xref: /netbsd-src/lib/libc/stdio/setvbuf.c (revision 76dfffe33547c37f8bdd446e3e4ab0f3c16cea4b)
1 /*	$NetBSD: setvbuf.c,v 1.8 1996/03/29 23:29:22 jtc Exp $	*/
2 
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. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #if defined(LIBC_SCCS) && !defined(lint)
40 #if 0
41 static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
42 #endif
43 static char rcsid[] = "$NetBSD: setvbuf.c,v 1.8 1996/03/29 23:29:22 jtc Exp $";
44 #endif /* LIBC_SCCS and not lint */
45 
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include "local.h"
49 
50 /*
51  * Set one of the three kinds of buffering, optionally including
52  * a buffer.
53  */
54 int
55 setvbuf(fp, buf, mode, size)
56 	register FILE *fp;
57 	char *buf;
58 	register int mode;
59 	register size_t size;
60 {
61 	register int ret, flags;
62 	size_t iosize;
63 	int ttyflag;
64 
65 	/*
66 	 * Verify arguments.  The `int' limit on `size' is due to this
67 	 * particular implementation.  Note, buf and size are ignored
68 	 * when setting _IONBF.
69 	 */
70 	if (mode != _IONBF)
71 		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
72 			return (EOF);
73 
74 	/*
75 	 * Write current buffer, if any.  Discard unread input (including
76 	 * ungetc data), cancel line buffering, and free old buffer if
77 	 * malloc()ed.  We also clear any eof condition, as if this were
78 	 * a seek.
79 	 */
80 	ret = 0;
81 	(void)__sflush(fp);
82 	if (HASUB(fp))
83 		FREEUB(fp);
84 	fp->_r = fp->_lbfsize = 0;
85 	flags = fp->_flags;
86 	if (flags & __SMBF)
87 		free((void *)fp->_bf._base);
88 	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
89 
90 	/* If setting unbuffered mode, skip all the hard work. */
91 	if (mode == _IONBF)
92 		goto nbf;
93 
94 	/*
95 	 * Find optimal I/O size for seek optimization.  This also returns
96 	 * a `tty flag' to suggest that we check isatty(fd), but we do not
97 	 * care since our caller told us how to buffer.
98 	 */
99 	flags |= __swhatbuf(fp, &iosize, &ttyflag);
100 	if (size == 0) {
101 		buf = NULL;	/* force local allocation */
102 		size = iosize;
103 	}
104 
105 	/* Allocate buffer if needed. */
106 	if (buf == NULL) {
107 		if ((buf = malloc(size)) == NULL) {
108 			/*
109 			 * Unable to honor user's request.  We will return
110 			 * failure, but try again with file system size.
111 			 */
112 			ret = EOF;
113 			if (size != iosize) {
114 				size = iosize;
115 				buf = malloc(size);
116 			}
117 		}
118 		if (buf == NULL) {
119 			/* No luck; switch to unbuffered I/O. */
120 nbf:
121 			fp->_flags = flags | __SNBF;
122 			fp->_w = 0;
123 			fp->_bf._base = fp->_p = fp->_nbuf;
124 			fp->_bf._size = 1;
125 			return (ret);
126 		}
127 		flags |= __SMBF;
128 	}
129 
130 	/*
131 	 * Kill any seek optimization if the buffer is not the
132 	 * right size.
133 	 *
134 	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
135 	 */
136 	if (size != iosize)
137 		flags |= __SNPT;
138 
139 	/*
140 	 * Fix up the FILE fields, and set __cleanup for output flush on
141 	 * exit (since we are buffered in some way).
142 	 */
143 	if (mode == _IOLBF)
144 		flags |= __SLBF;
145 	fp->_flags = flags;
146 	fp->_bf._base = fp->_p = (unsigned char *)buf;
147 	fp->_bf._size = size;
148 	/* fp->_lbfsize is still 0 */
149 	if (flags & __SWR) {
150 		/*
151 		 * Begin or continue writing: see __swsetup().  Note
152 		 * that __SNBF is impossible (it was handled earlier).
153 		 */
154 		if (flags & __SLBF) {
155 			fp->_w = 0;
156 			fp->_lbfsize = -fp->_bf._size;
157 		} else
158 			fp->_w = size;
159 	} else {
160 		/* begin/continue reading, or stay in intermediate state */
161 		fp->_w = 0;
162 	}
163 	__cleanup = _cleanup;
164 
165 	return (ret);
166 }
167