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/* $OpenBSD: freopen.c,v 1.18 2024/08/12 20:53:09 guenther 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/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <limits.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include "local.h"
/*
* Re-direct an existing, open (probably) file to some other file.
* ANSI is written such that the original file gets closed if at
* all possible, no matter what.
*/
FILE *
freopen(const char *file, const char *mode, FILE *fp)
{
int f;
int flags, isopen, oflags, sverrno, wantfd;
if ((flags = __sflags(mode, &oflags)) == 0) {
(void) fclose(fp);
return (NULL);
}
if (!__sdidinit)
__sinit();
FLOCKFILE(fp);
/*
* There are actually programs that depend on being able to "freopen"
* descriptors that weren't originally open. Keep this from breaking.
* Remember whether the stream was open to begin with, and which file
* descriptor (if any) was associated with it. If it was attached to
* a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
* should work. This is unnecessary if it was not a Unix file.
*/
if (fp->_flags == 0) {
fp->_flags = __SEOF; /* hold on to it */
isopen = 0;
wantfd = -1;
} else {
/* flush the stream; POSIX, not ANSI, requires this. */
(void) __sflush(fp);
/* if close is NULL, closing is a no-op, hence pointless */
isopen = fp->_close != NULL;
if ((wantfd = fp->_file) < 0 && isopen) {
(void) (*fp->_close)(fp->_cookie);
isopen = 0;
}
}
/* Get a new descriptor to refer to the new file. */
f = open(file, oflags, DEFFILEMODE);
if (f == -1 && isopen) {
/* If out of fd's close the old one and try again. */
if (errno == ENFILE || errno == EMFILE) {
(void) (*fp->_close)(fp->_cookie);
isopen = 0;
f = open(file, oflags, DEFFILEMODE);
}
}
sverrno = errno;
/*
* Finish closing fp. Even if the open succeeded above, we cannot
* keep fp->_base: it may be the wrong size. This loses the effect
* of any setbuffer calls, but stdio has always done this before.
*/
if (isopen && f != wantfd)
(void) (*fp->_close)(fp->_cookie);
if (fp->_flags & __SMBF)
free((char *)fp->_bf._base);
fp->_w = 0;
fp->_r = 0;
fp->_p = NULL;
fp->_bf._base = NULL;
fp->_bf._size = 0;
fp->_lbfsize = 0;
if (HASUB(fp))
FREEUB(fp);
_UB(fp)._size = 0;
WCIO_FREE(fp);
if (HASLB(fp))
FREELB(fp);
fp->_lb._size = 0;
if (f == -1) { /* did not get it after all */
fp->_flags = 0; /* set it free */
FUNLOCKFILE(fp);
errno = sverrno; /* restore in case _close clobbered */
return (NULL);
}
/*
* If reopening something that was open before on a real file, try
* to maintain the descriptor. Various C library routines (perror)
* assume stderr is always fd STDERR_FILENO, even if being freopen'd.
*/
if (wantfd >= 0 && f != wantfd) {
if (dup3(f, wantfd, oflags & O_CLOEXEC) >= 0) {
(void) close(f);
f = wantfd;
}
}
/* _file is only a short */
if (f > SHRT_MAX) {
fp->_flags = 0; /* set it free */
FUNLOCKFILE(fp);
errno = EMFILE;
return (NULL);
}
fp->_flags = flags;
fp->_file = f;
fp->_cookie = fp;
fp->_read = __sread;
fp->_write = __swrite;
fp->_seek = __sseek;
fp->_close = __sclose;
/*
* When opening in append mode, even though we use O_APPEND,
* we need to seek to the end so that ftell() gets the right
* answer. If the user then alters the seek pointer, or
* the file extends, this will fail, but there is not much
* we can do about this. (We could set __SAPP and check in
* fseek and ftell.)
*/
if (oflags & O_APPEND)
(void) __sseek(fp, 0, SEEK_END);
FUNLOCKFILE(fp);
return (fp);
}
DEF_STRONG(freopen);
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