3 * Portions Copyright (c) 1990-2009 Nokia Corporation and/or its subsidiary(-ies).
8 * Copyright (c) 1990 The Regents of the University of California.
11 * Redistribution and use in source and binary forms are permitted
12 * provided that the above copyright notice and this paragraph are
13 * duplicated in all such forms and that any documentation,
14 * advertising materials, and other materials related to such
15 * distribution and use acknowledge that the software was developed
16 * by the University of California, Berkeley. The name of the
17 * University may not be used to endorse or promote products derived
18 * from this software without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
26 <<setvbuf>>---specify file or stream buffering
33 int setvbuf(FILE *<[fp]>, char *<[buf]>,
34 int <[mode]>, size_t <[size]>);
38 int setvbuf(<[fp]>, <[buf]>, <[mode]>, <[size]>)
45 Use <<setvbuf>> to specify what kind of buffering you want for the
46 file or stream identified by <[fp]>, by using one of the following
47 values (from <<stdio.h>>) as the <[mode]> argument:
51 Do not use a buffer: send output directly to the host system for the
52 file or stream identified by <[fp]>.
55 Use full output buffering: output will be passed on to the host system
56 only when the buffer is full, or when an input operation intervenes.
59 Use line buffering: pass on output to the host system at every
60 newline, as well as when the buffer is full, or when an input
64 Use the <[size]> argument to specify how large a buffer you wish. You
65 can supply the buffer itself, if you wish, by passing a pointer to a
66 suitable area of memory as <[buf]>. Otherwise, you may pass <<NULL>>
67 as the <[buf]> argument, and <<setvbuf>> will allocate the buffer.
70 You may only use <<setvbuf>> before performing any file operation other
71 than opening the file.
73 If you supply a non-null <[buf]>, you must ensure that the associated
74 storage continues to be available until you close the stream
78 A <<0>> result indicates success, <<EOF>> failure (invalid <[mode]> or
79 <[size]> can cause failure).
82 Both ANSI C and the System V Interface Definition (Issue 2) require
83 <<setvbuf>>. However, they differ on the meaning of a <<NULL>> buffer
84 pointer: the SVID issue 2 specification says that a <<NULL>> buffer
85 pointer requests unbuffered output. For maximum portability, avoid
86 <<NULL>> buffer pointers.
88 Both specifications describe the result on failure only as a
91 Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
92 <<lseek>>, <<read>>, <<sbrk>>, <<write>>.
100 Change stream buffering.
101 Changes the buffer to be used for I/O operations with the specified stream.
102 Size and mode for the buffer can be specified.
103 This function should be called once the file associated with the stream
104 has been opened but before any input or output operation has been done.
105 The size of the buffer is specified by the size parameter,
106 and can be any value between 2 and 32767 in bytes,
107 this value may be rounded down by some system due to specific alignment.
109 @return If the buffer is correctly assigned to the file a 0 value is returned.
110 On error, a non-zero value is returned. This can be because an invalid type or size has been specified or because an error allocating memory (if NULL buffer was specified).
111 @param fp pointer to an open file.
112 @param buf User allocated buffer. Must have at least a size of size bytes.
113 @param mode Specifies a mode for file buffering
114 @param Buffer size in bytes, must be more than 0 and less than 32768, this value may be rounded down by some systems due to specific alignment, in which case the minimum value should be 2.
117 setvbuf (FILE * fp, char *buf, int mode, size_t size)
123 * Verify arguments. The `int' limit on `size' is due to this
124 * particular implementation.
127 if ((mode != _IOFBF && mode != _IOLBF && mode != _IONBF) || (int) size < 0)
131 * Write current buffer, if any; drop read count, if any.
132 * Make sure putc() will not think fp is line buffered.
133 * Free old buffer if it was from malloc(). Clear line and
134 * non buffer flags, and clear malloc flag.
140 if (fp->_flags & __SMBF)
141 _free_r (fp->_data, (void *) fp->_bf._base);
142 fp->_flags &= ~(__SLBF | __SNBF | __SMBF);
148 * Allocate buffer if needed. */
151 if ((buf = (char *)malloc (size)) == NULL)
154 /* Try another size... */
155 buf = (char *)malloc (BUFSIZ);
159 /* Can't allocate it, let's try another approach */
161 fp->_flags |= __SNBF;
163 fp->_bf._base = fp->_p = fp->_nbuf;
167 fp->_flags |= __SMBF;
170 * Now put back whichever flag is needed, and fix _lbfsize
171 * if line buffered. Ensure output flush on exit if the
172 * stream will be buffered at all.
173 * Force the buffer to be flushed and hence malloced on first use
179 fp->_flags |= __SLBF;
180 fp->_lbfsize = -(int)size;
185 fp->_data->__cleanup = _cleanup_r;
186 fp->_bf._base = fp->_p = (unsigned char *) buf;
187 fp->_bf._size = size;
192 * Patch up write count if necessary.
195 if (fp->_flags & __SWR)
196 fp->_w = fp->_flags & (__SLBF | __SNBF) ? 0 : size;