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
42size_t
43fread(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	while (resid > (r = fp->_r)) {
72		(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
73		fp->_p += r;
74		/* fp->_r = 0 ... done in __srefill */
75		p += r;
76		resid -= r;
77		if (__srefill(fp)) {
78			/* no more input: return partial result */
79			FUNLOCKFILE(fp);
80			return ((total - resid) / size);
81		}
82	}
83	(void)memcpy((void *)p, (void *)fp->_p, resid);
84	fp->_r -= resid;
85	fp->_p += resid;
86	FUNLOCKFILE(fp);
87	return (count);
88}
89