usr/src/lib/libc/port/stdio/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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 #include "lint.h"
  33 #include "file64.h"
  34 #include "mtlib.h"
  35 #include <sys/types.h>
  36 #include <stdio.h>
  37 #include <thread.h>
  38 #include <synch.h>
  39 #include "stdiom.h"
  40
  41 int _ungetc_unlocked(int c, FILE *iop);
  42
  43 int
  44 ungetc(int c, FILE *iop)
  45 {
  46         FLOCKRETURN(iop, _ungetc_unlocked(c, iop))
  47 }
  48
  49 /*
  50  * Called internally by the library (instead of the safe "ungetc") when
  51  * iop->_lock is already held at a higher level - required since we do not
  52  * have recursive locks.
  53  */
  54 int
  55 _ungetc_unlocked(int c, FILE *iop)
  56 {
  57         if (c == EOF)
  58                 return (EOF);
  59         if (iop->_ptr <= iop->_base) {
  60                 if (iop->_base == 0) {
  61                         if (_findbuf(iop) == 0)
  62                                 return (EOF);
  63                 } else if (iop->_ptr <= iop->_base - PUSHBACK)
  64                         return (EOF);
  65         }
  66         if ((iop->_flag & _IOREAD) == 0) /* basically a no-op on write stream */
  67                 ++iop->_ptr;
  68         if (*--iop->_ptr != (unsigned char) c)
  69                 *iop->_ptr = (unsigned char) c;  /* was *--iop->_ptr = c; */
  70         ++iop->_cnt;
  71         iop->_flag &= ~_IOEOF;
  72         return (c);
  73 }