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/*-
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)freopen.c   8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.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(file, mode, fp)
        const char *file, *mode;
        register FILE *fp;
{
        register int f;
        int flags, isopen, oflags, sverrno, wantfd;

        if ((flags = __sflags(mode, &oflags)) == 0) {
                (void) fclose(fp);
                return (NULL);
        }

        if (!__sdidinit)
                __sinit();

        /*
         * 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; ANSI doesn't require this. */
                if (fp->_flags & __SWR)
                        (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 < 0 && 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)
                (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);
        fp->_ub._size = 0;
        if (HASLB(fp))
                FREELB(fp);
        fp->_lb._size = 0;

        if (f < 0) {                    /* did not get it after all */
                fp->_flags = 0;         /* set it free */
                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 (dup2(f, wantfd) >= 0) {
                        (void) close(f);
                        f = wantfd;
                }
        }

        fp->_flags = flags;
        fp->_file = f;
        fp->_cookie = fp;
        fp->_read = __sread;
        fp->_write = __swrite;
        fp->_seek = __sseek;
        fp->_close = __sclose;
        return (fp);
}