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Diffstat (limited to 'src/share/classes/com/sun/org/apache/bcel/internal/generic/BranchInstruction.java')
| -rw-r--r-- | src/share/classes/com/sun/org/apache/bcel/internal/generic/BranchInstruction.java | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/src/share/classes/com/sun/org/apache/bcel/internal/generic/BranchInstruction.java b/src/share/classes/com/sun/org/apache/bcel/internal/generic/BranchInstruction.java new file mode 100644 index 0000000..d9a7625 --- /dev/null +++ b/src/share/classes/com/sun/org/apache/bcel/internal/generic/BranchInstruction.java @@ -0,0 +1,249 @@ +/* + * reserved comment block + * DO NOT REMOVE OR ALTER! + */ +package com.sun.org.apache.bcel.internal.generic; + +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2001 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, + * 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. + * + * 4. The names "Apache" and "Apache Software Foundation" and + * "Apache BCEL" must not be used to endorse or promote products + * derived from this software without prior written permission. For + * written permission, please contact apache@apache.org. + * + * 5. Products derived from this software may not be called "Apache", + * "Apache BCEL", nor may "Apache" appear in their name, without + * prior written permission of the Apache Software Foundation. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * 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 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 + */ + 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 + */ + 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 + */ + 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 void setTarget(InstructionHandle target) { + notifyTarget(this.target, target, this); + this.target = target; + } + + /** + * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen + */ + static final void notifyTarget(InstructionHandle old_ih, InstructionHandle new_ih, + InstructionTargeter t) { + if(old_ih != null) + old_ih.removeTargeter(t); + if(new_ih != null) + new_ih.addTargeter(t); + } + + /** + * @param old_ih old target + * @param new_ih new target + */ + 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 + */ + public boolean containsTarget(InstructionHandle ih) { + return (target == ih); + } + + /** + * Inform target that it's not targeted anymore. + */ + void dispose() { + setTarget(null); + index=-1; + position=-1; + } +} |