makebuf.c revision 92889 
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 * $FreeBSD: head/lib/libc/stdio/makebuf.c 92889 2002-03-21 18:49:23Z obrien $
37 */
38
39#if defined(LIBC_SCCS) && !defined(lint)
40static char sccsid[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
41#endif /* LIBC_SCCS and not lint */
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 "local.h"
50#include "un-namespace.h"
51
52/*
53 * Allocate a file buffer, or switch to unbuffered I/O.
54 * Per the ANSI C standard, ALL tty devices default to line buffered.
55 *
56 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
57 * optimisation) right after the _fstat() that finds the buffer size.
58 */
59void
60__smakebuf(fp)
61	FILE *fp;
62{
63	void *p;
64	int flags;
65	size_t size;
66	int couldbetty;
67
68	if (fp->_flags & __SNBF) {
69		fp->_bf._base = fp->_p = fp->_nbuf;
70		fp->_bf._size = 1;
71		return;
72	}
73	flags = __swhatbuf(fp, &size, &couldbetty);
74	if ((p = malloc(size)) == NULL) {
75		fp->_flags |= __SNBF;
76		fp->_bf._base = fp->_p = fp->_nbuf;
77		fp->_bf._size = 1;
78		return;
79	}
80	__cleanup = _cleanup;
81	flags |= __SMBF;
82	fp->_bf._base = fp->_p = p;
83	fp->_bf._size = size;
84	if (couldbetty && isatty(fp->_file))
85		flags |= __SLBF;
86	fp->_flags |= flags;
87}
88
89/*
90 * Internal routine to determine `proper' buffering for a file.
91 */
92int
93__swhatbuf(fp, bufsize, couldbetty)
94	FILE *fp;
95	size_t *bufsize;
96	int *couldbetty;
97{
98	struct stat st;
99
100	if (fp->_file < 0 || _fstat(fp->_file, &st) < 0) {
101		*couldbetty = 0;
102		*bufsize = BUFSIZ;
103		return (__SNPT);
104	}
105
106	/* could be a tty iff it is a character device */
107	*couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
108	if (st.st_blksize <= 0) {
109		*bufsize = BUFSIZ;
110		return (__SNPT);
111	}
112
113	/*
114	 * Optimise fseek() only if it is a regular file.  (The test for
115	 * __sseek is mainly paranoia.)  It is safe to set _blksize
116	 * unconditionally; it will only be used if __SOPT is also set.
117	 */
118	*bufsize = st.st_blksize;
119	fp->_blksize = st.st_blksize;
120	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
121	    __SOPT : __SNPT);
122}
123