package org.aspectj.apache.bcel.generic;

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import java.io.DataOutputStream;
import java.io.IOException;

import org.aspectj.apache.bcel.util.ByteSequence;

Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions.
Author:
M. Dahm
See Also:
LOOKUPSWITCH
TABLESWITCH
InstructionList
Version:
$Id: InstructionSelect.java,v 1.4 2009/10/05 17:35:36 aclement Exp $/**
 * Select - Abstract super class for LOOKUPSWITCH and TABLESWITCH instructions.
 * 
 * @version $Id: InstructionSelect.java,v 1.4 2009/10/05 17:35:36 aclement Exp $
 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 * @see LOOKUPSWITCH
 * @see TABLESWITCH
 * @see InstructionList
 */
public abstract class InstructionSelect extends InstructionBranch {
	protected int[] match; // matches, i.e., case 1: ...
	protected int[] indices; // target offsets
	protected InstructionHandle[] targets; // target objects in instruction list
	protected int fixedLength; // fixed length defined by subclasses
	protected int matchLength; // number of cases
	protected int padding = 0; // number of pad bytes for alignment

	protected short length;

	
(Match, target) pairs for switch. `Match' and `targets' must have the same length of course.
Params:
match – array of matching values
targets – instruction targets
target – default instruction target/**
	 * (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
	 */
	InstructionSelect(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 ((matchLength = match.length) != targets.length) {
			throw new ClassGenException("Match and target array have not the same length");
		}

		indices = new int[matchLength];
	}

	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 - positionOfThisInstruction;
	}

	
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.
Params:
offset – additional offset caused by preceding (variable length) instructions
max_offset – the maximum offset that may be caused by these instructions
Returns:
additional offset caused by possible change of this instruction's 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) {
		positionOfThisInstruction += 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 - (positionOfThisInstruction + 1) % 4) % 4;
		length = (short) (fixedLength + padding); // Update length

		return length - old_length;
	}

	
Dump instruction as byte code to stream out.
Params:
out – Output stream/**
	 * 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++) {
			out.writeByte(0);
		}

		targetIndex = getTargetOffset(); // Write default target offset
		out.writeInt(targetIndex);
	}

	public InstructionSelect(short opcode, ByteSequence bytes) throws IOException {
		super(opcode);
		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)
		targetIndex = bytes.readInt();
	}

	
Returns:
mnemonic for instruction/**
	 * @return mnemonic for instruction
	 */
	public String toString(boolean verbose) {
		StringBuffer buf = new StringBuffer(super.toString(verbose));

		if (verbose) {
			for (int i = 0; i < matchLength; 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
/**
	 * Set branch target for `i'th case
	 */
	public void setTarget(int i, InstructionHandle target) {
		notifyTarget(targets[i], target, this);
		targets[i] = target;
	}

	
Params:
old_ih – old target
new_ih – new target/**
	 * @param old_ih old target
	 * @param new_ih new target
	 */
	public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
		boolean targeted = false;

		if (targetInstruction == 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);
		}
	}

	
Returns:
true, if ih is target of this instruction/**
	 * @return true, if ih is target of this instruction
	 */
	public boolean containsTarget(InstructionHandle ih) {
		if (targetInstruction == 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.
/**
	 * Inform targets that they're not targeted anymore.
	 */
	void dispose() {
		super.dispose();

		for (int i = 0; i < targets.length; i++) {
			targets[i].removeTargeter(this);
		}
	}

	
Returns:
array of match indices/**
	 * @return array of match indices
	 */
	public int[] getMatchs() {
		return match;
	}

	
Returns:
array of match target offsets/**
	 * @return array of match target offsets
	 */
	public int[] getIndices() {
		return indices;
	}

	public boolean equals(Object other) {
		return this == other;
	}

	public int hashCode() {
		return opcode * 37;
	}

	
Returns:
array of match targets/**
	 * @return array of match targets
	 */
	public InstructionHandle[] getTargets() {
		return targets;
	}

	public int getLength() {
		return length;
	}
}