lib/libc/stdio/makebuf.c

   1 /*      $NetBSD: makebuf.c,v 1.18 2015/07/15 19:08:43 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 1.18 2015/07/15 19:08:43 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 <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 ULB<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 }