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 * 4. 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[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: src/lib/libc/stdio/makebuf.c,v 1.6 2007/01/09 00:28:07 imp Exp $");
38
39#include "namespace.h"
40#include <sys/types.h>
41#include <sys/stat.h>
42#include <unistd.h>
43#include <stdio.h>
44#include <stdlib.h>
45#include "un-namespace.h"
46
47#include "libc_private.h"
48#include "local.h"
49
50#ifdef FEATURE_SMALL_STDIOBUF
51# define MAXBUFSIZE	(1 << 12)
52#else
53# define MAXBUFSIZE	(1 << 16)
54#endif
55
56#define TTYBUFSIZE	4096
57
58/*
59 * Allocate a file buffer, or switch to unbuffered I/O.
60 * Per the ANSI C standard, ALL tty devices default to line buffered.
61 *
62 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
63 * optimisation) right after the _fstat() that finds the buffer size.
64 */
65void
66__smakebuf(fp)
67	FILE *fp;
68{
69	void *p;
70	int flags;
71	size_t size;
72	int couldbetty;
73
74	if (fp->_flags & __SNBF) {
75		fp->_bf._base = fp->_p = fp->_nbuf;
76		fp->_bf._size = 1;
77		return;
78	}
79	flags = __swhatbuf(fp, &size, &couldbetty);
80	if (couldbetty && isatty(fp->_file)) {
81		flags |= __SLBF;
82		/* st_blksize for ttys is 128K, so make it more reasonable */
83		if (size > TTYBUFSIZE)
84			fp->_blksize = size = TTYBUFSIZE;
85	}
86	if ((p = malloc(size)) == NULL) {
87		fp->_flags |= __SNBF;
88		fp->_bf._base = fp->_p = fp->_nbuf;
89		fp->_bf._size = 1;
90		return;
91	}
92	__cleanup = _cleanup;
93	flags |= __SMBF;
94	fp->_bf._base = fp->_p = p;
95	fp->_bf._size = size;
96	fp->_flags |= flags;
97}
98
99/*
100 * Internal routine to determine `proper' buffering for a file.
101 */
102int
103__swhatbuf(fp, bufsize, couldbetty)
104	FILE *fp;
105	size_t *bufsize;
106	int *couldbetty;
107{
108	struct stat st;
109
110	if (fp->_file < 0 || _fstat(fp->_file, &st) < 0) {
111		*couldbetty = 0;
112		*bufsize = BUFSIZ;
113		return (__SNPT);
114	}
115
116	/* could be a tty iff it is a character device */
117	*couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
118	if (st.st_blksize <= 0) {
119		*bufsize = BUFSIZ;
120		return (__SNPT);
121	}
122
123	/*
124	 * Optimise fseek() only if it is a regular file.  (The test for
125	 * __sseek is mainly paranoia.)  It is safe to set _blksize
126	 * unconditionally; it will only be used if __SOPT is also set.
127	 */
128	fp->_blksize = *bufsize = st.st_blksize > MAXBUFSIZE ? MAXBUFSIZE : st.st_blksize;
129	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
130	    __SOPT : __SNPT);
131}
132