/**
* Calls a function according to the given function number stating that the given number of
* arguments have been pushed onto the stack
*
* <p>If callerIsBuiltIn then the caller is a builtIn function that called this function through
* callFunctionFromBuiltIn. If address is -1 then a native function should be looked up and
* called.
*/
public void callFunction(
short address, short numberOfArguments, String functionName, boolean callerIsBuiltIn)
throws ProgramException {
stackFrames.addElement(new Integer(workingStackSegment.getStartAddress()));
workingStackSegment.setStartAddress(getSP() + 5);
if (callerIsBuiltIn) {
pushValue(MAIN_STACK, VMProgram.BUILTIN_FUNCTION_ADDRESS);
} else {
pushValue(MAIN_STACK, program.getPC());
}
pushFromRAM(MAIN_STACK, Definitions.LOCAL_POINTER_ADDRESS);
pushFromRAM(MAIN_STACK, Definitions.ARG_POINTER_ADDRESS);
pushFromRAM(MAIN_STACK, Definitions.THIS_POINTER_ADDRESS);
pushFromRAM(MAIN_STACK, Definitions.THAT_POINTER_ADDRESS);
ram.setValueAt(
Definitions.ARG_POINTER_ADDRESS, (short) (getSP() - numberOfArguments - 5), false);
ram.setValueAt(Definitions.LOCAL_POINTER_ADDRESS, getSP(), false);
// enable in the arg segment only the number of args that were sent to the called function.
argSegment.setEnabledRange(
argSegment.getStartAddress(), argSegment.getStartAddress() + numberOfArguments - 1, true);
if (address == VMProgram.BUILTIN_FUNCTION_ADDRESS) {
// Perform some actions normally done in the function() method
localSegment.setEnabledRange(
localSegment.getStartAddress(),
localSegment.getStartAddress() - 1,
true); // no local variables
callStack.pushFunction(functionName + " (built-in)");
staticSegment.setEnabledRange(0, -1, true); // empty static segment
// Read parameters from the stack
short[] params = new short[numberOfArguments];
for (int i = 0; i < numberOfArguments; ++i) {
params[i] = argSegment.getValueAt(i);
}
// Call the built-in implementation
builtInFunctionsRunner.callBuiltInFunction(functionName, params);
} else if (address >= 0 || address < program.getSize()) {
program.setPC(address);
program.setPC(address); // make sure previouspc isn't pc-1
// which might happen if the calling
// function called this function in the
// last line before the "return" and
// was declared just before this function.
// In this case encountering the "function"
// command will issue an error about
// "missing return"...
} else {
error("Illegal call address");
}
}
/**
* Here Starts the code of a function according to the given function name that has the given
* number of local variables.
*
* @param numberOfLocals The number of local variables
*/
public void function(short numberOfLocals) throws ProgramException {
short newSP = (short) (getSP() + numberOfLocals);
checkSP(newSP);
workingStackSegment.setStartAddress(newSP);
// disable non relevant range of the local segment - enable only the number
// of locals of this function.
localSegment.setEnabledRange(getSP(), newSP - 1, true);
for (int i = 0; i < numberOfLocals; i++) {
pushValue(MAIN_STACK, (short) 0);
}
String functionName = currentInstruction.getStringArg();
// adds the new function to the top of the call stack.
callStack.pushFunction(functionName);
// sets the static segment range
setStaticRange(functionName);
}