Symbols and Tables :: Cool Support Code

00-SymbolTable.java

class SymbolTable {
    private Stack tbl;
    
    public SymbolTable() { tbl = new Stack();}
    
    public void enterScope() { tbl.push(new Hashtable());}

    public void exitScope() {
	if (tbl.empty()) { Utilities.fatalError("existScope: can't remove scope from an empty symbol table.");}
	tbl.pop();
    }

    public void addId(AbstractSymbol id, Object info) {
	if (tbl.empty()) { Utilities.fatalError("addId: can't add a symbol without a scope.");	}
	((Hashtable)tbl.peek()).put(id, info);
    }

    public Object lookup(AbstractSymbol sym) {
	if (tbl.empty()) { Utilities.fatalError("lookup: no scope in symbol table.");}
	for (int i = tbl.size() - 1; i >= 0; i--) {
	    Object info = ((Hashtable)tbl.elementAt(i)).get(sym);
	    if (info != null) return info;
	}
	return null;
    }

    public Object probe(AbstractSymbol sym) {
	if (tbl.empty()) { Utilities.fatalError("lookup: no scope in symbol table.");}
	return ((Hashtable)tbl.peek()).get(sym);
    }
    
    public String toString() {
	String res = "";
	for (int i = tbl.size() - 1, j = 0; i >= 0; i--, j++) {
	    res += "Scope " + j + ": " + tbl.elementAt(i) + "\n";
	}
	return res;
    }
}

01-SymbolTableExample.java

public class SymtabExample {
    public static void main(String args[]) {
	SymbolTable map = new SymbolTable();

	AbstractSymbol fred = AbstractTable.stringtable.addString("Fred");
	AbstractSymbol mary = AbstractTable.stringtable.addString("Mary");
	AbstractSymbol miguel = AbstractTable.stringtable.addString("Miguel");
	
	map.enterScope();
	map.addId(fred, new Integer(22));
	map.addId(mary, new Integer(25));

	map.enterScope();
	map.addId(miguel, new Integer(35));
	map.addId(mary, new Integer(23));

	// check whether Fred is in the current scope; predicate is false
	System.out.println((map.probe(fred) != null) ? "Yes" : "No");
	
	// check whether Mary is in any scope; predicate is true
	System.out.println((map.lookup(mary) != null) ? "Yes" : "No");
	
	// print age of most-closely-nested Mary
	System.out.println(map.lookup(mary));

	// check whether Miguel is in the current scope; predicate is true
	System.out.println((map.probe(miguel) != null) ? "Yes" : "No");

	// leave a scope
	map.exitScope();

	// print age of most-closely-nested Mary
	System.out.println(map.lookup(mary));

	// check whether Fred is in the current scope; predicate is now true
	System.out.println((map.probe(fred) != null) ? "Yes" : "No");

	// check whether Miguel is in any scope; predicate is now false
	System.out.println((map.lookup(miguel) != null) ? "Yes" : "No");
    }	
}
 

02-Symbols.java

import java.io.PrintStream;

public abstract class AbstractSymbol {
    protected String str;
    protected int index;
    public AbstractSymbol(String str, int len, int index) {
	this.str = str.length() == len ? str : str.substring(0, len);
	this.index = index;
    }

    public boolean equalString(String str, int len) {
	String other = str.length() == len ? str : str.substring(0, len);
	return this.str.equals(other);
    }

    public boolean equalsIndex(int index) {
	return this.index == index;
    }

    public boolean equals(Object another) {
	return (another instanceof AbstractSymbol) && 
	    ((AbstractSymbol)another).index == this.index;
    }

    public String getString() {	return str; }
    public String toString()  { return str;}

    public abstract Object clone();
}

public class IdSymbol extends AbstractSymbol {
    public IdSymbol(String str, int len, int index) {
	super(str, len, index);
    }
    public Object clone() {
	return new IdSymbol(str, str.length(), index);
    }
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

// These are project skeleton files for PA5, but a regular support code
// for other assignments.

public class IntSymbol extends AbstractSymbol {
    public IntSymbol(String str, int len, int index) {
	super(str, len, index);
    }

    /** Generates code for the integer constant definition.  This method
     * is incomplete; you get to finish it up in programming assignment
     * 5.
     * @param intclasstag the class tag for string object
     * @param s the output stream
     *
     * */
    public void codeDef(int intclasstag, PrintStream s) {
	// Add -1 eye catcher
	s.println(CgenSupport.WORD + "-1");
	codeRef(s); s.print(CgenSupport.LABEL); // label
	s.println(CgenSupport.WORD + intclasstag); // tag
	s.println(CgenSupport.WORD + (CgenSupport.DEFAULT_OBJFIELDS + 
				      CgenSupport.INT_SLOTS)); // size
	s.print(CgenSupport.WORD);

	/* Add code to reference the dispatch table for class Int here */

	s.println("");		// dispatch table
	s.println(CgenSupport.WORD + str); // integer value
    }

    public void codeRef(PrintStream s) { s.print(CgenSupport.INTCONST_PREFIX + index); }

    public Object clone() { return new IntSymbol(str, str.length(), index);}
}



public class StringSymbol extends AbstractSymbol {
    public StringSymbol(String str, int len, int index) {
	super(str, len, index);
    }

    /** Generates code for the string constant definition.  This method
     * is incomplete; you get to finish it up in programming assignment
     * 5.
     * @param stringclasstag the class tag for string object
     * @param s the output stream
     *
     * */
    public void codeDef(int stringclasstag, PrintStream s) {
	IntSymbol lensym = (IntSymbol)AbstractTable.inttable.addInt(str.length());
	
