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. 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  * @(#)makebuf.c        8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: src/lib/libc/stdio/makebuf.c,v 1.6 2007/01/09 00:28:07 imp Exp $
  34  */
  35
  36 #include "namespace.h"
  37 #include <sys/types.h>
  38 #include <sys/stat.h>
  39 #include <unistd.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include "un-namespace.h"
  43
  44 #include "libc_private.h"
  45 #include "local.h"
  46
  47 /*
  48  * Allocate a file buffer, or switch to unbuffered I/O.
  49  * Per the ANSI C standard, ALL tty devices default to line buffered.
  50  *
  51  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  52  * optimisation) right after the _fstat() that finds the buffer size.
  53  */
  54 void
  55 __smakebuf(FILE *fp)
  56 {
  57         void *p;
  58         int flags;
  59         size_t size;
  60         int couldbetty;
  61
  62         if (fp->pub._flags & __SNBF) {
  63                 fp->_bf._base = fp->pub._p = fp->_nbuf;
  64                 fp->_bf._size = 1;
  65                 return;
  66         }
  67         flags = __swhatbuf(fp, &size, &couldbetty);
  68         if ((p = malloc(size)) == NULL) {
  69                 fp->pub._flags |= __SNBF;
  70                 fp->_bf._base = fp->pub._p = fp->_nbuf;
  71                 fp->_bf._size = 1;
  72                 return;
  73         }
  74         __cleanup = _cleanup;
  75         flags |= __SMBF;
  76         fp->_bf._base = fp->pub._p = p;
  77         fp->_bf._size = size;
  78         if (couldbetty && isatty(fp->pub._fileno))
  79                 flags |= __SLBF;
  80         fp->pub._flags |= flags;
  81 }
  82
  83 /*
  84  * Internal routine to determine `proper' buffering for a file.
  85  */
  86 int
  87 __swhatbuf(FILE *fp, size_t *bufsize, int *couldbetty)
  88 {
  89         struct stat st;
  90
  91         if (fp->pub._fileno < 0 || _fstat(fp->pub._fileno, &st) < 0) {
  92                 *couldbetty = 0;
  93                 *bufsize = BUFSIZ;
  94                 return (__SNPT);
  95         }
  96
  97         /* could be a tty iff it is a character device */
  98         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
  99         if (st.st_blksize <= 0) {
 100                 *bufsize = BUFSIZ;
 101                 return (__SNPT);
 102         }
 103
 104         /*
 105          * Optimise fseek() only if it is a regular file.  (The test for
 106          * __sseek is mainly paranoia.)  It is safe to set _blksize
 107          * unconditionally; it will only be used if __SOPT is also set.
 108          */
 109         *bufsize = st.st_blksize;
 110         fp->_blksize = st.st_blksize;
 111         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 112             __SOPT : __SNPT);
 113 }