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Java example source code file (BranchHandle.java)

This example Java source code file (BranchHandle.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

assigning, branchhandle, branchinstruction, classgenexception, instructionhandle, list

The BranchHandle.java Java example source code

/*
 * 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/>.
 */

/**
 * 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
 */
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;
  }
}

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