stdio/FreeBSD/makebuf.c

   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  * 4. 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 sccsid[] = "@(#)makebuf.c   8.1 (Berkeley) 6/4/93";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/makebuf.c,v 1.6 2007/01/09 00:28:07 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42 #include <unistd.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include "un-namespace.h"
  46
  47 #include "libc_private.h"
  48 #include "local.h"
  49
  50 #ifdef FEATURE_SMALL_STDIOBUF
  51 # define MAXBUFSIZE     (1 << 12)
  52 #else
  53 # define MAXBUFSIZE     (1 << 16)
  54 #endif
  55
  56 #define TTYBUFSIZE      4096
  57
  58 /*
  59  * Allocate a file buffer, or switch to unbuffered I/O.
  60  * Per the ANSI C standard, ALL tty devices default to line buffered.
  61  *
  62  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  63  * optimisation) right after the _fstat() that finds the buffer size.
  64  */
  65 void
  66 __smakebuf(fp)
  67         FILE *fp;
  68 {
  69         void *p;
  70         int flags;
  71         size_t size;
  72         int couldbetty;
  73
  74         if (fp->_flags & __SNBF) {
  75                 fp->_bf._base = fp->_p = fp->_nbuf;
  76                 fp->_bf._size = 1;
  77                 return;
  78         }
  79         flags = __swhatbuf(fp, &size, &couldbetty);
  80         if (couldbetty && isatty(fp->_file)) {
  81                 flags |= __SLBF;
  82                 /* st_blksize for ttys is 128K, so make it more reasonable */
  83                 if (size > TTYBUFSIZE)
  84                         fp->_blksize = size = TTYBUFSIZE;
  85         }
  86         if ((p = malloc(size)) == NULL) {
  87                 fp->_flags |= __SNBF;
  88                 fp->_bf._base = fp->_p = fp->_nbuf;
  89                 fp->_bf._size = 1;
  90                 return;
  91         }
  92         __cleanup = _cleanup;
  93         flags |= __SMBF;
  94         fp->_bf._base = fp->_p = p;
  95         fp->_bf._size = size;
  96         fp->_flags |= flags;
  97 }
  98
  99 /*
 100  * Internal routine to determine `proper' buffering for a file.
 101  */
 102 int
 103 __swhatbuf(fp, bufsize, couldbetty)
 104         FILE *fp;
 105         size_t *bufsize;
 106         int *couldbetty;
 107 {
 108         struct stat st;
 109
 110         if (fp->_file < 0 || _fstat(fp->_file, &st) < 0) {
 111                 *couldbetty = 0;
 112                 *bufsize = BUFSIZ;
 113                 return (__SNPT);
 114         }
 115
 116         /* could be a tty iff it is a character device */
 117         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
 118         if (st.st_blksize <= 0) {
 119                 *bufsize = BUFSIZ;
 120                 return (__SNPT);
 121         }
 122
 123         /*
 124          * Optimise fseek() only if it is a regular file.  (The test for
 125          * __sseek is mainly paranoia.)  It is safe to set _blksize
 126          * unconditionally; it will only be used if __SOPT is also set.
 127          */
 128         fp->_blksize = *bufsize = st.st_blksize > MAXBUFSIZE ? MAXBUFSIZE : st.st_blksize;
 129         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 130             __SOPT : __SNPT);
 131 }