xref: /src/lib/libc/stdio/fwrite.c

/*	$NetBSD: fwrite.c,v 1.19 2021/02/01 17:50:53 jdolecek Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)fwrite.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: fwrite.c,v 1.19 2021/02/01 17:50:53 jdolecek Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include "reentrant.h"
#include "local.h"
#include "fvwrite.h"

#define MUL_NO_OVERFLOW	(1UL << (sizeof(size_t) * 4))

/*
 * Write `count' objects (each size `size') from memory to the given file.
 * Return the number of whole objects written.
 */
size_t
fwrite(const void *buf, size_t size, size_t count, FILE *fp)
{
	size_t n;
	struct __suio uio;
	struct __siov iov;

	/*
	 * Extension:  Catch integer overflow
	 */
	if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) &&
	    size > 0 && count > SIZE_MAX / size) {
		errno = EOVERFLOW;
		fp->_flags |= __SERR;
		return (0);
	}

	/*
	 * SUSv2 requires a return value of 0 for a count or a size of 0.
	 */
	if ((n = count * size) == 0)
		return 0;

	iov.iov_base = __UNCONST(buf);
	uio.uio_resid = iov.iov_len = n;
	uio.uio_iov = &iov;
	uio.uio_iovcnt = 1;

	/*
	 * The usual case is success (__sfvwrite returns 0);
	 * skip the divide if this happens, since divides are
	 * generally slow and since this occurs whenever size==0.
	 */
	FLOCKFILE(fp);
	if (__sfvwrite(fp, &uio) != 0)
		count = ((n - uio.uio_resid) / size);
	FUNLOCKFILE(fp);
	return count;
}