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/* $Id: sfungetc.c,v 1.1.1.1 2004/12/23 04:04:15 ellson Exp $ $Revision: 1.1.1.1 $ */
/* vim:set shiftwidth=4 ts=8: */
/**********************************************************
* This software is part of the graphviz package *
* http://www.graphviz.org/ *
* *
* Copyright (c) 1994-2004 AT&T Corp. *
* and is licensed under the *
* Common Public License, Version 1.0 *
* by AT&T Corp. *
* *
* Information and Software Systems Research *
* AT&T Research, Florham Park NJ *
**********************************************************/
#include "sfhdr.h"
/* Push back one byte to a given SF_READ stream
**
** Written by Kiem-Phong Vo.
*/
#if __STD_C
static int _uexcept(reg Sfio_t * f, reg int type, Void_t * val,
reg Sfdisc_t * disc)
#else
static int _uexcept(f, type, val, disc)
reg Sfio_t *f;
reg int type;
Void_t *val;
reg Sfdisc_t *disc;
#endif
{
NOTUSED(val);
/* hmm! This should never happen */
if (disc != _Sfudisc)
return -1;
/* close the unget stream */
if (type != SF_CLOSING)
(void) sfclose((*_Sfstack) (f, NIL(Sfio_t *)));
return 1;
}
#if __STD_C
int sfungetc(reg Sfio_t * f, reg int c)
#else
int sfungetc(f, c)
reg Sfio_t *f; /* push back one byte to this stream */
reg int c; /* the value to be pushed back */
#endif
{
reg Sfio_t *uf;
SFMTXSTART(f, -1)
if (c < 0 || (f->mode != SF_READ && _sfmode(f, SF_READ, 0) < 0))
SFMTXRETURN(f, -1);
SFLOCK(f, 0);
/* fast handling of the typical unget */
if (f->next > f->data && f->next[-1] == (uchar) c) {
f->next -= 1;
goto done;
}
/* make a string stream for unget characters */
if (f->disc != _Sfudisc) {
if (!(uf = sfnew(NIL(Sfio_t *), NIL(char *), (size_t) SF_UNBOUND,
-1, SF_STRING | SF_READ))) {
c = -1;
goto done;
}
_Sfudisc->exceptf = _uexcept;
sfdisc(uf, _Sfudisc);
SFOPEN(f, 0);
(void) sfstack(f, uf);
SFLOCK(f, 0);
}
/* space for data */
if (f->next == f->data) {
reg uchar *data;
if (f->size < 0)
f->size = 0;
if (!(data = (uchar *) malloc(f->size + 16))) {
c = -1;
goto done;
}
f->flags |= SF_MALLOC;
if (f->data)
memcpy((char *) (data + 16), (char *) f->data, f->size);
f->size += 16;
f->data = data;
f->next = data + 16;
f->endb = data + f->size;
}
*--f->next = (uchar) c;
done:
SFOPEN(f, 0);
SFMTXRETURN(f, c);
}
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