lib/libc/stdio/makebuf.c

   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 #ifdef __minix
 125         if (st.st_blksize == 0) {
 126                 /* 0 in 2 cases: upgrade from old to new struct stat or
 127                  * there is a bug in underlying fs.
 128                  */
 129                 *bufsize = fp->_blksize = MINIX_ST_BLKSIZE;
 130         } else
 131 #endif
 132                 *bufsize = fp->_blksize = st.st_blksize;
 133         return (st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 134             __SOPT : __SNPT;
 135 }