:57Z delphij $"); 6584221Sdillon 6638451Smsmith#include "stand.h" 6738451Smsmith 6838451Smsmithoff_t 6965470Smsmithlseek(int fd, off_t offset, int where) 7038451Smsmith{ 7182526Sjdp off_t bufpos, filepos, target; 7265470Smsmith struct open_file *f = &files[fd]; 7338451Smsmith 7465470Smsmith if ((unsigned)fd >= SOPEN_MAX || f->f_flags == 0) { 7565470Smsmith errno = EBADF; 7665470Smsmith return (-1); 7765470Smsmith } 7838451Smsmith 7965470Smsmith if (f->f_flags & F_RAW) { 8065470Smsmith /* 8165470Smsmith * On RAW devices, update internal offset. 8265470Smsmith */ 8365470Smsmith switch (where) { 8465470Smsmith case SEEK_SET: 8565470Smsmith f->f_offset = offset; 8665470Smsmith break; 8765470Smsmith case SEEK_CUR: 8865470Smsmith f->f_offset += offset; 8965470Smsmith break; 9065470Smsmith default: 9165470Smsmith errno = EOFFSET; 9265470Smsmith return (-1); 9338451Smsmith } 9465470Smsmith return (f->f_offset); 9565470Smsmith } 9638451Smsmith 9765470Smsmith /* 9882526Sjdp * If there is some unconsumed data in the readahead buffer and it 9982526Sjdp * contains the desired offset, simply adjust the buffer offset and 10082526Sjdp * length. We don't bother with SEEK_END here, since the code to 10182526Sjdp * handle it would fail in the same cases where the non-readahead 10282526Sjdp * code fails (namely, for streams which cannot seek backward and whose 10382526Sjdp * size isn't known in advance). 10482526Sjdp */ 10582526Sjdp if (f->f_ralen != 0 && where != SEEK_END) { 10682526Sjdp if ((filepos = (f->f_ops->fo_seek)(f, (off_t)0, SEEK_CUR)) == -1) 10782526Sjdp return (-1); 10882526Sjdp bufpos = filepos - f->f_ralen; 10982526Sjdp switch (where) { 11082526Sjdp case SEEK_SET: 11182526Sjdp target = offset; 11282526Sjdp break; 11382526Sjdp case SEEK_CUR: 11482526Sjdp target = bufpos + offset; 11582526Sjdp break; 11682526Sjdp default: 11782526Sjdp errno = EINVAL; 11882526Sjdp return (-1); 11982526Sjdp } 12082526Sjdp if (bufpos <= target && target < filepos) { 12182526Sjdp f->f_raoffset += target - bufpos; 12282526Sjdp f->f_ralen -= target - bufpos; 12382526Sjdp return (target); 12482526Sjdp } 12582526Sjdp } 12682526Sjdp 12782526Sjdp /* 12865470Smsmith * If this is a relative seek, we need to correct the offset for 12965470Smsmith * bytes that we have already read but the caller doesn't know 13065470Smsmith * about. 13165470Smsmith */ 13265470Smsmith if (where == SEEK_CUR) 13365470Smsmith offset -= f->f_ralen; 13465470Smsmith 13565470Smsmith /* 13665470Smsmith * Invalidate the readahead buffer. 13765470Smsmith */ 13865470Smsmith f->f_ralen = 0; 13965470Smsmith 14065470Smsmith return (f->f_ops->fo_seek)(f, offset, where); 14138451Smsmith} 142