/* -*- mode: C++; tab-width: 4 -*- */
/* ===================================================================== *\
	Copyright (c) 2000-2001 Palm, Inc. or its subsidiaries.
	All rights reserved.

	This file is part of the Palm OS Emulator.

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.
\* ===================================================================== */

#include "EmCommon.h"
#include "EmLowMem.h"

#include "EmMemory.h"			// CEnableFullAccess
#include "EmPalmFunction.h"		// SysTrapIndex
#include "EmPatchState.h"		// EmPatchState::OSMajorVersion


#include "PalmPack.h"
#define NON_PORTABLE
#include "SysEvtPrv.h"			// SysEvtMgrGlobalsType
#undef NON_PORTABLE
#include "PalmPackPop.h"


EmAliasLowMemHdrType<PAS>	EmLowMem::fgLowMem (EmMemNULL);	


#pragma mark -

// ===========================================================================
//		 EmLowMem
// ===========================================================================

static uint16		gSysDispatchTableSize;

/***********************************************************************
 *
 * FUNCTION:	EmLowMem::Initialize
 *
 * DESCRIPTION: Standard initialization function.  Responsible for
 *				initializing this sub-system when a new session is
 *				created.  Will be followed by at least one call to
 *				Reset or Load.
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

void EmLowMem::Initialize (void)
{
	gSysDispatchTableSize = 0;
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::Reset
 *
 * DESCRIPTION: Standard reset function.  Sets the sub-system to a
 *				default state.	This occurs not only on a Reset (as
 *				from the menu item), but also when the sub-system
 *				is first initialized (Reset is called after Initialize)
 *				as well as when the system is re-loaded from an
 *				insufficient session file.
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

void EmLowMem::Reset (void)
{
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::Save
 *
 * DESCRIPTION: Standard save function.  Saves any sub-system state to
 *				the given session file.
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

void EmLowMem::Save (SessionFile&)
{
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::Load
 *
 * DESCRIPTION: Standard load function.  Loads any sub-system state
 *				from the given session file.
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

void EmLowMem::Load (SessionFile&)
{
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::Dispose
 *
 * DESCRIPTION: Standard dispose function.	Completely release any
 *				resources acquired or allocated in Initialize and/or
 *				Load.
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

void EmLowMem::Dispose (void)
{
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::GetEvtMgrIdle
 *
 * DESCRIPTION: .
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

uint8 EmLowMem::GetEvtMgrIdle (void)
{
	CEnableFullAccess	munge;	// Remove blocks on memory access.

	// First, get sysEvtMgrGlobalsP, which is a pointer in low-memory.

	emuptr sysEvtMgrGlobalsP	= EmLowMem_GetGlobal (sysEvtMgrGlobalsP);

	/*
	**	Next look at the "idle" boolean in the SysEvtMgrGlobalsPtr
	**	contained in sysEvtMgrGlobalsP:
	**
	**	struct SysEvtMgrGlobalsType
	**	{
	**		...
	**		Boolean 		idle;
	**		...
	**	};
	*/

	size_t	idleOffset = offsetof (SysEvtMgrGlobalsType, idle);

	// Under Palm OS 1.0, there was an extra 4-byte value at the
	// location currently holding "gremlinsFlag", which is before
	// the "idle" field.  Under that version of the OS, we therefore
	// have to add 4 to get the right offset.

	if (EmPatchState::OSMajorVersion () == 1)
	{
		idleOffset += sizeof (Int32);
	}

	uint8	idle = EmMemGet8 (sysEvtMgrGlobalsP + idleOffset);

	return idle;
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::TrapExists
 *
 * DESCRIPTION: .
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

Bool EmLowMem::TrapExists (uint16 iATrap)
{
#if 0
	// No longer cache the dispatch table size.  Handspring changes the
	// size of the dispatch table after the first system call, resulting
	// in Poser caching the old table size, and thus complaining that
	// some functions are not implemented when in fact they are.

	// If we haven't already, get the number of traps in this system.

	if (gSysDispatchTableSize == 0)
	{
		CEnableFullAccess	munge;	// Remove blocks on memory access.

		gSysDispatchTableSize = EmLowMem_GetGlobal (sysDispatchTableSize);
	}

	return (::SysTrapIndex (iATrap) == ::SysTrapIndex (sysTrapHostControl)) ||
			::SysTrapIndex (iATrap) < gSysDispatchTableSize;
#else
	CEnableFullAccess	munge;	// Remove blocks on memory access.
	uint16				sysDispatchTableSize = EmLowMem_GetGlobal (sysDispatchTableSize);
	return (::SysTrapIndex (iATrap) == ::SysTrapIndex (sysTrapHostControl)) ||
			::SysTrapIndex (iATrap) < sysDispatchTableSize;
#endif
}


/***********************************************************************
 *
 * FUNCTION:	EmLowMem::GetTrapAddress
 *
 * DESCRIPTION: .
 *
 * PARAMETERS:	None.
 *
 * RETURNED:	Nothing.
 *
 ***********************************************************************/

emuptr EmLowMem::GetTrapAddress (uint16 iATrap)
{
	emuptr address = EmMemNULL;

	CEnableFullAccess	munge;	// Remove blocks on memory access.

	// If the trap number is not in range, just return NULL to signal
	// that normal process of the TRAP $F should occur.

//	uint16	sysDispatchTableSize = EmLowMem_GetGlobal (sysDispatchTableSize);
	uint16	sysDispatchTableSize = EmMemGet16 (256 + 62);

	iATrap = ::SysTrapIndex (iATrap);

	if ((iATrap == ::SysTrapIndex (sysTrapHostControl)) ||
		(iATrap < sysDispatchTableSize))
	{
		// Get sysDispatchTableP, which is a pointer in low-memory.

//		uint32 sysDispatchTableP	= EmLowMem_GetGlobal (sysDispatchTableP);
		uint32 sysDispatchTableP	= EmMemGet32 (256 + 34);

		// If it's NULL, return NULL.

		if (sysDispatchTableP != EmMemNULL)
		{
			// Next, get the right guy from its contents.

			address = EmMemGet32 (sysDispatchTableP + iATrap * 4);
		}
	}

	return address;
}