1 /* $NetBSD: makebuf.c,v 1.5 1995/02/02 02:10:08 jtc 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 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 static char sccsid[] = "@(#)makebuf.c 8.1 (Berkeley) 6/4/93"; 42 #endif 43 static char rcsid[] = "$NetBSD: makebuf.c,v 1.5 1995/02/02 02:10:08 jtc Exp $"; 44 #endif /* LIBC_SCCS and not lint */ 45 46 #include <sys/types.h> 47 #include <sys/stat.h> 48 #include <unistd.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include "local.h" 52 53 /* 54 * Allocate a file buffer, or switch to unbuffered I/O. 55 * Per the ANSI C standard, ALL tty devices default to line buffered. 56 * 57 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 58 * optimisation) right after the fstat() that finds the buffer size. 59 */ 60 void 61 __smakebuf(fp) 62 register FILE *fp; 63 { 64 register void *p; 65 register int flags; 66 size_t size; 67 int couldbetty; 68 69 if (fp->_flags & __SNBF) { 70 fp->_bf._base = fp->_p = fp->_nbuf; 71 fp->_bf._size = 1; 72 return; 73 } 74 flags = __swhatbuf(fp, &size, &couldbetty); 75 if ((p = malloc(size)) == NULL) { 76 fp->_flags |= __SNBF; 77 fp->_bf._base = fp->_p = fp->_nbuf; 78 fp->_bf._size = 1; 79 return; 80 } 81 __cleanup = _cleanup; 82 flags |= __SMBF; 83 fp->_bf._base = fp->_p = p; 84 fp->_bf._size = size; 85 if (couldbetty && isatty(fp->_file)) 86 flags |= __SLBF; 87 fp->_flags |= flags; 88 } 89 90 /* 91 * Internal routine to determine `proper' buffering for a file. 92 */ 93 int 94 __swhatbuf(fp, bufsize, couldbetty) 95 register FILE *fp; 96 size_t *bufsize; 97 int *couldbetty; 98 { 99 struct stat st; 100 101 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 102 *couldbetty = 0; 103 *bufsize = BUFSIZ; 104 return (__SNPT); 105 } 106 107 /* could be a tty iff it is a character device */ 108 *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR; 109 if (st.st_blksize <= 0) { 110 *bufsize = BUFSIZ; 111 return (__SNPT); 112 } 113 114 /* 115 * Optimise fseek() only if it is a regular file. (The test for 116 * __sseek is mainly paranoia.) It is safe to set _blksize 117 * unconditionally; it will only be used if __SOPT is also set. 118 */ 119 *bufsize = st.st_blksize; 120 fp->_blksize = st.st_blksize; 121 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 122 __SOPT : __SNPT); 123 } 124