text: /*-
   * 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"
  
  int
  ungetc(c, fp)
  	int c;
  	FILE *fp;
  {
  	if (c == EOF)
  		return (EOF);
  	if (!__sdidinit)
  		__sinit();
  	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)
  			return (EOF);
  		if (fp->_flags & __SWR) {
  			if (__sflush(fp))
  				return (EOF);
  			fp->_flags &= ~__SWR;
  			fp->_w = 0;
  		}
  		fp->_flags |= __SRD;
  	}
  	c = (unsigned char)c;
  
  	/*
  	 * If we are in the middle of ungetc'ing, just continue.
  	 */
  	if (HASUB(fp)) {
  		if (fp->_r >= fp->_ub._size)
  			return (EOF);
  		*--fp->_p = c;
  		fp->_r++;
  		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--;
  		fp->_r++;
  		return (c);
  	}
  
  	/*
  	 * Create an ungetc buffer.
  	 * we will use the `reserve' buffer.
  	 */
  	fp->_ur = fp->_r;
  	fp->_up = fp->_p;
  	fp->_ub._base = fp->_ubuf;
  	fp->_ub._size = sizeof(fp->_ubuf);
  	fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
  	fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
  	fp->_r = 1;
  	return (c);
  }
  