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. 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
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)fflush.c	8.1 (Berkeley) 6/4/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/10/lib/libc/stdio/fflush.c 321074 2017-07-17 14:09:34Z kib $");
38
39#include "namespace.h"
40#include <errno.h>
41#include <stdio.h>
42#include "un-namespace.h"
43#include "libc_private.h"
44#include "local.h"
45
46static int	sflush_locked(FILE *);
47
48/*
49 * Flush a single file, or (if fp is NULL) all files.
50 * MT-safe version
51 */
52int
53fflush(FILE *fp)
54{
55	int retval;
56
57	if (fp == NULL)
58		return (_fwalk(sflush_locked));
59	FLOCKFILE_CANCELSAFE(fp);
60
61	/*
62	 * There is disagreement about the correct behaviour of fflush()
63	 * when passed a file which is not open for writing.  According to
64	 * the ISO C standard, the behaviour is undefined.
65	 * Under linux, such an fflush returns success and has no effect;
66	 * under Windows, such an fflush is documented as behaving instead
67	 * as fpurge().
68	 * Given that applications may be written with the expectation of
69	 * either of these two behaviours, the only safe (non-astonishing)
70	 * option is to return EBADF and ask that applications be fixed.
71	 * SUSv3 now requires that fflush() returns success on a read-only
72	 * stream.
73	 *
74	 */
75	if ((fp->_flags & (__SWR | __SRW)) == 0)
76		retval = 0;
77	else
78		retval = __sflush(fp);
79	FUNLOCKFILE_CANCELSAFE();
80	return (retval);
81}
82
83/*
84 * Flush a single file, or (if fp is NULL) all files.
85 * Non-MT-safe version
86 */
87int
88__fflush(FILE *fp)
89{
90	int retval;
91
92	if (fp == NULL)
93		return (_fwalk(sflush_locked));
94	if ((fp->_flags & (__SWR | __SRW)) == 0)
95		retval = 0;
96	else
97		retval = __sflush(fp);
98	return (retval);
99}
100
101int
102__sflush(FILE *fp)
103{
104	unsigned char *p;
105	int n, t;
106
107	t = fp->_flags;
108	if ((t & __SWR) == 0)
109		return (0);
110
111	if ((p = fp->_bf._base) == NULL)
112		return (0);
113
114	n = fp->_p - p;		/* write this much */
115
116	/*
117	 * Set these immediately to avoid problems with longjmp and to allow
118	 * exchange buffering (via setvbuf) in user write function.
119	 */
120	fp->_p = p;
121	fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
122
123	for (; n > 0; n -= t, p += t) {
124		t = _swrite(fp, (char *)p, n);
125		if (t <= 0) {
126			/* Reset _p and _w. */
127			if (p > fp->_p) {
128				/* Some was written. */
129				memmove(fp->_p, p, n);
130				fp->_p += n;
131				if ((fp->_flags & (__SLBF | __SNBF)) == 0)
132					fp->_w -= n;
133			}
134			fp->_flags |= __SERR;
135			return (EOF);
136		}
137	}
138	return (0);
139}
140
141static int
142sflush_locked(FILE *fp)
143{
144	int	ret;
145
146	FLOCKFILE_CANCELSAFE(fp);
147	ret = __sflush(fp);
148	FUNLOCKFILE_CANCELSAFE();
149	return (ret);
150}
151