tableswitch.java

Java Bytecode Editor 是一个 JAVA 的字节码反汇编和修改器。它可以很方便的修改已经编译成 Class 文件的 JAVA 文件。

package org.apache.bcel.generic;

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 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
import java.io.*;
import org.apache.bcel.util.ByteSequence;

/**
 * TABLESWITCH - Switch within given range of values, i.e., low..high
 * 
 * @version $Id: TABLESWITCH.java,v 1.5 2006/08/23 13:48:30 andos Exp $
 * @author <A HREF="mailto:[e-mail]">M. Dahm</A>. Modified by Ando Saabas
 * @see SWITCH
 */
public class TABLESWITCH extends Select {
	/**
	 * 
	 */
	private static final long serialVersionUID = -7000759502003600875L;

	/**
	 * Empty constructor needed for the Class.newInstance() statement in
	 * Instruction.readInstruction(). Not to be used otherwise.
	 */
	public TABLESWITCH() {
		super(org.apache.bcel.Constants.TABLESWITCH);
	}

	/**
	 * @param match
	 *            sorted array of match values, match[0] must be low value,
	 *            match[match_length - 1] high value
	 * @param targets
	 *            where to branch for matched values
	 * @param target
	 *            default branch
	 */
	public TABLESWITCH(int[] match, InstructionHandle[] targets,
			InstructionHandle target) {
		super(org.apache.bcel.Constants.TABLESWITCH, match, targets, target);

		length = (short) (13 + match_length * 4); /*
													 * Alignment remainder
													 * assumed 0 here, until
													 * dump time
													 */
		fixed_length = length;
	}

	/**
	 * Dump instruction as byte code to stream out.
	 * 
	 * @param out
	 *            Output stream
	 */
	public void dump(DataOutputStream out) throws IOException {
		super.dump(out);

		int low = (match_length > 0) ? match[0] : 0;
		out.writeInt(low);

		int high = (match_length > 0) ? match[match_length - 1] : 0;
		out.writeInt(high);

		for (int i = 0; i < match_length; i++)
			// jump offsets
			out.writeInt(indices[i] = getTargetOffset(targets[i]));
	}

	/**
	 * Read needed data (e.g. index) from file.
	 */
	protected void initFromFile(ByteSequence bytes, boolean wide)
			throws IOException {
		super.initFromFile(bytes, wide);

		int low = bytes.readInt();
		int high = bytes.readInt();

		match_length = high - low + 1;
		fixed_length = (short) (13 + match_length * 4);
		length = (short) (fixed_length + padding);

		match = new int[match_length];
		indices = new int[match_length];
		targets = new InstructionHandle[match_length];

		for (int i = low; i <= high; i++)
			match[i - low] = i;

		for (int i = 0; i < match_length; i++) {
			indices[i] = bytes.readInt();
		}
	}

	/**
	 * Call corresponding visitor method(s). The order is: Call visitor methods
	 * of implemented interfaces first, then call methods according to the class
	 * hierarchy in descending order, i.e., the most specific visitXXX() call
	 * comes last.
	 * 
	 * @param v
	 *            Visitor object
	 */
	public void accept(Visitor v) {
		v.visitVariableLengthInstruction(this);
		v.visitStackProducer(this);
		v.visitBranchInstruction(this);
		v.visitSelect(this);
		v.visitTABLESWITCH(this);
	}

	public void setMatchesTargets(int[] match, InstructionHandle[] targets) {
		super.setMatchesTargets(match, targets);
		length = (short) (13 + match_length * 4); /*
													 * Alignment remainder
													 * assumed 0 here, until
													 * dump time
													 */
		fixed_length = length;
	}
}