db.1.85/PORT/bsdi.1.0/local/makebuf.c

   1 /*-
   2  * Copyright (c) 1990 The Regents of the University of California.
   3  * 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 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)makebuf.c   5.3 (Berkeley) 5/6/93";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <sys/types.h>
  42 #include <sys/stat.h>
  43 #include <unistd.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include "local.h"
  47
  48 /*
  49  * Allocate a file buffer, or switch to unbuffered I/O.
  50  * Per the ANSI C standard, ALL tty devices default to line buffered.
  51  *
  52  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
  53  * optimisation) right after the fstat() that finds the buffer size.
  54  */
  55 void
  56 __smakebuf(fp)
  57         register FILE *fp;
  58 {
  59         register void *p;
  60         register int flags;
  61         size_t size;
  62         int couldbetty;
  63
  64         if (fp->_flags & __SNBF) {
  65                 fp->_bf._base = fp->_p = fp->_nbuf;
  66                 fp->_bf._size = 1;
  67                 return;
  68         }
  69         flags = __swhatbuf(fp, &size, &couldbetty);
  70         if ((p = malloc(size)) == NULL) {
  71                 fp->_flags |= __SNBF;
  72                 fp->_bf._base = fp->_p = fp->_nbuf;
  73                 fp->_bf._size = 1;
  74                 return;
  75         }
  76         __cleanup = _cleanup;
  77         flags |= __SMBF;
  78         fp->_bf._base = fp->_p = p;
  79         fp->_bf._size = size;
  80         if (couldbetty && isatty(fp->_file))
  81                 flags |= __SLBF;
  82         fp->_flags |= flags;
  83 }
  84
  85 /*
  86  * Internal routine to determine `proper' buffering for a file.
  87  */
  88 int
  89 __swhatbuf(fp, bufsize, couldbetty)
  90         register FILE *fp;
  91         size_t *bufsize;
  92         int *couldbetty;
  93 {
  94         struct stat st;
  95
  96         if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
  97                 *couldbetty = 0;
  98                 *bufsize = BUFSIZ;
  99                 return (__SNPT);
 100         }
 101
 102         /* could be a tty iff it is a character device */
 103         *couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
 104         if (st.st_blksize <= 0) {
 105                 *bufsize = BUFSIZ;
 106                 return (__SNPT);
 107         }
 108
 109         /*
 110          * Optimise fseek() only if it is a regular file.  (The test for
 111          * __sseek is mainly paranoia.)  It is safe to set _blksize
 112          * unconditionally; it will only be used if __SOPT is also set.
 113          */
 114         *bufsize = st.st_blksize;
 115         fp->_blksize = st.st_blksize;
 116         return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
 117             __SOPT : __SNPT);
 118 }