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/* $OpenBSD: ungetc.c,v 1.15 2016/09/21 04:38:56 guenther Exp $ */ |
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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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static int __submore(FILE *); |
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/* |
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* Expand the ungetc buffer `in place'. That is, adjust fp->_p when |
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* the buffer moves, so that it points the same distance from the end, |
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* and move the bytes in the buffer around as necessary so that they |
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* are all at the end (stack-style). |
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*/ |
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static int |
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__submore(FILE *fp) |
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{ |
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int i; |
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unsigned char *p; |
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if (_UB(fp)._base == fp->_ubuf) { |
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/* |
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* Get a new buffer (rather than expanding the old one). |
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*/ |
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if ((p = malloc(BUFSIZ)) == NULL) |
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return (EOF); |
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_UB(fp)._base = p; |
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_UB(fp)._size = BUFSIZ; |
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p += BUFSIZ - sizeof(fp->_ubuf); |
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for (i = sizeof(fp->_ubuf); --i >= 0;) |
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p[i] = fp->_ubuf[i]; |
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fp->_p = p; |
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return (0); |
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} |
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i = _UB(fp)._size; |
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p = reallocarray(_UB(fp)._base, i, 2); |
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if (p == NULL) |
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return (EOF); |
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/* no overlap (hence can use memcpy) because we doubled the size */ |
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(void)memcpy(p + i, p, i); |
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fp->_p = p + i; |
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_UB(fp)._base = p; |
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_UB(fp)._size = i * 2; |
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return (0); |
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} |
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int |
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ungetc(int c, 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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FLOCKFILE(fp); |
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_SET_ORIENTATION(fp, -1); |
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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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error: FUNLOCKFILE(fp); |
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return (EOF); |
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} |
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if (fp->_flags & __SWR) { |
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if (__sflush(fp)) |
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goto error; |
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fp->_flags &= ~__SWR; |
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fp->_w = 0; |
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fp->_lbfsize = 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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* This may require expanding the current ungetc buffer. |
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*/ |
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if (HASUB(fp)) { |
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if (fp->_r >= _UB(fp)._size && __submore(fp)) |
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goto error; |
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*--fp->_p = c; |
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inc_ret: fp->_r++; |
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FUNLOCKFILE(fp); |
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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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goto inc_ret; |
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} |
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/* |
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* Create an ungetc buffer. |
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* Initially, 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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_UB(fp)._base = fp->_ubuf; |
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_UB(fp)._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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FUNLOCKFILE(fp); |
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return (c); |
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} |
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DEF_STRONG(ungetc); |