Use CSTD and remove local CSTD settings which are no longer needed.
[dragonfly.git] / lib / libstand / lseek.c
CommitLineData
984263bc 1/* $FreeBSD: src/lib/libstand/lseek.c,v 1.1.1.1.6.2 2001/08/30 03:14:16 jdp Exp $ */
1de703da 2/* $DragonFly: src/lib/libstand/lseek.c,v 1.2 2003/06/17 04:26:51 dillon Exp $ */
984263bc
MD
3/* $NetBSD: lseek.c,v 1.4 1997/01/22 00:38:10 cgd Exp $ */
4
5/*-
6 * Copyright (c) 1993
7 * The Regents of the University of California. All rights reserved.
8 *
9 * This code is derived from software contributed to Berkeley by
10 * The Mach Operating System project at Carnegie-Mellon University.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * @(#)lseek.c 8.1 (Berkeley) 6/11/93
41 *
42 *
43 * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
44 * All Rights Reserved.
45 *
46 * Author: Alessandro Forin
47 *
48 * Permission to use, copy, modify and distribute this software and its
49 * documentation is hereby granted, provided that both the copyright
50 * notice and this permission notice appear in all copies of the
51 * software, derivative works or modified versions, and any portions
52 * thereof, and that both notices appear in supporting documentation.
53 *
54 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
55 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
56 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
57 *
58 * Carnegie Mellon requests users of this software to return to
59 *
60 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
61 * School of Computer Science
62 * Carnegie Mellon University
63 * Pittsburgh PA 15213-3890
64 *
65 * any improvements or extensions that they make and grant Carnegie the
66 * rights to redistribute these changes.
67 */
68
69#include "stand.h"
70
71off_t
72lseek(int fd, off_t offset, int where)
73{
74 off_t bufpos, filepos, target;
75 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 /*
102 * If there is some unconsumed data in the readahead buffer and it
103 * contains the desired offset, simply adjust the buffer offset and
104 * length. We don't bother with SEEK_END here, since the code to
105 * handle it would fail in the same cases where the non-readahead
106 * code fails (namely, for streams which cannot seek backward and whose
107 * size isn't known in advance).
108 */
109 if (f->f_ralen != 0 && where != SEEK_END) {
110 if ((filepos = (f->f_ops->fo_seek)(f, (off_t)0, SEEK_CUR)) == -1)
111 return (-1);
112 bufpos = filepos - f->f_ralen;
113 switch (where) {
114 case SEEK_SET:
115 target = offset;
116 break;
117 case SEEK_CUR:
118 target = bufpos + offset;
119 break;
120 default:
121 errno = EINVAL;
122 return (-1);
123 }
124 if (bufpos <= target && target < filepos) {
125 f->f_raoffset += target - bufpos;
126 f->f_ralen -= target - bufpos;
127 return (target);
128 }
129 }
130
131 /*
132 * If this is a relative seek, we need to correct the offset for
133 * bytes that we have already read but the caller doesn't know
134 * about.
135 */
136 if (where == SEEK_CUR)
137 offset -= f->f_ralen;
138
139 /*
140 * Invalidate the readahead buffer.
141 */
142 f->f_ralen = 0;
143
144 return (f->f_ops->fo_seek)(f, offset, where);
145}