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diskbuf.c revision 1.5 
      1 /*	$NetBSD: diskbuf.c,v 1.5 2005/06/28 21:00:41 junyoung 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 <lib/libsa/stand.h>
     32 #include "diskbuf.h"
     33 
     34 char *diskbufp;		/* allocated from heap */
     35 
     36 const 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  */
     45 char *
     46 alloc_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