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package com.sun.org.apache.bcel.internal.generic;
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import java.io.*;
import com.sun.org.apache.bcel.internal.util.ByteSequence;
/**
* Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions.
*
* @version $Id: Select.java,v 1.1.2.1 2005/07/31 23:45:26 jeffsuttor Exp $
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
* @see LOOKUPSWITCH
* @see TABLESWITCH
* @see InstructionList
*/
public abstract class Select extends BranchInstruction
implements VariableLengthInstruction, StackProducer
{
protected int[] match; // matches, i.e., case 1: ...
protected int[] indices; // target offsets
protected InstructionHandle[] targets; // target objects in instruction list
protected int fixed_length; // fixed length defined by subclasses
protected int match_length; // number of cases
protected int padding = 0; // number of pad bytes for alignment
/**
* Empty constructor needed for the Class.newInstance() statement in
* Instruction.readInstruction(). Not to be used otherwise.
*/
Select() {}
/**
* (Match, target) pairs for switch.
* `Match' and `targets' must have the same length of course.
*
* @param match array of matching values
* @param targets instruction targets
* @param target default instruction target
*/
Select(short opcode, int[] match, InstructionHandle[] targets,
InstructionHandle target) {
super(opcode, target);
this.targets = targets;
for(int i=0; i < targets.length; i++)
notifyTarget(null, targets[i], this);
this.match = match;
if((match_length = match.length) != targets.length)
throw new ClassGenException("Match and target array have not the same length");
indices = new int[match_length];
}
/**
* Since this is a variable length instruction, it may shift the following
* instructions which then need to update their position.
*
* 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; // Additional offset caused by preceding SWITCHs, GOTOs, etc.
short old_length = length;
/* Alignment on 4-byte-boundary, + 1, because of tag byte.
*/
padding = (4 - ((position + 1) % 4)) % 4;
length = (short)(fixed_length + padding); // Update length
return length - old_length;
}
/**
* Dump instruction as byte code to stream out.
* @param out Output stream
*/
public void dump(DataOutputStream out) throws IOException {
out.writeByte(opcode);
for(int i=0; i < padding; i++) // Padding bytes
out.writeByte(0);
index = getTargetOffset(); // Write default target offset
out.writeInt(index);
}
/**
* Read needed data (e.g. index) from file.
*/
protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException
{
padding = (4 - (bytes.getIndex() % 4)) % 4; // Compute number of pad bytes
for(int i=0; i < padding; i++) {
bytes.readByte();
}
// Default branch target common for both cases (TABLESWITCH, LOOKUPSWITCH)
index = bytes.readInt();
}
/**
* @return mnemonic for instruction
*/
public String toString(boolean verbose) {
StringBuffer buf = new StringBuffer(super.toString(verbose));
if(verbose) {
for(int i=0; i < match_length; i++) {
String s = "null";
if(targets[i] != null)
s = targets[i].getInstruction().toString();
buf.append("(" + match[i] + ", " + s + " = {" + indices[i] + "})");
}
}
else
buf.append(" ...");
return buf.toString();
}
/**
* Set branch target for `i'th case
*/
public void setTarget(int i, InstructionHandle target) {
notifyTarget(targets[i], target, this);
targets[i] = target;
}
/**
* @param old_ih old target
* @param new_ih new target
*/
public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
boolean targeted = false;
if(target == old_ih) {
targeted = true;
setTarget(new_ih);
}
for(int i=0; i < targets.length; i++) {
if(targets[i] == old_ih) {
targeted = true;
setTarget(i, new_ih);
}
}
if(!targeted)
throw new ClassGenException("Not targeting " + old_ih);
}
/**
* @return true, if ih is target of this instruction
*/
public boolean containsTarget(InstructionHandle ih) {
if(target == ih)
return true;
for(int i=0; i < targets.length; i++)
if(targets[i] == ih)
return true;
return false;
}
/**
* Inform targets that they're not targeted anymore.
*/
void dispose() {
super.dispose();
for(int i=0; i < targets.length; i++)
targets[i].removeTargeter(this);
}
/**
* @return array of match indices
*/
public int[] getMatchs() { return match; }
/**
* @return array of match target offsets
*/
public int[] getIndices() { return indices; }
/**
* @return array of match targets
*/
public InstructionHandle[] getTargets() { return targets; }
}