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Writing a compiler

A compiler plugin must either implement Compiler interface, or extend more bloat-free AbstractCompiler class. Common practice is to utilize JFLex and Java Cup parser generators, which has direct runtime support in emuStudio.

Sample implementation of a compiler might look as follows (just some methods are implemented):

public class CompilerImpl extends AbstractCompiler {
    private final static List<SourceFileExtension> SOURCE_FILE_EXTENSIONS = List.of(
        new SourceFileExtension("asm", "Assembler source file"),

    private final LexerImpl lexer;
    private final ParserImpl parser;
    private MemoryContext<Short> memory;
    private int programLocation;

    public CompilerImpl(long pluginID, ApplicationApi applicationApi, PluginSettings pluginSettings) {
        super(pluginID, applicationApi, pluginSettings);
        lexer = new LexerImpl(null);
        parser = new ParserImpl(lexer, this);

    public void initialize() {
        try {
            ContextPool pool = applicationApi.getContextPool();
            memory = pool.getMemoryContext(pluginID, MemoryContext.class);
            if (memory.getDataType() != Short.class) {
                throw new InvalidContextException(
                    "Unexpected memory cell type. Expected Short but was: " + memory.getDataType()
        } catch (ContextNotFoundException | InvalidContextException e) {
            System.err.println("Memory context is not available", e);

    public LexicalAnalyzer getLexer(Reader in) {
        return new LexerImpl(in);

    public boolean compile(String inputFileName, String outputFileName) {
        try {
            IntelHEX hex = compileToHex(inputFileName);

            programLocation = hex.getProgramLocation();
            notifyInfo("Compilation was successful.\n Output file: " + outputFileName);

            if (memory != null) {
                notifyInfo("Compiled file was loaded into memory.");
            } else {
                notifyWarning("Memory is not available.");
            return true;
        } catch (Exception e) {
            notifyError("Compilation error: " + e.getMessage());
            return false;
        } finally {

    public int getProgramLocation() {
        return programLocation;

    public List<SourceFileExtension> getSourceFileExtensions() {

    private IntelHEX compileToHex(String inputFileName) throws Exception {

The compiler does not register any context, but when initialized it obtains optional memory context. If the memory is available, it means that after compilation the program will be loaded in there, otherwise not.

Lexer and parser are not shown here, but they are created using mentioned JFlex and Java cup tools.

The compiler utilizes a helper class IntelHEX from emuLib, which generates Intel HEX files.

For more information, see the code of some existing compilers.