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