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fopen.c revision 1.19 
      1 /*	$NetBSD: fopen.c,v 1.19 2018/01/17 01:24:30 kamil 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[] = "@(#)fopen.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: fopen.c,v 1.19 2018/01/17 01:24:30 kamil Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <sys/types.h>
     45 #include <sys/stat.h>
     46 #include <assert.h>
     47 #include <fcntl.h>
     48 #include <unistd.h>
     49 #include <stdio.h>
     50 #include <errno.h>
     51 #include <limits.h>
     52 #include "reentrant.h"
     53 #include "local.h"
     54 
     55 FILE *
     56 fopen(const char *file, const char *mode)
     57 {
     58 	FILE *fp;
     59 	int f;
     60 	int flags, oflags;
     61 
     62 	_DIAGASSERT(file != NULL);
     63 	if ((flags = __sflags(mode, &oflags)) == 0)
     64 		return NULL;
     65 	if ((fp = __sfp()) == NULL)
     66 		return NULL;
     67 	if ((f = open(file, oflags, DEFFILEMODE)) < 0)
     68 		goto release;
     69 	/*
     70 	 * File descriptors are a full int, but _file is only a short.
     71 	 * If we get a valid file descriptor that is greater or equal to
     72 	 * USHRT_MAX, then the fd will get sign-extended into an
     73 	 * invalid file descriptor.  Handle this case by failing the
     74 	 * open. (We treat the short as unsigned, and special-case -1).
     75 	 */
     76 	if (f >= USHRT_MAX) {
     77 		(void)close(f);
     78 		errno = EMFILE;
     79 		goto release;
     80 	}
     81 
     82 	fp->_file = f;
     83 	fp->_flags = flags;
     84 	fp->_cookie = fp;
     85 	fp->_read = __sread;
     86 	fp->_write = __swrite;
     87 	fp->_seek = __sseek;
     88 	fp->_close = __sclose;
     89 
     90 	/*
     91 	 * When opening in append mode, even though we use O_APPEND,
     92 	 * we need to seek to the end so that ftell() gets the right
     93 	 * answer.  If the user then alters the seek pointer, or
     94 	 * the file extends, this will fail, but there is not much
     95 	 * we can do about this.  (We could set __SAPP and check in
     96 	 * fseek and ftell.)
     97 	 */
     98 	if (oflags & O_APPEND)
     99 		(void) __sseek((void *)fp, (off_t)0, SEEK_END);
    100 	return fp;
    101 release:
    102 	fp->_flags = 0;			/* release */
    103 	return NULL;
    104 }
    105