1 /*
2 * Copyright (c) 1990 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are permitted
6 * provided that the above copyright notice and this paragraph are
7 * duplicated in all such forms and that any documentation,
8 * and/or other materials related to such
9 * distribution and use acknowledge that the software was developed
10 * by the University of California, Berkeley. The name of the
11 * University may not be used to endorse or promote products derived
12 * from this software without specific prior written permission.
13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16 */
17
18 /*
19 FUNCTION
20 <<setvbuf>>---specify file or stream buffering
21
22 INDEX
23 setvbuf
24
25 SYNOPSIS
26 #include <stdio.h>
27 int setvbuf(FILE *<[fp]>, char *<[buf]>,
28 int <[mode]>, size_t <[size]>);
29
30 DESCRIPTION
31 Use <<setvbuf>> to specify what kind of buffering you want for the
32 file or stream identified by <[fp]>, by using one of the following
33 values (from <<stdio.h>>) as the <[mode]> argument:
34
35 o+
36 o _IONBF
37 Do not use a buffer: send output directly to the host system for the
38 file or stream identified by <[fp]>.
39
40 o _IOFBF
41 Use full output buffering: output will be passed on to the host system
42 only when the buffer is full, or when an input operation intervenes.
43
44 o _IOLBF
45 Use line buffering: pass on output to the host system at every
46 newline, as well as when the buffer is full, or when an input
47 operation intervenes.
48 o-
49
50 Use the <[size]> argument to specify how large a buffer you wish. You
51 can supply the buffer itself, if you wish, by passing a pointer to a
52 suitable area of memory as <[buf]>. Otherwise, you may pass <<NULL>>
53 as the <[buf]> argument, and <<setvbuf>> will allocate the buffer.
54
55 WARNINGS
56 You may only use <<setvbuf>> before performing any file operation other
57 than opening the file.
58
59 If you supply a non-null <[buf]>, you must ensure that the associated
60 storage continues to be available until you close the stream
61 identified by <[fp]>.
62
63 RETURNS
64 A <<0>> result indicates success, <<EOF>> failure (invalid <[mode]> or
65 <[size]> can cause failure).
66
67 PORTABILITY
68 Both ANSI C and the System V Interface Definition (Issue 2) require
69 <<setvbuf>>. However, they differ on the meaning of a <<NULL>> buffer
70 pointer: the SVID issue 2 specification says that a <<NULL>> buffer
71 pointer requests unbuffered output. For maximum portability, avoid
72 <<NULL>> buffer pointers.
73
74 Both specifications describe the result on failure only as a
75 nonzero value.
76
77 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
78 <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
79 */
80
81 #define _DEFAULT_SOURCE
82 #include <_ansi.h>
83 #include <stdio.h>
84 #include <stdlib.h>
85 #include "local.h"
86
87 /*
88 * Set one of the three kinds of buffering, optionally including a buffer.
89 */
90
91 int
setvbuf(register FILE * fp,char * buf,register int mode,register size_t size)92 setvbuf (register FILE * fp,
93 char *buf,
94 register int mode,
95 register size_t size)
96 {
97 int ret = 0;
98 size_t iosize;
99 int ttyflag;
100
101 CHECK_INIT (reent, fp);
102
103 /*
104 * Verify arguments. The `int' limit on `size' is due to this
105 * particular implementation. Note, buf and size are ignored
106 * when setting _IONBF.
107 */
108 if (mode != _IONBF)
109 if ((mode != _IOFBF && mode != _IOLBF) || (int)(_POINTER_INT) size < 0)
110 return (EOF);
111
112
113 /*
114 * Write current buffer, if any; drop read count, if any.
115 * Make sure putc() will not think fp is line buffered.
116 * Free old buffer if it was from malloc(). Clear line and
117 * non buffer flags, and clear malloc flag.
118 */
119 _newlib_flockfile_start (fp);
120 fflush ( fp);
121 if (HASUB(fp))
122 FREEUB(reent, fp);
123 fp->_r = fp->_lbfsize = 0;
124 if (fp->_flags & __SMBF)
125 free ((void *) fp->_bf._base);
126 fp->_flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
127
128 if (mode == _IONBF)
129 goto nbf;
130
131 /*
132 * Find optimal I/O size for seek optimization. This also returns
133 * a `tty flag' to suggest that we check isatty(fd), but we do not
134 * care since our caller told us how to buffer.
135 */
136 fp->_flags |= _swhatbuf ( fp, &iosize, &ttyflag);
137 if (size == 0)
138 {
139 buf = NULL;
140 size = iosize;
141 }
142
143 /* Allocate buffer if needed. */
144 if (buf == NULL)
145 {
146 if ((buf = malloc (size)) == NULL)
147 {
148 /*
149 * Unable to honor user's request. We will return
150 * failure, but try again with file system size.
151 */
152 ret = EOF;
153 if (size != iosize)
154 {
155 size = iosize;
156 buf = malloc (size);
157 }
158 }
159 if (buf == NULL)
160 {
161 /* No luck; switch to unbuffered I/O. */
162 nbf:
163 fp->_flags |= __SNBF;
164 fp->_w = 0;
165 fp->_bf._base = fp->_p = fp->_nbuf;
166 fp->_bf._size = 1;
167 _newlib_flockfile_exit (fp);
168 return (ret);
169 }
170 fp->_flags |= __SMBF;
171 }
172
173 /*
174 * We're committed to buffering from here, so make sure we've
175 * registered to flush buffers on exit.
176 */
177 if (!_REENT_CLEANUP(reent))
178 __sinit();
179
180 #ifdef _FSEEK_OPTIMIZATION
181 /*
182 * Kill any seek optimization if the buffer is not the
183 * right size.
184 *
185 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
186 */
187 if (size != iosize)
188 fp->_flags |= __SNPT;
189 #endif
190
191 /*
192 * Fix up the FILE fields, and set __cleanup for output flush on
193 * exit (since we are buffered in some way).
194 */
195 if (mode == _IOLBF)
196 fp->_flags |= __SLBF;
197 fp->_bf._base = fp->_p = (unsigned char *) buf;
198 fp->_bf._size = size;
199 /* fp->_lbfsize is still 0 */
200 if (fp->_flags & __SWR)
201 {
202 /*
203 * Begin or continue writing: see __swsetup(). Note
204 * that __SNBF is impossible (it was handled earlier).
205 */
206 if (fp->_flags & __SLBF)
207 {
208 fp->_w = 0;
209 fp->_lbfsize = -fp->_bf._size;
210 }
211 else
212 fp->_w = size;
213 }
214 else
215 {
216 /* begin/continue reading, or stay in intermediate state */
217 fp->_w = 0;
218 }
219
220 _newlib_flockfile_end (fp);
221 return 0;
222 }
223
