fdopen.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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 "namespace.h"
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include "un-namespace.h"
#include "local.h"

FILE *
fdopen(int fd, const char *mode)
{
	FILE *fp;
	int flags, oflags, fdflags, rc, tmp;

	/*
	 * File descriptors are a full int, but _file is only a short.
	 * If we get a valid file descriptor that is greater than
	 * SHRT_MAX, then the fd will get sign-extended into an
	 * invalid file descriptor.  Handle this case by failing the
	 * open.
	 */
	if (fd > SHRT_MAX) {
		errno = EMFILE;
		return (NULL);
	}

	if ((flags = __sflags(mode, &oflags)) == 0)
		return (NULL);

	/* Make sure the mode the user wants is a subset of the actual mode. */
	if ((fdflags = _fcntl(fd, F_GETFL, 0)) < 0)
		return (NULL);
	/* Work around incorrect O_ACCMODE. */
	tmp = fdflags & (O_ACCMODE | O_EXEC);
	if (tmp != O_RDWR && (tmp != (oflags & O_ACCMODE))) {
		errno = EINVAL;
		return (NULL);
	}

	if ((fp = __sfp()) == NULL)
		return (NULL);

	if ((oflags & O_CLOEXEC) != 0) {
		tmp = _fcntl(fd, F_GETFD, 0);
		if (tmp == -1) {
			fp->_flags = 0;
			return (NULL);
		}
		if ((tmp & FD_CLOEXEC) == 0) {
			rc = _fcntl(fd, F_SETFD, tmp | FD_CLOEXEC);
			if (rc == -1) {
				fp->_flags = 0;
				return (NULL);
			}
		}
	}

	fp->_flags = flags;
	/*
	 * If opened for appending, but underlying descriptor does not have
	 * O_APPEND bit set, assert __SAPP so that __swrite() caller
	 * will _sseek() to the end before write.
	 */
	if (fdflags & O_APPEND)
		fp->_flags2 |= __S2OAP;
	else if (oflags & O_APPEND)
		fp->_flags |= __SAPP;
	fp->_file = fd;
	fp->_cookie = fp;
	fp->_read = __sread;
	fp->_write = __swrite;
	fp->_seek = __sseek;
	fp->_close = __sclose;
	return (fp);
}