	// Add -1 eye catcher
	s.println(CgenSupport.WORD + "-1");
	codeRef(s); s.print(CgenSupport.LABEL); // label
	s.println(CgenSupport.WORD + stringclasstag); // tag
	s.println(CgenSupport.WORD + (CgenSupport.DEFAULT_OBJFIELDS +
				      CgenSupport.STRING_SLOTS +
				      (str.length() + 4) / 4)); // object size
	s.print(CgenSupport.WORD);

	/* Add code to reference the dispatch table for class String here */

	s.println("");		// dispatch table
	s.print(CgenSupport.WORD); lensym.codeRef(s); s.println(""); // length
	CgenSupport.emitStringConstant(str, s); // ascii string
	s.print(CgenSupport.ALIGN); // align to word
    }

    public void codeRef(PrintStream s) {
	s.print(CgenSupport.STRCONST_PREFIX + index);
    }

    public Object clone() {
	return new StringSymbol(str, str.length(), index);
    }
}

03-Tables.java

public abstract class AbstractTable {

    public static StringTable stringtable = new StringTable();
    public static IdTable idtable         = new IdTable();
    public static IntTable inttable       = new IntTable();

    private static int MAXSIZE = 1000000;

    protected Vector tbl = new Vector();

    protected abstract AbstractSymbol getNewSymbol(String s, int len, int index);

    public AbstractSymbol addString(String s, int maxchars) {
	int len = Math.min(s.length(), maxchars);
	AbstractSymbol sym = null;
	for (int i = 0; i < tbl.size(); i++) {
	    try {
		sym = (AbstractSymbol)tbl.elementAt(i);
	    } catch (ArrayIndexOutOfBoundsException ex) {
		Utilities.fatalError("Unexpected exception: " + ex);
	    }
	    if (sym.equalString(s, len)) {
		return sym;
	    }
	}
	sym = getNewSymbol(s, len, tbl.size());
	tbl.addElement(sym);
	return sym;
    }
		
    public AbstractSymbol addString(String s) {
	return addString(s, MAXSIZE);
    }

    public AbstractSymbol addInt(int i) {
	return addString(Integer.toString(i), MAXSIZE);
    }
    
    public Enumeration getSymbols() {
	return tbl.elements();
    }

    public AbstractSymbol lookup(int index) { 
	AbstractSymbol sym = null;
	try {
	    sym = (AbstractSymbol)tbl.elementAt(index);
	} catch (ArrayIndexOutOfBoundsException ex) {
	    Utilities.fatalError("Symbol index out of bounds: " + index);
	}
	return sym;
    }

    public AbstractSymbol lookup(String s) {
	int len = s.length();
	AbstractSymbol sym = null;
	for (int i = 0; i < tbl.size(); i++) {
	    try {
		sym = (AbstractSymbol)tbl.elementAt(i);
	    } catch (ArrayIndexOutOfBoundsException ex) {
		Utilities.fatalError("Unexpected exception: " + ex);
	    }
	    if (sym.equalString(s, len)) {
		return sym;
	    }
	}
	Utilities.fatalError("String table lookup failed on string: " + s);
	return null;
    }

    public String toString() {
	String res = "[\n";
	AbstractSymbol sym = null;
	for (int i = 0; i < tbl.size(); i++) {
	    try {
		sym = (AbstractSymbol)tbl.elementAt(i);
	    } catch (ArrayIndexOutOfBoundsException ex) {
		Utilities.fatalError("Unexpected exception: " + ex);
	    }
	    res += "  " + sym.toString() + "\n";
	}
	res += "]\n";
	return res;
    }
}

////////////////////////////////////////////////////////////////////////////

import java.io.PrintStream;

public class IdTable extends AbstractTable {
    protected AbstractSymbol getNewSymbol(String s, int len, int index) {
	return new IdSymbol(s, len, index);
    }
}

public class StringTable extends AbstractTable {

    protected AbstractSymbol getNewSymbol(String s, int len, int index) {
	return new StringSymbol(s, len, index);
    }

    public void codeStringTable(int stringclasstag, PrintStream s) {
	StringSymbol sym = null;
	for (int i = tbl.size() - 1; i >= 0; i--) {
	    try {
		sym = (StringSymbol)tbl.elementAt(i);
	    } catch (ArrayIndexOutOfBoundsException ex) {
		Utilities.fatalError("Unexpected exception: " + ex);
	    }
	    sym.codeDef(stringclasstag, s);
	}
    }
}

public class IntTable extends AbstractTable {
    protected AbstractSymbol getNewSymbol(String s, int len, int index) {
	return new IntSymbol(s, len, index);
    }

    public void codeStringTable(int intclasstag, PrintStream s) {
	IntSymbol sym = null;
	for (int i = tbl.size() - 1; i >= 0; i--) {
	    try {
		sym = (IntSymbol)tbl.elementAt(i);
	    } catch (ArrayIndexOutOfBoundsException ex) {
		Utilities.fatalError("Unexpected exception: " + ex);
	    }
	    sym.codeDef(intclasstag, s);
	}
    }
}

copyright.txt

/*
Copyright (c) 2000 The Regents of the University of California.
All rights reserved.

Permission to use, copy, modify, and distribute this software for any
purpose, without fee, and without written agreement is hereby granted,
provided that the above copyright notice and the following two
paragraphs appear in all copies of this software.

IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/