fpurge.c revision 16586 
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 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)fpurge.c	8.1 (Berkeley) 6/4/93";
40#endif
41static const char rcsid[] =
42		"$Id$";
43#endif /* LIBC_SCCS and not lint */
44
45#include <errno.h>
46#include <stdio.h>
47#include <stdlib.h>
48#include "local.h"
49#ifdef _THREAD_SAFE
50#include <pthread.h>
51#include "pthread_private.h"
52#endif
53
54/*
55 * fpurge: like fflush, but without writing anything: leave the
56 * given FILE's buffer empty.
57 */
58int
59fpurge(fp)
60	register FILE *fp;
61{
62	int retval;
63#ifdef _THREAD_SAFE
64	_thread_flockfile(fp,__FILE__,__LINE__);
65#endif
66	if (!fp->_flags) {
67		errno = EBADF;
68		retval = EOF;
69	} else {
70		if (HASUB(fp))
71			FREEUB(fp);
72		fp->_p = fp->_bf._base;
73		fp->_r = 0;
74		fp->_w = fp->_flags & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
75		retval = 0;
76	}
77#ifdef _THREAD_SAFE
78	_thread_funlockfile(fp);
79#endif
80	return (retval);
81}
82