/**
* Consume the first work on the input tape
*
* @return The word of input
* @throws EmptyInputException
*/
public StackValue<?> consumeInput() throws EmptyInputException {
if (hasInput()) {
StackValue<?> value = input.get(inputIndex++);
for (StackMachineListener l : listeners) l.inputConsumed(inputIndex);
return value;
} else throw new EmptyInputException(programCounter);
}
/** Resets the stack machine to the state it was in before it started running the stack program */
public void reset() {
this.programCounter = 0;
this.stack.clear();
this.numInstructions = 0;
this.store = new StackValue<?>[STORE_SIZE];
this.inputIndex = 0;
this.output = new ArrayList<StackValue<?>>();
for (int i = 0; i < STORE_SIZE; i++) {
store[i] = new IntStackValue(0);
for (StackMachineListener l : listeners) l.storeChanged(i);
}
for (StackMachineListener l : listeners) l.machineReset();
}
/**
* Load a new program into the machine and reset it
*
* @param instructions The program to load into the machine
*/
public void loadInstructions(List<Instruction> instructions) {
this.instructions = instructions;
if (instructions != null) {
int i = 0;
for (Instruction op : instructions) {
if (op.name.equals("label")) labels.put((String) op.arg.getValue(), i);
i++;
}
} else instructions = new ArrayList<Instruction>();
for (StackMachineListener l : listeners) l.programChanged(instructions);
reset();
}
private void notifyListeners() {
for (StackMachineListener l : listeners) l.stackChanged(this);
}
/**
* Sets the program counter to the next instruction to be executed
*
* @param programCounter The line of the next instruction
*/
private void setProgramCounter(int programCounter) {
this.programCounter = programCounter;
for (StackMachineListener l : listeners) l.programCounterChanged(programCounter);
}
/**
* Add a value to the end of the output tape
*
* @param value The value to add to the output tape
*/
public void addOutput(StackValue<?> value) {
output.add(value);
for (StackMachineListener l : listeners) l.outputChanged(output.iterator());
}
/**
* Set a particular address in store
*
* @param address The address to set
* @param value The value to set the address to
* @throws InvalidAddressException
*/
public void setStore(int address, StackValue<?> value) throws InvalidAddressException {
if (0 <= address && address < STORE_SIZE) {
store[address] = value;
for (StackMachineListener l : listeners) l.storeChanged(address);
} else throw new InvalidAddressException(address, programCounter);
}