// Scans the given file and creates symbols for its functions & label names.
private void updateSymbolTable(File file, Hashtable symbols, Hashtable functions)
throws ProgramException {
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(file.getAbsolutePath()));
} catch (FileNotFoundException fnfe) {
throw new ProgramException("file " + file.getName() + " does not exist");
}
String line;
String currentFunction = null;
String label;
int lineNumber = 0;
isSlashStar = false;
try {
while ((line = unCommentLine(reader.readLine())) != null) {
lineNumber++;
if (!line.trim().equals("")) {
if (line.startsWith("function ")) {
StringTokenizer tokenizer = new StringTokenizer(line);
tokenizer.nextToken();
currentFunction = tokenizer.nextToken();
if (symbols.containsKey(currentFunction))
throw new ProgramException("subroutine " + currentFunction + " already exists");
functions.put(currentFunction, new Short(nextPC));
symbols.put(currentFunction, new Short(nextPC));
} else if (line.startsWith("label ")) {
StringTokenizer tokenizer = new StringTokenizer(line);
tokenizer.nextToken();
label = currentFunction + "$" + tokenizer.nextToken();
symbols.put(label, new Short((short) (nextPC + 1)));
}
nextPC++;
}
}
reader.close();
} catch (IOException ioe) {
throw new ProgramException("Error while reading from file");
} catch (NoSuchElementException nsee) {
throw new ProgramException("In line " + lineNumber + ": unexpected end of command");
}
if (isSlashStar) {
throw new ProgramException("Unterminated /* comment at end of file");
}
}
/**
* Creates a vm program. If the given file is a dir, creates a program composed of the vm files in
* the dir. The vm files are scanned twice: in the first scan a symbol table (that maps function &
* label names into addresses) is built. In the second scan, the instructions array is built.
* Throws ProgramException if an error occurs while loading the program.
*/
public void loadProgram(String fileName) throws ProgramException {
File file = new File(fileName);
if (!file.exists()) throw new ProgramException("cannot find " + fileName);
File[] files;
if (file.isDirectory()) {
files = file.listFiles(new HackFileFilter(".vm"));
if (files == null || files.length == 0)
throw new ProgramException("No vm files found in " + fileName);
} else files = new File[] {file};
if (displayChanges) gui.showMessage("Loading...");
// First scan
staticRange.clear();
functions.clear();
builtInAccessStatus = BUILTIN_ACCESS_UNDECIDED;
Hashtable symbols = new Hashtable();
nextPC = 0;
for (int i = 0; i < files.length; i++) {
String name = files[i].getName();
String className = name.substring(0, name.indexOf("."));
// put some dummy into static range - just to tell the function
// getAddress in the second pass which classes exist
staticRange.put(className, new Boolean(true));
try {
updateSymbolTable(files[i], symbols, functions);
} catch (ProgramException pe) {
if (displayChanges) gui.hideMessage();
throw new ProgramException(name + ": " + pe.getMessage());
}
}
boolean addCallBuiltInSysInit = false;
if ((file.isDirectory() || symbols.get("Main.main") != null)
&& symbols.get("Sys.init") == null) {
// If the program is in multiple files or there's a Main.main
// function it is assumed that it should be run by calling Sys.init.
// If no Sys.init is found, add an invisible line with a call
// to Sys.init to start on - the builtin version will be called.
addCallBuiltInSysInit = true;
getAddress("Sys.init"); // confirm calling the built-in Sys.init
++nextPC; // A "call Sys.init 0" line will be added
}
instructions = new VMEmulatorInstruction[nextPC + 4];
// Second scan
nextPC = 0;
currentStaticIndex = Definitions.VAR_START_ADDRESS;
for (int i = 0; i < files.length; i++) {
String name = files[i].getName();
String className = name.substring(0, name.indexOf("."));
largestStaticIndex = -1;
int[] range = new int[2];
range[0] = currentStaticIndex;
try {
// functions is not passed as an argument since it is accessed
// through getAddress()
buildProgram(files[i], symbols);
} catch (ProgramException pe) {
if (displayChanges) gui.hideMessage();
throw new ProgramException(name + ": " + pe.getMessage());
}
currentStaticIndex += largestStaticIndex + 1;
range[1] = currentStaticIndex - 1;
staticRange.put(className, range);
}
instructionsLength = visibleInstructionsLength = nextPC;
if (builtInAccessStatus == BUILTIN_ACCESS_AUTHORIZED) {
// Add some "invisible" code in the end to make everything work
instructionsLength += 4;
if (addCallBuiltInSysInit) {
instructionsLength += 1;
}
short indexInInvisibleCode = 0;
// Add a jump to the end (noone should get here since
// both calls to built-in functions indicate that
// that this is a function-based program and not a script
// a-la proj7, but just to be on the safe side...).
instructions[nextPC] =
new VMEmulatorInstruction(
HVMInstructionSet.GOTO_CODE, (short) instructionsLength, indexInInvisibleCode);
instructions[nextPC].setStringArg("afterInvisibleCode");
nextPC++;
// Add a small infinite loop for built-in
// methods to call (for example when Sys.halt is
// called it must call a non-built-in infinite loop
// because otherwise the current script would not
// finish running - a problem for the OS tests.
instructions[nextPC] = new VMEmulatorInstruction(HVMInstructionSet.LABEL_CODE, (short) -1);
instructions[nextPC].setStringArg("infiniteLoopForBuiltIns");
nextPC++;
infiniteLoopForBuiltInsAddress = nextPC;
instructions[nextPC] =
new VMEmulatorInstruction(HVMInstructionSet.GOTO_CODE, nextPC, ++indexInInvisibleCode);
instructions[nextPC].setStringArg("infiniteLoopForBuiltIns");
nextPC++;
if (addCallBuiltInSysInit) { // Add a call to the built-in Sys.init
instructions[nextPC] =
new VMEmulatorInstruction(
HVMInstructionSet.CALL_CODE,
getAddress("Sys.init"),
(short) 0,
++indexInInvisibleCode);
instructions[nextPC].setStringArg("Sys.init");
startAddress = nextPC;
nextPC++;
}
// Add the label that the first invisible code line jumps to
instructions[nextPC] = new VMEmulatorInstruction(HVMInstructionSet.LABEL_CODE, (short) -1);
instructions[nextPC].setStringArg("afterInvisibleCode");
nextPC++;
}
if (!addCallBuiltInSysInit) {
Short sysInitAddress = (Short) symbols.get("Sys.init");
if (sysInitAddress == null) // Single file, no Sys.init - start at 0
startAddress = 0;
else // Implemented Sys.init - start there
startAddress = sysInitAddress.shortValue();
}
if (displayChanges) gui.hideMessage();
nextPC = startAddress;
setGUIContents();
notifyProgramListeners(ProgramEvent.LOAD, fileName);
}