| /* |
| * reserved comment block |
| * DO NOT REMOVE OR ALTER! |
| */ |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.sun.org.apache.bcel.internal.generic; |
| |
| |
| import java.io.*; |
| import com.sun.org.apache.bcel.internal.util.ByteSequence; |
| |
| /** |
| * Abstract super class for branching instructions like GOTO, IFEQ, etc.. |
| * Branch instructions may have a variable length, namely GOTO, JSR, |
| * LOOKUPSWITCH and TABLESWITCH. |
| * |
| * @see InstructionList |
| * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> |
| */ |
| public abstract class BranchInstruction extends Instruction implements InstructionTargeter { |
| protected int index; // Branch target relative to this instruction |
| protected InstructionHandle target; // Target object in instruction list |
| protected int position; // Byte code offset |
| |
| /** |
| * Empty constructor needed for the Class.newInstance() statement in |
| * Instruction.readInstruction(). Not to be used otherwise. |
| */ |
| BranchInstruction() {} |
| |
| /** Common super constructor |
| * @param opcodee Instruction opcode |
| * @param target instruction to branch to |
| */ |
| protected BranchInstruction(short opcode, InstructionHandle target) { |
| super(opcode, (short)3); |
| setTarget(target); |
| } |
| |
| /** |
| * Dump instruction as byte code to stream out. |
| * @param out Output stream |
| */ |
| @Override |
| public void dump(DataOutputStream out) throws IOException { |
| out.writeByte(opcode); |
| |
| index = getTargetOffset(); |
| |
| if(Math.abs(index) >= 32767) // too large for short |
| throw new ClassGenException("Branch target offset too large for short"); |
| |
| out.writeShort(index); // May be negative, i.e., point backwards |
| } |
| |
| /** |
| * @param target branch target |
| * @return the offset to `target' relative to this instruction |
| */ |
| protected int getTargetOffset(InstructionHandle target) { |
| if(target == null) |
| throw new ClassGenException("Target of " + super.toString(true) + |
| " is invalid null handle"); |
| |
| int t = target.getPosition(); |
| |
| if(t < 0) |
| throw new ClassGenException("Invalid branch target position offset for " + |
| super.toString(true) + ":" + t + ":" + target); |
| |
| return t - position; |
| } |
| |
| /** |
| * @return the offset to this instruction's target |
| */ |
| protected int getTargetOffset() { return getTargetOffset(target); } |
| |
| /** |
| * Called by InstructionList.setPositions when setting the position for every |
| * instruction. In the presence of variable length instructions `setPositions' |
| * performs multiple passes over the instruction list to calculate the |
| * correct (byte) positions and offsets by calling this function. |
| * |
| * @param offset additional offset caused by preceding (variable length) instructions |
| * @param max_offset the maximum offset that may be caused by these instructions |
| * @return additional offset caused by possible change of this instruction's length |
| */ |
| protected int updatePosition(int offset, int max_offset) { |
| position += offset; |
| return 0; |
| } |
| |
| /** |
| * Long output format: |
| * |
| * <position in byte code> |
| * <name of opcode> "["<opcode number>"]" |
| * "("<length of instruction>")" |
| * "<"<target instruction>">" "@"<branch target offset> |
| * |
| * @param verbose long/short format switch |
| * @return mnemonic for instruction |
| */ |
| @Override |
| public String toString(boolean verbose) { |
| String s = super.toString(verbose); |
| String t = "null"; |
| |
| if(verbose) { |
| if(target != null) { |
| if(target.getInstruction() == this) |
| t = "<points to itself>"; |
| else if(target.getInstruction() == null) |
| t = "<null instruction!!!?>"; |
| else |
| t = target.getInstruction().toString(false); // Avoid circles |
| } |
| } else { |
| if(target != null) { |
| index = getTargetOffset(); |
| t = "" + (index + position); |
| } |
| } |
| |
| return s + " -> " + t; |
| } |
| |
| /** |
| * Read needed data (e.g. index) from file. Conversion to a InstructionHandle |
| * is done in InstructionList(byte[]). |
| * |
| * @param bytes input stream |
| * @param wide wide prefix? |
| * @see InstructionList |
| */ |
| @Override |
| protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException |
| { |
| length = 3; |
| index = bytes.readShort(); |
| } |
| |
| /** |
| * @return target offset in byte code |
| */ |
| public final int getIndex() { return index; } |
| |
| /** |
| * @return target of branch instruction |
| */ |
| public InstructionHandle getTarget() { return target; } |
| |
| /** |
| * Set branch target |
| * @param target branch target |
| */ |
| public final void setTarget(InstructionHandle target) { |
| notifyTargetChanging(this.target, this); |
| this.target = target; |
| notifyTargetChanged(this.target, this); |
| } |
| |
| /** |
| * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen. |
| * Must be called before the target is actually changed in the |
| * InstructionTargeter. |
| */ |
| static void notifyTargetChanging(InstructionHandle old_ih, |
| InstructionTargeter t) { |
| if(old_ih != null) { |
| old_ih.removeTargeter(t); |
| } |
| } |
| |
| /** |
| * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen. |
| * Must be called after the target is actually changed in the |
| * InstructionTargeter. |
| */ |
| static void notifyTargetChanged(InstructionHandle new_ih, |
| InstructionTargeter t) { |
| if(new_ih != null) { |
| new_ih.addTargeter(t); |
| } |
| } |
| |
| /** |
| * @param old_ih old target |
| * @param new_ih new target |
| */ |
| @Override |
| public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) { |
| if(target == old_ih) |
| setTarget(new_ih); |
| else |
| throw new ClassGenException("Not targeting " + old_ih + ", but " + target); |
| } |
| |
| /** |
| * @return true, if ih is target of this instruction |
| */ |
| @Override |
| public boolean containsTarget(InstructionHandle ih) { |
| return (target == ih); |
| } |
| |
| /** |
| * Inform target that it's not targeted anymore. |
| */ |
| @Override |
| void dispose() { |
| setTarget(null); |
| index=-1; |
| position=-1; |
| } |
| } |