1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/10/lib/libc/stdio/fread.c 321074 2017-07-17 14:09:34Z kib $");
38
39#include "namespace.h"
40#include <errno.h>
41#include <stdint.h>
42#include <stdio.h>
43#include <string.h>
44#include "un-namespace.h"
45#include "local.h"
46#include "libc_private.h"
47
48/*
49 * MT-safe version
50 */
51
52size_t
53fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
54{
55	size_t ret;
56
57	FLOCKFILE_CANCELSAFE(fp);
58	ret = __fread(buf, size, count, fp);
59	FUNLOCKFILE_CANCELSAFE();
60	return (ret);
61}
62
63size_t
64__fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
65{
66	size_t resid;
67	char *p;
68	int r;
69	size_t total;
70
71	/*
72	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
73	 */
74	if ((count == 0) || (size == 0))
75		return (0);
76
77	/*
78	 * Check for integer overflow.  As an optimization, first check that
79	 * at least one of {count, size} is at least 2^16, since if both
80	 * values are less than that, their product can't possible overflow
81	 * (size_t is always at least 32 bits on FreeBSD).
82	 */
83	if (((count | size) > 0xFFFF) &&
84	    (count > SIZE_MAX / size)) {
85		errno = EINVAL;
86		fp->_flags |= __SERR;
87		return (0);
88	}
89
90	/*
91	 * Compute the (now required to not overflow) number of bytes to
92	 * read and actually do the work.
93	 */
94	resid = count * size;
95	ORIENT(fp, -1);
96	if (fp->_r < 0)
97		fp->_r = 0;
98	total = resid;
99	p = buf;
100	while (resid > (r = fp->_r)) {
101		(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
102		fp->_p += r;
103		/* fp->_r = 0 ... done in __srefill */
104		p += r;
105		resid -= r;
106		if (__srefill(fp)) {
107			/* no more input: return partial result */
108			return ((total - resid) / size);
109		}
110	}
111	(void)memcpy((void *)p, (void *)fp->_p, resid);
112	fp->_r -= resid;
113	fp->_p += resid;
114	return (count);
115}
116