lib/libc/stdio/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  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * $FreeBSD: src/lib/libc/stdio/makebuf.c,v 1.1.1.1.14.1 2001/03/05 11:27:49 obrien Exp $
  37  * $DragonFly: src/lib/libc/stdio/makebuf.c,v 1.6 2005/07/23 20:23:06 joerg Exp $
  38  *
  39  * @(#)makebuf.c        8.1 (Berkeley) 6/4/93
  40  */
  41
  42 #include "namespace.h"
  43 #include <sys/types.h>
  44 #include <sys/stat.h>
  45 #include <unistd.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include "un-namespace.h"
  49
  50 #include "local.h"
  51 #include "priv_stdio.h"
  52
  53 /*
  54  * Allocate a file buffer, or switch to unbuffered I/O.
  55  * Per the ANSI C standard, ALL tty devices default to line buffered.
  56  *
  57  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  58  * optimisation) right after the _fstat() that finds the buffer size.
  59  */
  60 void
  61 __smakebuf(FILE *fp)
  62 {
  63         void *p;
  64         int flags;
  65         size_t size;
  66         int couldbetty;
  67
  68         if (fp->pub._flags & __SNBF) {
  69                 fp->_bf._base = fp->pub._p = fp->_nbuf;
  70                 fp->_bf._size = 1;
  71                 return;
  72         }
  73         flags = __swhatbuf(fp, &size, &couldbetty);
  74         if ((p = malloc(size)) == NULL) {
  75                 fp->pub._flags |= __SNBF;
  76                 fp->_bf._base = fp->pub._p = fp->_nbuf;
  77                 fp->_bf._size = 1;
  78                 return;
  79         }
  80         __cleanup = _cleanup;
  81         flags |= __SMBF;
  82         fp->_bf._base = fp->pub._p = p;
  83         fp->_bf._size = size;
  84         if (couldbetty && isatty(fp->pub._fileno))
  85                 flags |= __SLBF;
  86         fp->pub._flags |= flags;
  87 }
  88
  89 /*
  90  * Internal routine to determine `proper' buffering for a file.
  91  */
  92 int
  93 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
  94 {
  95         struct stat st;
  96
  97         if (fp->pub._fileno < 0 || _fstat(fp->pub._fileno, &st) < 0) {
  98                 *couldbetty = 0;
  99                 *bufsize = BUFSIZ;
 100                 return (__SNPT);
 101         }
 102
 103         /* could be a tty iff it is a character device */
 104         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
 105         if (st.st_blksize <= 0) {
 106                 *bufsize = BUFSIZ;
 107                 return (__SNPT);
 108         }
 109
 110         /*
 111          * Optimise fseek() only if it is a regular file.  (The test for
 112          * __sseek is mainly paranoia.)  It is safe to set _blksize
 113          * unconditionally; it will only be used if __SOPT is also set.
 114          */
 115         *bufsize = st.st_blksize;
 116         fp->_blksize = st.st_blksize;
 117         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 118             __SOPT : __SNPT);
 119 }