stdio/makebuf.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Chris Torek.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61
  62 #include <sys/types.h>
  63 #include <sys/stat.h>
  64 #include <unistd.h>
  65 #include <stdio.h>
  66 #include <stdlib.h>
  67 #include "local.h"
  68
  69 /*
  70  * Allocate a file buffer, or switch to unbuffered I/O.
  71  * Per the ANSI C standard, ALL tty devices default to line buffered.
  72  *
  73  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  74  * optimisation) right after the fstat() that finds the buffer size.
  75  */
  76 void
  77 __smakebuf(fp)
  78         register FILE *fp;
  79 {
  80         register void *p;
  81         register int flags;
  82         size_t size;
  83         int couldbetty;
  84
  85         if (fp->_flags & __SNBF) {
  86                 fp->_bf._base = fp->_p = fp->_nbuf;
  87                 fp->_bf._size = 1;
  88                 return;
  89         }
  90         flags = __swhatbuf(fp, &size, &couldbetty);
  91         if ((p = malloc(size)) == NULL) {
  92                 fp->_flags |= __SNBF;
  93                 fp->_bf._base = fp->_p = fp->_nbuf;
  94                 fp->_bf._size = 1;
  95                 return;
  96         }
  97         __cleanup = _cleanup;
  98         flags |= __SMBF;
  99         fp->_bf._base = fp->_p = p;
 100         fp->_bf._size = size;
 101         if (couldbetty && isatty(fp->_file))
 102                 flags |= __SLBF;
 103         fp->_flags |= flags;
 104 }
 105
 106 /*
 107  * Internal routine to determine `proper' buffering for a file.
 108  */
 109 int
 110 __swhatbuf(fp, bufsize, couldbetty)
 111         register FILE *fp;
 112         size_t *bufsize;
 113         int *couldbetty;
 114 {
 115         struct stat st;
 116
 117         if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
 118                 *couldbetty = 0;
 119                 *bufsize = BUFSIZ;
 120                 return (__SNPT);
 121         }
 122
 123         /* could be a tty iff it is a character device */
 124         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
 125         if (st.st_blksize <= 0) {
 126                 *bufsize = BUFSIZ;
 127                 return (__SNPT);
 128         }
 129
 130         /*
 131          * Optimise fseek() only if it is a regular file.  (The test for
 132          * __sseek is mainly paranoia.)  It is safe to set _blksize
 133          * unconditionally; it will only be used if __SOPT is also set.
 134          */
 135         *bufsize = st.st_blksize;
 136         fp->_blksize = st.st_blksize;
 137         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 138             __SOPT : __SNPT);
 139 }