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scoutos / prex-0.9.0 / usr / lib / libc / stdio / freopen.c @ 03e9c04a

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/*-
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 * Copyright (c) 1990, 1993
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 *        The Regents of the University of California.  All rights reserved.
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 *
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 * This code is derived from software contributed to Berkeley by
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 * Chris Torek.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "local.h"
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/*
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 * Re-direct an existing, open (probably) file to some other file.
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 * ANSI is written such that the original file gets closed if at
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 * all possible, no matter what.
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 */
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FILE *
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freopen(file, mode, fp)
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        const char *file, *mode;
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        FILE *fp;
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{
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        int f;
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        int flags, isopen, oflags, sverrno, wantfd;
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        if ((flags = __sflags(mode, &oflags)) == 0) {
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                (void) fclose(fp);
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                return (NULL);
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        }
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        if (!__sdidinit)
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                __sinit();
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        /*
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         * There are actually programs that depend on being able to "freopen"
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         * descriptors that weren't originally open.  Keep this from breaking.
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         * Remember whether the stream was open to begin with, and which file
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         * descriptor (if any) was associated with it.  If it was attached to
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         * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
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         * should work.  This is unnecessary if it was not a Unix file.
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         */
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        if (fp->_flags == 0) {
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                fp->_flags = __SEOF;        /* hold on to it */
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                isopen = 0;
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                wantfd = -1;
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        } else {
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                /* flush the stream; ANSI doesn't require this. */
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                if (fp->_flags & __SWR)
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                        (void) __sflush(fp);
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                /* if close is NULL, closing is a no-op, hence pointless */
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                isopen = 1;
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                if ((wantfd = fp->_file) < 0 && isopen) {
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                        (void) __sclose(fp);
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                        isopen = 0;
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                }
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        }
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        /* Get a new descriptor to refer to the new file. */
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        f = open(file, oflags, DEFFILEMODE);
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        if (f < 0 && isopen) {
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                /* If out of fd's close the old one and try again. */
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                if (errno == ENFILE || errno == EMFILE) {
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                        (void) __sclose(fp);
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                        isopen = 0;
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                        f = open(file, oflags, DEFFILEMODE);
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                }
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        }
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        sverrno = errno;
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        /*
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         * Finish closing fp.  Even if the open succeeded above, we cannot
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         * keep fp->_base: it may be the wrong size.  This loses the effect
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         * of any setbuffer calls, but stdio has always done this before.
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         */
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        if (isopen)
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                (void) __sclose(fp);
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        if (fp->_flags & __SMBF)
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                free((char *)fp->_bf._base);
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        fp->_w = 0;
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        fp->_r = 0;
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        fp->_p = NULL;
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        fp->_bf._base = NULL;
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        fp->_bf._size = 0;
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        if (HASUB(fp))
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                FREEUB(fp);
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        fp->_ub._size = 0;
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        if (f < 0) {                        /* did not get it after all */
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                fp->_flags = 0;                /* set it free */
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                errno = sverrno;        /* restore in case _close clobbered */
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                return (NULL);
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        }
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        /*
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         * If reopening something that was open before on a real file, try
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         * to maintain the descriptor.  Various C library routines (perror)
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         * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
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         */
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        if (wantfd >= 0 && f != wantfd) {
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                if (dup2(f, wantfd) >= 0) {
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                        (void) close(f);
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                        f = wantfd;
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                }
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        }
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        fp->_flags = flags;
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        fp->_file = f;
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        return (fp);
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}