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#include "namespace.h"
36#include <errno.h>
37#include <stdio.h>
38#include "un-namespace.h"
39#include "libc_private.h"
40#include "local.h"
41
42static int	sflush_locked(FILE *);
43
44/*
45 * Flush a single file, or (if fp is NULL) all files.
46 * MT-safe version
47 */
48int
49fflush(FILE *fp)
50{
51	int retval;
52
53	if (fp == NULL)
54		return (_fwalk(sflush_locked));
55	FLOCKFILE_CANCELSAFE(fp);
56
57	/*
58	 * There is disagreement about the correct behaviour of fflush()
59	 * when passed a file which is not open for writing.  According to
60	 * the ISO C standard, the behaviour is undefined.
61	 * Under linux, such an fflush returns success and has no effect;
62	 * under Windows, such an fflush is documented as behaving instead
63	 * as fpurge().
64	 * Given that applications may be written with the expectation of
65	 * either of these two behaviours, the only safe (non-astonishing)
66	 * option is to return EBADF and ask that applications be fixed.
67	 * SUSv3 now requires that fflush() returns success on a read-only
68	 * stream.
69	 *
70	 */
71	if ((fp->_flags & (__SWR | __SRW)) == 0)
72		retval = 0;
73	else
74		retval = __sflush(fp);
75	FUNLOCKFILE_CANCELSAFE();
76	return (retval);
77}
78
79/*
80 * Flush a single file, or (if fp is NULL) all files.
81 * Non-MT-safe version
82 */
83int
84__fflush(FILE *fp)
85{
86	int retval;
87
88	if (fp == NULL)
89		return (_fwalk(sflush_locked));
90	if ((fp->_flags & (__SWR | __SRW)) == 0)
91		retval = 0;
92	else
93		retval = __sflush(fp);
94	return (retval);
95}
96
97__weak_reference(__fflush, fflush_unlocked);
98
99int
100__sflush(FILE *fp)
101{
102	unsigned char *p;
103	int n, f, t;
104
105	f = fp->_flags;
106	if ((f & __SWR) == 0)
107		return (0);
108
109	if ((p = fp->_bf._base) == NULL)
110		return (0);
111
112	n = fp->_p - p;		/* write this much */
113
114	/*
115	 * Set these immediately to avoid problems with longjmp and to allow
116	 * exchange buffering (via setvbuf) in user write function.
117	 */
118	fp->_p = p;
119	fp->_w = f & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
120
121	for (; n > 0; n -= t, p += t) {
122		t = _swrite(fp, (char *)p, n);
123		if (t <= 0) {
124			if (p > fp->_p)
125				/* Some was written. */
126				memmove(fp->_p, p, n);
127			/* Reset _p and _w. */
128			fp->_p += n;
129			if ((fp->_flags & __SNBF) == 0)
130				fp->_w -= n;
131			fp->_flags |= __SERR;
132			return (EOF);
133		}
134	}
135	return (0);
136}
137
138static int
139sflush_locked(FILE *fp)
140{
141	int	ret;
142
143	FLOCKFILE_CANCELSAFE(fp);
144	ret = __sflush(fp);
145	FUNLOCKFILE_CANCELSAFE();
146	return (ret);
147}
148