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/* $OpenBSD: ungetc.c,v 1.12 2009/11/09 00:18:27 kurt Exp $ */
/*-
* 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. 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.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "local.h"
static int __submore(FILE *);
/*
* Expand the ungetc buffer `in place'. That is, adjust fp->_p when
* the buffer moves, so that it points the same distance from the end,
* and move the bytes in the buffer around as necessary so that they
* are all at the end (stack-style).
*/
static int
__submore(FILE *fp)
{
int i;
unsigned char *p;
if (_UB(fp)._base == fp->_ubuf) {
/*
* Get a new buffer (rather than expanding the old one).
*/
if ((p = malloc((size_t)BUFSIZ)) == NULL)
return (EOF);
_UB(fp)._base = p;
_UB(fp)._size = BUFSIZ;
p += BUFSIZ - sizeof(fp->_ubuf);
for (i = sizeof(fp->_ubuf); --i >= 0;)
p[i] = fp->_ubuf[i];
fp->_p = p;
return (0);
}
i = _UB(fp)._size;
p = realloc(_UB(fp)._base, i << 1);
if (p == NULL)
return (EOF);
/* no overlap (hence can use memcpy) because we doubled the size */
(void)memcpy((void *)(p + i), (void *)p, (size_t)i);
fp->_p = p + i;
_UB(fp)._base = p;
_UB(fp)._size = i << 1;
return (0);
}
int
ungetc(int c, FILE *fp)
{
if (c == EOF)
return (EOF);
if (!__sdidinit)
__sinit();
FLOCKFILE(fp);
_SET_ORIENTATION(fp, -1);
if ((fp->_flags & __SRD) == 0) {
/*
* Not already reading: no good unless reading-and-writing.
* Otherwise, flush any current write stuff.
*/
if ((fp->_flags & __SRW) == 0) {
error: FUNLOCKFILE(fp);
return (EOF);
}
if (fp->_flags & __SWR) {
if (__sflush(fp))
goto error;
fp->_flags &= ~__SWR;
fp->_w = 0;
fp->_lbfsize = 0;
}
fp->_flags |= __SRD;
}
c = (unsigned char)c;
/*
* If we are in the middle of ungetc'ing, just continue.
* This may require expanding the current ungetc buffer.
*/
if (HASUB(fp)) {
if (fp->_r >= _UB(fp)._size && __submore(fp))
goto error;
*--fp->_p = c;
inc_ret: fp->_r++;
FUNLOCKFILE(fp);
return (c);
}
fp->_flags &= ~__SEOF;
/*
* If we can handle this by simply backing up, do so,
* but never replace the original character.
* (This makes sscanf() work when scanning `const' data.)
*/
if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
fp->_p[-1] == c) {
fp->_p--;
goto inc_ret;
}
/*
* Create an ungetc buffer.
* Initially, we will use the `reserve' buffer.
*/
fp->_ur = fp->_r;
fp->_up = fp->_p;
_UB(fp)._base = fp->_ubuf;
_UB(fp)._size = sizeof(fp->_ubuf);
fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
fp->_r = 1;
FUNLOCKFILE(fp);
return (c);
}
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