exceptionentry.java

已经移植好的java虚拟机

/*
 *	ExceptionEntry.java	1.4	99/04/06 SMI
 *
 * Copyright (c) 1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * Use is subject to license terms.
 */

package components;
import java.io.DataOutput;
import java.io.IOException;
import vm.Const;
import util.DataFormatException;

/*
 * An ExceptionEntry represents a range of Java bytecode PC values,
 * a Java exception type, and an action to take should that exception be
 * thrown in that range.
 *
 * Exception entries are read by components.MethodInfo, though perhaps
 * that code should be moved here. At least we know how to write ourselves
 * out.
 */

public
class ExceptionEntry
{
    public ClassConstant catchType;

    public int startPC, endPC;
    public int handlerPC;

    public static final int size = 8; // bytes in class files

    ExceptionEntry( int s, int e, int h, ClassConstant c ){
	startPC = s;
	endPC = e;
	handlerPC= h;
	catchType = c;
    }

    public void write( DataOutput o ) throws IOException {
	o.writeShort( startPC );
	o.writeShort( endPC );
	o.writeShort( handlerPC );
	o.writeShort( (catchType==null) ? 0 : catchType.index );
    }

    /*
     * A class referenced from an ExceptionEntry
     * is in the local constant pool, not the shared one.
     *
     * Thus it must not be externalized, but must be counted.
     * These decisions could be exposed at a higher level, for some
     * savings in performance, and should be when I have the
     * courage of my convictions.
     */
    public void externalize( ConstantPool p ){
	// do nothing.
    }

    public void countConstantReferences( ){
	if ( catchType != null )
	    catchType.incReference();
    }
}