// Parse ID ('=' EXP)
static String getVariables(SamTokenizer f) throws TokenizerException {
try {
// Name of the variable.
String var = f.getWord();
// Check if the name already exists.
if (symTables.lastElement().containsKey(var) || symMap.containsKey(var))
throw new TokenizerException("Error: Duplicate declaration of " + var + ".");
// Add the variable with the address to the symbol table.
symTables.lastElement().put(var, varCounter);
++varCounter;
// Reserve the space in stack for the variable declaration.
String asmCode = "PUSHIMM 0\n";
if (f.check('=')) {
asmCode += getExp(f);
asmCode += ("STOREOFF " + Integer.toString(varCounter - 1) + "\n");
}
if (f.check(',')) {
asmCode += getVariables(f);
}
return asmCode;
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid variable 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");
}
}
// 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.");
}
}
static String getBody(SamTokenizer f) throws TokenizerException {
try {
String asmCode = "";
Boolean returnFlag = false;
Boolean tempFlag;
myCheck(f, '{');
switch (f.peekAtKind()) {
case WORD:
// Check if it is a variable declaration.
while (f.check("int")) {
asmCode += getVariables(f);
myCheck(f, ';');
}
// Parse all the statement before }.
while (!f.check('}')) {
asmCode += getStmt(f);
tempFlag = returnFlags.pop();
if (tempFlag) {
returnFlag = true;
}
}
if (!returnFlag) throw new TokenizerException("Error: No return.");
return asmCode;
case OPERATOR:
while (!f.check('}')) {
asmCode += getStmt(f);
tempFlag = returnFlags.pop();
if (tempFlag) {
returnFlag = true;
}
}
if (!returnFlag) throw new TokenizerException("Error: No return.");
return asmCode;
default:
throw new TokenizerException("Error: Invalid body.");
}
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid body.");
}
}
// For all functions that return the SaM code, the string of the code is named as asmCode.
static String getProgram(SamTokenizer f) {
try {
// SaM code for running the main method.
String asmCode = "PUSHIMM 0\n" + "LINK\n" + "JSR main\n" + "POPFBR\n" + "STOP\n";
while (f.peekAtKind() != TokenType.EOF) {
asmCode += getMethod(f);
}
// Add the final stop command.
return asmCode + "STOP\n";
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Fatal error: could not compile program");
}
}
static String getActuals(SamTokenizer f, String methodName) throws TokenizerException {
try {
int actualCounter = 0;
++actualCounter;
String asmCode = "";
asmCode += getExp(f);
while (f.check(',')) {
++actualCounter;
asmCode += getExp(f);
}
if (actualCounter != actMap.get(methodName))
throw new TokenizerException("Error: Invalid number of actuals.");
globalCounter = actualCounter;
actualCounter = 0;
return asmCode;
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid actuals");
}
}
static String getBlock(SamTokenizer f) throws TokenizerException {
try {
String asmCode = "";
Boolean returnFlag = false;
Boolean tempFlag;
while (!f.check('}')) {
asmCode += getStmt(f);
tempFlag = returnFlags.pop();
if (tempFlag) {
returnFlag = true;
}
}
if (!returnFlag) returnFlags.push(false);
else returnFlags.push(true);
return asmCode;
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Invalid block.");
}
}
static void myCheck(SamTokenizer f, String s) throws TokenizerException {
if (!f.check(s)) throw new TokenizerException("Error: Expected " + s + " is lost.");
}
// The following two functions can check if a char or a string is as expected in the grammar.
// If not, we will throw a TokenizerException along with message about the expected symbol.
static void myCheck(SamTokenizer f, char sym) throws TokenizerException {
if (!f.check(sym)) throw new TokenizerException("Error: Expected " + sym + " is lost.");
}
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.");
}
}
// Parse an expression.
static String getExp(SamTokenizer f) throws TokenizerException {
try {
String asmCode = "";
switch (f.peekAtKind()) {
// Single int
case INTEGER:
return "PUSHIMM " + f.getInt() + "\n";
case OPERATOR:
myCheck(f, '(');
if (f.check('-')) {
// Negative of x = 0 - x;
asmCode += "PUSHIMM 0\n";
asmCode += getExp(f);
asmCode += "SUB\n";
} else if (f.check('!')) {
// Negate x
// Return 1 for 0 and return 0 for all the others.
asmCode += getExp(f);
asmCode += "ISNIL\n";
} else {
asmCode += getExp(f);
// System.out.println(asmCode);
if (f.check(')')) return asmCode;
else if (f.check('+') || f.check('|')) asmCode += (getExp(f) + "ADD\n");
else if (f.check('-')) asmCode += (getExp(f) + "SUB\n");
else if (f.check('*') || f.check('&')) asmCode += (getExp(f) + "TIMES\n");
else if (f.check('/')) asmCode += (getExp(f) + "DIV\n");
else if (f.check('<')) asmCode += (getExp(f) + "CMP\n" + "ISPOS\n");
else if (f.check('>')) asmCode += (getExp(f) + "CMP\n" + "ISNEG\n");
else if (f.check('=')) asmCode += (getExp(f) + "CMP\n" + "ISNIL\n");
else throw new TokenizerException("Error: Invalid expression");
}
myCheck(f, ')');
return asmCode;
case WORD:
String newWord = f.getWord();
switch (newWord) {
case "true":
return "PUSHIMM " + "1" + "\n";
case "false":
return "PUSHIMM " + "0" + "\n";
default:
// If there is a (, it is an invocation of a method.
// EXP->METHOD '(' ACTUALS? ')'
if (f.check('(')) {
// Check if the name of the method is declared before.
if (!symMap.containsKey(newWord))
throw new TokenizerException("Error: Method not declared.");
asmCode += "PUSHIMM 0\n";
String sp = "";
if (f.check(')')) {
// No actuals
if (actMap.get(newWord) != 0)
throw new TokenizerException("Error: Invalid number of actuals.");
} else {
asmCode += getActuals(f, newWord);
myCheck(f, ')');
// Store the command for popping out parameters temporarily in this case.
sp = "ADDSP -" + Integer.toString(globalCounter) + "\n";
}
// Invocation of the method.
// If there is no actuals for this method, then the string sp is an empty string.
asmCode += ("LINK\n" + "JSR " + newWord + "\n" + "POPFBR\n" + sp);
return asmCode;
} else {
// EXP->LOCATION
// Check if the variable is already declared.
if (!symTables.lastElement().containsKey(newWord))
throw new TokenizerException("Error: Variable not declared.");
// Get the address of the variable from the symbol table.
int addr = symTables.lastElement().get(newWord);
asmCode += ("PUSHOFF " + Integer.toString(addr) + "\n");
return asmCode;
}
}
default:
throw new TokenizerException("Error: Invalid expression.");
}
} catch (Exception e) {
System.out.println(e.getMessage());
throw new TokenizerException("Error: Cannot parse the expression.");
}
}