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Lexer.java
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Lexer.java
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/*c
* Scanner Class to convert Pascal Source Code to Tokens
*
* @author Justin Chin
* @since 2018.04.03
*/
import java.io.*;
import java.util.*;
public final class Lexer {
// final used to make sure cannot be changed
// static used to ensure it belongs to the class and not instance
private static int col = 0;
private static int row = 0;
private static String tkValue = "";
private static ArrayList<Token> tkList = new ArrayList<Token>();
private static boolean isReal = false;
private static State currState = State.SOTHER;
//---------------------------------------------
// ENUMS
// -------------------------------------------
/*
* FSM STATES
*
* SSTRING = when we see a quote
* SNUMBER = when we see a number (integer vs real)
* SCOMMENT = when we see a (*, ignore till *)
* SOTHER = build tokens here
*/
private enum State {
SSTRING, SNUMBER, SCOMMENT, SOTHER
}
/*
* CHARACTER TYPES
*
* sfdf
*/
private enum Type {
WHITESPACE, OPERATOR, NUMBER, DOT,SEMI,EQUALS,LETTER, EOF, QUOTE, STAR, PAREN
}
//----------------------------------------------
// TABLES
//
// Create & Populate a static final HashTable
//----------------------------------------------
// OPERATORS -----------------------------------
private static final HashMap<String,String> TK_OPERATORS;
static {
TK_OPERATORS = new HashMap<String,String>();
TK_OPERATORS.put("+","TK_PLUS");
TK_OPERATORS.put("-","TK_MINUS");
TK_OPERATORS.put("*","TK_TIMES");
TK_OPERATORS.put("/","TK_DIVIDE");
TK_OPERATORS.put("%","TK_MOD");
TK_OPERATORS.put("=","TK_EQUAL");
TK_OPERATORS.put("<>","TK_NOT_EQUAL");
TK_OPERATORS.put(">","TK_GREATER_THAN");
TK_OPERATORS.put("<","TK_LESS_THAN");
TK_OPERATORS.put(">=","TK_GREATER_THAN_EQUAL");
TK_OPERATORS.put("<=","TK_LESS_THAN_EQUAL");
TK_OPERATORS.put("[","TK_OPEN_BRACKET");
TK_OPERATORS.put("]","TK_CLOSE_BRACKET");
TK_OPERATORS.put("(","TK_OPEN_PARENTHESIS");
TK_OPERATORS.put(")","TK_CLOSE_PARENTHESIS");
TK_OPERATORS.put(".","TK_PERIOD");
TK_OPERATORS.put(",","TK_COMMA");
TK_OPERATORS.put(":","TK_COLON");
TK_OPERATORS.put(";","TK_SEMICOLON");
TK_OPERATORS.put(":=","TK_ASSIGNMENT");
};
// TYPE ----------------------------------------
// Note:
// Decided to put into hashmap instead of if statements
// because it is easier to add more special cases
private static final HashMap<String,Type> CHARACTER_TYPE;
static {
CHARACTER_TYPE = new HashMap<>();
for (int i = 1; i <= 32; i++){
// populating WhiteSpaces
CHARACTER_TYPE.put(Character.toString((char) i), Type.WHITESPACE);
}
for (int i = 48; i <= 57; i++){
// populating Numbers
CHARACTER_TYPE.put(Character.toString((char) i), Type.NUMBER);
}
for (int i = 65; i <= 90; i++){
// populating UpperCase Letters
CHARACTER_TYPE.put(Character.toString((char) i), Type.LETTER);
}
for (int i = 97; i <= 122; i++){
// populating LowerCase Letters
CHARACTER_TYPE.put(Character.toString((char) i), Type.LETTER);
}
// populate Quote for String
CHARACTER_TYPE.put("'", Type.QUOTE);
// populate Operates
for (String key: TK_OPERATORS.keySet()){
CHARACTER_TYPE.put(key,Type.OPERATOR);
}
};
// KEYWORDS -------------------------------------
private static final HashMap<String,String> TK_KEYWORDS;
static {
TK_KEYWORDS = new HashMap<String,String>();
try{
Scanner input = new Scanner(new File("keywords.txt"));
while(input.hasNext()){
String keyword = input.next().toUpperCase();
TK_KEYWORDS.put(keyword,"TK_"+keyword);
}}
catch(FileNotFoundException e){
System.out.println("Keywords.txt File Not Found...");
System.out.println("Exiting Compiler. Goodbye.");
System.exit(0);
}
};
//----------------------------------------------
// PUBLIC METHODS
//----------------------------------------------
/*
* Method called to scan a file
*
* @param file a pascal file
* @return an arrayList of Tokens
*/
public static ArrayList<Token> scan(File file) throws IOException {
Scanner input = new Scanner(file).useDelimiter(""); // remove delimiter;
// Loop through each char until there is no more
while(input.hasNext()){
// convert to character
String element = String.valueOf(input.next().charAt(0));
// System.out.println("row"+" col"+" character");
// System.out.println(row+" "+col+" "+element);
