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---
makebuf.c (3860B)
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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 static char rcsid[] = "$OpenBSD: makebuf.c,v 1.2 1996/08/19 08:32:54 tholo Exp $";
39 #endif /* LIBC_SCCS and not lint */
40
41 #include <sys/types.h>
42 #include <sys/stat.h>
43 #include <unistd.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include "local.h"
47
48 /*
49 * Allocate a file buffer, or switch to unbuffered I/O.
50 * Per the ANSI C standard, ALL tty devices default to line buffered.
51 *
52 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
53 * optimisation) right after the fstat() that finds the buffer size.
54 */
55 void
56 __smakebuf(fp)
57 register FILE *fp;
58 {
59 register void *p;
60 register int flags;
61 size_t size;
62 int couldbetty;
63
64 if (fp->_flags & __SNBF) {
65 fp->_bf._base = fp->_p = fp->_nbuf;
66 fp->_bf._size = 1;
67 return;
68 }
69 flags = __swhatbuf(fp, &size, &couldbetty);
70 if ((p = malloc(size)) == NULL) {
71 fp->_flags |= __SNBF;
72 fp->_bf._base = fp->_p = fp->_nbuf;
73 fp->_bf._size = 1;
74 return;
75 }
76 __cleanup = _cleanup;
77 flags |= __SMBF;
78 fp->_bf._base = fp->_p = p;
79 fp->_bf._size = size;
80 if (couldbetty && isatty(fp->_file))
81 flags |= __SLBF;
82 fp->_flags |= flags;
83 }
84
85 /*
86 * Internal routine to determine `proper' buffering for a file.
87 */
88 int
89 __swhatbuf(fp, bufsize, couldbetty)
90 register FILE *fp;
91 size_t *bufsize;
92 int *couldbetty;
93 {
94 struct stat st;
95
96 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
97 *couldbetty = 0;
98 *bufsize = BUFSIZ;
99 return (__SNPT);
100 }
101
102 /* could be a tty iff it is a character device */
103 *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
104 if (st.st_blksize <= 0) {
105 *bufsize = BUFSIZ;
106 return (__SNPT);
107 }
108
109 /*
110 * Optimise fseek() only if it is a regular file. (The test for
111 * __sseek is mainly paranoia.) It is safe to set _blksize
112 * unconditionally; it will only be used if __SOPT is also set.
113 */
114 *bufsize = st.st_blksize;
115 fp->_blksize = st.st_blksize;
116 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
117 __SOPT : __SNPT);
118 }