1/*	$OpenBSD: makebuf.c,v 1.9 2015/01/13 07:18:21 guenther Exp $ */
2/*-
3 * Copyright (c) 1990, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <sys/types.h>
35#include <sys/stat.h>
36#include <unistd.h>
37#include <stdio.h>
38#include <stdlib.h>
39#include "local.h"
40
41/*
42 * Allocate a file buffer, or switch to unbuffered I/O.
43 * Per the ANSI C standard, ALL tty devices default to line buffered.
44 *
45 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
46 * optimisation) right after the fstat() that finds the buffer size.
47 */
48void
49__smakebuf(FILE *fp)
50{
51	void *p;
52	int flags;
53	size_t size;
54	int couldbetty;
55
56	if (fp->_flags & __SNBF) {
57		fp->_bf._base = fp->_p = fp->_nbuf;
58		fp->_bf._size = 1;
59		return;
60	}
61	flags = __swhatbuf(fp, &size, &couldbetty);
62	if ((p = malloc(size)) == NULL) {
63		fp->_flags |= __SNBF;
64		fp->_bf._base = fp->_p = fp->_nbuf;
65		fp->_bf._size = 1;
66		return;
67	}
68	flags |= __SMBF;
69	fp->_bf._base = fp->_p = p;
70	fp->_bf._size = size;
71	if (couldbetty && isatty(fp->_file))
72		flags |= __SLBF;
73	fp->_flags |= flags;
74}
75
76/*
77 * Internal routine to determine `proper' buffering for a file.
78 */
79int
80__swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
81{
82	struct stat st;
83
84	if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
85		*couldbetty = 0;
86		*bufsize = BUFSIZ;
87		return (__SNPT);
88	}
89
90	/* could be a tty iff it is a character device */
91	*couldbetty = S_ISCHR(st.st_mode);
92	if (st.st_blksize == 0) {
93		*bufsize = BUFSIZ;
94		return (__SNPT);
95	}
96
97	/*
98	 * Optimise fseek() only if it is a regular file.  (The test for
99	 * __sseek is mainly paranoia.)  It is safe to set _blksize
100	 * unconditionally; it will only be used if __SOPT is also set.
101	 */
102	*bufsize = st.st_blksize;
103	fp->_blksize = st.st_blksize;
104	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
105	    __SOPT : __SNPT);
106}
107