fflush.c revision 131592 
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)
38static char sccsid[] = "@(#)fflush.c	8.1 (Berkeley) 6/4/93";
39#endif /* LIBC_SCCS and not lint */
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/lib/libc/stdio/fflush.c 131592 2004-07-04 20:17:00Z cperciva $");
42
43#include "namespace.h"
44#include <errno.h>
45#include <stdio.h>
46#include "un-namespace.h"
47#include "libc_private.h"
48#include "local.h"
49
50static int	sflush_locked(FILE *);
51
52/*
53 * Flush a single file, or (if fp is NULL) all files.
54 * MT-safe version
55 */
56int
57fflush(FILE *fp)
58{
59	int retval;
60
61	if (fp == NULL)
62		return (_fwalk(sflush_locked));
63	FLOCKFILE(fp);
64
65	/*
66	 * There is disagreement about the correct behaviour of fflush()
67	 * when passed a file which is not open for reading.  According to
68	 * the ISO C standard, the behaviour is undefined.
69	 * Under linux, such an fflush returns success and has no effect;
70	 * under Windows, such an fflush is documented as behaving instead
71	 * as fpurge().
72	 * Given that applications may be written with the expectation of
73	 * either of these two behaviours, the only safe (non-astonishing)
74	 * option is to return EBADF and ask that applications be fixed.
75	 */
76	if ((fp->_flags & (__SWR | __SRW)) == 0) {
77		errno = EBADF;
78		retval = EOF;
79	} else
80		retval = __sflush(fp);
81	FUNLOCKFILE(fp);
82	return (retval);
83}
84
85/*
86 * Flush a single file, or (if fp is NULL) all files.
87 * Non-MT-safe version
88 */
89int
90__fflush(FILE *fp)
91{
92	int retval;
93
94	if (fp == NULL)
95		return (_fwalk(sflush_locked));
96	if ((fp->_flags & (__SWR | __SRW)) == 0) {
97		errno = EBADF;
98		retval = EOF;
99	} else
100		retval = __sflush(fp);
101	return (retval);
102}
103
104int
105__sflush(FILE *fp)
106{
107	unsigned char *p;
108	int n, t;
109
110	t = fp->_flags;
111	if ((t & __SWR) == 0)
112		return (0);
113
114	if ((p = fp->_bf._base) == NULL)
115		return (0);
116
117	n = fp->_p - p;		/* write this much */
118
119	/*
120	 * Set these immediately to avoid problems with longjmp and to allow
121	 * exchange buffering (via setvbuf) in user write function.
122	 */
123	fp->_p = p;
124	fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
125
126	for (; n > 0; n -= t, p += t) {
127		t = _swrite(fp, (char *)p, n);
128		if (t <= 0) {
129			fp->_flags |= __SERR;
130			return (EOF);
131		}
132	}
133	return (0);
134}
135
136static int
137sflush_locked(FILE *fp)
138{
139	int	ret;
140
141	FLOCKFILE(fp);
142	ret = __sflush(fp);
143	FUNLOCKFILE(fp);
144	return (ret);
145}
146