package test.antlr.assembler;
/***
 * Excerpted from "Language Implementation Patterns",
 * published by The Pragmatic Bookshelf.
 * Copyrights apply to this code. It may not be used to create training material, 
 * courses, books, articles, and the like. Contact us if you are in doubt.
 * We make no guarantees that this code is fit for any purpose. 
 * Visit http://www.pragmaticprogrammer.com/titles/tpdsl for more book information.
***/
import java.util.*;

public class LabelSymbol {
    String name;

    /** Address in code memory */
    int address;

    /** Is this ref'd before def'd. */
    boolean isForwardRef = false;

    /** Set when we see actual ID: definition */
    boolean isDefined = true;

    /** List of operands in memory we need to update after seeing def */
    Vector<Integer> forwardReferences = null;

    public LabelSymbol(String name) {
	    this.name = name;
    }

    public LabelSymbol(String name, int address) {
        this(name);
        this.address = address;
    }

    public LabelSymbol(String name, int address, boolean forward) {
        this(name);
        isForwardRef = forward;
        if ( forward ) {
            // if forward reference, then address is address to update
            addForwardReference(address);
        }
        else {
            this.address = address;
        }
    }

    public void addForwardReference(int address) {
        if ( forwardReferences==null ) {
            forwardReferences = new Vector<Integer>();
        }
        forwardReferences.addElement(new Integer(address));
    }

    public void resolveForwardReferences(byte[] code) {
        isForwardRef = false;
        // need to patch up all references to this symbol
        Vector<Integer> opndsToPatch = forwardReferences;
        for (int addrToPatch : opndsToPatch) {
            /*
		    System.out.println("updating operand at addr "+
                    addr+" to be "+getAddress());
		    */
            BytecodeAssembler.writeInt(code, addrToPatch, address);
        }
    }

    public String toString() {
        String refs = "";
        if ( forwardReferences!=null ) {
            refs = "[refs="+forwardReferences.toString()+"]";
        }
        return name+"@"+address+refs;
    }
}