// Parse a method declaration.
static String getMethod(SamTokenizer f) throws TokenizerException {
try {
// The return type for all methods must be int.
myCheck(f, "int");
// methodName stores the name of the method.
String methodName = f.getWord();
if (symMap.containsKey(methodName))
throw new TokenizerException("Error: Duplicate declaration of method " + methodName);
String asmCode = methodName;
// The name of the method <-> index of the symbol table of the method in the symTables vector
symMap.put(methodName, symTables.size());
symTables.addElement(new LinkedHashMap<String, Integer>());
// Since there cannot be another method declaration inside of a, the symbol table we are
// dealing with is
// always the last element of the symTables vector.
symTables.lastElement().put(methodName, 0);
asmCode += ":\n";
myCheck(f, '(');
if (!f.check(')')) {
// No SaM code generated by getFormals
getFormals(f);
myCheck(f, ')');
}
actMap.put(methodName, params.size());
for (int i = 1; i <= params.size(); ++i) {
// Add all formals to the symbol tabel
symTables.lastElement().put(params.elementAt(params.size() - i), -i);
}
asmCode += getBody(f);
// Clear the params vector and set varCounter back to 2.
params.clear();
varCounter = 2;
return asmCode;
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid method declaration.");
}
}
// No return value for this function.
static void getFormals(SamTokenizer f) throws TokenizerException {
try {
// The only type for formals is int.
myCheck(f, "int");
String paramName = f.getWord();
// Check if the name already exists.
if (symTables.lastElement().containsKey(paramName))
throw new TokenizerException("Error: Duplicate declaration of " + paramName + ".");
params.add(paramName);
if (f.check(',')) {
getFormals(f);
}
return;
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid formals");
}
}
static String getStmt(SamTokenizer f) throws TokenizerException {
try {
String asmCode = "";
Boolean returnFlag1;
Boolean returnFlag2;
switch (f.peekAtKind()) {
case WORD:
{
String newWord = f.getWord();
switch (newWord) {
case "return":
{
asmCode += getExp(f);
myCheck(f, ';');
// SaM code for return.
asmCode +=
"STOREOFF -"
+ Integer.toString(params.size() + 1)
+ "\n"
+ "ADDSP -"
+ Integer.toString(varCounter - 2)
+ "\n"
+ "JUMPIND\n";
returnFlags.push(true);
return asmCode;
}
case "if":
{
// Generate two valid lables for divergence.
String label1 = getLabel();
String label2 = getLabel();
myCheck(f, '(');
asmCode += getExp(f);
myCheck(f, ')');
asmCode += ("JUMPC " + label1 + "\n");
// Buffer the statements for if condition.
String tempString = getStmt(f);
returnFlag1 = returnFlags.pop();
myCheck(f, "else");
asmCode += getStmt(f);
returnFlag2 = returnFlags.pop();
// Manage the divergence.
asmCode +=
("JUMP " + label2 + "\n" + label1 + ":\n" + tempString + label2 + ":\n");
if (returnFlag1 && returnFlag2) returnFlags.push(true);
else returnFlags.push(false);
return asmCode;
}
case "while":
{
String label1 = getLabel();
String label2 = getLabel();
// Push the label as the return position.
labels.push(label2);
myCheck(f, '(');
asmCode += (label1 + ":\n");
asmCode += getExp(f);
asmCode += ("ISNIL\n" + "JUMPC " + label2 + "\n");
myCheck(f, ')');
// Flag indicating that we are in a while loop (possibly nested while loops.)
flags.push(true);
asmCode += getStmt(f);
asmCode += ("JUMP " + label1 + "\n" + label2 + ":\n");
// Once finish parsing the while loop, pop out the labels and flags.
labels.pop();
flags.pop();
return asmCode;
}
case "break":
{
// flags.empty() indicates that we are not currently in a while loop.
if (flags.empty())
throw new TokenizerException("Error: Invalid break statement.");
myCheck(f, ';');
returnFlags.push(false);
// Jump to the current inner most return postion.
return "JUMP " + labels.peek() + "\n";
}
default:
// Assign statement
// Check if the variable is already defined.
if (!symTables.lastElement().containsKey(newWord))
throw new TokenizerException("Error: Variable not declared.");
myCheck(f, '=');
asmCode += getExp(f);
myCheck(f, ';');
// Get the address of the variable from the symbol table.
int addr = symTables.lastElement().get(newWord);
asmCode += ("STOREOFF " + Integer.toString(addr) + "\n");
returnFlags.push(false);
return asmCode;
}
}
case OPERATOR:
{
switch (f.getOp()) {
case '{':
{
asmCode += getBlock(f);
return asmCode;
}
case ';':
returnFlags.push(false);
return asmCode;
default:
throw new TokenizerException("Error: Invalid operator inside a statement.");
}
}
default:
throw new TokenizerException("Error: Invalid Statement.");
}
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid Statement.");
}
}