usr/src/lib/libbc/libc/stdio/common/ungetc.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1988 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"  /* from S5R2 2.1 */
  31
  32 /*LINTLIBRARY*/
  33 #include <stdio.h>
  34
  35 int
  36 ungetc(c, iop)
  37 int     c;
  38 register FILE *iop;
  39 {
  40         if(c == EOF)
  41                 return(EOF);
  42         if((iop->_flag & (_IOREAD|_IORW)) == 0)
  43                 return(EOF);
  44
  45         if (iop->_base == NULL)  /* get buffer if we don't have one */
  46                 _findbuf(iop);
  47
  48         if((iop->_flag & _IOREAD) == 0 || iop->_ptr <= iop->_base)
  49                 if(iop->_ptr == iop->_base && iop->_cnt == 0)
  50                         ++iop->_ptr;
  51                 else
  52                         return(EOF);
  53         if (*--iop->_ptr != c) *iop->_ptr = c;  /* was *--iop->_ptr = c; */
  54         ++iop->_cnt;
  55         return(c);
  56 }