HardenedBSD/lib/libstand/lseek.c
Mike Smith ba20acfdb2 Implement readahead buffering for non-raw files. This drastically improves
the efficiency of byte-by-byte read operations on filesystems not already
supported by the block cache (especially NFS).

This should be a welcome change for users booting via PXE, as the loader
now reads its startup files almost instantly, instead of taking tens of
seconds.
2000-09-05 09:52:50 +00:00

114 lines
3.9 KiB
C

/* $FreeBSD$ */
/* $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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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 "stand.h"
off_t
lseek(int fd, off_t offset, int where)
{
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;
case SEEK_END:
default:
errno = EOFFSET;
return (-1);
}
return (f->f_offset);
}
/*
* 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);
}