setvbuf.c revision 331722 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/setvbuf.c 331722 2018-03-29 02:50:57Z eadler $");
38
39#include "namespace.h"
40#include <stdio.h>
41#include <stdlib.h>
42#include "un-namespace.h"
43#include "local.h"
44#include "libc_private.h"
45
46/*
47 * Set one of the three kinds of buffering, optionally including
48 * a buffer.
49 */
50int
51setvbuf(FILE * __restrict fp, char * __restrict buf, int mode, size_t size)
52{
53	int ret, flags;
54	size_t iosize;
55	int ttyflag;
56
57	/*
58	 * Verify arguments.  The `int' limit on `size' is due to this
59	 * particular implementation.  Note, buf and size are ignored
60	 * when setting _IONBF.
61	 */
62	if (mode != _IONBF)
63		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
64			return (EOF);
65
66	FLOCKFILE_CANCELSAFE(fp);
67	/*
68	 * Write current buffer, if any.  Discard unread input (including
69	 * ungetc data), cancel line buffering, and free old buffer if
70	 * malloc()ed.  We also clear any eof condition, as if this were
71	 * a seek.
72	 */
73	ret = 0;
74	(void)__sflush(fp);
75	if (HASUB(fp))
76		FREEUB(fp);
77	fp->_r = fp->_lbfsize = 0;
78	flags = fp->_flags;
79	if (flags & __SMBF)
80		free((void *)fp->_bf._base);
81	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SOFF | __SNPT | __SEOF);
82
83	/* If setting unbuffered mode, skip all the hard work. */
84	if (mode == _IONBF)
85		goto nbf;
86
87	/*
88	 * Find optimal I/O size for seek optimization.  This also returns
89	 * a `tty flag' to suggest that we check isatty(fd), but we do not
90	 * care since our caller told us how to buffer.
91	 */
92	flags |= __swhatbuf(fp, &iosize, &ttyflag);
93	if (size == 0) {
94		buf = NULL;	/* force local allocation */
95		size = iosize;
96	}
97
98	/* Allocate buffer if needed. */
99	if (buf == NULL) {
100		if ((buf = malloc(size)) == NULL) {
101			/*
102			 * Unable to honor user's request.  We will return
103			 * failure, but try again with file system size.
104			 */
105			ret = EOF;
106			if (size != iosize) {
107				size = iosize;
108				buf = malloc(size);
109			}
110		}
111		if (buf == NULL) {
112			/* No luck; switch to unbuffered I/O. */
113nbf:
114			fp->_flags = flags | __SNBF;
115			fp->_w = 0;
116			fp->_bf._base = fp->_p = fp->_nbuf;
117			fp->_bf._size = 1;
118			goto end;
119		}
120		flags |= __SMBF;
121	}
122
123	/*
124	 * Kill any seek optimization if the buffer is not the
125	 * right size.
126	 *
127	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
128	 */
129	if (size != iosize)
130		flags |= __SNPT;
131
132	/*
133	 * Fix up the FILE fields, and set __cleanup for output flush on
134	 * exit (since we are buffered in some way).
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	__cleanup = _cleanup;
157
158end:
159	FUNLOCKFILE_CANCELSAFE();
160	return (ret);
161}
162