1 /* $OpenBSD: makebuf.c,v 1.9 2015/01/13 07:18:21 guenther Exp $ */ 2 /*- 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <sys/types.h> 35 #include <sys/stat.h> 36 #include <unistd.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include "local.h" 40 41 /* 42 * Allocate a file buffer, or switch to unbuffered I/O. 43 * Per the ANSI C standard, ALL tty devices default to line buffered. 44 * 45 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 46 * optimisation) right after the fstat() that finds the buffer size. 47 */ 48 void 49 __smakebuf(FILE *fp) 50 { 51 void *p; 52 int flags; 53 size_t size; 54 int couldbetty; 55 56 if (fp->_flags & __SNBF) { 57 fp->_bf._base = fp->_p = fp->_nbuf; 58 fp->_bf._size = 1; 59 return; 60 } 61 flags = __swhatbuf(fp, &size, &couldbetty); 62 if ((p = malloc(size)) == NULL) { 63 fp->_flags |= __SNBF; 64 fp->_bf._base = fp->_p = fp->_nbuf; 65 fp->_bf._size = 1; 66 return; 67 } 68 flags |= __SMBF; 69 fp->_bf._base = fp->_p = p; 70 fp->_bf._size = size; 71 if (couldbetty && isatty(fp->_file)) 72 flags |= __SLBF; 73 fp->_flags |= flags; 74 } 75 76 /* 77 * Internal routine to determine `proper' buffering for a file. 78 */ 79 int 80 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty) 81 { 82 struct stat st; 83 84 if (fp->_file < 0 || fstat(fp->_file, &st) < 0) { 85 *couldbetty = 0; 86 *bufsize = BUFSIZ; 87 return (__SNPT); 88 } 89 90 /* could be a tty iff it is a character device */ 91 *couldbetty = S_ISCHR(st.st_mode); 92 if (st.st_blksize == 0) { 93 *bufsize = BUFSIZ; 94 return (__SNPT); 95 } 96 97 /* 98 * Optimise fseek() only if it is a regular file. (The test for 99 * __sseek is mainly paranoia.) It is safe to set _blksize 100 * unconditionally; it will only be used if __SOPT is also set. 101 */ 102 *bufsize = st.st_blksize; 103 fp->_blksize = st.st_blksize; 104 return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 105 __SOPT : __SNPT); 106 } 107
