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 <stdio.h>
83 #include <stdlib.h>
84 #include "local.h"
85
86 /*
87 * Set one of the three kinds of buffering, optionally including a buffer.
88 */
89
90 int
setvbuf(register FILE * fp,char * buf,register int mode,register size_t size)91 setvbuf (register FILE * fp,
92 char *buf,
93 register int mode,
94 register size_t size)
95 {
96 int ret = 0;
97 size_t iosize;
98 int ttyflag;
99
100 CHECK_INIT (reent, fp);
101
102 /*
103 * Verify arguments. The `int' limit on `size' is due to this
104 * particular implementation. Note, buf and size are ignored
105 * when setting _IONBF.
106 */
107 if (mode != _IONBF)
108 if ((mode != _IOFBF && mode != _IOLBF) || (int)(_POINTER_INT) size < 0)
109 return (EOF);
110
111
112 /*
113 * Write current buffer, if any; drop read count, if any.
114 * Make sure putc() will not think fp is line buffered.
115 * Free old buffer if it was from malloc(). Clear line and
116 * non buffer flags, and clear malloc flag.
117 */
118 _newlib_flockfile_start (fp);
119 fflush ( fp);
120 if (HASUB(fp))
121 FREEUB(reent, fp);
122 fp->_r = fp->_lbfsize = 0;
123 if (fp->_flags & __SMBF)
124 free ((void *) fp->_bf._base);
125 fp->_flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
126
127 if (mode == _IONBF)
128 goto nbf;
129
130 /*
131 * Find optimal I/O size for seek optimization. This also returns
132 * a `tty flag' to suggest that we check isatty(fd), but we do not
133 * care since our caller told us how to buffer.
134 */
135 fp->_flags |= _swhatbuf ( fp, &iosize, &ttyflag);
136 if (size == 0)
137 {
138 buf = NULL;
139 size = iosize;
140 }
141
142 /* Allocate buffer if needed. */
143 if (buf == NULL)
144 {
145 if ((buf = malloc (size)) == NULL)
146 {
147 /*
148 * Unable to honor user's request. We will return
149 * failure, but try again with file system size.
150 */
151 ret = EOF;
152 if (size != iosize)
153 {
154 size = iosize;
155 buf = malloc (size);
156 }
157 }
158 if (buf == NULL)
159 {
160 /* No luck; switch to unbuffered I/O. */
161 nbf:
162 fp->_flags |= __SNBF;
163 fp->_w = 0;
164 fp->_bf._base = fp->_p = fp->_nbuf;
165 fp->_bf._size = 1;
166 _newlib_flockfile_exit (fp);
167 return (ret);
168 }
169 fp->_flags |= __SMBF;
170 }
171
172 /*
173 * We're committed to buffering from here, so make sure we've
174 * registered to flush buffers on exit.
175 */
176 if (!_REENT_CLEANUP(reent))
177 __sinit();
178
179 #ifdef _FSEEK_OPTIMIZATION
180 /*
181 * Kill any seek optimization if the buffer is not the
182 * right size.
183 *
184 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
185 */
186 if (size != iosize)
187 fp->_flags |= __SNPT;
188 #endif
189
190 /*
191 * Fix up the FILE fields, and set __cleanup for output flush on
192 * exit (since we are buffered in some way).
193 */
194 if (mode == _IOLBF)
195 fp->_flags |= __SLBF;
196 fp->_bf._base = fp->_p = (unsigned char *) buf;
197 fp->_bf._size = size;
198 /* fp->_lbfsize is still 0 */
199 if (fp->_flags & __SWR)
200 {
201 /*
202 * Begin or continue writing: see __swsetup(). Note
203 * that __SNBF is impossible (it was handled earlier).
204 */
205 if (fp->_flags & __SLBF)
206 {
207 fp->_w = 0;
208 fp->_lbfsize = -fp->_bf._size;
209 }
210 else
211 fp->_w = size;
212 }
213 else
214 {
215 /* begin/continue reading, or stay in intermediate state */
216 fp->_w = 0;
217 }
218
219 _newlib_flockfile_end (fp);
220 return 0;
221 }
222
