Source code of MARS Assembler
First commit of the 4.5 version (latest version available)
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package mars.assembler;
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import mars.*;
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import java.util.*;
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/*
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Copyright (c) 2003-2006, Pete Sanderson and Kenneth Vollmar
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Developed by Pete Sanderson (psanderson@otterbein.edu)
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and Kenneth Vollmar (kenvollmar@missouristate.edu)
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject
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to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
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ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
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CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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(MIT license, http://www.opensource.org/licenses/mit-license.html)
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*/
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/**
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* Creats a table of Symbol objects.
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* @author Jason Bumgarner, Jason Shrewsbury
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* @version June 2003
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**/
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public class SymbolTable {
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private static String startLabel = "main";
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private String filename;
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private ArrayList table;
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// Note -1 is legal 32 bit address (0xFFFFFFFF) but it is the high address in
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// kernel address space so highly unlikely that any symbol will have this as
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// its associated address!
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public static final int NOT_FOUND = -1;
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/**
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* Create a new empty symbol table for given file
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* @param filename name of file this symbol table is associated with. Will be
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* used only for output/display so it can be any descriptive string.
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*/
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public SymbolTable(String filename) {
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this.filename = filename;
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this.table = new ArrayList();
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}
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/**
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* Adds a Symbol object into the array of Symbols.
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* @param token The token representing the Symbol.
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* @param address The address of the Symbol.
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* @param b The type of Symbol, true for data, false for text.
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* @param errors List to which to add any processing errors that occur.
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**/
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public void addSymbol(Token token, int address, boolean b, ErrorList errors) {
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String label = token.getValue();
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if (getSymbol(label) != null) {
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errors.add(new ErrorMessage(token.getSourceMIPSprogram(), token.getSourceLine(),token.getStartPos(),"label \""+label+"\" already defined"));
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}
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else {
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Symbol s= new Symbol(label, address, b);
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table.add(s);
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if (Globals.debug) System.out.println("The symbol " + label + " with address " + address + " has been added to the "+this.filename+" symbol table.");
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}
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}
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/**
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* Removes a symbol from the Symbol table. If not found, it does nothing.
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* This will rarely happen (only when variable is declared .globl after already
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* being defined in the local symbol table).
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* @param token The token representing the Symbol.
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**/
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public void removeSymbol(Token token) {
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String label = token.getValue();
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for (int i=0; i < table.size(); i++) {
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if (((Symbol)(table.get(i))).getName().equals(label)){
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table.remove(i);
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if (Globals.debug) System.out.println("The symbol " + label + " has been removed from the "+this.filename+" symbol table.");
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break;
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}
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}
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return;
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}
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/**
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* Method to return the address associated with the given label.
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* @param s The label.
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* @return The memory address of the label given, or NOT_FOUND if not found in symbol table.
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**/
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public int getAddress(String s){
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for(int i=0; i < table.size(); i++){
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if (((Symbol)(table.get(i))).getName().equals(s)){
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return((Symbol) table.get(i)).getAddress();
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}
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}
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return NOT_FOUND;
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}
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/**
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* Method to return the address associated with the given label. Look first
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* in this (local) symbol table then in symbol table of labels declared
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* global (.globl directive).
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* @param s The label.
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* @return The memory address of the label given, or NOT_FOUND if not found in symbol table.
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**/
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public int getAddressLocalOrGlobal(String s) {
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int address = this.getAddress(s);
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return (address==NOT_FOUND) ? Globals.symbolTable.getAddress(s) : address ;
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}
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/**
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* Produce Symbol object from symbol table that corresponds to given String.
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* @param s target String
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* @return Symbol object for requested target, null if not found in symbol table.
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**/
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public Symbol getSymbol(String s){
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for(int i=0; i < table.size(); i++){
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if (((Symbol)(table.get(i))).getName().equals(s)){
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return (Symbol) table.get(i);
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}
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}
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return null;
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}
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/**
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* Produce Symbol object from symbol table that has the given address.
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* @param s String representing address
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* @return Symbol object having requested address, null if address not found in symbol table.
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**/
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public Symbol getSymbolGivenAddress(String s){
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int address = 0;
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try {
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address = mars.util.Binary.stringToInt(s);// DPS 2-Aug-2010: was Integer.parseInt(s) but croaked on hex
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}
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catch (NumberFormatException e) {
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return null;
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}
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for(int i=0; i < table.size(); i++){
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if (((Symbol)(table.get(i))).getAddress() == address){
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return (Symbol) table.get(i);
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}
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}
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return null;
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}
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/**
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* Produce Symbol object from either local or global symbol table that has the
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* given address.
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* @param s String representing address
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* @return Symbol object having requested address, null if address not found in symbol table.
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**/
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public Symbol getSymbolGivenAddressLocalOrGlobal(String s){
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Symbol sym = this.getSymbolGivenAddress(s);
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return (sym==null) ? Globals.symbolTable.getSymbolGivenAddress(s) : sym ;
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}
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/**
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* For obtaining the Data Symbols.
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* @return An ArrayList of Symbol objects.
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**/
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public ArrayList getDataSymbols(){
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ArrayList list= new ArrayList();
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for(int i=0; i<table.size(); i++){
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if(((Symbol)table.get(i)).getType()){
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list.add(table.get(i));
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}
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}
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return list;
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}
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/**
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* For obtaining the Text Symbols.
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* @return An ArrayList of Symbol objects.
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**/
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public ArrayList getTextSymbols(){
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ArrayList list= new ArrayList();
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for(int i=0; i<table.size(); i++){
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if(!((Symbol)table.get(i)).getType()){
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list.add(table.get(i));
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}
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}
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return list;
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}
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/**
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* For obtaining all the Symbols.
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* @return An ArrayList of Symbol objects.
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**/
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public ArrayList getAllSymbols(){
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ArrayList list= new ArrayList();
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for(int i=0; i<table.size(); i++){
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list.add(table.get(i));
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}
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return list;
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}
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/**
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* Get the count of entries currently in the table.
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* @return Number of symbol table entries.
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**/
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public int getSize(){
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return table.size();
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}
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/**
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* Creates a fresh arrayList for a new table.
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**/
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public void clear(){
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table= new ArrayList();
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}
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/**
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* Fix address in symbol table entry. Any and all entries that match the original
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* address will be modified to contain the replacement address. There is no effect,
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* if none of the addresses matches.
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* @param originalAddress Address associated with 0 or more symtab entries.
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* @param replacementAddress Any entry that has originalAddress will have its
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* address updated to this value. Does nothing if none do.
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*/
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public void fixSymbolTableAddress(int originalAddress, int replacementAddress) {
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Symbol label = getSymbolGivenAddress(Integer.toString(originalAddress));
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while (label != null) {
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label.setAddress(replacementAddress);
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label = getSymbolGivenAddress(Integer.toString(originalAddress));
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}
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return;
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}
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/**
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* Fetches the text segment label (symbol) which, if declared global, indicates
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* the starting address for execution.
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* @return String containing global label whose text segment address is starting address for program execution.
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**/
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public static String getStartLabel() {
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return startLabel;
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}
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}
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