1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)fflush.c	8.1 (Berkeley) 6/4/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD$");
40
41#include "namespace.h"
42#include <errno.h>
43#include <stdio.h>
44#include "un-namespace.h"
45#include "libc_private.h"
46#include "local.h"
47
48static int	sflush_locked(FILE *);
49
50/*
51 * Flush a single file, or (if fp is NULL) all files.
52 * MT-safe version
53 */
54int
55fflush(FILE *fp)
56{
57	int retval;
58
59	if (fp == NULL)
60		return (_fwalk(sflush_locked));
61	FLOCKFILE_CANCELSAFE(fp);
62
63	/*
64	 * There is disagreement about the correct behaviour of fflush()
65	 * when passed a file which is not open for writing.  According to
66	 * the ISO C standard, the behaviour is undefined.
67	 * Under linux, such an fflush returns success and has no effect;
68	 * under Windows, such an fflush is documented as behaving instead
69	 * as fpurge().
70	 * Given that applications may be written with the expectation of
71	 * either of these two behaviours, the only safe (non-astonishing)
72	 * option is to return EBADF and ask that applications be fixed.
73	 * SUSv3 now requires that fflush() returns success on a read-only
74	 * stream.
75	 *
76	 */
77	if ((fp->_flags & (__SWR | __SRW)) == 0)
78		retval = 0;
79	else
80		retval = __sflush(fp);
81	FUNLOCKFILE_CANCELSAFE();
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		retval = 0;
98	else
99		retval = __sflush(fp);
100	return (retval);
101}
102
103__weak_reference(__fflush, fflush_unlocked);
104
105int
106__sflush(FILE *fp)
107{
108	unsigned char *p;
109	int n, t;
110
111	t = fp->_flags;
112	if ((t & __SWR) == 0)
113		return (0);
114
115	if ((p = fp->_bf._base) == NULL)
116		return (0);
117
118	n = fp->_p - p;		/* write this much */
119
120	/*
121	 * Set these immediately to avoid problems with longjmp and to allow
122	 * exchange buffering (via setvbuf) in user write function.
123	 */
124	fp->_p = p;
125	fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
126
127	for (; n > 0; n -= t, p += t) {
128		t = _swrite(fp, (char *)p, n);
129		if (t <= 0) {
130			/* Reset _p and _w. */
131			if (p > fp->_p) {
132				/* Some was written. */
133				memmove(fp->_p, p, n);
134				fp->_p += n;
135				if ((fp->_flags & (__SLBF | __SNBF)) == 0)
136					fp->_w -= n;
137			}
138			fp->_flags |= __SERR;
139			return (EOF);
140		}
141	}
142	return (0);
143}
144
145static int
146sflush_locked(FILE *fp)
147{
148	int	ret;
149
150	FLOCKFILE_CANCELSAFE(fp);
151	ret = __sflush(fp);
152	FUNLOCKFILE_CANCELSAFE();
153	return (ret);
154}
155