/*

 * reserved comment block

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package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================

 * The Apache Software License, Version 1.1

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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

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 */

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

   */

    this.target = target;

  }

  /**

   */

                                 InstructionTargeter t) {

      old_ih.removeTargeter(t);

      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;

  }

}