col += 1;
if (element.equals("\n")){
row += 1;
col = 0;
}
// handle character depending on the state
switch (currState){
case SSTRING:
handleString(element);
break;
case SNUMBER:
handleNumber(element);
break;
case SCOMMENT:
handleComment(element);
break;
default:
// SOTHER
handleOther(element);
break;
}
}
// Broke out of loop so EOF
col += 1;
tkValue = "EOF";
createTk("TK_EOF");
return tkList;
}
/*
* Clears Info After Assigning Token
*
*/
public static void clear(){
tkValue = "";
}
/*
* Creates Tokens and adds them the tkList
*
* @param tkString String
*/
public static void createTk(String tkString){
Token tk = new Token(tkString, tkValue, col, row);
tkList.add(tk);
//System.out.println(tkString);
clear();
}
//----------------------------------------------
// STATE HANDLING METHODS
//----------------------------------------------
/*
* Handles String State
* checks the kind of element in the table
*
* @param char element
*
*/
public static void handleString(String element){
switch (CHARACTER_TYPE.get(element)){
case QUOTE:
// end string building
tkValue += element;
createTk("TK_STRING");
currState = State.SOTHER;
break;
default:
// continue string building
tkValue += element;
break;
}
}
/*
* Handles Number State
*
* @param char element
*
*/
public static void handleNumber(String element){
switch(CHARACTER_TYPE.get(element)){
case NUMBER:
// continue number building
tkValue += element;
break;
case OPERATOR:
if (element.equals(".")){
// real number building
tkValue += element;
isReal = true;
break;
}
if (element.equals(";")){
currState = State.SOTHER;
if (isReal)
createTk("TK_REAL");
else
createTk("TK_INTEGER");
tkValue += element;
if (TK_OPERATORS.containsKey(element)){
createTk(TK_OPERATORS.get(element));
}
}
break;
default:
// end number building
currState = State.SOTHER;
if (isReal)
createTk("TK_REAL");
else
createTk("TK_INTEGER");
break;
}
}
/*
* Handles Comment State
*
* @param char element
*/
public static void handleComment(String element){
switch(CHARACTER_TYPE.get(element)){
case OPERATOR:
if (element.equals("*")){
// signals possible comment end
tkValue = "TK_TIMES";
break;
}
case PAREN:
// end comment building
if (!tkValue.equals("")){
currState = State.SOTHER;
createTk("TK_COMMENT");
}
break;
default:
// continue comment building
tkValue += element;
break;
}
}
/*
* Checks if tkValue is an operator or keywords and creates tk if so
*/
public static void checkOPKEY(){
//System.out.println("checkOPKEY....tkValue....."+ tkValue);
//OPERATOR
if (TK_OPERATORS.containsKey(tkValue)){
createTk(TK_OPERATORS.get(tkValue));
} // KEYWORDS
else if (TK_KEYWORDS.containsKey(tkValue.toUpperCase())){
createTk(TK_KEYWORDS.get(tkValue.toUpperCase()));
} // ID
else {
if (!tkValue.equals("")){
createTk("TK_ID");
}
}
}
/*
* Handles Other State
*
* @param char element
*/
public static void handleOther(String element){
//System.out.println("CharacterType: "+CHARACTER_TYPE.get(element));
switch(CHARACTER_TYPE.get(element)){
case NUMBER:
// start number state
currState = State.SNUMBER;
tkValue += element;
break;
case QUOTE:
// start string state
checkOPKEY();
currState = State.SSTRING;
tkValue += element;
break;
case WHITESPACE:
if (!tkValue.equals("")){
checkOPKEY();
}
break;
case OPERATOR:
// Equals
if (element.equals("=")){
if (tkValue.equals(":")){
tkValue += element;
createTk(TK_OPERATORS.get(tkValue));
}
else {
createTk(TK_OPERATORS.get(element));
}
break;
}
// Star
if (element.equals("*")){
if (tkValue.equals("(")){
// start comment state
currState = State.SCOMMENT;
tkValue += element;
}
else {
createTk(TK_OPERATORS.get(element));
}
break;
}
// Semicolon
if (element.equals(";")){
if (TK_OPERATORS.containsKey(tkValue.toUpperCase())){
// OPERATORS
createTk(TK_OPERATORS.get(tkValue.toUpperCase()));
}
else if (TK_KEYWORDS.containsKey(tkValue.toUpperCase())){
// KEYWORDS
createTk(TK_KEYWORDS.get(tkValue.toUpperCase()));
}
else if (tkValue.equals("")){
}
else {
// IDENTIFIER TK
createTk("TK_ID");
}
// Create SEMI TK
tkValue = element;
createTk(TK_OPERATORS.get(element));
break;
}
// Any other operate, create token
checkOPKEY();
tkValue += element;
break;
default:
// if OPERATOR
if (TK_OPERATORS.containsKey(tkValue.toUpperCase())){
createTk(TK_OPERATORS.get(tkValue.toUpperCase()));
}
// we have a letter
tkValue += element;
break;
}
}
}