setvbuf.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
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. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/setvbuf.c 330897 2018-03-14 03:19:51Z eadler $");
40
41#include "namespace.h"
42#include <stdio.h>
43#include <stdlib.h>
44#include "un-namespace.h"
45#include "local.h"
46#include "libc_private.h"
47
48/*
49 * Set one of the three kinds of buffering, optionally including
50 * a buffer.
51 */
52int
53setvbuf(FILE * __restrict fp, char * __restrict buf, int mode, size_t size)
54{
55	int ret, flags;
56	size_t iosize;
57	int ttyflag;
58
59	/*
60	 * Verify arguments.  The `int' limit on `size' is due to this
61	 * particular implementation.  Note, buf and size are ignored
62	 * when setting _IONBF.
63	 */
64	if (mode != _IONBF)
65		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
66			return (EOF);
67
68	FLOCKFILE_CANCELSAFE(fp);
69	/*
70	 * Write current buffer, if any.  Discard unread input (including
71	 * ungetc data), cancel line buffering, and free old buffer if
72	 * malloc()ed.  We also clear any eof condition, as if this were
73	 * a seek.
74	 */
75	ret = 0;
76	(void)__sflush(fp);
77	if (HASUB(fp))
78		FREEUB(fp);
79	fp->_r = fp->_lbfsize = 0;
80	flags = fp->_flags;
81	if (flags & __SMBF)
82		free((void *)fp->_bf._base);
83	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SOFF | __SNPT | __SEOF);
84
85	/* If setting unbuffered mode, skip all the hard work. */
86	if (mode == _IONBF)
87		goto nbf;
88
89	/*
90	 * Find optimal I/O size for seek optimization.  This also returns
91	 * a `tty flag' to suggest that we check isatty(fd), but we do not
92	 * care since our caller told us how to buffer.
93	 */
94	flags |= __swhatbuf(fp, &iosize, &ttyflag);
95	if (size == 0) {
96		buf = NULL;	/* force local allocation */
97		size = iosize;
98	}
99
100	/* Allocate buffer if needed. */
101	if (buf == NULL) {
102		if ((buf = malloc(size)) == NULL) {
103			/*
104			 * Unable to honor user's request.  We will return
105			 * failure, but try again with file system size.
106			 */
107			ret = EOF;
108			if (size != iosize) {
109				size = iosize;
110				buf = malloc(size);
111			}
112		}
113		if (buf == NULL) {
114			/* No luck; switch to unbuffered I/O. */
115nbf:
116			fp->_flags = flags | __SNBF;
117			fp->_w = 0;
118			fp->_bf._base = fp->_p = fp->_nbuf;
119			fp->_bf._size = 1;
120			goto end;
121		}
122		flags |= __SMBF;
123	}
124
125	/*
126	 * Kill any seek optimization if the buffer is not the
127	 * right size.
128	 *
129	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
130	 */
131	if (size != iosize)
132		flags |= __SNPT;
133
134	/*
135	 * Fix up the FILE fields, and set __cleanup for output flush on
136	 * exit (since we are buffered in some way).
137	 */
138	if (mode == _IOLBF)
139		flags |= __SLBF;
140	fp->_flags = flags;
141	fp->_bf._base = fp->_p = (unsigned char *)buf;
142	fp->_bf._size = size;
143	/* fp->_lbfsize is still 0 */
144	if (flags & __SWR) {
145		/*
146		 * Begin or continue writing: see __swsetup().  Note
147		 * that __SNBF is impossible (it was handled earlier).
148		 */
149		if (flags & __SLBF) {
150			fp->_w = 0;
151			fp->_lbfsize = -fp->_bf._size;
152		} else
153			fp->_w = size;
154	} else {
155		/* begin/continue reading, or stay in intermediate state */
156		fp->_w = 0;
157	}
158	__cleanup = _cleanup;
159
160end:
161	FUNLOCKFILE_CANCELSAFE();
162	return (ret);
163}
164