1 /* $OpenBSD: setvbuf.c,v 1.15 2022/09/28 16:44:14 gnezdo Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <limits.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include "local.h"
38
39 /*
40 * Set one of the three kinds of buffering, optionally including
41 * a buffer.
42 */
43 int
setvbuf(FILE * fp,char * buf,int mode,size_t size)44 setvbuf(FILE *fp, char *buf, int mode, size_t size)
45 {
46 int ret, flags;
47 size_t iosize;
48 int ttyflag;
49
50 /*
51 * Verify arguments. The `int' limit on `size' is due to this
52 * particular implementation. Note, buf and size are ignored
53 * when setting _IONBF.
54 */
55 if (mode != _IONBF)
56 if ((mode != _IOFBF && mode != _IOLBF) || size > INT_MAX)
57 return (EOF);
58
59 /*
60 * Write current buffer, if any. Discard unread input (including
61 * ungetc data), cancel line buffering, and free old buffer if
62 * malloc()ed. We also clear any eof condition, as if this were
63 * a seek.
64 */
65 FLOCKFILE(fp);
66 ret = 0;
67 (void)__sflush(fp);
68 if (HASUB(fp))
69 FREEUB(fp);
70 WCIO_FREE(fp);
71 fp->_r = fp->_lbfsize = 0;
72 flags = fp->_flags;
73 if (flags & __SMBF)
74 free(fp->_bf._base);
75 flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
76
77 /* If setting unbuffered mode, skip all the hard work. */
78 if (mode == _IONBF)
79 goto nbf;
80
81 /*
82 * Find optimal I/O size for seek optimization. This also returns
83 * a `tty flag' to suggest that we check isatty(fd), but we do not
84 * care since our caller told us how to buffer.
85 */
86 flags |= __swhatbuf(fp, &iosize, &ttyflag);
87 if (size == 0) {
88 buf = NULL; /* force local allocation */
89 size = iosize;
90 }
91
92 /* Allocate buffer if needed. */
93 if (buf == NULL) {
94 if ((buf = malloc(size)) == NULL) {
95 /*
96 * Unable to honor user's request. We will return
97 * failure, but try again with file system size.
98 */
99 ret = EOF;
100 if (size != iosize) {
101 size = iosize;
102 buf = malloc(size);
103 }
104 }
105 if (buf == NULL) {
106 /* No luck; switch to unbuffered I/O. */
107 nbf:
108 fp->_flags = flags | __SNBF;
109 fp->_w = 0;
110 fp->_bf._base = fp->_p = fp->_nbuf;
111 fp->_bf._size = 1;
112 FUNLOCKFILE(fp);
113 return (ret);
114 }
115 flags |= __SMBF;
116 }
117
118 /*
119 * We're committed to buffering from here, so make sure we've
120 * registered to flush buffers on exit.
121 */
122 if (!__sdidinit)
123 __sinit();
124
125 /*
126 * Kill any seek optimization if the buffer is not the
127 * right size.
128 *
129 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
130 */
131 if (size != iosize)
132 flags |= __SNPT;
133
134 /*
135 * Fix up the FILE fields, and set __cleanup for output flush on
136 * exit (since we are buffered in some way).
137 */
138 if (mode == _IOLBF)
139 flags |= __SLBF;
140 fp->_flags = flags;
141 fp->_bf._base = fp->_p = (unsigned char *)buf;
142 fp->_bf._size = size;
143 /* fp->_lbfsize is still 0 */
144 if (flags & __SWR) {
145 /*
146 * Begin or continue writing: see __swsetup(). Note
147 * that __SNBF is impossible (it was handled earlier).
148 */
149 if (flags & __SLBF) {
150 fp->_w = 0;
151 fp->_lbfsize = -fp->_bf._size;
152 } else
153 fp->_w = size;
154 } else {
155 /* begin/continue reading, or stay in intermediate state */
156 fp->_w = 0;
157 }
158 FUNLOCKFILE(fp);
159
160 return (ret);
161 }
162 DEF_STRONG(setvbuf);
163