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    1   package org.apache.bcel.generic;
    2
    3   /* ====================================================================
    4    * The Apache Software License, Version 1.1
    5    *
    6    * Copyright (c) 2001 The Apache Software Foundation.  All rights
    7    * reserved.
    8    *
    9    * Redistribution and use in source and binary forms, with or without
    10   * modification, are permitted provided that the following conditions
    11   * are met:
    12   *
    13   * 1. Redistributions of source code must retain the above copyright
    14   *    notice, this list of conditions and the following disclaimer.
    15   *
    16   * 2. Redistributions in binary form must reproduce the above copyright
    17   *    notice, this list of conditions and the following disclaimer in
    18   *    the documentation and/or other materials provided with the
    19   *    distribution.
    20   *
    21   * 3. The end-user documentation included with the redistribution,
    22   *    if any, must include the following acknowledgment:
    23   *       "This product includes software developed by the
    24   *        Apache Software Foundation (http://www.apache.org/)."
    25   *    Alternately, this acknowledgment may appear in the software itself,
    26   *    if and wherever such third-party acknowledgments normally appear.
    27   *
    28   * 4. The names "Apache" and "Apache Software Foundation" and
    29   *    "Apache BCEL" must not be used to endorse or promote products
    30   *    derived from this software without prior written permission. For
    31   *    written permission, please contact apache@apache.org.
    32   *
    33   * 5. Products derived from this software may not be called "Apache",
    34   *    "Apache BCEL", nor may "Apache" appear in their name, without
    35   *    prior written permission of the Apache Software Foundation.
    36   *
    37   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    38   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    39   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    40   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
    41   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    42   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    43   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    44   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    45   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    46   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    47   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    48   * SUCH DAMAGE.
    49   * ====================================================================
    50   *
    51   * This software consists of voluntary contributions made by many
    52   * individuals on behalf of the Apache Software Foundation.  For more
    53   * information on the Apache Software Foundation, please see
    54   * <http://www.apache.org/>;.
    55   */
    56
    57  /***
    58   * BranchHandle is returned by specialized InstructionList.append() whenever a
    59   * BranchInstruction is appended. This is useful when the target of this
    60   * instruction is not known at time of creation and must be set later
    61   * via setTarget().
    62   *
    63   * @see InstructionHandle
    64   * @see Instruction
    65   * @see InstructionList
    66   * @version $Id: BranchHandle.java,v 1.1.1.1 2001/10/29 20:00:06 jvanzyl Exp $
    67   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
    68   */
    69  public final class BranchHandle extends InstructionHandle {
    70    private BranchInstruction bi; // An alias in fact, but saves lots of casts
    71
    72    private BranchHandle(BranchInstruction i) {
    73      super(i);
    74      bi = i;
    75    }
    76
    77    /*** Factory methods.
    78     */
    79    private static BranchHandle bh_list = null; // List of reusable handles
    80
    81    static final BranchHandle getBranchHandle(BranchInstruction i) {
    82      if(bh_list == null)
    83        return new BranchHandle(i);
    84      else {
    85        BranchHandle bh = bh_list;
    86        bh_list = (BranchHandle)bh.next;
    87
    88        bh.setInstruction(i);
    89
    90        return bh;
    91      }
    92    }
    93
    94    /*** Handle adds itself to the list of resuable handles.
    95     */
    96    protected void addHandle() {
    97      next    = bh_list;
    98      bh_list = this;
    99    }
    100
    101   /* Override InstructionHandle methods: delegate to branch instruction.
    102    * Through this overriding all access to the private i_position field should
    103    * be prevented.
    104    */
    105   public int getPosition() { return bi.position; }
    106
    107   void setPosition(int pos) {
    108     i_position = bi.position = pos;
    109   }
    110
    111   protected int updatePosition(int offset, int max_offset) {
    112     int x = bi.updatePosition(offset, max_offset);
    113     i_position = bi.position;
    114     return x;
    115   }
    116
    117   /***
    118    * Pass new target to instruction.
    119    */
    120   public void setTarget(InstructionHandle ih) {
    121     bi.setTarget(ih);
    122   }
    123
    124   /***
    125    * Update target of instruction.
    126    */
    127   public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
    128     bi.updateTarget(old_ih, new_ih);
    129   }
    130
    131   /***
    132    * @return target of instruction.
    133    */
    134   public InstructionHandle getTarget() {
    135     return bi.getTarget();
    136   }
    137
    138   /***
    139    * Set new contents. Old instruction is disposed and may not be used anymore.
    140    */
    141   public void setInstruction(Instruction i) {
    142     super.setInstruction(i);
    143
    144     if(!(i instanceof BranchInstruction))
    145       throw new ClassGenException("Assigning " + i +
    146 				  " to branch handle which is not a branch instruction");
    147
    148     bi = (BranchInstruction)i;
    149   }
    150 }
    151

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