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      1 /*	$NetBSD: fdopen.c,v 1.18 2017/11/09 20:30:02 christos Exp $	*/
      2 
      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 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)fdopen.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: fdopen.c,v 1.18 2017/11/09 20:30:02 christos Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include "namespace.h"
     45 
     46 #include <sys/types.h>
     47 #include <sys/stat.h>
     48 
     49 #include <assert.h>
     50 #include <errno.h>
     51 #include <fcntl.h>
     52 #include <unistd.h>
     53 #include <stdio.h>
     54 #include <limits.h>
     55 
     56 #include "reentrant.h"
     57 #include "local.h"
     58 
     59 #ifdef __weak_alias
     60 __weak_alias(fdopen,_fdopen)
     61 #endif
     62 
     63 FILE *
     64 fdopen(int fd, const char *mode)
     65 {
     66 	FILE *fp;
     67 	int flags, oflags, fdflags, tmp;
     68 
     69 	_DIAGASSERT(fd != -1);
     70 
     71 	/*
     72 	 * File descriptors are a full int, but _file is only a short.
     73 	 * If we get a valid file descriptor that is greater or equal to
     74 	 * USHRT_MAX, then the fd will get sign-extended into an
     75 	 * invalid file descriptor.  Handle this case by failing the
     76 	 * open. (We treat the short as unsigned, and special-case -1).
     77 	 */
     78 	if (fd >= USHRT_MAX) {
     79 		errno = EMFILE;
     80 		return NULL;
     81 	}
     82 
     83 	if ((flags = __sflags(mode, &oflags)) == 0)
     84 		return NULL;
     85 
     86 	/* Make sure the mode the user wants is a subset of the actual mode. */
     87 	if ((fdflags = fcntl(fd, F_GETFL, 0)) < 0)
     88 		return NULL;
     89 	tmp = fdflags & O_ACCMODE;
     90 	if (tmp != O_RDWR && (tmp != (oflags & O_ACCMODE))) {
     91 		errno = EINVAL;
     92 		return NULL;
     93 	}
     94 
     95 	if (oflags & O_REGULAR) {
     96 		struct stat st;
     97 		if (fstat(fd, &st) == -1) {
     98 			return NULL;
     99 		}
    100 		if (!S_ISREG(st.st_mode)) {
    101 			errno = EFTYPE;
    102 			return NULL;
    103 		}
    104 	}
    105 
    106 	if ((fp = __sfp()) == NULL)
    107 		return NULL;
    108 	fp->_flags = flags;
    109 	/*
    110 	 * If opened for appending, but underlying descriptor does not have
    111 	 * O_APPEND bit set, assert __SAPP so that __swrite() will lseek to
    112 	 * end before each write.
    113 	 */
    114 	if ((oflags & O_APPEND) && !(fdflags & O_APPEND))
    115 		fp->_flags |= __SAPP;
    116 	fp->_file = fd;
    117 	fp->_cookie = fp;
    118 	fp->_read = __sread;
    119 	fp->_write = __swrite;
    120 	fp->_seek = __sseek;
    121 	fp->_close = __sclose;
    122 	return fp;
    123 }
    124