1 /* $NetBSD: makebuf.c,v 1.7 1997/10/19 18:07:29 mycroft 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 1.7 1997/10/19 18:07:29 mycroft Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 #include <sys/types.h> 49 #include <sys/stat.h> 50 #include <unistd.h> 51 #include <stdio.h> 52 #include <stdlib.h> 53 #include "local.h" 54 55 /* 56 * Allocate a file buffer, or switch to unbuffered I/O. 57 * Per the ANSI C standard, ALL tty devices default to line buffered. 58 * 59 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 60 * optimisation) right after the fstat() that finds the buffer size. 61 */ 62 void 63 __smakebuf(fp) 64 register FILE *fp; 65 { 66 register void *p; 67 register int flags; 68 size_t size; 69 int couldbetty; 70 71 if (fp->_flags & __SNBF) { 72 fp->_bf._base = fp->_p = fp->_nbuf; 73 fp->_bf._size = 1; 74 return; 75 } 76 flags = __swhatbuf(fp, &size, &couldbetty); 77 if ((p = malloc(size)) == NULL) { 78 fp->_flags |= __SNBF; 79 fp->_bf._base = fp->_p = fp->_nbuf; 80 fp->_bf._size = 1; 81 return; 82 } 83 __cleanup = _cleanup; 84 flags |= __SMBF; 85 fp->_bf._base = fp->_p = p; 86 fp->_bf._size = size; 87 if (couldbetty && isatty(fp->_file)) 88 flags |= __SLBF; 89 fp->_flags |= flags; 90 } 91 92 /* 93 * Internal routine to determine `proper' buffering for a file. 94 */ 95 int 96 __swhatbuf(fp, bufsize, couldbetty) 97 register FILE *fp; 98 size_t *bufsize; 99 int *couldbetty; 100 { 101 struct stat st; 102 103 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 104 *couldbetty = 0; 105 *bufsize = BUFSIZ; 106 return (__SNPT); 107 } 108 109 /* could be a tty iff it is a character device */ 110 *couldbetty = S_ISCHR(st.st_mode); 111 if (st.st_blksize <= 0) { 112 *bufsize = BUFSIZ; 113 return (__SNPT); 114 } 115 116 /* 117 * Optimise fseek() only if it is a regular file. (The test for 118 * __sseek is mainly paranoia.) It is safe to set _blksize 119 * unconditionally; it will only be used if __SOPT is also set. 120 */ 121 *bufsize = st.st_blksize; 122 fp->_blksize = st.st_blksize; 123 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 124 __SOPT : __SNPT); 125 } 126