1*479ab7f0SSascha Wildner /* $FreeBSD: src/lib/libstand/read.c,v 1.1.1.1.6.1 2000/09/10 01:32:06 ps Exp $ */
2*479ab7f0SSascha Wildner /* $DragonFly: src/lib/libstand/read.c,v 1.2 2003/06/17 04:26:51 dillon Exp $ */
3*479ab7f0SSascha Wildner /* $NetBSD: read.c,v 1.8 1997/01/22 00:38:12 cgd Exp $ */
4*479ab7f0SSascha Wildner
5*479ab7f0SSascha Wildner /*-
6*479ab7f0SSascha Wildner * Copyright (c) 1993
7*479ab7f0SSascha Wildner * The Regents of the University of California. All rights reserved.
8*479ab7f0SSascha Wildner *
9*479ab7f0SSascha Wildner * This code is derived from software contributed to Berkeley by
10*479ab7f0SSascha Wildner * The Mach Operating System project at Carnegie-Mellon University.
11*479ab7f0SSascha Wildner *
12*479ab7f0SSascha Wildner * Redistribution and use in source and binary forms, with or without
13*479ab7f0SSascha Wildner * modification, are permitted provided that the following conditions
14*479ab7f0SSascha Wildner * are met:
15*479ab7f0SSascha Wildner * 1. Redistributions of source code must retain the above copyright
16*479ab7f0SSascha Wildner * notice, this list of conditions and the following disclaimer.
17*479ab7f0SSascha Wildner * 2. Redistributions in binary form must reproduce the above copyright
18*479ab7f0SSascha Wildner * notice, this list of conditions and the following disclaimer in the
19*479ab7f0SSascha Wildner * documentation and/or other materials provided with the distribution.
20*479ab7f0SSascha Wildner * 3. Neither the name of the University nor the names of its contributors
21*479ab7f0SSascha Wildner * may be used to endorse or promote products derived from this software
22*479ab7f0SSascha Wildner * without specific prior written permission.
23*479ab7f0SSascha Wildner *
24*479ab7f0SSascha Wildner * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25*479ab7f0SSascha Wildner * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26*479ab7f0SSascha Wildner * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27*479ab7f0SSascha Wildner * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28*479ab7f0SSascha Wildner * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29*479ab7f0SSascha Wildner * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30*479ab7f0SSascha Wildner * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31*479ab7f0SSascha Wildner * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32*479ab7f0SSascha Wildner * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33*479ab7f0SSascha Wildner * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34*479ab7f0SSascha Wildner * SUCH DAMAGE.
35*479ab7f0SSascha Wildner *
36*479ab7f0SSascha Wildner * @(#)read.c 8.1 (Berkeley) 6/11/93
37*479ab7f0SSascha Wildner *
38*479ab7f0SSascha Wildner *
39*479ab7f0SSascha Wildner * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
40*479ab7f0SSascha Wildner * All Rights Reserved.
41*479ab7f0SSascha Wildner *
42*479ab7f0SSascha Wildner * Author: Alessandro Forin
43*479ab7f0SSascha Wildner *
44*479ab7f0SSascha Wildner * Permission to use, copy, modify and distribute this software and its
45*479ab7f0SSascha Wildner * documentation is hereby granted, provided that both the copyright
46*479ab7f0SSascha Wildner * notice and this permission notice appear in all copies of the
47*479ab7f0SSascha Wildner * software, derivative works or modified versions, and any portions
48*479ab7f0SSascha Wildner * thereof, and that both notices appear in supporting documentation.
49*479ab7f0SSascha Wildner *
50*479ab7f0SSascha Wildner * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
51*479ab7f0SSascha Wildner * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
52*479ab7f0SSascha Wildner * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
53*479ab7f0SSascha Wildner *
54*479ab7f0SSascha Wildner * Carnegie Mellon requests users of this software to return to
55*479ab7f0SSascha Wildner *
56*479ab7f0SSascha Wildner * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
57*479ab7f0SSascha Wildner * School of Computer Science
58*479ab7f0SSascha Wildner * Carnegie Mellon University
59*479ab7f0SSascha Wildner * Pittsburgh PA 15213-3890
60*479ab7f0SSascha Wildner *
61*479ab7f0SSascha Wildner * any improvements or extensions that they make and grant Carnegie the
62*479ab7f0SSascha Wildner * rights to redistribute these changes.
