xref: /netbsd-src/lib/libc/stdio/makebuf.c (revision dc306354b0b29af51801a7632f1e95265a68cd81)
1 /*	$NetBSD: makebuf.c,v 1.10 1998/11/15 17:16:27 christos Exp $	*/
2 
3 /*-
4  * Copyright (c) 1990, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Chris Torek.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *	This product includes software developed by the University of
21  *	California, Berkeley and its contributors.
22  * 4. Neither the name of the University nor the names of its contributors
23  *    may be used to endorse or promote products derived from this software
24  *    without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36  * SUCH DAMAGE.
37  */
38 
39 #include <sys/cdefs.h>
40 #if defined(LIBC_SCCS) && !defined(lint)
41 #if 0
42 static char sccsid[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
43 #else
44 __RCSID("$NetBSD: makebuf.c,v 1.10 1998/11/15 17:16:27 christos Exp $");
45 #endif
46 #endif /* LIBC_SCCS and not lint */
47 
48 #include "namespace.h"
49 #include <sys/types.h>
50 #include <sys/stat.h>
51 #include <unistd.h>
52 #include <stdio.h>
53 #include <stdlib.h>
54 #include "local.h"
55 
56 /*
57  * Allocate a file buffer, or switch to unbuffered I/O.
58  * Per the ANSI C standard, ALL tty devices default to line buffered.
59  *
60  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
61  * optimisation) right after the fstat() that finds the buffer size.
62  */
63 void
64 __smakebuf(fp)
65 	FILE *fp;
66 {
67 	void *p;
68 	int flags;
69 	size_t size;
70 	int couldbetty;
71 
72 	if (fp->_flags & __SNBF) {
73 		fp->_bf._base = fp->_p = fp->_nbuf;
74 		fp->_bf._size = 1;
75 		return;
76 	}
77 	flags = __swhatbuf(fp, &size, &couldbetty);
78 	if ((p = malloc(size)) == NULL) {
79 		fp->_flags |= __SNBF;
80 		fp->_bf._base = fp->_p = fp->_nbuf;
81 		fp->_bf._size = 1;
82 		return;
83 	}
84 	__cleanup = _cleanup;
85 	flags |= __SMBF;
86 	fp->_bf._base = fp->_p = p;
87 	fp->_bf._size = size;
88 	if (couldbetty && isatty(fp->_file))
89 		flags |= __SLBF;
90 	fp->_flags |= flags;
91 }
92 
93 /*
94  * Internal routine to determine `proper' buffering for a file.
95  */
96 int
97 __swhatbuf(fp, bufsize, couldbetty)
98 	FILE *fp;
99 	size_t *bufsize;
100 	int *couldbetty;
101 {
102 	struct stat st;
103 
104 	if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
105 		*couldbetty = 0;
106 		*bufsize = BUFSIZ;
107 		return (__SNPT);
108 	}
109 
110 	/* could be a tty iff it is a character device */
111 	*couldbetty = S_ISCHR(st.st_mode);
112 	if (st.st_blksize == 0) {
113 		*bufsize = BUFSIZ;
114 		return (__SNPT);
115 	}
116 
117 	/*
118 	 * Optimise fseek() only if it is a regular file.  (The test for
119 	 * __sseek is mainly paranoia.)  It is safe to set _blksize
120 	 * unconditionally; it will only be used if __SOPT is also set.
121 	 */
122 	*bufsize = st.st_blksize;
123 	fp->_blksize = st.st_blksize;
124 	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
125 	    __SOPT : __SNPT);
126 }
127