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 <sys/cdefs.h>
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
46 static int sflush_locked(FILE *);
47
48 /*
49 * Flush a single file, or (if fp is NULL) all files.
50 * MT-safe version
51 */
52 int
fflush(FILE * fp)53 fflush(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 */
87 int
__fflush(FILE * fp)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
101 __weak_reference(__fflush, fflush_unlocked);
102
103 int
__sflush(FILE * fp)104 __sflush(FILE *fp)
105 {
106 unsigned char *p;
107 int n, f, t;
108
109 f = fp->_flags;
110 if ((f & __SWR) == 0)
111 return (0);
112
113 if ((p = fp->_bf._base) == NULL)
114 return (0);
115
116 n = fp->_p - p; /* write this much */
117
118 /*
119 * Set these immediately to avoid problems with longjmp and to allow
120 * exchange buffering (via setvbuf) in user write function.
121 */
122 fp->_p = p;
123 fp->_w = f & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
124
125 for (; n > 0; n -= t, p += t) {
126 t = _swrite(fp, (char *)p, n);
127 if (t <= 0) {
128 if (p > fp->_p)
129 /* Some was written. */
130 memmove(fp->_p, p, n);
131 /* Reset _p and _w. */
132 fp->_p += n;
133 if ((fp->_flags & __SNBF) == 0)
134 fp->_w -= n;
135 fp->_flags |= __SERR;
136 return (EOF);
137 }
138 }
139 return (0);
140 }
141
142 static int
sflush_locked(FILE * fp)143 sflush_locked(FILE *fp)
144 {
145 int ret;
146
147 FLOCKFILE_CANCELSAFE(fp);
148 ret = __sflush(fp);
149 FUNLOCKFILE_CANCELSAFE();
150 return (ret);
151 }
152