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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 <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "local.h"
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int
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ungetc(c, fp)
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        int c;
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        FILE *fp;
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{
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        if (c == EOF)
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                return (EOF);
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        if (!__sdidinit)
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                __sinit();
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        if ((fp->_flags & __SRD) == 0) {
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                /*
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                 * Not already reading: no good unless reading-and-writing.
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                 * Otherwise, flush any current write stuff.
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                 */
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                if ((fp->_flags & __SRW) == 0)
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                        return (EOF);
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                if (fp->_flags & __SWR) {
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                        if (__sflush(fp))
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                                return (EOF);
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                        fp->_flags &= ~__SWR;
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                        fp->_w = 0;
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                }
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                fp->_flags |= __SRD;
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        }
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        c = (unsigned char)c;
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        /*
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         * If we are in the middle of ungetc'ing, just continue.
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         */
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        if (HASUB(fp)) {
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                if (fp->_r >= fp->_ub._size)
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                        return (EOF);
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                *--fp->_p = c;
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                fp->_r++;
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                return (c);
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        }
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        fp->_flags &= ~__SEOF;
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        /*
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         * If we can handle this by simply backing up, do so,
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         * but never replace the original character.
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         * (This makes sscanf() work when scanning `const' data.)
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         */
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        if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
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            fp->_p[-1] == c) {
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                fp->_p--;
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                fp->_r++;
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                return (c);
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        }
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        /*
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         * Create an ungetc buffer.
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         * we will use the `reserve' buffer.
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         */
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        fp->_ur = fp->_r;
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        fp->_up = fp->_p;
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        fp->_ub._base = fp->_ubuf;
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        fp->_ub._size = sizeof(fp->_ubuf);
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        fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
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        fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
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        fp->_r = 1;
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        return (c);
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}