/*
 *    ClassConstant.java    1.3    99/04/06 SMI
 *
 * Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package components;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import util.DataFormatException;
import vm.Const;

// ClassConstant represents a CONSTANT_Class stored in a constant pool.

public
class ClassConstant extends ConstantObject
{
    public UnicodeConstant name;
    
    private boolean     didLookup;
    private ClassInfo     theClass;

    public int nameIndex;

    ClassConstant( int t, int n ){ 
    tag = t;
    nameIndex = n;
    nSlots = 1;
    }

    public ClassConstant( UnicodeConstant n ){
    tag = Const.CONSTANT_CLASS;
    name = n;
    nSlots = 1;
    resolved = true;
    }

    // Read from constant pool.
    public static
    ClassConstant read( int tag, DataInput in ) throws IOException {
    return new ClassConstant( tag, in.readUnsignedShort() );
    }

    public void
    resolve( ConstantObject table[] ){
    if (resolved) return;
    name = (UnicodeConstant)table[nameIndex];
    resolved = true;
    }

    public void externalize( ConstantPool p ){
    name = (UnicodeConstant)p.add( name );
    }

    // Write out reference to the ClassClass data structure
    public void write( DataOutput o ) throws IOException{
    o.writeByte( tag );
    if ( ! resolved )
        throw new DataFormatException("unresolved ClassConstant");
    int x = name.index;
    if ( x == 0 )
        throw new DataFormatException("0 name index for "+name.string);
    o.writeShort( x );
    }

    public String toString(){
    if ( resolved )
        return "Class: "+name.toString();
    else
        return "Class: ["+nameIndex+"]";
    }

    public int hashCode() {
    return tag + name.hashCode();
    }

    public void incReference() {
    references++;
    name.incReference();
    }

    public void decReference() {
    references--;
    name.decReference();
    }

    public boolean equals(Object o) {
    if (o instanceof ClassConstant) {
        ClassConstant c = (ClassConstant) o;
        return name.string.equals(c.name.string);
    } else {
        return false;
    }
    }

    public ClassInfo find(){
    if ( !didLookup ){
        theClass = ClassInfo.lookupClass( name.string );
        didLookup = true;
    }
    return theClass; // which may be null
    }

    public void forget(){
    didLookup = false;
    theClass = null;
    }

    public boolean isResolved(){ return find() != null; }
}