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Traps.c
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1994-06-06
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/*
Commodore 64 Emulator v0.4 Earle F. Philhower III
Copyright (C) 1993-4 (st916w9r@dunx1.ocs.drexel.edu)
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.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "Processor.h"
#include "Memory.h"
#include "Error.h"
#include "Traps.h"
#define MAXTRAPS 16
static trap trapList[MAXTRAPS];
static byte numTraps;
int TrapInitialize()
{
numTraps=0;
return kNoError;
}
int AddTrap(trap t)
{
/* If we are at out limit for traps, then internal error */
if (numTraps==MAXTRAPS) InternalError(kTrapStorageOverflow);
/* Check to see if the ROMs and the trap agree */
if (t.check[0]!=ByteAt(t.addr)) return kWrongROMError;
if (t.check[1]!=ByteAt(t.addr+1)) return kWrongROMError;
if (t.check[2]!=ByteAt(t.addr+2)) return kWrongROMError;
/* Add this trap to out list */
trapList[numTraps++]=t;
/* Either modify the low ROM or high ROM, as per address specified */
if (t.addr < 0xc000) loROM[t.addr&0x1fff]=0xff;
else hiROM[t.addr&0x1fff]=0xff;
return kNoError;
}
int DeleteTrap(word addr)
{
int x, y;
/* Search through traps added for the address to remove from */
for (x=0; x<numTraps; x++)
if (trapList[x].addr==addr) {
/* Fix ROM to its initial state */
if (addr <= 0xc000) loROM[addr&0x1fff]=trapList[x].check[0];
else hiROM[addr&0x1fff]=trapList[x].check[0];
/* Shift all of the traps down one slot */
for (y=x; y<numTraps-1; y++) trapList[y]=trapList[y+1];
numTraps--;
return kNoError; }
/* Attempted to remove a trap not added */
InternalError(kTrapNotInstalled);
}
void TrapExecute()
{
int x;
/* Search for a trap at the current pc location, and if so execute it */
for (x=0; x<numTraps; x++)
if (trapList[x].addr==(pc-1)) {
(*trapList[x].call)();
return; }
/* This is not OUR trap code, so it's a nonimplemented instruction */
ini();
}