xref: /netbsd-src/lib/libc/stdio/fopen.c (revision 1bcc014257d0e5cf59594dba464f13ec8bd0845c)

/*	$NetBSD: fopen.c,v 1.19 2018/01/17 01:24:30 kamil 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[] = "@(#)fopen.c	8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: fopen.c,v 1.19 2018/01/17 01:24:30 kamil Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include "reentrant.h"
#include "local.h"

FILE *
fopen(const char *file, const char *mode)
{
	FILE *fp;
	int f;
	int flags, oflags;

	_DIAGASSERT(file != NULL);
	if ((flags = __sflags(mode, &oflags)) == 0)
		return NULL;
	if ((fp = __sfp()) == NULL)
		return NULL;
	if ((f = open(file, oflags, DEFFILEMODE)) < 0)
		goto release;
	/*
	 * File descriptors are a full int, but _file is only a short.
	 * If we get a valid file descriptor that is greater or equal to
	 * USHRT_MAX, then the fd will get sign-extended into an
	 * invalid file descriptor.  Handle this case by failing the
	 * open. (We treat the short as unsigned, and special-case -1).
	 */
	if (f >= USHRT_MAX) {
		(void)close(f);
		errno = EMFILE;
		goto release;
	}

	fp->_file = f;
	fp->_flags = flags;
	fp->_cookie = fp;
	fp->_read = __sread;
	fp->_write = __swrite;
	fp->_seek = __sseek;
	fp->_close = __sclose;

	/*
	 * When opening in append mode, even though we use O_APPEND,
	 * we need to seek to the end so that ftell() gets the right
	 * answer.  If the user then alters the seek pointer, or
	 * the file extends, this will fail, but there is not much
	 * we can do about this.  (We could set __SAPP and check in
	 * fseek and ftell.)
	 */
	if (oflags & O_APPEND)
		(void) __sseek((void *)fp, (off_t)0, SEEK_END);
	return fp;
release:
	fp->_flags = 0;			/* release */
	return NULL;
}