lib/libc/stdio/fpurge.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)fpurge.c 8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: src/lib/libc/stdio/fpurge.c,v 1.11 2007/01/09 00:28:06 imp Exp $
  34  * $DragonFly: src/lib/libc/stdio/fpurge.c,v 1.6 2005/07/23 20:23:06 joerg Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <errno.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include "un-namespace.h"
  42 #include "local.h"
  43 #include "libc_private.h"
  44 #include "priv_stdio.h"
  45
  46 /*
  47  * fpurge: like fflush, but without writing anything: leave the
  48  * given FILE's buffer empty.
  49  */
  50 int
  51 fpurge(FILE *fp)
  52 {
  53         int retval;
  54         FLOCKFILE(fp);
  55         if (!fp->pub._flags) {
  56                 errno = EBADF;
  57                 retval = EOF;
  58         } else {
  59                 if (HASUB(fp))
  60                         FREEUB(fp);
  61                 fp->pub._p = fp->_bf._base;
  62                 fp->pub._r = 0;
  63                 fp->pub._w = fp->pub._flags & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
  64                 retval = 0;
  65         }
  66         FUNLOCKFILE(fp);
  67         return (retval);
  68 }