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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  }