diskbuf.c revision 1.4 
1/*	$NetBSD: diskbuf.c,v 1.4 2004/03/24 16:46:27 drochner 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 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 */
28
29/* data buffer for BIOS disk / DOS I/O  */
30
31#include "diskbuf.h"
32#include "stand.h"
33
34char *diskbufp;		/* allocated from heap */
35
36const void *diskbuf_user;
37
38/*
39 * Global shared "diskbuf" is used as read ahead buffer.
40 * This MAY have to not cross a 64k boundary.
41 * In practise it is allocated out of the heap early on...
42 * NB a statically allocated diskbuf is not guaranteed to not
43 * cross a 64k boundary.
44 */
45char *
46alloc_diskbuf(const void *user)
47{
48	diskbuf_user = user;
49	if (!diskbufp) {
50		diskbufp = alloc(DISKBUFSIZE);
51		if (((int)diskbufp & 0xffff) + DISKBUFSIZE > 0x10000) {
52			printf("diskbufp %x\n", (unsigned)diskbufp);
53			panic("diskbuf crosses 64k boundary");
54		}
55	}
56	return diskbufp;
57}
58