Use CSTD and remove local CSTD settings which are no longer needed.
[dragonfly.git] / lib / libstand / read.c
CommitLineData
984263bc 1/* $FreeBSD: src/lib/libstand/read.c,v 1.1.1.1.6.1 2000/09/10 01:32:06 ps Exp $ */
1de703da 2/* $DragonFly: src/lib/libstand/read.c,v 1.2 2003/06/17 04:26:51 dillon Exp $ */
984263bc
MD
3/* $NetBSD: read.c,v 1.8 1997/01/22 00:38:12 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 * @(#)read.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 <sys/param.h>
70#include "stand.h"
71
72ssize_t
73read(int fd, void *dest, size_t bcount)
74{
75 struct open_file *f = &files[fd];
76 size_t resid;
77
78 if ((unsigned)fd >= SOPEN_MAX || !(f->f_flags & F_READ)) {
79 errno = EBADF;
80 return (-1);
81 }
82 if (f->f_flags & F_RAW) {
83 twiddle();
84 errno = (f->f_dev->dv_strategy)(f->f_devdata, F_READ,
85 btodb(f->f_offset), bcount, dest, &resid);
86 if (errno)
87 return (-1);
88 f->f_offset += resid;
89 return (resid);
90 }
91
92 /*
93 * Optimise reads from regular files using a readahead buffer.
94 * If the request can't be satisfied from the current buffer contents,
95 * check to see if it should be bypassed, or refill the buffer and complete
96 * the request.
97 */
98 resid = bcount;
99 for (;;) {
100 size_t ccount, cresid;
101 /* how much can we supply? */
102 ccount = imin(f->f_ralen, resid);
103 if (ccount > 0) {
104 bcopy(f->f_rabuf + f->f_raoffset, dest, ccount);
105 f->f_raoffset += ccount;
106 f->f_ralen -= ccount;
107 resid -= ccount;
108 if (resid == 0)
109 return(bcount);
110 dest += ccount;
111 }
112
113 /* will filling the readahead buffer again not help? */
114 if (resid >= SOPEN_RASIZE) {
115 /* bypass the rest of the request and leave the buffer empty */
116 if ((errno = (f->f_ops->fo_read)(f, dest, resid, &cresid)))
117 return(bcount - resid);
118 return(bcount - cresid);
119 }
120
121 /* fetch more data */
122 if ((errno = (f->f_ops->fo_read)(f, f->f_rabuf, SOPEN_RASIZE, &cresid)))
123 return(bcount - resid); /* behave like fread() */
124 f->f_raoffset = 0;
125 f->f_ralen = SOPEN_RASIZE - cresid;
126 /* no more data, return what we had */
127 if (f->f_ralen == 0)
128 return(bcount - resid);
129 }
130}