stdio/makebuf.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Chris Torek.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <sys/types.h>
  60 #include <sys/stat.h>
  61 #include <unistd.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64 #include "local.h"
  65
  66 /*
  67  * Allocate a file buffer, or switch to unbuffered I/O.
  68  * Per the ANSI C standard, ALL tty devices default to line buffered.
  69  *
  70  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  71  * optimisation) right after the fstat() that finds the buffer size.
  72  */
  73 void
  74 __smakebuf(fp)
  75         register FILE *fp;
  76 {
  77         register void *p;
  78         register int flags;
  79         size_t size;
  80         int couldbetty;
  81
  82         if (fp->_flags & __SNBF) {
  83                 fp->_bf._base = fp->_p = fp->_nbuf;
  84                 fp->_bf._size = 1;
  85                 return;
  86         }
  87         flags = __swhatbuf(fp, &size, &couldbetty);
  88         if ((p = malloc(size)) == NULL) {
  89                 fp->_flags |= __SNBF;
  90                 fp->_bf._base = fp->_p = fp->_nbuf;
  91                 fp->_bf._size = 1;
  92                 return;
  93         }
  94         __cleanup = _cleanup;
  95         flags |= __SMBF;
  96         fp->_bf._base = fp->_p = p;
  97         fp->_bf._size = size;
  98         if (couldbetty && isatty(fp->_file))
  99                 flags |= __SLBF;
 100         fp->_flags |= flags;
 101 }
 102
 103 /*
 104  * Internal routine to determine `proper' buffering for a file.
 105  */
 106 int
 107 __swhatbuf(fp, bufsize, couldbetty)
 108         register FILE *fp;
 109         size_t *bufsize;
 110         int *couldbetty;
 111 {
 112         struct stat st;
 113
 114         if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
 115                 *couldbetty = 0;
 116                 *bufsize = BUFSIZ;
 117                 return (__SNPT);
 118         }
 119
 120         /* could be a tty iff it is a character device */
 121         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
 122         if (st.st_blksize <= 0) {
 123                 *bufsize = BUFSIZ;
 124                 return (__SNPT);
 125         }
 126
 127         /*
 128          * Optimise fseek() only if it is a regular file.  (The test for
 129          * __sseek is mainly paranoia.)  It is safe to set _blksize
 130          * unconditionally; it will only be used if __SOPT is also set.
 131          */
 132         *bufsize = st.st_blksize;
 133         fp->_blksize = st.st_blksize;
 134         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 135             __SOPT : __SNPT);
 136 }