2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
7 * This code is derived from software contributed to Berkeley by
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11 * modification, are permitted provided that the following conditions
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14 * notice, this list of conditions and the following disclaimer.
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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)makebuf.c 8.1 (Berkeley) 6/4/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include "namespace.h"
42 #include <sys/types.h>
47 #include "un-namespace.h"
49 #include "libc_private.h"
53 * Allocate a file buffer, or switch to unbuffered I/O.
54 * Per the ANSI C standard, ALL tty devices default to line buffered.
56 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
57 * optimisation) right after the _fstat() that finds the buffer size.
67 if (fp->_flags & __SNBF) {
68 fp->_bf._base = fp->_p = fp->_nbuf;
72 flags = __swhatbuf(fp, &size, &couldbetty);
73 if ((p = malloc(size)) == NULL) {
75 fp->_bf._base = fp->_p = fp->_nbuf;
81 fp->_bf._base = fp->_p = p;
83 if (couldbetty && isatty(fp->_file))
89 * Internal routine to determine `proper' buffering for a file.
92 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
96 if (fp->_file < 0 || _fstat(fp->_file, &st) < 0) {
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) {
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.
114 *bufsize = st.st_blksize;
115 fp->_blksize = st.st_blksize;
116 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?