/*								AsyncSCSIPresent.c								*/
/*
 * AsyncSCSIPresent.c
 * Copyright © 1992-94 Apple Computer Inc. All Rights Reserved.
 */
#include <OSUtils.h>
#include <Traps.h>
#ifndef _SCSIAtomic
/*
 * This is needed if you don't have Universal Headers.
 */
#define _SCSIAtomic	0xA089
#endif

Boolean						AsyncSCSIPresent(void);
static Boolean				TrapAvailable(
		short					theTrap
	);

Boolean
AsyncSCSIPresent(void)
{
		return (TrapAvailable(_SCSIAtomic));
}

/*
 * TrapAvailable (see Inside Mac VI 3-8)
 */
#define NumToolboxTraps() (								\
		(NGetTrapAddress(_InitGraf, ToolTrap)			\
				== NGetTrapAddress(0xAA6E, ToolTrap))	\
			? 0x200 : 0x400								\
	)
#define GetTrapType(theTrap) (							\
		(((theTrap) & 0x0800) != 0) ? ToolTrap : OSTrap	\
	)

static Boolean
TrapAvailable(
		short					theTrap
	)
{
		TrapType				trapType;
		
		trapType = GetTrapType(theTrap);
		if (trapType == ToolTrap) {
			theTrap &= 0x07FF;
			if (theTrap >= NumToolboxTraps())
				theTrap = _Unimplemented;
		}
		return (
			NGetTrapAddress(theTrap, trapType)
			!= NGetTrapAddress(_Unimplemented, ToolTrap)
		);
}