1 /* $OpenBSD: fread.c,v 1.12 2014/05/01 16:40:36 deraadt 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 <stdint.h>
37 #include <errno.h>
38 #include "local.h"
39
40 #define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
41
42 size_t
fread(void * buf,size_t size,size_t count,FILE * fp)43 fread(void *buf, size_t size, size_t count, FILE *fp)
44 {
45 size_t resid;
46 char *p;
47 int r;
48 size_t total;
49
50 /*
51 * Extension: Catch integer overflow
52 */
53 if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) &&
54 size > 0 && SIZE_MAX / size < count) {
55 errno = EOVERFLOW;
56 fp->_flags |= __SERR;
57 return (0);
58 }
59
60 /*
61 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
62 */
63 if ((resid = count * size) == 0)
64 return (0);
65 FLOCKFILE(fp);
66 _SET_ORIENTATION(fp, -1);
67 if (fp->_r < 0)
68 fp->_r = 0;
69 total = resid;
70 p = buf;
71
72 // BEGIN android-added
73 // Avoid pathological behavior on unbuffered files. OpenBSD
74 // will loop reading one byte then memcpying one byte!
75 if ((fp->_flags & __SNBF) != 0) {
76 // We know if we're unbuffered that our buffer is empty, so
77 // we can just read directly.
78 while (resid > 0 && (r = (*fp->_read)(fp->_cookie, p, resid)) > 0) {
79 p += r;
80 resid -= r;
81 }
82 FUNLOCKFILE(fp);
83 return ((total - resid) / size);
84 }
85 // END android-added
86
87 while (resid > (size_t)(r = fp->_r)) {
88 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
89 fp->_p += r;
90 /* fp->_r = 0 ... done in __srefill */
91 p += r;
92 resid -= r;
93 if (__srefill(fp)) {
94 /* no more input: return partial result */
95 FUNLOCKFILE(fp);
96 return ((total - resid) / size);
97 }
98 }
99 (void)memcpy((void *)p, (void *)fp->_p, resid);
100 fp->_r -= resid;
101 fp->_p += resid;
102 FUNLOCKFILE(fp);
103 return (count);
104 }
105