setvbuf.c revision 22993 
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. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
40#endif
41static const char rcsid[] =
42		"$Id$";
43#endif /* LIBC_SCCS and not lint */
44
45#include <stdio.h>
46#include <stdlib.h>
47#include "local.h"
48#ifdef _THREAD_SAFE
49#include <pthread.h>
50#include "pthread_private.h"
51#endif
52
53/*
54 * Set one of the three kinds of buffering, optionally including
55 * a buffer.
56 */
57int
58setvbuf(fp, buf, mode, size)
59	register FILE *fp;
60	char *buf;
61	register int mode;
62	register size_t size;
63{
64	register int ret, flags;
65	size_t iosize;
66	int ttyflag;
67
68	/*
69	 * Verify arguments.  The `int' limit on `size' is due to this
70	 * particular implementation.  Note, buf and size are ignored
71	 * when setting _IONBF.
72	 */
73	if (mode != _IONBF)
74		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
75			return (EOF);
76
77#ifdef _THREAD_SAFE
78	_thread_flockfile(fp,__FILE__,__LINE__);
79#endif
80	/*
81	 * Write current buffer, if any.  Discard unread input (including
82	 * ungetc data), cancel line buffering, and free old buffer if
83	 * malloc()ed.  We also clear any eof condition, as if this were
84	 * a seek.
85	 */
86	ret = 0;
87	(void)__sflush(fp);
88	if (HASUB(fp))
89		FREEUB(fp);
90	fp->_r = fp->_lbfsize = 0;
91	flags = fp->_flags;
92	if (flags & __SMBF)
93		free((void *)fp->_bf._base);
94	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
95
96	/* If setting unbuffered mode, skip all the hard work. */
97	if (mode == _IONBF)
98		goto nbf;
99
100	/*
101	 * Find optimal I/O size for seek optimization.  This also returns
102	 * a `tty flag' to suggest that we check isatty(fd), but we do not
103	 * care since our caller told us how to buffer.
104	 */
105	flags |= __swhatbuf(fp, &iosize, &ttyflag);
106	if (size == 0) {
107		buf = NULL;	/* force local allocation */
108		size = iosize;
109	}
110
111	/* Allocate buffer if needed. */
112	if (buf == NULL) {
113		if ((buf = malloc(size)) == NULL) {
114			/*
115			 * Unable to honor user's request.  We will return
116			 * failure, but try again with file system size.
117			 */
118			ret = EOF;
119			if (size != iosize) {
120				size = iosize;
121				buf = malloc(size);
122			}
123		}
124		if (buf == NULL) {
125			/* No luck; switch to unbuffered I/O. */
126nbf:
127			fp->_flags = flags | __SNBF;
128			fp->_w = 0;
129			fp->_bf._base = fp->_p = fp->_nbuf;
130			fp->_bf._size = 1;
131#ifdef _THREAD_SAFE
132			_thread_funlockfile(fp);
133#endif
134			return (ret);
135		}
136		flags |= __SMBF;
137	}
138
139	/*
140	 * Kill any seek optimization if the buffer is not the
141	 * right size.
142	 *
143	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
144	 */
145	if (size != iosize)
146		flags |= __SNPT;
147
148	/*
149	 * Fix up the FILE fields, and set __cleanup for output flush on
150	 * exit (since we are buffered in some way).
151	 */
152	if (mode == _IOLBF)
153		flags |= __SLBF;
154	fp->_flags = flags;
155	fp->_bf._base = fp->_p = (unsigned char *)buf;
156	fp->_bf._size = size;
157	/* fp->_lbfsize is still 0 */
158	if (flags & __SWR) {
159		/*
160		 * Begin or continue writing: see __swsetup().  Note
161		 * that __SNBF is impossible (it was handled earlier).
162		 */
163		if (flags & __SLBF) {
164			fp->_w = 0;
165			fp->_lbfsize = -fp->_bf._size;
166		} else
167			fp->_w = size;
168	} else {
169		/* begin/continue reading, or stay in intermediate state */
170		fp->_w = 0;
171	}
172	__cleanup = _cleanup;
173
174#ifdef _THREAD_SAFE
175	_thread_funlockfile(fp);
176#endif
177	return (ret);
178}
179