63*479ab7f0SSascha Wildner */
64*479ab7f0SSascha Wildner
65*479ab7f0SSascha Wildner #include <sys/param.h>
66*479ab7f0SSascha Wildner #include "stand.h"
67*479ab7f0SSascha Wildner
68*479ab7f0SSascha Wildner int no_io_error;
69*479ab7f0SSascha Wildner
70*479ab7f0SSascha Wildner ssize_t
read(int fd,void * dest,size_t bcount)71*479ab7f0SSascha Wildner read(int fd, void *dest, size_t bcount)
72*479ab7f0SSascha Wildner {
73*479ab7f0SSascha Wildner struct open_file *f = &files[fd];
74*479ab7f0SSascha Wildner size_t resid;
75*479ab7f0SSascha Wildner
76*479ab7f0SSascha Wildner if ((unsigned)fd >= SOPEN_MAX || !(f->f_flags & F_READ)) {
77*479ab7f0SSascha Wildner errno = EBADF;
78*479ab7f0SSascha Wildner return (-1);
79*479ab7f0SSascha Wildner }
80*479ab7f0SSascha Wildner if (f->f_flags & F_RAW) {
81*479ab7f0SSascha Wildner twiddle();
82*479ab7f0SSascha Wildner errno = (f->f_dev->dv_strategy)(f->f_devdata, F_READ,
83*479ab7f0SSascha Wildner btodb(f->f_offset), bcount, dest, &resid);
84*479ab7f0SSascha Wildner if (errno)
85*479ab7f0SSascha Wildner return (-1);
86*479ab7f0SSascha Wildner f->f_offset += resid;
87*479ab7f0SSascha Wildner return (resid);
88*479ab7f0SSascha Wildner }
89*479ab7f0SSascha Wildner
90*479ab7f0SSascha Wildner /*
91*479ab7f0SSascha Wildner * Optimise reads from regular files using a readahead buffer.
92*479ab7f0SSascha Wildner * If the request can't be satisfied from the current buffer contents,
93*479ab7f0SSascha Wildner * check to see if it should be bypassed, or refill the buffer and complete
94*479ab7f0SSascha Wildner * the request.
95*479ab7f0SSascha Wildner */
96*479ab7f0SSascha Wildner resid = bcount;
97*479ab7f0SSascha Wildner for (;;) {
98*479ab7f0SSascha Wildner size_t ccount, cresid;
99*479ab7f0SSascha Wildner /* how much can we supply? */
100*479ab7f0SSascha Wildner ccount = imin(f->f_ralen, resid);
101*479ab7f0SSascha Wildner if (ccount > 0) {
102*479ab7f0SSascha Wildner bcopy(f->f_rabuf + f->f_raoffset, dest, ccount);
103*479ab7f0SSascha Wildner f->f_raoffset += ccount;
104*479ab7f0SSascha Wildner f->f_ralen -= ccount;
105*479ab7f0SSascha Wildner resid -= ccount;
106*479ab7f0SSascha Wildner if (resid == 0)
107*479ab7f0SSascha Wildner return(bcount);
108*479ab7f0SSascha Wildner dest += ccount;
109*479ab7f0SSascha Wildner }
110*479ab7f0SSascha Wildner
111*479ab7f0SSascha Wildner /* will filling the readahead buffer again not help? */
112*479ab7f0SSascha Wildner if (resid >= SOPEN_RASIZE) {
113*479ab7f0SSascha Wildner /* bypass the rest of the request and leave the buffer empty */
114*479ab7f0SSascha Wildner if ((errno = (f->f_ops->fo_read)(f, dest, resid, &cresid)))
115*479ab7f0SSascha Wildner return(bcount - resid);
116*479ab7f0SSascha Wildner return(bcount - cresid);
117*479ab7f0SSascha Wildner }
118*479ab7f0SSascha Wildner
119*479ab7f0SSascha Wildner /* fetch more data */
120*479ab7f0SSascha Wildner if ((errno = (f->f_ops->fo_read)(f, f->f_rabuf, SOPEN_RASIZE, &cresid)))
121*479ab7f0SSascha Wildner return(bcount - resid); /* behave like fread() */
122*479ab7f0SSascha Wildner f->f_raoffset = 0;
123*479ab7f0SSascha Wildner f->f_ralen = SOPEN_RASIZE - cresid;
124*479ab7f0SSascha Wildner /* no more data, return what we had */
125*479ab7f0SSascha Wildner if (f->f_ralen == 0)
126*479ab7f0SSascha Wildner return(bcount - resid);
127*479ab7f0SSascha Wildner }
128*479ab7f0SSascha Wildner }
129