1 /* $NetBSD: makebuf.c,v 1.19 2018/12/14 03:29:54 uwe 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 1.19 2018/12/14 03:29:54 uwe 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 <inttypes.h> 53 #include <ctype.h> 54 #include "reentrant.h" 55 #include "local.h" 56 57 /* 58 * Override the file buffering based on the environment setting STDBUF%d 59 * (for the specific file descriptor) and STDBUF (for all descriptors). 60 * the setting is ULF<num> standing for "Unbuffered", "Linebuffered", 61 * and Fullybuffered", and <num> is a value from 0 to 1M. 62 */ 63 static int 64 __senvbuf(FILE *fp, size_t *size, int *couldbetty) 65 { 66 char evb[64], *evp; 67 int flags, e; 68 intmax_t s; 69 70 flags = 0; 71 if (snprintf(evb, sizeof(evb), "STDBUF%d", fp->_file) < 0) 72 return flags; 73 74 if ((evp = getenv(evb)) == NULL && (evp = getenv("STDBUF")) == NULL) 75 return flags; 76 77 switch (*evp) { 78 case 'u': 79 case 'U': 80 evp++; 81 flags |= __SNBF; 82 break; 83 case 'l': 84 case 'L': 85 evp++; 86 flags |= __SLBF; 87 break; 88 case 'f': 89 case 'F': 90 evp++; 91 *couldbetty = 0; 92 break; 93 } 94 95 if (!isdigit((unsigned char)*evp)) 96 return flags; 97 98 s = strtoi(evp, NULL, 0, 0, 1024 * 1024, &e); 99 if (e != 0) 100 return flags; 101 102 *size = (size_t)s; 103 if (*size == 0) 104 return __SNBF; 105 106 return flags; 107 } 108 109 /* 110 * Allocate a file buffer, or switch to unbuffered I/O. 111 * Per the ANSI C standard, ALL tty devices default to line buffered. 112 * 113 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek 114 * optimisation) right after the fstat() that finds the buffer size. 115 */ 116 void 117 __smakebuf(FILE *fp) 118 { 119 void *p; 120 int flags; 121 size_t size; 122 int couldbetty; 123 124 _DIAGASSERT(fp != NULL); 125 126 if (fp->_flags & __SNBF) 127 goto unbuf; 128 129 flags = __swhatbuf(fp, &size, &couldbetty); 130 131 if ((fp->_flags & (__SLBF|__SNBF|__SMBF)) == 0 132 && fp->_cookie == fp && fp->_file >= 0) { 133 flags |= __senvbuf(fp, &size, &couldbetty); 134 if (flags & __SNBF) 135 goto unbuf; 136 } 137 138 if ((p = malloc(size)) == NULL) 139 goto unbuf; 140 141 __cleanup = _cleanup; 142 flags |= __SMBF; 143 fp->_bf._base = fp->_p = p; 144 _DIAGASSERT(__type_fit(int, size)); 145 fp->_bf._size = (int)size; 146 if (couldbetty && isatty(__sfileno(fp))) 147 flags |= __SLBF; 148 fp->_flags |= flags; 149 return; 150 unbuf: 151 fp->_flags |= __SNBF; 152 fp->_bf._base = fp->_p = fp->_nbuf; 153 fp->_bf._size = 1; 154 } 155 156 /* 157 * Internal routine to determine `proper' buffering for a file. 158 */ 159 int 160 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty) 161 { 162 struct stat st; 163 164 _DIAGASSERT(fp != NULL); 165 _DIAGASSERT(bufsize != NULL); 166 _DIAGASSERT(couldbetty != NULL); 167 168 if (__sfileno(fp) == -1 || fstat(__sfileno(fp), &st) < 0) { 169 *couldbetty = 0; 170 *bufsize = BUFSIZ; 171 return __SNPT; 172 } 173 174 /* could be a tty iff it is a character device */ 175 *couldbetty = S_ISCHR(st.st_mode); 176 if (st.st_blksize == 0) { 177 *bufsize = BUFSIZ; 178 return __SNPT; 179 } 180 181 /* 182 * Optimise fseek() only if it is a regular file. (The test for 183 * __sseek is mainly paranoia.) It is safe to set _blksize 184 * unconditionally; it will only be used if __SOPT is also set. 185 */ 186 *bufsize = st.st_blksize; 187 fp->_blksize = st.st_blksize; 188 return (st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ? 189 __SOPT : __SNPT; 190 } 191
Indexes created Sat Sep 20 22:09:52 GMT 2025