1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #if defined(LIBC_SCCS) && !defined(lint) 34 static char rcsid[] = "$OpenBSD: makebuf.c,v 1.5 2003/06/02 20:18:37 millert Exp $"; 35 #endif /* LIBC_SCCS and not lint */ 36 37 #include <sys/types.h> 38 #include <sys/stat.h> 39 #include <unistd.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include "local.h" 43 44 /* 45 * Allocate a file buffer, or switch to unbuffered I/O. 46 * Per the ANSI C standard, ALL tty devices default to line buffered. 47 * 48 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 49 * optimisation) right after the fstat() that finds the buffer size. 50 */ 51 void 52 __smakebuf(fp) 53 register FILE *fp; 54 { 55 register void *p; 56 register int flags; 57 size_t size; 58 int couldbetty; 59 60 if (fp->_flags & __SNBF) { 61 fp->_bf._base = fp->_p = fp->_nbuf; 62 fp->_bf._size = 1; 63 return; 64 } 65 flags = __swhatbuf(fp, &size, &couldbetty); 66 if ((p = malloc(size)) == NULL) { 67 fp->_flags |= __SNBF; 68 fp->_bf._base = fp->_p = fp->_nbuf; 69 fp->_bf._size = 1; 70 return; 71 } 72 __atexit_register_cleanup(_cleanup); 73 flags |= __SMBF; 74 fp->_bf._base = fp->_p = p; 75 fp->_bf._size = size; 76 if (couldbetty && isatty(fp->_file)) 77 flags |= __SLBF; 78 fp->_flags |= flags; 79 } 80 81 /* 82 * Internal routine to determine `proper' buffering for a file. 83 */ 84 int 85 __swhatbuf(fp, bufsize, couldbetty) 86 register FILE *fp; 87 size_t *bufsize; 88 int *couldbetty; 89 { 90 struct stat st; 91 92 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 93 *couldbetty = 0; 94 *bufsize = BUFSIZ; 95 return (__SNPT); 96 } 97 98 /* could be a tty iff it is a character device */ 99 *couldbetty = S_ISCHR(st.st_mode); 100 if (st.st_blksize == 0) { 101 *bufsize = BUFSIZ; 102 return (__SNPT); 103 } 104 105 /* 106 * Optimise fseek() only if it is a regular file. (The test for 107 * __sseek is mainly paranoia.) It is safe to set _blksize 108 * unconditionally; it will only be used if __SOPT is also set. 109 */ 110 if ((fp->_flags & __SSTR) == 0) { 111 *bufsize = st.st_blksize; 112 fp->_blksize = st.st_blksize; 113 } 114 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 115 __SOPT : __SNPT); 116 } 117