/*      $NetBSD: fdopen.c,v 1.18 2017/11/09 20:30:02 christos 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[] = "@(#)fdopen.c    8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: fdopen.c,v 1.18 2017/11/09 20:30:02 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <limits.h>

#include "reentrant.h"
#include "local.h"

#ifdef __weak_alias
__weak_alias(fdopen,_fdopen)
#endif

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

        _DIAGASSERT(fd != -1);

        /*
         * 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 (fd >= USHRT_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;
        tmp = fdflags & O_ACCMODE;
        if (tmp != O_RDWR && (tmp != (oflags & O_ACCMODE))) {
                errno = EINVAL;
                return NULL;
        }

        if (oflags & O_REGULAR) {
                struct stat st;
                if (fstat(fd, &st) == -1) {
                        return NULL;
                }
                if (!S_ISREG(st.st_mode)) {
                        errno = EFTYPE;
                        return NULL;
                }
        }

        if ((fp = __sfp()) == NULL)
                return NULL;
        fp->_flags = flags;
        /*
         * If opened for appending, but underlying descriptor does not have
         * O_APPEND bit set, assert __SAPP so that __swrite() will lseek to
         * end before each write.
         */
        if ((oflags & O_APPEND) && !(fdflags & 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;
}