/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

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

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

 * The Apache Software License, Version 1.1

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 * reserved.

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 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

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 *    if any, must include the following acknowledgment:

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 *        Apache Software Foundation (http://www.apache.org/)."

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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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/**

 * BranchHandle is returned by specialized InstructionList.append() whenever a

 * BranchInstruction is appended. This is useful when the target of this

 * instruction is not known at time of creation and must be set later

 * via setTarget().

 *

 * @see InstructionHandle

 * @see Instruction

 * @see InstructionList

 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>

 */

public final class BranchHandle extends InstructionHandle {

  private BranchInstruction bi; // An alias in fact, but saves lots of casts

  private BranchHandle(BranchInstruction i) {

    super(i);

    bi = i;

  }

  /** Factory methods.

   */

  private static BranchHandle bh_list = null; // List of reusable handles

  static final BranchHandle getBranchHandle(BranchInstruction i) {

    if(bh_list == null)

      return new BranchHandle(i);

    else {

      BranchHandle bh = bh_list;

      bh_list = (BranchHandle)bh.next;

      bh.setInstruction(i);

      return bh;

    }

  }

  /** Handle adds itself to the list of resuable handles.

   */

  protected void addHandle() {

    next    = bh_list;

    bh_list = this;

  }

  /* Override InstructionHandle methods: delegate to branch instruction.

   * Through this overriding all access to the private i_position field should

   * be prevented.

   */

  public int getPosition() { return bi.position; }

  void setPosition(int pos) {

    i_position = bi.position = pos;

  }

  protected int updatePosition(int offset, int max_offset) {

    int x = bi.updatePosition(offset, max_offset);

    i_position = bi.position;

    return x;

  }

  /**

   * Pass new target to instruction.

   */

  public void setTarget(InstructionHandle ih) {

    bi.setTarget(ih);

  }

  /**

   * Update target of instruction.

   */

  public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {

    bi.updateTarget(old_ih, new_ih);

  }

  /**

   * @return target of instruction.

   */

  public InstructionHandle getTarget() {

    return bi.getTarget();

  }

  /**

   * Set new contents. Old instruction is disposed and may not be used anymore.

   */

  public void setInstruction(Instruction i) {

    super.setInstruction(i);

    if(!(i instanceof BranchInstruction))

      throw new ClassGenException("Assigning " + i +

                                  " to branch handle which is not a branch instruction");

    bi = (BranchInstruction)i;

  }

}