makebuf.c revision 150040 
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)
38static char sccsid[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
39#endif /* LIBC_SCCS and not lint */
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/lib/libc/stdio/makebuf.c 150040 2005-09-12 13:46:32Z stefanf $");
42
43#include "namespace.h"
44#include <sys/types.h>
45#include <sys/stat.h>
46#include <unistd.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include "un-namespace.h"
50
51#include "libc_private.h"
52#include "local.h"
53
54/*
55 * Allocate a file buffer, or switch to unbuffered I/O.
56 * Per the ANSI C standard, ALL tty devices default to line buffered.
57 *
58 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
59 * optimisation) right after the _fstat() that finds the buffer size.
60 */
61void
62__smakebuf(fp)
63	FILE *fp;
64{
65	void *p;
66	int flags;
67	size_t size;
68	int couldbetty;
69
70	if (fp->_flags & __SNBF) {
71		fp->_bf._base = fp->_p = fp->_nbuf;
72		fp->_bf._size = 1;
73		return;
74	}
75	flags = __swhatbuf(fp, &size, &couldbetty);
76	if ((p = malloc(size)) == NULL) {
77		fp->_flags |= __SNBF;
78		fp->_bf._base = fp->_p = fp->_nbuf;
79		fp->_bf._size = 1;
80		return;
81	}
82	__cleanup = _cleanup;
83	flags |= __SMBF;
84	fp->_bf._base = fp->_p = p;
85	fp->_bf._size = size;
86	if (couldbetty && isatty(fp->_file))
87		flags |= __SLBF;
88	fp->_flags |= flags;
89}
90
91/*
92 * Internal routine to determine `proper' buffering for a file.
93 */
94int
95__swhatbuf(fp, bufsize, couldbetty)
96	FILE *fp;
97	size_t *bufsize;
98	int *couldbetty;
99{
100	struct stat st;
101
102	if (fp->_file < 0 || _fstat(fp->_file, &st) < 0) {
103		*couldbetty = 0;
104		*bufsize = BUFSIZ;
105		return (__SNPT);
106	}
107
108	/* could be a tty iff it is a character device */
109	*couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
110	if (st.st_blksize <= 0) {
111		*bufsize = BUFSIZ;
112		return (__SNPT);
113	}
114
115	/*
116	 * Optimise fseek() only if it is a regular file.  (The test for
117	 * __sseek is mainly paranoia.)  It is safe to set _blksize
118	 * unconditionally; it will only be used if __SOPT is also set.
119	 */
120	*bufsize = st.st_blksize;
121	fp->_blksize = st.st_blksize;
122	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
123	    __SOPT : __SNPT);
124}
125