diskbuf.c revision 1.3 
1/*	$NetBSD: diskbuf.c,v 1.3 2003/04/02 10:39:33 fvdl Exp $	*/
2
3/*
4 * Copyright (c) 1996
5 *	Matthias Drochner.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 *    must display the following acknowledgement:
17 *	This product includes software developed for the NetBSD Project
18 *	by Matthias Drochner.
19 * 4. The name of the author may not be used to endorse or promote products
20 *    derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 *
33 */
34
35/* data buffer for BIOS disk / DOS I/O  */
36
37#include "diskbuf.h"
38#include "stand.h"
39
40char *diskbufp;		/* allocated from heap */
41
42const void *diskbuf_user;
43
44/*
45 * Global shared "diskbuf" is used as read ahead buffer.
46 * This MAY have to not cross a 64k boundary.
47 * In practise it is allocated out of the heap early on...
48 * NB a statically allocated diskbuf is not guaranteed to not
49 * cross a 64k boundary.
50 */
51char *
52alloc_diskbuf(const void *user)
53{
54	diskbuf_user = user;
55	if (!diskbufp) {
56		diskbufp = alloc(DISKBUFSIZE);
57		if (((int)diskbufp & 0xffff) + DISKBUFSIZE > 0x10000) {
58			printf("diskbufp %x\n", (unsigned)diskbufp);
59			panic("diskbuf crosses 64k boundary");
60		}
61	}
62	return diskbufp;
63}
64