1 /* $NetBSD: makebuf.c,v 1.17 2012/03/15 18:22:30 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #if defined(LIBC_SCCS) && !defined(lint) 37 #if 0 38 static char sccsid[] = "@(#)makebuf.c 8.1 (Berkeley) 6/4/93"; 39 #else 40 __RCSID("$NetBSD: makebuf.c,v 1.17 2012/03/15 18:22:30 christos Exp $"); 41 #endif 42 #endif /* LIBC_SCCS and not lint */ 43 44 #include "namespace.h" 45 46 #include <sys/types.h> 47 #include <sys/stat.h> 48 #include <assert.h> 49 #include <stdio.h> 50 #include <stdlib.h> 51 #include <unistd.h> 52 #include "reentrant.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(FILE *fp) 64 { 65 void *p; 66 int flags; 67 size_t size; 68 int couldbetty; 69 70 _DIAGASSERT(fp != NULL); 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 _DIAGASSERT(__type_fit(int, size)); 88 fp->_bf._size = (int)size; 89 if (couldbetty && isatty(__sfileno(fp))) 90 flags |= __SLBF; 91 fp->_flags |= flags; 92 } 93 94 /* 95 * Internal routine to determine `proper' buffering for a file. 96 */ 97 int 98 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty) 99 { 100 struct stat st; 101 102 _DIAGASSERT(fp != NULL); 103 _DIAGASSERT(bufsize != NULL); 104 _DIAGASSERT(couldbetty != NULL); 105 106 if (__sfileno(fp) == -1 || fstat(__sfileno(fp), &st) < 0) { 107 *couldbetty = 0; 108 *bufsize = BUFSIZ; 109 return __SNPT; 110 } 111 112 /* could be a tty iff it is a character device */ 113 *couldbetty = S_ISCHR(st.st_mode); 114 if (st.st_blksize == 0) { 115 *bufsize = BUFSIZ; 116 return __SNPT; 117 } 118 119 /* 120 * Optimise fseek() only if it is a regular file. (The test for 121 * __sseek is mainly paranoia.) It is safe to set _blksize 122 * unconditionally; it will only be used if __SOPT is also set. 123 */ 124 *bufsize = st.st_blksize; 125 fp->_blksize = st.st_blksize; 126 return (st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 127 __SOPT : __SNPT; 128 } 129