1 /* $OpenBSD: fread.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <stdio.h>
35 #include <string.h>
36 #include <errno.h>
37 #include "local.h"
38
39 static int
lflush(FILE * fp)40 lflush(FILE *fp)
41 {
42
43 if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
44 return (__sflush(fp));
45 return (0);
46 }
47
48 size_t
fread(void * buf,size_t size,size_t count,FILE * fp)49 fread(void *buf, size_t size, size_t count, FILE *fp)
50 {
51 size_t resid;
52 char *p;
53 int r;
54 size_t total;
55
56 /*
57 * The ANSI standard requires a return value of 0 for a count
58 * or a size of 0. Peculiarily, it imposes no such requirements
59 * on fwrite; it only requires fread to be broken.
60 */
61 if ((resid = count * size) == 0)
62 return (0);
63 if (fp->_r < 0)
64 fp->_r = 0;
65 total = resid;
66 p = buf;
67
68 #if 1 /* BIONIC: optimize unbuffered reads */
69 if (fp->_flags & __SNBF && fp->_ur == 0)
70 {
71 /* the following comes mainly from __srefill(), with slight
72 * modifications
73 */
74
75 /* make sure stdio is set up */
76 if (!__sdidinit)
77 __sinit();
78
79 fp->_r = 0; /* largely a convenience for callers */
80
81 /* SysV does not make this test; take it out for compatibility */
82 if (fp->_flags & __SEOF)
83 return (EOF);
84
85 /* if not already reading, have to be reading and writing */
86 if ((fp->_flags & __SRD) == 0) {
87 if ((fp->_flags & __SRW) == 0) {
88 errno = EBADF;
89 fp->_flags |= __SERR;
90 return (EOF);
91 }
92 /* switch to reading */
93 if (fp->_flags & __SWR) {
94 if (__sflush(fp))
95 return (EOF);
96 fp->_flags &= ~__SWR;
97 fp->_w = 0;
98 fp->_lbfsize = 0;
99 }
100 fp->_flags |= __SRD;
101 } else {
102 /*
103 * We were reading. If there is an ungetc buffer,
104 * we must have been reading from that. Drop it,
105 * restoring the previous buffer (if any). If there
106 * is anything in that buffer, return.
107 */
108 if (HASUB(fp)) {
109 FREEUB(fp);
110 }
111 }
112
113 /*
114 * Before reading from a line buffered or unbuffered file,
115 * flush all line buffered output files, per the ANSI C
116 * standard.
117 */
118
119 if (fp->_flags & (__SLBF|__SNBF))
120 (void) _fwalk(lflush);
121
122 while (resid > 0) {
123 int len = (*fp->_read)(fp->_cookie, p, resid );
124 fp->_flags &= ~__SMOD;
125 if (len <= 0) {
126 if (len == 0)
127 fp->_flags |= __SEOF;
128 else {
129 fp->_flags |= __SERR;
130 }
131 return ((total - resid) / size);
132 }
133 p += len;
134 resid -= len;
135 }
136 return (count);
137 }
138 else
139 #endif
140 {
141 while (resid > (size_t)(r = fp->_r)) {
142 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
143 fp->_p += r;
144 /* fp->_r = 0 ... done in __srefill */
145 p += r;
146 resid -= r;
147 if (__srefill(fp)) {
148 /* no more input: return partial result */
149 return ((total - resid) / size);
150 }
151 }
152 }
153
154 (void)memcpy((void *)p, (void *)fp->_p, resid);
155 fp->_r -= resid;
156 fp->_p += resid;
157 return (count);
158 }
159