ConstantObject.java

/*
 *   
 *
 * Copyright  1990-2009 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 only, as published by the Free Software Foundation.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License version 2 for more details (a copy is
 * included at /legal/license.txt).
 * 
 * You should have received a copy of the GNU General Public License
 * version 2 along with this work; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 * 
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions.
 */

package components;
import java.io.DataInput;
import java.io.IOException;
import util.DataFormatException;
import jcc.Const;

/*
 * An abstract class for representing objects in the constant pools
 * All constants are derived from here.
 * Note how this and all its derivatives are Cloneable.
 */

public
abstract class ConstantObject extends ClassComponent implements Cloneable
{
    public int references = 0;
    public int ldcReferences = 0;
    public boolean shared = false;
    public ConstantPool containingPool; // if shared == true, then container.

    public int index;

    // The type of constant pool entry.
    public int tag;

    // The number of slots this thing "uses" -- usually 1, sometimes 2
    public int nSlots;

    public void incldcReference() {
        ldcReferences++;
    }

    public void decldcReference() {
        ldcReferences--;
    }
 
    public void clearldcReference(){
        ldcReferences = 0;
    }

    // Some items are reference counted so that the most frequently
    // accessed ones can be placed in the first 256 entries of the
    // constant table.  Others are just marked as used so we know
    // to include them somewhere in the table.
    public void incReference() {
	references++;
    }

    public void decReference() {
	references--;
    }

    public void clearReference(){
	references = 0;
    }

    public Object clone(){
	ConstantObject newC;
	try {
	    newC = (ConstantObject)super.clone();
	    newC.references = 0;
	    newC.shared     = false;
	    newC.index      = 0;
	    return newC;
	} catch( CloneNotSupportedException e ){
	    e.printStackTrace();
	    System.exit(1);
	}
	return null;
    }

    public abstract boolean isResolved();

    static public ConstantObject readObject( DataInput i ) throws IOException{
	// read the tag and dispatch accordingly
	int tag = i.readUnsignedByte();
	switch( tag ){
	case Const.CONSTANT_UTF8:
	    return UnicodeConstant.read( tag, i );
	case Const.CONSTANT_INTEGER:
	case Const.CONSTANT_FLOAT:
	    return SingleValueConstant.read( tag, i );
	case Const.CONSTANT_DOUBLE:
	case Const.CONSTANT_LONG:
	    return DoubleValueConstant.read( tag, i );
	case Const.CONSTANT_STRING:
	    return StringConstant.read( tag, i );
	case Const.CONSTANT_NAMEANDTYPE:
	    return NameAndTypeConstant.read( tag, i );
	case Const.CONSTANT_CLASS:
	    return ClassConstant.read( tag, i );
	case Const.CONSTANT_FIELD:
	    return FieldConstant.read( tag, i );
	case Const.CONSTANT_METHOD:
	    return MethodConstant.read( tag, i );
	case Const.CONSTANT_INTERFACEMETHOD:
	    return InterfaceConstant.read( tag, i );
	default:
	    throw new DataFormatException("Format error (constant tag "+tag+" )");
	}
    }
}