1/*	$NetBSD: freopen.c,v 1.16 2010/01/11 20:39:29 joerg 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
38static char sccsid[] = "@(#)freopen.c	8.1 (Berkeley) 6/4/93";
39#else
40__RCSID("$NetBSD: freopen.c,v 1.16 2010/01/11 20:39:29 joerg Exp $");
41#endif
42#endif /* LIBC_SCCS and not lint */
43
44#include <sys/types.h>
45#include <sys/stat.h>
46
47#include <assert.h>
48#include <errno.h>
49#include <fcntl.h>
50#include <unistd.h>
51#include <stdio.h>
52#include <stdlib.h>
53#include <wchar.h>
54#include <limits.h>
55#include "reentrant.h"
56#include "local.h"
57
58/*
59 * Re-direct an existing, open (probably) file to some other file.
60 * ANSI is written such that the original file gets closed if at
61 * all possible, no matter what.
62 */
63FILE *
64freopen(file, mode, fp)
65	const char *file, *mode;
66	FILE *fp;
67{
68	int f;
69	int flags, isopen, oflags, sverrno, wantfd;
70
71	_DIAGASSERT(file != NULL);
72	_DIAGASSERT(mode != NULL);
73	_DIAGASSERT(fp != NULL);
74
75	if ((flags = __sflags(mode, &oflags)) == 0) {
76		(void) fclose(fp);
77		return (NULL);
78	}
79
80	if (!__sdidinit)
81		__sinit();
82
83	/*
84	 * There are actually programs that depend on being able to "freopen"
85	 * descriptors that weren't originally open.  Keep this from breaking.
86	 * Remember whether the stream was open to begin with, and which file
87	 * descriptor (if any) was associated with it.  If it was attached to
88	 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
89	 * should work.  This is unnecessary if it was not a Unix file.
90	 */
91	if (fp->_flags == 0) {
92		fp->_flags = __SEOF;	/* hold on to it */
93		isopen = 0;
94		wantfd = -1;
95	} else {
96		/* flush the stream; ANSI doesn't require this. */
97		if (fp->_flags & __SWR)
98			(void) __sflush(fp);
99		/* if close is NULL, closing is a no-op, hence pointless */
100		isopen = fp->_close != NULL;
101		if ((wantfd = __sfileno(fp)) == -1 && isopen) {
102			(void) (*fp->_close)(fp->_cookie);
103			isopen = 0;
104		}
105	}
106
107	/* Get a new descriptor to refer to the new file. */
108	f = open(file, oflags, DEFFILEMODE);
109	if (f < 0 && isopen) {
110		/* If out of fd's close the old one and try again. */
111		if (errno == ENFILE || errno == EMFILE) {
112			(void) (*fp->_close)(fp->_cookie);
113			isopen = 0;
114			f = open(file, oflags, DEFFILEMODE);
115		}
116	}
117	sverrno = errno;
118
119	/*
120	 * Finish closing fp.  Even if the open succeeded above, we cannot
121	 * keep fp->_base: it may be the wrong size.  This loses the effect
122	 * of any setbuffer calls, but stdio has always done this before.
123	 */
124	if (isopen && f != wantfd)
125		(void) (*fp->_close)(fp->_cookie);
126	if (fp->_flags & __SMBF)
127		free((char *)fp->_bf._base);
128	fp->_w = 0;
129	fp->_r = 0;
130	fp->_p = NULL;
131	fp->_bf._base = NULL;
132	fp->_bf._size = 0;
133	fp->_lbfsize = 0;
134	if (HASUB(fp))
135		FREEUB(fp);
136	WCIO_FREE(fp);
137	_UB(fp)._size = 0;
138	FREELB(fp);
139
140	if (f < 0) {			/* did not get it after all */
141		fp->_flags = 0;		/* set it free */
142		errno = sverrno;	/* restore in case _close clobbered */
143		return (NULL);
144	}
145
146	if (oflags & O_NONBLOCK) {
147		struct stat st;
148		if (fstat(f, &st) == -1) {
149			sverrno = errno;
150			(void)close(f);
151			errno = sverrno;
152			return (NULL);
153		}
154		if (!S_ISREG(st.st_mode)) {
155			(void)close(f);
156			errno = EFTYPE;
157			return (NULL);
158		}
159	}
160
161	/*
162	 * If reopening something that was open before on a real file, try
163	 * to maintain the descriptor.  Various C library routines (perror)
164	 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
165	 */
166	if (wantfd >= 0 && f != wantfd) {
167		if (dup2(f, wantfd) >= 0) {
168			(void) close(f);
169			f = wantfd;
170		}
171	}
172
173	/*
174	 * File descriptors are a full int, but _file is only a short.
175	 * If we get a valid file descriptor that is greater or equal to
176	 * USHRT_MAX, then the fd will get sign-extended into an
177	 * invalid file descriptor.  Handle this case by failing the
178	 * open. (We treat the short as unsigned, and special-case -1).
179	 */
180	if (f >= USHRT_MAX) {
181		(void)close(f);
182		errno = EMFILE;
183		return NULL;
184	}
185
186	fp->_flags = flags;
187	fp->_file = f;
188	fp->_cookie = fp;
189	fp->_read = __sread;
190	fp->_write = __swrite;
191	fp->_seek = __sseek;
192	fp->_close = __sclose;
193
194	/*
195	 * When reopening in append mode, even though we use O_APPEND,
196	 * we need to seek to the end so that ftell() gets the right
197	 * answer.  If the user then alters the seek pointer, or
198	 * the file extends, this will fail, but there is not much
199	 * we can do about this.  (We could set __SAPP and check in
200	 * fseek and ftell.)
201	 */
202	if (oflags & O_APPEND)
203		(void) __sseek((void *)fp, (off_t)0, SEEK_END);
204	return (fp);
205}
206