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diskbuf.c revision 1.2 
      1 /*	$NetBSD: diskbuf.c,v 1.2 2003/02/01 14:48:18 dsl 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 
     40 char *diskbufp;		/* allocated from heap */
     41 
     42 const 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  */
     51 char *
     52 alloc_diskbuf(const void *user)
     53 {
     54 	diskbuf_user = user;
     55 	if (!diskbufp) {
     56 		diskbufp = alloc(DISKBUFSIZE);
     57 		if (((int)diskbufp & 0xffff) + DISKBUFSIZE > 0x10000)
     58 			panic("diskbuf crosses 64k boundary");
     59 	}
     60 	return diskbufp;
     61 }
     62