141 lines
4.1 KiB
C
141 lines
4.1 KiB
C
/* $OpenBSD: ungetc.c,v 1.9 2005/08/08 08:05:36 espie 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((size_t)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 = realloc(_UB(fp)._base, i << 1);
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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((void *)(p + i), (void *)p, (size_t)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 << 1;
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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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_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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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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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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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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* 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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return (c);
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}
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