fwrite.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)fwrite.c	8.1 (Berkeley) 6/4/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/fwrite.c 330897 2018-03-14 03:19:51Z eadler $");
40
41#include "namespace.h"
42#include <errno.h>
43#include <stdint.h>
44#include <stdio.h>
45#include "un-namespace.h"
46#include "local.h"
47#include "fvwrite.h"
48#include "libc_private.h"
49
50/*
51 * Write `count' objects (each size `size') from memory to the given file.
52 * Return the number of whole objects written.
53 */
54size_t
55fwrite(const void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
56{
57	size_t n;
58	struct __suio uio;
59	struct __siov iov;
60
61	/*
62	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
63	 */
64	if ((count == 0) || (size == 0))
65		return (0);
66
67	/*
68	 * Check for integer overflow.  As an optimization, first check that
69	 * at least one of {count, size} is at least 2^16, since if both
70	 * values are less than that, their product can't possibly overflow
71	 * (size_t is always at least 32 bits on FreeBSD).
72	 */
73	if (((count | size) > 0xFFFF) &&
74	    (count > SIZE_MAX / size)) {
75		errno = EINVAL;
76		fp->_flags |= __SERR;
77		return (0);
78	}
79
80	n = count * size;
81
82	iov.iov_base = (void *)buf;
83	uio.uio_resid = iov.iov_len = n;
84	uio.uio_iov = &iov;
85	uio.uio_iovcnt = 1;
86
87	FLOCKFILE_CANCELSAFE(fp);
88	ORIENT(fp, -1);
89	/*
90	 * The usual case is success (__sfvwrite returns 0);
91	 * skip the divide if this happens, since divides are
92	 * generally slow and since this occurs whenever size==0.
93	 */
94	if (__sfvwrite(fp, &uio) != 0)
95	    count = (n - uio.uio_resid) / size;
96	FUNLOCKFILE_CANCELSAFE();
97	return (count);
98}
99