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lseek.c revision 1.3 
      1 /*	$NetBSD: lseek.c,v 1.3 1996/06/21 20:09:03 pk Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * The Mach Operating System project at Carnegie-Mellon University.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  *
     38  *	@(#)lseek.c	8.1 (Berkeley) 6/11/93
     39  *
     40  *
     41  * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
     42  * All Rights Reserved.
     43  *
     44  * Author: Alessandro Forin
     45  *
     46  * Permission to use, copy, modify and distribute this software and its
     47  * documentation is hereby granted, provided that both the copyright
     48  * notice and this permission notice appear in all copies of the
     49  * software, derivative works or modified versions, and any portions
     50  * thereof, and that both notices appear in supporting documentation.
     51  *
     52  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     53  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
     54  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     55  *
     56  * Carnegie Mellon requests users of this software to return to
     57  *
     58  *  Software Distribution Coordinator  or  Software.Distribution (at) CS.CMU.EDU
     59  *  School of Computer Science
     60  *  Carnegie Mellon University
     61  *  Pittsburgh PA 15213-3890
     62  *
     63  * any improvements or extensions that they make and grant Carnegie the
     64  * rights to redistribute these changes.
     65  */
     66 
     67 #include "stand.h"
     68 
     69 off_t
     70 lseek(fd, offset, where)
     71 	int fd;
     72 	off_t offset;
     73 	int where;
     74 {
     75 	register struct open_file *f = &files[fd];
     76 
     77 	if ((unsigned)fd >= SOPEN_MAX || f->f_flags == 0) {
     78 		errno = EBADF;
     79 		return (-1);
     80 	}
     81 
     82 	if (f->f_flags & F_RAW) {
     83 		/*
     84 		 * On RAW devices, update internal offset.
     85 		 */
     86 		switch (where) {
     87 		case SEEK_SET:
     88 			f->f_offset = offset;
     89 			break;
     90 		case SEEK_CUR:
     91 			f->f_offset += offset;
     92 			break;
     93 		case SEEK_END:
     94 		default:
     95 			errno = EOFFSET;
     96 			return (-1);
     97 		}
     98 		return (f->f_offset);
     99 	}
    100 
    101 	return (f->f_ops->seek)(f, offset, where);
    102 }
    103