diff options
Diffstat (limited to 'lib/libstand/lseek.c')
| -rw-r--r-- | lib/libstand/lseek.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/lib/libstand/lseek.c b/lib/libstand/lseek.c new file mode 100644 index 0000000..6880ef9 --- /dev/null +++ b/lib/libstand/lseek.c @@ -0,0 +1,146 @@ +/* $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 <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; + case SEEK_END: + 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); +} |
