1/*	$OpenBSD: setvbuf.c,v 1.14 2016/09/21 04:38:56 guenther 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 <stdio.h>
35#include <stdlib.h>
36#include "local.h"
37
38/*
39 * Set one of the three kinds of buffering, optionally including
40 * a buffer.
41 */
42int
43setvbuf(FILE *fp, char *buf, int mode, size_t size)
44{
45	int ret, flags;
46	size_t iosize;
47	int ttyflag;
48
49	/*
50	 * Verify arguments.  The `int' limit on `size' is due to this
51	 * particular implementation.  Note, buf and size are ignored
52	 * when setting _IONBF.
53	 */
54	if (mode != _IONBF)
55		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
56			return (EOF);
57
58	/*
59	 * Write current buffer, if any.  Discard unread input (including
60	 * ungetc data), cancel line buffering, and free old buffer if
61	 * malloc()ed.  We also clear any eof condition, as if this were
62	 * a seek.
63	 */
64	FLOCKFILE(fp);
65	ret = 0;
66	(void)__sflush(fp);
67	if (HASUB(fp))
68		FREEUB(fp);
69	WCIO_FREE(fp);
70	fp->_r = fp->_lbfsize = 0;
71	flags = fp->_flags;
72	if (flags & __SMBF)
73		free(fp->_bf._base);
74	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
75
76	/* If setting unbuffered mode, skip all the hard work. */
77	if (mode == _IONBF)
78		goto nbf;
79
80	/*
81	 * Find optimal I/O size for seek optimization.  This also returns
82	 * a `tty flag' to suggest that we check isatty(fd), but we do not
83	 * care since our caller told us how to buffer.
84	 */
85	flags |= __swhatbuf(fp, &iosize, &ttyflag);
86	if (size == 0) {
87		buf = NULL;	/* force local allocation */
88		size = iosize;
89	}
90
91	/* Allocate buffer if needed. */
92	if (buf == NULL) {
93		if ((buf = malloc(size)) == NULL) {
94			/*
95			 * Unable to honor user's request.  We will return
96			 * failure, but try again with file system size.
97			 */
98			ret = EOF;
99			if (size != iosize) {
100				size = iosize;
101				buf = malloc(size);
102			}
103		}
104		if (buf == NULL) {
105			/* No luck; switch to unbuffered I/O. */
106nbf:
107			fp->_flags = flags | __SNBF;
108			fp->_w = 0;
109			fp->_bf._base = fp->_p = fp->_nbuf;
110			fp->_bf._size = 1;
111			FUNLOCKFILE(fp);
112			return (ret);
113		}
114		flags |= __SMBF;
115	}
116
117	/*
118	 * We're committed to buffering from here, so make sure we've
119	 * registered to flush buffers on exit.
120	 */
121	if (!__sdidinit)
122		__sinit();
123
124	/*
125	 * Kill any seek optimization if the buffer is not the
126	 * right size.
127	 *
128	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
129	 */
130	if (size != iosize)
131		flags |= __SNPT;
132
133	/*
134	 * Fix up the FILE fields.
135	 */
136	if (mode == _IOLBF)
137		flags |= __SLBF;
138	fp->_flags = flags;
139	fp->_bf._base = fp->_p = (unsigned char *)buf;
140	fp->_bf._size = size;
141	/* fp->_lbfsize is still 0 */
142	if (flags & __SWR) {
143		/*
144		 * Begin or continue writing: see __swsetup().  Note
145		 * that __SNBF is impossible (it was handled earlier).
146		 */
147		if (flags & __SLBF) {
148			fp->_w = 0;
149			fp->_lbfsize = -fp->_bf._size;
150		} else
151			fp->_w = size;
152	} else {
153		/* begin/continue reading, or stay in intermediate state */
154		fp->_w = 0;
155	}
156	FUNLOCKFILE(fp);
157
158	return (ret);
159}
160DEF_STRONG(setvbuf);
161