src/system/libroot/posix/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
  37 #include <ktypes.h>
  38 #include <sys/stat.h>
  39 #include <unistd.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include "local.h"
  43
  44 /*
  45  * Allocate a file buffer, or switch to unbuffered I/O.
  46  * Per the ANSI C standard, ALL tty devices default to line buffered.
  47  *
  48  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  49  * optimisation) right after the fstat() that finds the buffer size.
  50  */
  51 void
  52 __smakebuf(fp)
  53         register FILE *fp;
  54 {
  55         register void *p;
  56         register int flags;
  57         size_t size;
  58         int couldbetty;
  59         if (fp->_flags & __SNBF) {
  60                 fp->_bf._base = fp->_p = fp->_nbuf;
  61                 fp->_bf._size = 1;
  62                 return;
  63         }
  64         flags = __swhatbuf(fp, &size, &couldbetty);
  65         if ((p = malloc(size)) == NULL) {
  66                 fp->_flags |= __SNBF;
  67                 fp->_bf._base = fp->_p = fp->_nbuf;
  68                 fp->_bf._size = 1;
  69                 return;
  70         }
  71         _IO_cleanup = _cleanup;
  72         flags |= __SMBF;
  73         fp->_bf._base = fp->_p = p;
  74         fp->_bf._size = size;
  75         /* XXX - once stat is fixed and we have isatty() */
  76         if (couldbetty && fp->_file < 3) //isatty(fp->_file))
  77                 flags |= __SLBF;
  78         fp->_flags |= flags;
  79 }
  80
  81 /*
  82  * Internal routine to determine `proper' buffering for a file.
  83  */
  84 int
  85 __swhatbuf(fp, bufsize, couldbetty)
  86         register FILE *fp;
  87         size_t *bufsize;
  88         int *couldbetty;
  89 {
  90         struct stat st;
  91
  92         if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
  93                 *couldbetty = 0;
  94                 *bufsize = BUFSIZ;
  95                 return (__SNPT);
  96         }
  97
  98         /* XXX - we don't have stat working yet, so simply do
  99          * this to make sure we don't segfault due to buffer sizes!
 100          */
 101         st.st_blksize = 0;
 102
 103         /* could be a tty if it is a character device */
 104         *couldbetty = S_ISCHR(st.st_mode);
 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         if ((fp->_flags & __SSTR) == 0) {
 116                 *bufsize = st.st_blksize;
 117                 fp->_blksize = st.st_blksize;
 118         }
 119         return (S_ISREG(st.st_mode) && fp->_seek == __sseek ?
 120             __SOPT : __SNPT);
 121 }