1 /* $OpenBSD: makebuf.c,v 1.10 2019/06/28 13:32:42 deraadt 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 */
48 void
__smakebuf(FILE * fp)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 */
79 int
__swhatbuf(FILE * fp,size_t * bufsize,int * couldbetty)80 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
81 {
82 struct stat st;
83
84 if (fp->_file < 0 || fstat(fp->_file, &st) == -1) {
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