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/* $NetBSD: lseek.c,v 1.4 1997/01/22 00:38:10 cgd Exp $ */
/*-
* Copyright (c) 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)lseek.c 8.1 (Berkeley) 6/11/93
*
*
* Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Author: Alessandro Forin
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "stand.h"
off_t
lseek(int fd, off_t offset, int where)
{
off_t bufpos, filepos, target;
struct open_file *f = &files[fd];
if ((unsigned)fd >= SOPEN_MAX || f->f_flags == 0) {
errno = EBADF;
return (-1);
}
if (f->f_flags & F_RAW) {
/*
* On RAW devices, update internal offset.
*/
switch (where) {
case SEEK_SET:
f->f_offset = offset;
break;
case SEEK_CUR:
f->f_offset += offset;
break;
default:
errno = EOFFSET;
return (-1);
}
return (f->f_offset);
}
/*
* If there is some unconsumed data in the readahead buffer and it
* contains the desired offset, simply adjust the buffer offset and
* length. We don't bother with SEEK_END here, since the code to
* handle it would fail in the same cases where the non-readahead
* code fails (namely, for streams which cannot seek backward and whose
* size isn't known in advance).
*/
if (f->f_ralen != 0 && where != SEEK_END) {
if ((filepos = (f->f_ops->fo_seek)(f, (off_t)0, SEEK_CUR)) == -1)
return (-1);
bufpos = filepos - f->f_ralen;
switch (where) {
case SEEK_SET:
target = offset;
break;
case SEEK_CUR:
target = bufpos + offset;
break;
default:
errno = EINVAL;
return (-1);
}
if (bufpos <= target && target < filepos) {
f->f_raoffset += target - bufpos;
f->f_ralen -= target - bufpos;
return (target);
}
}
/*
* If this is a relative seek, we need to correct the offset for
* bytes that we have already read but the caller doesn't know
* about.
*/
if (where == SEEK_CUR)
offset -= f->f_ralen;
/*
* Invalidate the readahead buffer.
*/
f->f_ralen = 0;
return (f->f_ops->fo_seek)(f, offset, where);
}
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