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makebuf.c revision 1.16 
      1 /*	$NetBSD: makebuf.c,v 1.16 2012/03/13 21:13:46 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)makebuf.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: makebuf.c,v 1.16 2012/03/13 21:13:46 christos Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include "namespace.h"
     45 
     46 #include <sys/types.h>
     47 #include <sys/stat.h>
     48 #include <assert.h>
     49 #include <stdio.h>
     50 #include <stdlib.h>
     51 #include <unistd.h>
     52 #include "reentrant.h"
     53 #include "local.h"
     54 
     55 /*
     56  * Allocate a file buffer, or switch to unbuffered I/O.
     57  * Per the ANSI C standard, ALL tty devices default to line buffered.
     58  *
     59  * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
     60  * optimisation) right after the fstat() that finds the buffer size.
     61  */
     62 void
     63 __smakebuf(fp)
     64 	FILE *fp;
     65 {
     66 	void *p;
     67 	int flags;
     68 	size_t size;
     69 	int couldbetty;
     70 
     71 	_DIAGASSERT(fp != NULL);
     72 
     73 	if (fp->_flags & __SNBF) {
     74 		fp->_bf._base = fp->_p = fp->_nbuf;
     75 		fp->_bf._size = 1;
     76 		return;
     77 	}
     78 	flags = __swhatbuf(fp, &size, &couldbetty);
     79 	if ((p = malloc(size)) == NULL) {
     80 		fp->_flags |= __SNBF;
     81 		fp->_bf._base = fp->_p = fp->_nbuf;
     82 		fp->_bf._size = 1;
     83 		return;
     84 	}
     85 	__cleanup = _cleanup;
     86 	flags |= __SMBF;
     87 	fp->_bf._base = fp->_p = p;
     88 	_DIAGASSERT(__type_fit(int, size));
     89 	fp->_bf._size = (int)size;
     90 	if (couldbetty && isatty(__sfileno(fp)))
     91 		flags |= __SLBF;
     92 	fp->_flags |= flags;
     93 }
     94 
     95 /*
     96  * Internal routine to determine `proper' buffering for a file.
     97  */
     98 int
     99 __swhatbuf(fp, bufsize, couldbetty)
    100 	FILE *fp;
    101 	size_t *bufsize;
    102 	int *couldbetty;
    103 {
    104 	struct stat st;
    105 
    106 	_DIAGASSERT(fp != NULL);
    107 	_DIAGASSERT(bufsize != NULL);
    108 	_DIAGASSERT(couldbetty != NULL);
    109 
    110 	if (__sfileno(fp) == -1 || fstat(__sfileno(fp), &st) < 0) {
    111 		*couldbetty = 0;
    112 		*bufsize = BUFSIZ;
    113 		return (__SNPT);
    114 	}
    115 
    116 	/* could be a tty iff it is a character device */
    117 	*couldbetty = S_ISCHR(st.st_mode);
    118 	if (st.st_blksize == 0) {
    119 		*bufsize = BUFSIZ;
    120 		return (__SNPT);
    121 	}
    122 
    123 	/*
    124 	 * Optimise fseek() only if it is a regular file.  (The test for
    125 	 * __sseek is mainly paranoia.)  It is safe to set _blksize
    126 	 * unconditionally; it will only be used if __SOPT is also set.
    127 	 */
    128 	*bufsize = st.st_blksize;
    129 	fp->_blksize = st.st_blksize;
    130 	return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?
    131 	    __SOPT : __SNPT);
    132 }
    133