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// StackFrameFSM.cpp: implementation of the StackFrameFSM class.
/*
Pep8-1 is a virtual machine for writing machine language and assembly
language programs.
Copyright (C) 2009 J. Stanley Warford, Pepperdine University
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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "stackframefsm.h"
#include "sim.h"
#include "pep.h"
// #include <QDebug>
StackFrameFSM::StackFrameFSM()
{
}
void StackFrameFSM::reset()
{
stackState = EStart;
numCellsFromSubSP = 0;
numCellsFromCall = 0;
}
// the states: EStart, ESubSP, ECall
int StackFrameFSM::makeTransition(int numCellsToAdd)
{
Enu::EMnemonic mnemon = Pep::decodeMnemonic[Sim::instructionSpecifier];
switch(stackState)
{
case(EStart):
if (mnemon == Enu::SUBSP) {
numCellsFromSubSP = numCellsToAdd;
stackState = ESubSP;
}
else if (mnemon == Enu::CALL) {
numCellsFromSubSP = 0;
numCellsFromCall = 1; // = numCellsToAdd; // ECall = 1
stackState = ECall;
}
break;
case(ESubSP):
if (mnemon == Enu::CALL) {
numCellsFromCall = 1; // = numCellsToAdd; // ECall = 1
stackState = ECall;
}
else { // not ECall
stackState = EStart;
return numCellsFromSubSP; // lone subsp
}
break;
case(ECall):
if (mnemon == Enu::SUBSP) { // function with 1 or more locals and 0 or more parameters
stackState = EStart;
return (numCellsFromSubSP + numCellsFromCall + numCellsToAdd);
}
else { // not ESubSP
stackState = EStart; // no locals
return (numCellsFromSubSP + numCellsFromCall);
}
break;
default:;
}
return 0; // don't add a frame yet
}
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