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    1   /*
    2    * Copyright  2000-2004 The Apache Software Foundation
    3    *
    4    *  Licensed under the Apache License, Version 2.0 (the "License");
    5    *  you may not use this file except in compliance with the License.
    6    *  You may obtain a copy of the License at
    7    *
    8    *      http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   *  Unless required by applicable law or agreed to in writing, software
    11   *  distributed under the License is distributed on an "AS IS" BASIS,
    12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   *  See the License for the specific language governing permissions and
    14   *  limitations under the License.
    15   *
    16   */
    17  package org.apache.bcel.generic;
    18
    19  import java.io.DataOutputStream;
    20  import java.io.IOException;
    21
    22  /***
    23   * GOTO - Branch always (to relative offset, not absolute address)
    24   *
    25   * @version $Id: GOTO.java 386056 2006-03-15 11:31:56Z tcurdt $
    26   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
    27   */
    28  public class GOTO extends GotoInstruction implements VariableLengthInstruction {
    29
    30      /***
    31       * Empty constructor needed for the Class.newInstance() statement in
    32       * Instruction.readInstruction(). Not to be used otherwise.
    33       */
    34      GOTO() {
    35      }
    36
    37
    38      public GOTO(InstructionHandle target) {
    39          super(org.apache.bcel.Constants.GOTO, target);
    40      }
    41
    42
    43      /***
    44       * Dump instruction as byte code to stream out.
    45       * @param out Output stream
    46       */
    47      public void dump( DataOutputStream out ) throws IOException {
    48          index = getTargetOffset();
    49          if (opcode == org.apache.bcel.Constants.GOTO) {
    50              super.dump(out);
    51          } else { // GOTO_W
    52              index = getTargetOffset();
    53              out.writeByte(opcode);
    54              out.writeInt(index);
    55          }
    56      }
    57
    58
    59      /*** Called in pass 2 of InstructionList.setPositions() in order to update
    60       * the branch target, that may shift due to variable length instructions.
    61       */
    62      protected int updatePosition( int offset, int max_offset ) {
    63          int i = getTargetOffset(); // Depending on old position value
    64          position += offset; // Position may be shifted by preceding expansions
    65          if (Math.abs(i) >= (32767 - max_offset)) { // to large for short (estimate)
    66              opcode = org.apache.bcel.Constants.GOTO_W;
    67              length = 5;
    68              return 2; // 5 - 3
    69          }
    70          return 0;
    71      }
    72
    73
    74      /***
    75       * Call corresponding visitor method(s). The order is:
    76       * Call visitor methods of implemented interfaces first, then
    77       * call methods according to the class hierarchy in descending order,
    78       * i.e., the most specific visitXXX() call comes last.
    79       *
    80       * @param v Visitor object
    81       */
    82      public void accept( Visitor v ) {
    83          v.visitVariableLengthInstruction(this);
    84          v.visitUnconditionalBranch(this);
    85          v.visitBranchInstruction(this);
    86          v.visitGotoInstruction(this);
    87          v.visitGOTO(this);
    88      }
    89  }